Technical

An image showing the difference between a monocrystalline and polycrystalline solar cell

What Are the Differences Between Monocrystalline and Polycrystalline Solar Panels?

What Are the Differences Between Monocrystalline and Polycrystalline Solar Panels?

Leonardo

Written by qualified solar engineer Leonardo. Last updated:

The main differences between monocrystalline and polycrystalline solar panels are their efficiency, color, shape, and material composition. Monocrystalline panels have solar cells made from a single silicon crystal, characterized by their black color and higher efficiency. Polycrystalline panels have cells made from multiple silicon crystals, with a blue color and a slightly lower efficiency.

Thin film solar panels are a less common type. They have a lower price than the two crystalline types, but this is offset by a much lower efficiency. This article will focus on monocrystalline and polycrystalline solar panels.

Before installing a solar power system for your home or business, you must decide which type of solar panel will be used. Polycrystalline panels are the most common, followed by monocrystalline panels. Both types use solar cells made from silicon, but their microscopic structure changes.

Do Monocrystalline and Polycrystalline Solar Panels Have the Same Quality?

Monocrystalline solar panels have a higher efficiency, but this does not mean that polycrystalline panels have a lower quality. The efficiency is determined by the material properties of solar cells, and should not be viewed as an indicator of product quality. If your solar panels are from the top global brands, both monocrystalline and polycrystalline panels are subject to stringent quality standards.

Comparing the two types of solar panels is similar to comparing a sedan with an SUV. High-quality cars of both types are available, but a compact car will have a better gas mileage thanks to its lower weight.

Since high quality is available with both types of solar panels, you can expect an excellent return on investment regardless of the type chosen. The best recommendation is purchasing panels in the Tier 1 list from Bloomberg New Energy Finance: they offer high quality, and they are supplied by companies with a solid financial condition. Having a good product is important, but you should also ensure the manufacturer will be around in the future, in case of a warranty claim. The Tier 1 list includes both monocrystalline and polycrystalline solar panels.

Choosing Between Monocrystalline and Polycrystalline Solar Panels

As mentioned above, quality is not an issue when comparing monocrystalline and polycrystalline panels. Assuming you have an available space that is not covered by shadows, both types will work well. However, monocrystalline solar panels become the best option under the following conditions:

  • You have limited space for solar panels.
  • Your priority is generating as much electricity as possible.

When space is limited, you cannot make your solar system larger to produce more electricity. The maximum production with the available space is only obtained with the more efficient monocrystalline panels.

Assuming space is not a limitation, you can use any type of solar panel. The best recommendation is getting quotes from multiple solar companies, to find the one that offers the highest return on investment and the quickest payback period.

If you plan to use all your available roof area for solar panels, you will probably have plenty of surplus generation around noon. All the electricity you don’t consume is sent to the power grid, and this may be viable or not depending on how the utility company gives credit. Assuming you fill the roof with solar panels, their surplus production will be higher if they are monocrystalline.

  • Some power companies purchase surplus generation from your solar system at the retail price of electricity.
  • However, other power companies only give partial credit for every kilowatt-hour sent to the grid by your solar panels.

If the local power company gives full credit for surplus generation, it makes sense to fill your rooftop with monocrystalline panels and maximize production. On the other hand, if you only get partial credit, you can use polycrystalline panels and take advantage of their lower price.

At the end of the month, the balance in your favor is subtracted from the power bill. By producing enough surplus electricity, it may be possible to reduce the power bill to zero. If the balance in your favor exceeds your power bill, the difference is normally carried to the next month. Some electric companies may also even pay you in cash, but this is less common.

Physical Differences Between Monocrystalline and Polycrystalline Solar Panels

Monocrystalline and polycrystalline solar panels differ in both appearance and efficiency. Their manufacturing processes have key differences, which are reflected in the final product.

The materials of a solar panel are the same in both cases: solar cells are made mostly from silicon, with small amounts of other elements. However, the structure of the silicon crystals changes depending on the type of solar panel. Monocrystalline panels have solar cells that are composed of a single silicon crystal, as implied by their name. On the other hand, polycrystalline panels have solar cells that are composed of multiple silicon crystals fused together.

  • Monocrystalline panels are more expensive because their manufacturing process is more difficult. Molten silicon must be grown carefully into large crystals called ingots, which are then cut into individual solar cells.
  • Polycrystalline panels have a less demanding manufacturing process, since there is no need to grow single crystals from molten silicon. Instead, silicon solidifies into a multi-crystalline block, which is then cut into individual solar cells.

side by side monocrystalline and polycrystalline solar panels

Electric current travels more easily through monocrystalline cells, since they have an ordered crystal structure. On the other hand, polycrystalline cells have divisions in their crystal structure, which cause a slight disruption of electric current. This is exactly why polycrystalline panels have a lower efficiency. However, they are the most popular type because they are easier to produce and more affordable.

Monocrystalline and polycrystalline solar panels also differ in how their solar cells are cut, and this affects the appearance of the finished product. As mentioned above, monocrystalline solar cells are cut from single-crystal silicon ingots. Due to how the ingot is cut, these solar cells have an octagonal shape. On the other hand, the silicon wafers used for polycrystalline cells are made with square molds, and the solar cells have a square shape with straight edges. Polycrystalline solar panels have a lower cost for two main reasons:

  • Their manufacturing process is simpler.
  • Less silicon is wasted while cutting the wafers into solar cells.

The weight of the solar panel does not change much between the monocrystalline and polycrystalline types. Consider that both panel types use the same material, and what changes is the crystalline structure of silicon.

  • The 60-cell panels that are commonly used in home solar systems weigh between 42 and 44 pounds each.
  • On the other hand, the larger 72-cell panels weigh between 51 and 53 pounds.
  • Therefore, the structural requirements for roofs are the same for both types of solar panels.

The color in solar panels is determined by how sunlight interacts with the solar cell materials. Since polycrystalline panels have solar cells made from multiple silicon crystals, sunlight spreads in multiple directions, causing a blue color and a shiny appearance. On the other hand, monocrystalline solar panels appear black because they absorb sunlight more effectively.

Manufacturer warranties and the expected service life are the same for both solar panel types. Normally, you can expect a 10-year or 12-year warranty against manufacturing defects. There is also a 25-year warranty against the loss of energy production. Solar panel manufacturers guarantee that energy production will not drop below 80% over a 25-year period.

Advantages and Disadvantages of Each Type of Solar Panel

When comparing monocrystalline and polycrystalline panels, it is not possible to say that one type is better than the other. The following table summarizes the advantages and disadvantages of each solar panel type:

Solar Panel Type

Advantages

Disadvantages

Monocrystalline

-Highest efficiency available

-More electricity generation per square foot

-The solar power system can be more compact

-Higher price

-Their manufacturing process produces more waste

Polycrystalline

-Lower price than monocrystalline modules

-Their manufacturing process produces less waste

-Technical support is widely available, since this is the most common type of solar panel

-Lower efficiency than monocrystalline modules

-Lower electricity generation per square foot

-For a given system capacity, they use more space than monocrystalline modules

In general, monocrystalline solar panels are a more expensive option to maximize electricity production with the space available. On the other hand, polycrystalline panels offer a more affordable option when space is not a limitation.

Comparing Monocrystalline and Polycrystalline Panels: A Simple Example

If you ask for a specific solar system capacity, such as 10 kilowatts, polycrystalline panels will tend to use more space. Since these panels have lower efficiency, they need to cover more space than monocrystalline panels. However, keep in mind that polycrystalline panels also have a lower cost.

As an example, assume you are comparing the two following solar panel options for a 10-kilowatt installation:

  • 275-watt polycrystalline panels, with a retail price of $250 each
  • 305-watt monocrystalline panels, with a retail price of $340 each
  • Both options have 60 cells, and they have the standard solar panel size of 65” x 39”.

You need 37 of the polycrystalline panels to reach 10 kW of capacity, but you only need 33 of the monocrystalline panels. In other words, you need four additional panels if they are polycrystalline, and the solar system will cover 12 percent more area.

Each solar panel covers around 17.6 square feet. You will cover around 652 square feet with the polycrystalline panels, and around 581 square feet with the monocrystalline panels. However, this is not an issue if you have abundant space. On the other hand, if you only have 600 square feet available, you can only reach 10 kW with the monocrystalline panels.

With the data in this example, the total price of the 37 polycrystalline panels is $9,250. On the other hand, the 33 monocrystalline panels cost $11,220. In this case, one monocrystalline panel is 36% more expensive than one polycrystalline panel. However, reaching 10 kilowatts is only 21% more expensive with monocrystalline modules, since you need less of them.

Keep in mind this is just an example, and solar panel prices vary depending on the model, manufacturer, and project location. In the US you can expect to pay less than $1 per watt if the panels are polycrystalline, and above $1 per watt if they are monocrystalline. Lower prices are possible in large-scale solar systems, such as those in commercial and industrial buildings.

In home solar systems, the cost of solar panels is only around one-third of the total project cost. Consider that panels also need racking for support, as well as inverters, which convert their electricity output into the AC power used by home appliances. A solar power system also requires electrical protection devices, which protect your investment from short circuits and other electrical faults. These costs are similar for monocrystalline and polycrystalline panels.

References

  1. Photovoltaics -Department of Energy
  2. Photovoltaics – SEIA

We hope you liked this article. Please rate it or leave us a comment.

Average rating 4.3 / 5. Vote count: 13

No votes so far! Be the first to rate this post.

a man carrying a solar panel

Solar Panel Weights

How Much Does an Average Solar Panel Weigh?

Aniket

Written by qualified solar engineer Aniket. Last updated:

On average, a solar panel weighs about 40 pounds, but it could be as light as 33 pounds and as heavy as up to 50 pounds. This depends on the manufacturers and technology used. Weight is an important criterion in solar panels as a solar rooftop plant with several panels could exert significant load on the roof.

With the advancement in technology, solar panels have become more compact and lighter than before. However, they are installed for a life of almost three decades. The world is rapidly moving towards solar power and rooftop solar is becoming more popular than ever. This fact makes it important to understand the implications of the solar panel weights. Let us dive into some more details.

Contributors to a Solar Panel’s Weight

If we were to focus only on the solar cells, the main power generating component of panels, the weights in consideration would be merely a few hundred grams! And yet, a solar panel weighs 2-4 pounds for every square foot of it based on the average size of a solar panel.

A solar panel is a matrix of solar cells laminated between glass, EVA (ethylene vinyl acetate) sheets and a Tedlar (Polyvinyl fluoride) back sheet.

Diagram showing the different layers of a solar panel and what they are called

Among these, the glass constitutes for a major portion of the weight, while another significant percentage comes from the aluminum frame. The encapsulating EVA sheets (also used in making shoes), and the back sheet are thin flexible sheets and together contribute at number three. The materials used to make the panels are key for the solar panels to function.

What Panel Weights Mean for Roofs

Why does the weight of solar panel matter? As far as ground mounted systems are concerned, it does not make a lot of difference. But looking at rooftop systems — a rapidly growing sector — the quality and load-bearing ability of a roof has to be given due consideration before installing anything on it.

The most common roofing type in the United States is the asphalt shingled roof, followed by ceramic tiles and metal roofs. Typically, a roof is designed to sustain a load of 20 or more pounds per square foot. This means that it can quite easily carry the 2 to 4 pounds per sq. ft. weight of the system.

Split image of two houses with different styles of roofs

Estimate Re-Roofing Costs (Source – Roofcalc)

However, roofs that are old and deteriorated in quality are a lot unlikely to go by the above numbers. In such a case, it is always recommended to consult experts. You can get advice from solar installers or roofing experts based on the condition and age of your roof. In a lot of cases, it turns out to be a sensible option to renovate your older roof at the time of installing a solar plant. This also brings with it the advantage of customizing the roof design to some extent to suit for a rooftop solar system.

In the rare case that a roof design that cannot handle the specified weights and installing a new roof is not a desired option, one can examine the option of thin film panels. Thin film panels, as opposed to crystalline ones, weigh less per unit watt or per unit square foot.

Another query many home-owners have is whether installing solar panels will damage the roofs, but if done correctly, the panels won’t damage your roof as a variety of installation technologies are developed to suit a variety of roof types.

Future Technologies and Weights 

As efficiencies of PV cells keep climbing, panels generate more power in smaller areas and hence, in lesser weights. As mentioned previously, thin film panels are already lighter for unit size. 

Some innovative products such as bifacial solar panels have cells on both sides of a panel, harnessing reflected sunlight from the rear end as well. Ideally there can be twice the number of cells on a bifacial panel, meaning lesser weight per unit of power generation. 

Some engineers have also perfected the technique of ‘Building Integrated Photovoltaics’. Here, panels are integrated into or replace walls and windows. Technologies such as solar roof tiles can be thought of another type of building integration, and again we no more need. This turns the question of ‘additional’ weight invalid. 

Conclusion

We can finally say that most conventional panels weigh anywhere between 40 and 50 pounds, based on size and type. The future, however, does promise materials and techniques that push solar towards being significantly lighter.

Additionally, most roofs are capable of carrying the load of a solar system, thanks to the evenly distributed weight of solar panels and installation components. Despite that, some roofs toward the end of their life may certainly need assessment before installing solar panels on them.

In the end, it is always wise to let the experts have it checked out for you.

We hope you liked this article. Please rate it or leave us a comment.

Average rating 3.8 / 5. Vote count: 23

No votes so far! Be the first to rate this post.

a engineer checking how much energy a set of solar panels are producing

How Much Energy Does a Solar Panel Produce?

How Much Energy Does a Solar Panel Produce?

Leonardo

Written by qualified solar engineer Leonardo. Last updated:

Each solar panel can be expected to produce between 400 and 600 kilowatt-hours per year. The exact electricity production depends on the panel specifications and the amount of sunshine received. Smart design decisions can also improve the productivity of a solar power system.

Assuming that sunshine does not change, there are two main ways to increase the amount of energy a solar panel produces:

  • Making the panel larger, to capture more sunlight.
  • Achieving a higher efficiency with an improved solar panel design.

Solar panel manufacturers prefer to work with standard sizes, since this simplifies fabrication. For this reason, you will find that most panels have either 60 or 72 solar cells. Current research focuses on improving cell efficiency to increase energy production with the same panel sizes.

How much energy a solar panel produces depends on several factors. Solar panel efficiency and size are important, since they determine how much sunlight is captured and converted into electricity. Solar productivity also depends on the local climate, since more sunshine translates into a higher energy output. Finally, the panel orientation affects the amount of sunlight hitting its surface. The best solar companies make sure that no panels are covered by shadows, while finding the orientation that captures the most sunlight.

What Is the Average Wattage of Solar Panels?

The power rating of solar panels is commonly misunderstood. All panels are tested under equivalent laboratory conditions, and the resulting wattage becomes their rated power. However, the operating conditions in actual projects differ from the ideal lab scenario, and energy production also varies.

Solar panels with 60 cells normally have a wattage in the range of 250 to 350 watts. Some 72-cell panels go above 400 watts, since they have 12 additional solar cells producing electricity.

The controlled laboratory conditions for panel wattage tests differ from those found in most project sites. However, the power rating gives an idea of how solar panels compare with each other. A 360-watt panel will tend to produce around 20% more energy than a 300-watt panel, even if they don’t operate at their rated wattage in actual projects.

Based on the efficiency of the average solar panel, you can expect to convert between 15% and 20% of sunshine into electricity. However, some of the most efficient solar panels available go above 22%.

How Solar Panel Specifications Affect Energy Production

The productivity of solar panels depends on site conditions and the properties of the panels themselves. Site conditions cannot be changed, but the panels can be positioned to get maximum sunshine. With respect to the panels themselves, energy production is strongly dependent on the following specifications:

Panel size

A 72-cell panel has 20% more area than a 60-cell panel, thanks to the 12 additional solar cells. They are more productive simply because they capture more sunlight.

Panel material

Assuming the same size, monocrystalline panels have the highest energy production, followed closely by polycrystalline panels. Thin-film panels produce the least energy per square foot.

Temperature coefficient

Solar panels lose wattage as temperature increases, and this is represented as a percentage loss per degree Celsius. Thin-film panels are the least affected, with losses under 0.30% per °C. On the other hand, mono and polycrystalline panels normally lose over 0.40% power per °C.

Consider that performance loss with temperature is a temporary effect, and it does not represent permanent damage. When the temperature drops, panels recover their lost wattage.

You will notice that 60-cell panels are rated at 20 volts, while 72-cell panels have 24 volts. This data is used by solar installers to design electrical connections, but wattage is the value that matters when estimating the amount of energy produced. Under equal conditions, a 20V 350W panel will have the same productivity as a 24V 350W panel.

close up of a 72 cell black solar panel

Solar panel specifications can change a lot from vendor to vendor, but the way they function stays the same. Installation costs are roughly equivalent for all types.

How Much Electricity Do Solar Panels Produce Each Year?

Solar panels are characterized by their versatility. They can be used in nearly all buildings and climate zones, as long as the following conditions are met:

  • Having a roof with enough structural capacity for the panels, or a large enough property for a ground installation.
  • The prospective area for solar panels should not have serious shading issues. Solar panels produce a lot more energy when there are no shadows.

How much electricity does a solar panel produce? An accurate answer is only possible if a solar company inspects your property, to then design a suitable solar power system. However, there are online solar calculators that provide a broad estimate of production based on your geographic location and electricity consumption.

When comparing sites, a very useful metric is the yearly kilowatt-hour production per kilowatt of installed capacity, or kWh / kW.

  • For example, if your home solar system has an installed capacity of 10 kilowatts, and the output in year was 14,500 kWh, you are getting 1450 kWh per kW.
  • This production rate increases in sunny locations, since there is more solar radiation that can be converted to electricity.

NASA and other scientific institutions have compiled solar productivity data based on location. The SOLARGIS website has solar productivity maps for over 180 countries, and you can check the expected kilowatt-hour production for every kilowatt of solar capacity.

Annual Productivity with Various Solar Panel Wattages and Sunshine Conditions

The following table estimates the kilowatt-hours a solar panel can produce per year, considering five panel wattages and five sunshine conditions:

Solar Panel Wattage

1300 kWh/kW

1500 kWh/kW

1700 kWh/kW

1900 kWh/kW

2100 kWh/kW

240 W

312

360

408

456

504

270 W

351

405

459

513

567

300 W

390

450

510

570

630

330 W

429

495

561

627

693

360 W

468

540

612

684

756

This table provides an idea of what production to expect from a single solar panel, based on wattage and the local sunshine. However, only a solar company can provide an accurate estimate. A solar system design considers factors like rooftop orientation and the presence of shadows, which are unique for each site.

Solar productivity values in kWh per installed kilowatt normally include the conversion from direct current to alternating current. The DC power output from panels is not suitable for home appliances directly, and it must be converted to AC by an inverter. The best solar inverters have an efficiency of over 97%, but losses are unavoidable because no energy conversion system is perfect.

Since solar panels only operate at rated wattage in laboratory settings, you will find that the inverter is specified smaller than the total wattage of solar panels. For example, you may find that a 5-kW inverter is connected to panels that add up 5.5 or 6 kW of capacity. This may seem like a design mistake at first, but actually it is the best decision:

  • Solar panels operate below their rated wattage most of the time. A larger inverter would simply be wasting capacity while being more expensive.
  • Inverters can “clip” any solar production that exceeds their capacity. They will not be damaged if there is a sudden peak in the amount of power from panels.

How Much Electricity Does a Solar Panel Produce per Month and per Day?

The annual productivity of solar power systems is relatively constant. However, the monthly productivity is more variable due to the effect of the seasons. As you might expect, solar panels are more productive in summer and less productive in winter.

A set of solar panels on a roof that are covered in snow

Using an example from the table above, a 360W panel will produce around 684 kWh per year in a site that offers 1900 kWh/kW. On average, this is equivalent to 57 kWh per month and 1.87 kWh per day. However, the monthly and daily productivity will be above the average value during summer, and below the average value during winter.

Having a higher productivity during the summer months is actually useful, since that is when air conditioners operate at full capacity. The additional power consumption of air conditioners can be offset by the extra production from solar energy systems.

Solar offers from the best companies will normally include production estimates by month. These can give you a better idea of how the productivity of your solar panels will change throughout the year.

Why Solar Panel Output Matters

The productivity of panels is important when designing solar systems, since it determines how many are needed to reach a certain energy production target. When the square feet available are limited, getting the highest possible output from each panel is important.

The sufficient number of solar panels needed to power your home depends on your electricity consumption and savings goal. For example, reducing a power bill by 80% requires more panels that reducing it by 50%. If energy storage is added to use electricity from solar panels at night, the production calculations must also consider the kilowatt-hours required to charge batteries.

Solar shingle installations follow a completely different approach, since solar cells are embedded in roof shingles. This makes them worth installing in new homes, since there is no need to install a separate roof and solar energy system. Conventional solar panels are still the best option for existing homes. Solar shingles would require a complete roof removal in this case, which is very expensive.

We hope you liked this article. Please rate it or leave us a comment.

Average rating 4.2 / 5. Vote count: 29

No votes so far! Be the first to rate this post.

two different sizes of solar panels side by side behind a fence

Solar Panel Sizes

What is the Average Size of a Solar Panel?

Aniket

Written by qualified solar engineer Aniket. Last updated:

The average solar panel size is 77 × 39 inches or 65 × 39 inches depending on whether they are for commercial or residential use. The size of an average solar panel is dependent on the number of cells encapsulated in it and the panels’ application. Understanding panel sizes (and weights) can be important from the point of view of selecting sizes based on roof-space and the customer type (residential/commercial).

Solar Energy is arguably the most versatile of all energy sources. There are one-inch solar strips powering calculators, and there are hundreds of acres of a solar plant powering several towns. It can be used for any size of application. Naturally, it is neither easy nor wise to manufacture a single panel covering an entire rooftop or several acres of land. Thus, the need for the manufacturing of panels in different sizes.

The Difference Between Residential and Commercial Solar Panels

Although the underlying technology and system structure is pretty much the same everywhere, the panel sizes may vary based on available space of installation. Residential systems, typically rooftop systems, usually require a few hundred square feet. They also require due consideration to the roof’s ability to carry weight.

As such, residential systems usually employ slightly smaller panels as compared to a commercial system. But exactly how big are solar panels that are employed for residential spaces? Usually these are 65 inches by 39 inches, or 5.4 feet by 3.25 feet. Speaking of commercial systems that have a comparatively much larger number of panels, the size is normally 77 by 39 inches, or 6.4 feet by 3.25 feet. The depth of a solar panel may be anywhere between 1 and 2 inches, and depends mainly on the frame thickness.

You may have noticed that in both the cases, the width remains same. This factor is governed by the way solar cells are placed inside of a panel. Generally, there are six columns of cells, for both cases. For the smaller panels, there are 10 rows along the length, making 60 cells in one panel. For the larger one, there are 12 rows, making it 72 cells per panel.

diagram to show the different measurements of solar panels by the number of cells they have

Solar Panel Size for Residential, Commercial and Portable Applications (source – Sunmetrix)

When going for rooftop systems, an important thing to consider is the weight of solar panel. With all of the glass, frame, and laminating sheets contributing, the average weight of a solar panel is 40-50 pounds depending on size. Alternatively, it can be also said that panels weigh 2-4 pounds per square foot.

Besides the length and width, the word ‘size’ may mean different things to different people. Especially for people working in the solar industry, panel size usually refers to the maximum power a panel can generate. This is measured in Wp (Watt peak – Watts generated in standard or ideal conditions). For instance, a 77 x 39 panel may have a power rating of 320 Wp.

How Do Physical Size and Power Rating Relate?

Though both are spoken in different numbers, the physical size does control the power rating. This depends totally on the power generating capacity of individual cells. PV cells come in the power ratings of 4 to 5 watts. A high efficiency cell with 5Wp rating used for a 72-cell panel will give us a 5*72 = 360Wp panel. The same cells for a smaller sized (60 cell) panel would mean a 5*60 = 300Wp panel.

In a remarkably short duration, the energy produced per cell has been steeply increased.  Solar cells are becoming more and more efficient. Consequently, as time progresses, solar panels will continue to get smaller for the power they generate, and they will require less space on roofs or the ground.

Knowing How Many Solar Panels Can Fit on Your Roof

Residential, rooftop solar systems are slowly becoming more and more popular. The technologies are advancing rapidly, including installation systems. With a host of available types, roof mountings are safer and they don’t damage the roof in any way, if done the right way.

In the design of any such system, an essential criterion is the available space. Besides, as far as energy consumption is concerned, a ‘one-size fits all’ approach never works. Thus, the other essential criterion is the energy consumption. Local solar panel installers in your vicinity can always calculate a system size and provide a quotation, but it certainly helps to know how to calculate the amount of solar panels you need yourself. This depends on two things – ‘how big is a solar panel?’ and ‘how much space does my roof have?

A house with two big sets of solar panels fitted on the roof

From the numbers in the previous sections, you can calculate the area of a single solar panel. Dividing your roof area by a single panel’s area will give you an approximate number of solar panels that can fit on your roof.

For example, a 60-cell panel will be about 17.5 square feet large. Assuming you have a 1500 square feet roof, that would mean you can ideally install 1500/17.5 = 85 panels. However, there can be shaded areas on the roof where the panels won’t perform well, and should be avoided.

As mentioned earlier, it is also important to know the required size in terms of energy consumption. The average system size in the United States is 6kW, and assuming a single panel is of 300Wp, one would need 6000/300 = 20 such panels for an average house.

Thus, we can see that area-wise the maximum number of panels ‘that can fit’ can be larger than the actual number of panels ‘required’ based on the energy utilized.

Finally, we can summarize saying that the size is controlled by the number of cells on the production side and by customer type on the installation side. It continues to get smaller though, and the future will see high efficiency panels that don’t eat up a lot of space.

We hope you liked this article. Please rate it or leave us a comment.

Average rating 3.8 / 5. Vote count: 11

No votes so far! Be the first to rate this post.

a bright blue set of solar panels with reflection of the sky in them

Why are Solar Panels Blue?

Why Are Solar Panels Blue?

Aniket

Written by qualified solar engineer Aniket. Last updated:

Most solar panels are blue because of the manufacturing of polycrystalline cells from multiple silicon crystals, and a special anti-reflective layer on the panels for higher light absorption. Although blue claims the majority, some panels can also be black, based on their respective manufacturing methods.

Technically, the color black is known to absorb the highest amount of light. Yet, most solar panels are blue in color, since polycrystalline panels make up the majority. This is why most people will recall an image of several blue rectangular panels on hearing the word ‘solar’. We will see these things in the following paragraphs. Understanding the reason behind the panel color is important as it can help identify the type of panel that is used.

Silicon – The Blue-Black Building Block

Understanding the color of solar panels requires us to look into the material they are made from. The discovery of photovoltaics and the first ever solar cells involved elements such as silver chloride and selenium. Yet, interestingly, almost all commercially used PV cells are made from Silicon. Silicon is a brittle element, and the eighth most abundant in the universe, though a bit rare in its pure form.

Silicon (Si) and its compounds are used in a myriad of applications from glass, cements, electronic elements, etc. A semiconductor material, Si has a blue tinge to itself (the reason most solar panels look blue) and a metallic greyish luster.

pure raw silicon

Silicon cells are of three main types, based on the method of manufacturing. The most common type is polycrystalline or multicrystalline cell, which is made from several small silicon crystals. This type of cell has a noticeable blue color to it.

The next type is monocrystalline, made from a single large silicon crystal. Mono cells have a black or almost black hue to it. There are other, lesser used types such as thin film, which are also close to black in color. The reason most solar panels are blue is the widespread use of polycrystalline solar panels worldwide.

The Role of Anti-Reflective Coating in Color

Anti-Reflective Coating, as one can guess from the name, is a layer over the panel that reduces reflection of incident sunlight. This means maximum light enters the panel and cells and the minimum is lost, so efficiency is improved.

AR coatings, however, change the way light waves interact with the glass top of the panel. This causes the panels to look slightly more bluish in color.

Color and Efficiency

Despite polycrystalline panels’ stronghold on the worldwide markets, black still remains the more efficient color.

Some other upcoming technologies such as CIGS thin film also produce pitch black panels, but are expensive. To keep the cost in range while making the color blacker, some companies have come up with AR coatings that do not add to the blue hue.

Color and Aesthetics

The availability of free and clean energy, according to many people, outweighs the apparent change in a building’s looks. However, not everyone believes that. For some reason, some owners feel wary of having rows of blue rectangular plates on their roofs.

To solve this problem, several companies have come up with interesting solutions. One of them is the development of nanotube patterns that give the panels a green color (in cases where owners don’t mind green). It comes at a small cost of efficiency.

Some other companies have devised pixelated printed patterns that allow any color to be printed on the glass. This allows the possibility of matching colors with the building exterior, or simply having a multicolored and fun looking array. Going a step further, it has also become possible to print images on solar panels, turning panels into possible advertisement sheets.

It should, however, be kept in mind that all of this will always lead to some extent of efficiency loss, around 10%, as said by the inventors.

Conclusion

To conclude, we can say that not all panels are blue but the most common ones certainly are, and this is due to the polycrystalline silicon and AR coating.

As technology progresses, the color may shift to black in favor of higher efficiency, provided costs can be kept low in manufacturing. If the preference however happens to be the aesthetics more than the efficiency, colored or photo-printed panels are an interesting trend to investigate.

We hope you liked this article. Please rate it or leave us a comment.

Average rating 4.4 / 5. Vote count: 16

No votes so far! Be the first to rate this post.

a small diagram to show the different parts and operations of solar cells

What are Solar Panels Made Of?

What Are Solar Panels Made Of?

Leonardo

Written by qualified solar engineer Leonardo. Last updated:

Most solar panels are manufactured from silicon. Depending on how silicon is processed, it can be monocrystalline, polycrystalline, or amorphous. Crystalline panels are the most common, while amorphous silicon panels are part of the “thin-film” category, which is used less.

Solar panels generate electricity without moving or producing noise, making them an excellent renewable energy source for buildings. Nobody is exposed to heavy machinery in movement, and the distracting effect of noise is prevented. With these unique features, one of the first questions asked by home or building owners is: “what are solar panels made of?”.

All monocrystalline and polycrystalline panels are made from silicon, but thin-film panels can be produced with other substances. The materials used in solar roofs of the thin-film type include cadmium telluride (CdTe) and copper indium gallium diselenide (CIGS).

Processing Silicon into Solar Cells

By itself, pure silicon does not produce electricity under sunlight. However, other elements can be added in small amounts to achieve this effect. Adding phosphorus produces a surplus of electrons to carry electricity, and the result is N-type silicon. On the other hand, the addition of boron or gallium causes an electron deficit, and the product is called P-type silicon. When both types of silicon are arranged in layers, light induces an electron movement between them, producing an electric power output.

Pure silicon is not found in nature, and instead it must be obtained from silicon dioxide, which contains impurities. Silicon dioxide is melted, and unwanted elements are removed with physical and chemical processes. Once the silicon has been purified, it is converted into N-type or P-type silicon by adding other elements in controlled amounts.

Amorphous silicon is the type used in some thin-film panels, and it gets its name because the molecular structure is not crystalline.

How to Identify the Different Types of Solar Panels

The language used when describing the types of solar panels may sound very technical. However, the three main types can be easily identified based on their appearance.

If a panel has a grid-like surface that is separated into solar cells, it belongs to one of the crystalline types. Monocrystalline panels use only one silicon crystal per cell, and they are characterized by their black color. On the other hand, polycrystalline cells are made of multiple crystals, and they have a lighter blue tone. Solar cells are produced from molten silicon in both cases. However, monocrystalline cells demand more process control to ensure they are made from a single crystal.

set of solar panels with a bright blue sky in the background

Identifying thin-film panels is even easier, since they have a uniform surface without divisions. This is due to their manufacturing process, where the solar material is deposited in layers rather than individual cells.

Before choosing between the solar panel types, the first step is understanding how they work. Consider that electricity is only produced when sunlight is available, and the maximum production is only achieved around noon. If you want to use solar energy 24/7, you must add battery storage for the night or cloudy days.

Comparing the Types of Solar Panels: Advantages and Disadvantages

The different types of solar panels have pros and cons, like in most other decisions that deal with technology.

  • Monocrystalline panels are the most efficient, which means the production of electricity per square foot is higher. Therefore, these panels are the best option if you have limited space for the solar energy system. However, monocrystalline panels are also the most expensive, since they are the most difficult to produce.
  • Polycrystalline panels have a moderate efficiency, but they are also more affordable than monocrystalline panels. They are also the most common type.
  • Thin-film solar panels have the lowest cost and weight. However, they are also the least efficient panels, having the lowest electricity production per square foot. In other words, thin-film panels need more space than crystalline panels to reach a specified capacity. All three types of solar panels lose performance when they heat up, but thin-film panels suffer less from this effect.

The costs associated with installation are similar for all types of solar panels. Thin-film panels are easier to handle thanks to their low weight, but you also need to install more of them. Polycrystalline and monocrystalline panels are similar in terms of weight and size.

The appearance of solar panels is a subjective factor, but it can also influence purchasing decisions. While some users may like the smooth surface of thin-film panels, other may prefer the traditional appearance of crystalline panels. All three types of solar panels achieve good results when installed by a qualified company. However, if you prefer thin-film panels, make sure you have the roof space to accommodate a larger installation.

A worker installing a large set of solar panels on a roof

The solar panel buying information provided by manufacturers contains many details about the panel type and efficiency. Solar installers use these technical specifications to select the best option for your property.

Additional Materials Needed to Produce Solar Panels

Silicon solar cells are the core of solar panels, but other materials are needed to allow their use in outdoor settings. Solar cells are protected by a housing, which is normally produced from aluminum or fiberglass. Also, the side of solar cells that faces the sun is covered by glass, so sunlight can reach them. Most commercial solar panels use either 60 or 72 cells per unit.

Solar panels also have internal wiring, since the solar cells must be connected together to gather their electricity production. The connection terminals of a solar panel are really the ends of a circuit that connects all the cells inside.

It is important to note that solar panel manufacturing methods have evolved over time. At first, solar power was regarded as a technology for satellites and other outer space applications. Therefore, manufacturers focused on lightweight designs. When solar power became a viable electricity source for homes and businesses, panel designs became more robust and durable.

We hope you liked this article. Please rate it or leave us a comment.

Average rating 4.5 / 5. Vote count: 13

No votes so far! Be the first to rate this post.

References

  1. Solar Photovoltaic cell Basics – Department of Energy
  2. Photovoltaics – SEIA
man checking on the status of his solar panels

How Long do Solar Panels Last?

How Long Do Solar Panels Last?

Leonardo

Written by qualified solar engineer Leonardo. Last updated:

High-quality solar panels last more than 25 years, and their payback period is only between 4 and 8 years. If you purchase panels with a solid warranty, the return on investment is assured. However, keep in mind that warranties are only valid if the panels are installed properly. Working with a qualified solar installer is strongly recommended.

Installing solar panels is one of the most effective ways to reduce your electricity bills. They may seem expensive at first, but their long-term savings are greater than their upfront cost. In other words, every dollar spent on a solar power system is recovered tenfold. After understanding how long solar panels last, it makes complete sense as an investment.

Understanding the Two Types of Solar Panel Warranties

When purchasing warranties, you will notice there are two types. One of them covers manufacturing defects, while the other covers electricity production. Each warranty protects your investment from different issues.

The warranty against manufacturing defects is normally for 10 to 12 years. If your solar panels are correctly installed and any of them fail, this warranty gives you replacements at no cost. Just keep in mind that the faulty panels must be removed and replaced, so make sure your solar provider offers support.

The energy production warranty is much longer, and leading solar manufacturers offer 25 years or more. Solar panels degrade over time like any power generation system, but this warranty covers you if they degrade faster than normal. High-quality panels will have at least 80% of their initial capacity after 25 years, and many warranties use this value.

  • A panel with a power rating of 330W will have dropped to 264W after 25 years.
  • If you use 20 of them in a 6.6-kilowatt system, the capacity after 25 years will be 5.28 kW.

Warranties are only useful if the manufacturer will be around in the future to make them valid. The best recommendation is purchasing panels from Tier 1 solar manufacturers: they offer quality products while being companies with financial health. Your solar warranty becomes useless if the manufacturer goes bankrupt!

Like with any other product, high-quality solar panels from top brands tend have a higher price. However, they are worth it when you consider performance and warranty coverage. Panels can last even longer than their 25-year warranty with adequate maintenance. However, keep in mind that energy production will wane over time, even with top-tier panels.

The long warranty period is one of the main factors that makes solar panels a good investment. Since the typical payback period is shorter than the warranty period, your power bill savings are assured. Just be warned that warranties are voided by an incorrect installation, hence the importance of working with a qualified installer.

Do Solar Panels Save Less Electricity over Time?

Due to the degradation rates of solar panels, you may be thinking that electricity savings will shrink each year. However, consider that kilowatt-hour prices tend to increase over time.

  • If your panels lose 0.8% of their capacity in a year, but the local power company raises its tariffs by 3%, your electricity savings will increase.
  • According to a research project by the National Renewable Energy Laboratory (NREL), most panels degrade at a rate of less than 1% per year.

When solar companies estimate the electricity savings and payback period of a solar energy system, they consider degradation rates. In other words, solar panels are a good investment even with their loss of production over time. Solar panel roofs have become popular for the simple reason that they make financial sense.

Technician checking the performance of a solar panel

If you are planning a home addition in the future, you can simply increase the number of panels. This way, they can keep up with your electricity needs. You must only make sure that the additional panels are compatible with the original installation. You can also ask your solar installer to leave the provisions for an eventual expansion.

How Long Do Solar Inverters and Batteries Last?

Consider that the panels are only one part of an operational solar power system. Components like racking and wiring are very durable, and you can expect them to last as long as the panels. However, solar inverters have a shorter service life than panels, and you must plan for an eventual replacement. The same applies for batteries, in case your solar power system uses them.

Due to the way they work, solar panels produce electric power in the form of direct current (DC). However, your home appliances need alternating current (AC), which is the type of power provided by utility companies. Solar inverters gather the electricity produced by panels, converting it into AC power. However, the life expectancy of an inverter is only around 10 years, which means your panels will eventually need a new one.

The quality of your inverter is just as important as the quality of your panels. The leading inverter suppliers normally offer a 10-year warranty, similar to the panel warranty against manufacturing defects.

A solar power system can work without batteries, making them an optional component. However, they bring additional benefits when present:

  • You can store solar energy for nighttime and cloudy days, which means you rely even less on the local power company.
  • The battery system can assume the role of a backup generator during a blackout.

Lithium-ion batteries are now available with a 10-year warranty. Conventional lead-acid batteries last much less, normally between 1 and 3 years. Lithium-ion batteries are also more flexible and efficient, while lead-acid batteries must be fully charged between discharging periods.

The shorter service life of inverters and batteries does not mean they have a lower quality than solar panels. That is simply the current development stage of those technologies, and it is likely that more durable versions will be available in the near future.

Do Solar Panels Need Maintenance?

Compared with other renewable energy systems, solar panels have simple maintenance needs. If they are kept clean and protected from damage, a long service life is assured. In addition, since the panels don’t have moving parts, they are not exposed to mechanical wear.

Solar providers follow different procedures when calculating the cost of solar panels. When you receive offers, ask the providers about solar maintenance services. In fact, some companies may include a period of free maintenance after installing the solar system.

Worker on his ladders fixing a solar panel

If you get solar power through a lease or Power Purchase Agreement (PPA), the contract will normally make the provider responsible for maintenance. This includes inverter and battery replacements after around 10 years, so you don’t have to plan and budget that purchase. In solar leases and PPAs, the price to pay for these benefits is sharing your savings with the provider.

Like any electrical device, solar panels must be protected with suitable circuit breakers. Panels without adequate electrical protection are more vulnerable to faults, and there is also a higher risk of fire or electric shock. However, this aspect is covered if your system is designed and installed by a qualified solar company.

Consider that 25 years is a long time, and your home surroundings can change. For example, trees around your home can cast shadows on the panels or on your solar panel roof, reducing their energy production. Avoid planting trees in locations where they can cause shading issues for your solar energy system, and make sure you trim any branches that block the sun.

We hope you liked this article. Please rate it or leave us a comment.

Average rating 4.9 / 5. Vote count: 13

No votes so far! Be the first to rate this post.

a small diagram showing how solar panels work

How do Solar Panels Work?

How do Solar Panels Work?

Leonardo

Written by qualified solar engineer Leonardo. Last updated:

Solar panels work by converting sunlight into electricity at the atomic scale. When solar cells are struck by light, they produce a flow of electrons, or electric current. Since this process happens at such a small scale, it is invisible for humans. Compared with other renewable energy systems, panels are characterized by their lack of movement.

Solar panels produce a certain amount of energy that is determined by two main factors: the amount of sunlight reaching the panel, and the material composition. Some panel materials can collect more sunlight per square foot, leading to a more efficient and compact installation.

Solar panels have become a popular renewable energy option for homes and businesses, and this makes perfect sense when you weigh their costs and benefits. Solar power systems become more affordable each year, while electricity costs continue to rise. From a financial standpoint, adding panels to a building is an excellent investment. In this article we will be answering the common question of “how do solar panels work”?

How Exactly Does a Solar Panel Work?

A solar panel can be viewed as the opposite to an LED bulb, which is also an electronic device that uses semiconductor materials. Just like an LED bulb converts electricity into lighting, a solar panel absorbs light to produce electricity. This behavior is called the photoelectric effect, and it was first studied in the 19th century.

Small diagram of a house with small solar panels and how the convert sunlight to electricity

The name of solar panels can be misleading, since they work with any type of light. If you place a panel under an artificial bright light, it will start to produce electricity. However, only sunlight is a viable energy input, since it is delivered for free. Other light sources have either a fuel cost or an electricity cost.

The material used to make solar panels is normally silicon, which has many applications in the electronics industry. With a special chemical process, silicon can be treated so it will produce electricity in response to ligh541t.

  • Energy conversion begins when a solar cell is hit by photons, which are the elemental particles of light.
  • Photons separate electrons from the silicon atoms, and the movement of electrons is equivalent to electric current.
  • The combined movement of electrons from multiple solar cells provides the total output of a solar panel.
  • The concept is then repeated when the panels are wired together, adding up their individual production.

Producing electricity without moving is a significant advantage of solar power systems. Other generation systems like wind turbines and diesel generators have moving parts, which are subject to mechanical wear. In these cases, the constant need for lubrication and part replacements makes maintenance difficult. Taking care of solar power systems is much easier, since the most demanding maintenance task is keeping their surface clean.

Why Are Solar Panels Connected to an Inverter?

You may have noticed that panels are not connected directly to home appliances. Instead, they are wired together and their electricity production passes through an inverter. This is necessary because the electricity produced by panels does not have the properties required by home appliances.

Solar panels produce direct current (DC) electricity, while home devices use alternating current. A DC power source provides a constant voltage, while an AC source has a voltage that oscillates between positive and negative. Electric companies use AC power because it provides many advantages in electricity generation and transmission.

Basically, a solar inverter converts the DC output of panels into an AC power supply that is suitable for home appliances. Since the power grid also uses AC voltage, it can be synchronized with the solar power system. This has several advantages:

  • When solar power production is not enough for home appliances, any additional electricity can be drawn from the grid without changing any connections.
  • Surplus production can be exported to the grid, to be subtracted from your power bill.

When a solar power system is synchronized with the power network, it is called a grid-tied installation. This is the most affordable system configuration, and also the most common.

What are the Different Types of Solar Panels?

As previously mentioned, solar panels use materials that produce electricity when exposed to light. Most panels are made of crystalline silicon cells that are wired together to add up their voltage. Typically, a panel will have either 60 or 72 cells.

  • A 60-cell panel has 10 rows of six cells.
  • On the other hand, a 72-cell panel has 12 rows of six, making it 20% longer.
  • The amount of solar panels needed for a specific building will change depending on the type. Since 72-cell panels have more cells, they typically have a higher wattage.

60-cell panels are more common in the residential sector, while 72-cell panels are more common in business applications and solar farms. Nothing limits the use of 72-cell panels in home solar systems, but their larger size can be an issue when roof space is limited. 60-cell panels can be used without problem in large commercial buildings as well, but the need to use more of them can increase labor costs.

Two men installing solar panels on a large commercial building

Crystalline silicon panels can be classified into two subtypes. Monocrystalline panels have solar cells made from a single silicon crystal, and their surface is black. On the other hand, polycrystalline panels have blue cells that are made from several crystals. The efficiency of solar panels is higher if they have monocrystalline cells, but their price is also increased.

Some panels do not have silicon cells, and instead they have a uniform surface. These are called thin-film panels, since the material that converts sunlight into electricity is deposited as a layer.

  • These panels have a lower cost that the crystalline ones, but they also need more space to compensate for their lower efficiency.
  • The cost per watt of capacity ends up being similar since the panel has a lower cost — but you need more of them.

Monocrystalline, polycrystalline, and thin-film panels are the three main options available, and the polycrystalline ones have dominated the market. Solar shingles are emerging as a fourth option. They combine roof shingles and panels into a single element.

Understanding the Cost of Installing Solar Panels

The panels themselves only represent a fraction of the cost of a complete solar power system. The costs involved when installing solar panels include special racking, the solar inverter, and electrical protection devices. When all solar costs are factored in, you can expect to pay $3 per watt of capacity in the United States.

As previously discussed, an inverter converts the output of panels into AC power for home appliances. Special racking is used to attach the panels to the roof, since they are not designed for direct installation. Also, solar panels need circuit breakers like any other electrical device. Electrical faults such as short circuits and ground faults can severely damage solar panels and their associated components.

Knowing how to install solar panels has become a useful asset in the United States job market, due to the high demand for solar systems.

Managing Solar Energy Production Effectively

Solar power is clean, and its cost continues to drop each year. However, solar systems still have a limitation that is shared with wind turbines: they depend on variable energy inputs to produce electricity. For this reason, you cannot go off-grid with solar panels alone, and batteries become necessary for nighttime and cloudy days.

Governments and power companies have developed and interesting concept to manage the variable nature of solar power, which is called net metering:

  • Surplus energy production from your solar energy system can be exported to the grid.
  • The power company gives credit for that energy on the next electricity bill.

With net metering, your home can get savings for unused solar energy production. If your solar system is large enough to produce surplus electricity at noon, it can be exported to the grid and deducted from your nighttime consumption.

Solar panels work better when they receive direct sunlight. They can be mounted on tracking mechanisms to always face the sun, but this approach is only recommended when space is a limitation. In most cases, adding more panels is a better option than using a few panels with a solar tracker.

We hope you liked this article. Please rate it or leave us a comment.

Average rating 5 / 5. Vote count: 17

No votes so far! Be the first to rate this post.

solar panels in the middle of the hot desert

Can Solar Panels Overheat?

Can Solar Panels Overheat?

Carlos

Written by qualified solar engineer Carlos. Last updated:

Solar panels can overheat. It is a common assumption to relate hot climates with excellent conditions for solar panels, however, the truth is that high ambient temperature conditions are not good for solar panels. Actually, this is one of the major causes of a drop-in performance and can reduce energy yields if not considered properly. Therefore, if your location is very hot then it will be great for products such as camping solar showers, but definitely not for solar PV.

In order to accurately describe how solar panels can overheat, we must first understand some basic theory behind solar PV system designs.

Solar Panels and Test Conditions

New solar panel models must pass through a set of lab tests known as Standard Test Conditions (STC) and Nominal Operating Cell Temperature (NOCT) which are related to the performance and power output of the module under specific environmental conditions. This post is useful to learn more about how solar panels are rated.

STC are referred to the following lab conditions:

Irradiance = 1kW/m2                

Temperature = 25°C

Air Mass = 1.5 AM.

On the other hand, NOCT conditions test solar panels under the following parameters:

Irradiance = 800 W/m2          

Wind Speed = 1 m/s     

Ambient Temperature= 20°C

Surface Temperature = 45°C

As you can see, there are important differences between STC and NOCT. NOCT conditions represent a more realistic approach than STC because they consider irradiance values of 800 W/m2 and operation temperatures of 45°C in the solar cell.

However, STC is considered as the main reference for sizing PV systems. Power outputs, efficiencies, voltages, and current values are generally referred to STC conditions. The problem lies in the fact that real-world conditions can be very different from STC, therefore solar designers must use technical mathematical expressions to estimate the new values according to real-world conditions.

The Influence of Temperature in Solar Panel’s Performance

Temperature is an environmental parameter that deeply affects the voltage of the PV module. The effect in the power output is also important since the voltage is deeply affected. On the other hand, the effect of temperature in current values is technically negligible.

Low-temperature values rise the voltage in the module, while high-temperature values reduce the voltage of the solar panel. Since power is equal to current multiplied by voltage (P= V*I), low-temperature conditions improve the performance and efficiency of the module, while high temperatures reduce the power output and lead to other thermal losses.

Operation temperatures values of the PV cell change according to ambient temperatures and irradiance values. To estimate the new operating temperature values of the module, solar designers use the expression below, where Ic represents the estimated irradiance on the module.

expression to estimate the new operating temperature values of the module

Then, using this new operation temperature (Tcell), another important parameter must be considered and can be found in any datasheet of any solar panel: the temperature coefficient of voltage. This coefficient indicates the rate at which the solar panel will change its voltage output according to an increase of 1°C in the operating temperature of the module. 

Using another expression and this coefficient, it is possible to estimate the new open circuit and maximum power point voltages. This expression can be found below, where is the temperature coefficient of open circuit voltage.

estimate the new open circuit and maximum power point voltages

Solar panels under cool temperature conditions are similar to the NOCT temperature value (45°C), however, under hot temperature conditions, operating cell temperatures can reach values as high as 70°C.

How Do Solar Panels Work in Hot Climates?

We have learned that solar panels use solar radiation to generate electricity, but this source of energy has two components: light and heat. Solar panels use the incoming particles of light as the main source of energy to be transformed into electricity, however, the heat component is not used to generate electricity.

Heat is generally associated with high temperatures and high relative humidity. As we discussed above, high temperatures have a negative effect on the performance of the solar panels. Elevated relative humidity values are not good either for PV systems because they can lead to other problems like the presence of moisture, delamination, leakage currents, module degradation, and reduction in current values.

Moreover, if we are installing solar panels in a sloped roof, then another problem arises as well in hot climates. Air circulation behind the module is necessary to keep the module cool and to reduce thermal losses as well.

If the module is too close to the roof, then there is not enough airflow behind it, which also leads to higher temperature values, further losses in power, and reductions in voltage values as well. Ground mounting systems do not have that problem because air flows freely behind the module.

In other words, solar panels can indeed overheat. If your solar panel is overheating, then it will mean a reduction in the efficiency and performance of the module. That being said, it won’t mean that the module will be damaged by the excess of heat.

Depending on the application that you are using solar technology for, the effects of overheating can be bigger or smaller. If you intend to use solar technology to power some solar LED camping lanterns or a solar sliding gate opener which serve very small applications, the effects of overheating can be neglected. However, on residential and commercial scale PV systems the effects of overheating on solar panels can be considerable.

Solar panels are tested under damp heat tests, which submit the module to 1,000 hours of elevated temperature values such as 85°C with 85% relative humidity. In order for a module to be commercially available, it must pass this test and the thermal cycling test as well, which includes 200 cycles of temperature variations between -40°C and 85°C.  As you can imagine, if the solar panel could pass that, then it is unlikely that it will get damaged by the temperature values available in your location.

What to Do if Your Location is Hot

The first thing that you need know is that if your location can reach to ambient temperature values as high as 40°C – 50°C during the summer season, then your solar panels will not perform at high efficiency, and unfortunately, there is nothing you can do about it.

However, there are a few details that you might want to think about when installing the PV system to minimize those losses.

We discussed the influence of temperature coefficients in the solar panel’s voltage. Choosing a solar panel with a high-temperature coefficient in an extremely hot location is an extremely bad idea. Here, it is a duty of the solar designer to pay attention to temperature coefficient values and choose the solar panels that have the lowest coefficients in order to minimize the effect of temperature in the module.

If you are wondering which is the solar panel with the lowest temperature coefficient of the industry, then check the HIT modules from Panasonic (the temperature coefficient is -0.258 % / °C – the lowest of the industry).

Moreover, forget about a rooftop mounting system. In a hot climate environment, you must maximize air cooling, therefore you must install a ground mounting system to allow the module to cool itself as much as possible.

Finally, hot locations are generally attributed with deserts or areas with a lot of dust. Considering the presence of dust, sandstorms, and the impact that soiling factors could have in the energy yields of the PV system, is also important the solar designer of your array takes that into account.

We hope you liked this article. Please rate it or leave us a comment.

Average rating 4.6 / 5. Vote count: 20

No votes so far! Be the first to rate this post.

multiple solar panels oduring the night time

Can Solar Panels Work at Night?

Can Solar Panels Work at Night?

Carlos

Written by qualified solar engineer Carlos. Last updated:

Solar panels won’t work at night because they depend on sunlight to generate electricity. Some people get confused with the simple way that we commonly refer to solar energy and how we use it. However, the truth is that solar panels cannot generate electricity at night.

What is possible is that you can use solar power generated during the day and store it in devices such as lithium-ion batteries that will allow you to use it during the night. In other words, if for instance you need some light during the night, you can use solar powered lanterns which will generate electricity during the day to charge the internal battery, and then work during the night to light up your yard.

Let’s give you a little technical approach on how electricity is generated from solar panels and how you can use this generated energy during the night.

How is Solar Power Generated?

Solar panels are electronic devices designed with an aluminum frame, glass, wires, and semiconducting materials that are placed in thin layers called solar cells.

The semiconducting material used by excellence in solar panels is silicon, one of the most abundant semiconductors in the Earth. The silicon has a crystal structure composed of strong bonds between atoms. However, by adding or “doping” the structure with other components such as boron and phosphorous, it is possible to increase the conductivity of the layer. In other words, increases the amount of electricity that can be generated.

Now, sunlight can be described as a particle or a wave. If we refer to sunlight as a particle, then we are referring to atom level particles called photons that impact the surface of the Earth every instant during the day.

When these photons reach the silicon solar cell doped with boron and phosphorous, they release free charge carriers (called electrons). The movement of electrons leads to the generation of electricity, therefore, while more electrons are released, more power is generated.

Summarizing, photons reach the surface of the solar panel, photon’s kinetic energy is transmitted to electrons, releases electrons, generates electricity, and they are then conducted to harnessing points called busbars that are connected to the output of the PV cell.

image showing how solar energy is generated

(Source – Solar Energy Technologies and Project Delivery for Buildings, Andy Walker)

As you can see, the main source of energy in photovoltaic electricity is the kinetic energy of the photons. Therefore, if there is no sunlight, then there are non-photons. If there are non-photons, then it is impossible to harness electricity from solar panels.

Then, How is It Possible That My Neighbor’s House is Powered at Night By Solar Energy?

Solar energy harnessing has a particular curve shape that can be usually simulated as a Gaussian Curve.

solar power self-consumption

Solar Power Self-Consumption (Source – My Solar Quotes)

As you can see above, solar harnessing starts producing a little energy in the early hours, maximizes its production during midday, and reduces as evening hours get closer.

However, in many instances, solar energy production exceeds the consumption during midday hours when loads are low because you are outside of the house working or doing businesses. Then, the patterns of consumption generally increase at night, when we turn on the lights of our homes, turn on the TV, start cooking, doing laundry, etc. Unfortunately, solar energy is no longer being generated by then.

Since these two peaks of generation and consumption cannot be mixed, a solution needed to be put in place to make the balance of electricity possible. Actually, in the US, there are two solutions for this issue: Net Metering and Energy Storage.

Net Metering

The Net Metering scheme allows any homeowner or user that produces excess solar energy during the day to sell it to the utility grid and receive a credit for the electricity injected on the energy bill. In other words, the credit offsets any consumed electricity from the grid overnight, it translates into a reduction of the energy bill cost every month.

The problem with net metering is that the tariff or credit that you obtain to offset your production overnight changes from State to State and from time to time in the US. Some States also have capacity limits that can be applied for distributed energy generation, others have restrictions in renewable energy sources that can apply, and others simply do not have that scheme.

However, around 38 States have implemented the Net Metering policy, so it’s not a bad number either as you can see below.

map of the United States to show the state net metering policies for each individual state

(Source – National Conference of State Legislatures)

Other States have special tariff rates, like Minnesota and Texas (specifically Austin). These offer a Value of Solar rate that take into account not only the energy injected to the grid, but also the benefits that solar energy offers to balance the grid every day. The main difference with Net Metering is that Value of Solar rate is fixed over 20 years, which offers stability in your electricity earnings.

Energy Storage

The other solution that came out to the market was to install PV systems with batteries for backup. These systems are usually called grid-tied with battery backup because they do not normally work off-grid, yet when there is a blackout they can power your house.

Coupling energy storage with PV systems has become very popular thanks to the appearance of hybrid inverters that do not require the presence of a charge controller that increases costs. They are also popular now thanks to companies like Tesla, LG Chem, and Sonnen that have promoted lithium-ion batteries that are more efficient, safer, occupy less space, last longer, and are certainly prettier than previous lead-acid battery models.

Based on this approach, some solar designers take into account the use of batteries to improve your self-consumption. The reason for this is that sometimes, net metering schemes may not compensate you enough for the value of solar energy when compared to the electricity rate that you must pay later.

That’s how models like the AC battery from Enphase Energy came out. They do not provide backup, but they save the excess energy generated during the day to use it later at night.

However, when comparing the extra capital costs of improving self-consumption through a battery with the earnings obtained by saving your solar energy for later use, the average answer is that it is not worth it.

Therefore, the true purpose of adding a battery must be to provide safety against blackouts to your house or business, and the additional benefit must be that you can increase your self-consumption and possibly obtain better savings in the long term.

Will Solar Panels Ever Produce Electricity at Night?

Now you know that the “solar energy” used by your neighbor at night is actually stored in batteries or in the grid (Net Metering case).

But, will it be possible that solar panels eventually come to generate electricity at night as well? That would be amazing, right?

Nevertheless, there are still no signs that it can be possible (in the near future, at least).

Attempts of technologies that approach this idea are the nanoantennas from the Idaho National Laboratory that tried to harvest energy from the Sun using the heat generated during the day to generate it later at night, but that research got lost in time because it was from 2008 and we never saw it on the market.

Other technologies as Solar Thermophotovoltaics (STPV) may be able to use the heat during the day to produce electricity for later use, however, it is still too soon to jump to conclusions. Time will let us know if it can be possible!

We hope you liked this article. Please rate it or leave us a comment.

Average rating 4.9 / 5. Vote count: 11

No votes so far! Be the first to rate this post.

health and safety inspectors looking at solar panels

Are Solar Panels Dangerous?

Are Solar Panels Dangerous?

Carlos

Written by qualified solar engineer Carlos. Last updated:

Solar panels are not dangerous if you know how to handle them safely and how they work. The truth is that they are not any more dangerous than the main panelboard that you have installed in your property.

Getting familiarized with something that we do not completely understand may be scary sometimes, however, in most cases it all comes down to know how to use or how to interact with it.

To give you an example, about this, think about electricity, today we all use it in our homes, and feel comfortable using products that work with it. However, there was a time when this was not that simple.

A Short Travel Back in Time

Back in the Nineteenth Century, Thomas Edison and Nikola Tesla were fighting each other over the control of the electricity industry in the United States. Thomas Edison was the advocate of DC while Nikola Tesla was the advocate of AC electricity.

Since DC electricity came first with the invention of the light bulb from Thomas Edison, people were more interested in this type of electricity. Nikola Tesla stood up for a new type of electricity, AC, which required high voltages to generate power; a scary for most people.

Actually, Edison’s campaign to discredit Nikola Tesla’s inventions was focused on promoting that AC electricity was dangerous and that it could kill people. As a matter of fact, the first electric chair execution was done with AC, and it was a disaster.

On the other hand, Tesla challenged public opinion by exposing himself to amazing public experiments that included a lot of lightning and sparks as you can see below. Moreover, he showed people that he could light up the entire Science Fair with AC electricity.

nikola tesla seated in his lab with electrical discharges around him

Nikola Tesla Seated in His Lab with Electrical Discharges Around Him (Source: INC)

Today, the whole power grid works with AC electricity.

What I am trying to say is that AC electricity was considered dangerous, but today we all use it in our homes. In the same context, solar panels were once considered possibly dangerous or unsafe. But the truth is that they are very safe if you have the knowledge required to use them properly. On our website you will find an interesting article all about the history of solar panels.

Possible Dangers from Solar Panels

Electrical Shock Due to Improper Handling

Solar panels are sources of DC electricity generation. As such, their terminal outputs have voltage and current.

Most solar panel installations today generally contain modules above 300W. A typical size solar panel around 300W could have open circuit voltage values close to 40 V and current values that could be between 7 A and 9 A. When you realize that 1 A could easily kill you, then you realize what could happen to you if you put your hands in the terminal outputs of a solar panel.

The thing about solar panels is that you cannot turn them off; there is no switch in every module to reduce their voltage to zero. Therefore, as long as there is sunlight, the solar panel will have an open circuit voltage in its terminals, waiting for some media (wire, metal or in bad cases human hands) to close the path between the terminals in order for current to flow.

If you are not aware of this and you think that your solar panels are turned off just because they are not connected to the grid, then you are making a mistake that could cost you your life.

Things can get as creative as we want. Actually, solar panels can be used to power a small solar electric fence charger. These devices designed to contain animals within a fence can generate a discharge of up to 5,000 volts! This does not kill them or anything close to that, but it definitely gives them a good shock, giving them a mental barrier and keeping the animals away from the fence and inside the desired perimeter.

Of course, here the solar panel is only used as a source of power to charge up a capacitor that provides such discharge to ground throughout the fence whenever an animal touches it. However, this provides an idea that solar panels can be small and safe, but they can also be used to power dangerous applications.

Nevertheless, it is important to know that this doesn’t mean that you cannot touch the solar panels. Actually, installers need to touch the frame to put them in place. Solar panels are designed to be safe and to be touched, as long as you touch the glass or the aluminum frame.

Moreover, once the solar panels are installed, the system is grounded via copper wire to avoid any possibility of shock hazard from touching solar panels (even if they are installed in a 1,500 V PV system). In any case, solar installers generally use electrically insulated gloves to make the connections of the PV system

Fire

This is maybe the greatest danger with solar panel installations, however, cases related to fire caused by PV arrays are extremely rare. Actually, a German research study from 2013 concluded that in the last 20 years, only 0.006% of the 1.3 million PV systems in that country caused a fire, of which only 75 caused damages.

Fires in solar panel installations could be caused by damaged wires (arc fault creation), bad installation procedures, or electrical surges.

Arc fault creation is probably the most dangerous cause of fire related to solar panels. This is created when there is a high DC voltage installed and there is a sudden interruption in the electrical current flow of the circuit, mainly related to a cut wire or to an abrupt disconnection of the wires between the panels while they are still connected in a closed circuit. Depending on the voltage of the PV system, a small or a large arc fault can be created as an attempt of the electrical current to keep flowing through the close circuit by breaking the dielectric resistance of the air.

These arc faults have very high energy concentrations and heat up everything near them, most likely to cause a fire if anything that can catch a flame is near them.

Does this mean that you should avoid solar? Not at all. Just as you do not have to keep your solar LED Christmas lights off for the next Christmas season to avoid your tree from getting burned, you also must not be afraid of solar.

Keep in mind that this is not common and it can only happen in solar panel strings that have a DC voltage of 400VDC or higher. It is not very common in residential PV systems. This means that if you want to install a simple solar light system for a shed or install a small solar attic fan, it is impossible that an arc fault would occur because to break the dielectric resistance of the air, a high DC voltage is required and these are more typical in large commercial and utility scale applications.

To avoid arc faults wire insulation is also very important. Wire insulation can be very different from one model to another, and this is why it is important to know that not just any wire can be placed in a PV system. PV wires are specially designed wires with insulations capable of resisting constant ultraviolet (UV) radiation. That way, they do not get damaged over time and do not lead to short circuits that could cause a fire.

Despite the fact that it is unlikely for this to happen, it is recommended that every now and then, you check if there are any possible damaged wires. If possible, also check for any signs of burned wires or burned panels.

Regarding electrical surges, they are related to high peaks in the voltage waves that come from the grid or from nearby lightning strikes. These elevated waves could reach your house and destroy appliances or even your modules if they do not have the proper grounding path to deviate the wave.

To protect your PV system from electrical surges, it is recommended to install surge protection devices (SPD) in areas with high lightning activities. SPD’s are able to safely deviate the high voltage wave to a ground path, protecting your PV system from damage and eliminating the possibility of fire. One of the most popular SPD’s are the ones from Midnite’s Solar.

Hazards for Firefighters

When firefighters reach a house on fire and they find that the house has solar panels installed, it becomes annoying for them. Whether the cause of fire was the PV system or not, a commercial property or house on fire with an electrical system in one of the most common access points for firefighters is never pleasant.

During a fire, the probabilities that the wires of the PV system get damaged, or that the mounting structure fails, increase radically. Therefore, stepping out and walking around a roof with damaged wires conducting electricity is not the safest environment. Here you can watch a video describing the situation from a firefighter’s perspective

Experience has shown us that it is important for firefighters to be trained and to understand how to effectively deactivate PV systems. According to the National Electrical Code 2017, all new PV systems are required to have pathways for firefighters to pass safely. They are also required to install a Rapid Shutdown System that instantly reduces the voltage of the solar array to zero. There are several options to do this in the market, but again, Midnite’s Solar Birdhouse is a nice choice.

PV systems with microinverters or DC optimizers perform perfectly on this aspect because not only the system is deactivated, but since these products act at module level, they reduce the voltage of each module to zero! Totally eliminating the possibility of damage from solar panels. Here you can watch another video explaining the advantage of a microinverter against arc fault risks in PV systems.

Solar Panels Are Not Dangerous, but They Are Not Toys Either

PV technology in general is not dangerous. Think about it, if it were dangerous, companies would have never manufactured a product such as a solar power backpack which is so often in close contact with the consumer. Moreover, if it were dangerous scientists wouldn’t have considered solar technologies to power the international space station which is so expensive and sophisticated.

Now on a more specific installation aspect, Millions and millions of PV systems are already installed across the world, and they will continue to be installed because the advantages of solar energy deeply overcome the low probability scenarios in which they can represent danger.

Solar panels are not more dangerous than any other electrical installation, after all, we all know the dangers that electricity represents and we still use it. Look at all the progress humankind has made thanks to electricity, it’s not like we are going to stop using it, it just means that we need to learn how to use it and establish safety measures to protect ourselves from its dangers. We must do the same with solar panels. Fortunately, the US is quite advanced in this aspect. It is one of the few nations that require Rapid Shutdown in PV systems.

We hope you liked this article. Please rate it or leave us a comment.

Average rating 3.4 / 5. Vote count: 16

No votes so far! Be the first to rate this post.

Rain pouring down on to a set of solar panels

Are Solar Panels Waterproof?

Are Solar Panels Waterproof?

Carlos

Written by qualified solar engineer Carlos. Last updated:

All solar panels are manufactured to be waterproof, and the junction boxes behind them also have an IP rating protection. Therefore, if it rains, storms, or even hails, you do not need to be worried about your panels getting damaged. The key to the waterproof design is related to the composition and manufacturing parts of the panel.

Can My Solar Panels Resist Rainwater?

Since solar panels need to be placed outdoors to capture sunlight and transform it into electricity, they need to be designed to endure and resist multiple harsh environmental conditions. Solar panel manufacturers must submit their modules to lab tests that will ensure the performance of these devices under severe outdoor conditions. Tests include thermal cycling, humidity freeze tests, damp heat, hail tests, mechanical load tests, leakage current tests and more.

Since raining is a natural phenomenon that occurs everywhere, solar panel manufacturers design their modules to be waterproof and to keep producing electricity after water falls on the module. This applies to every solar panel that has a frame and a glass to protect it and it means that you can leave for instance a solar panel for camping out there in the wild during your next outdoor adventure with no worries about the rainy days. Actually, a common maintenance practice is to set the minimum angle of the solar panels at no less than 15° in order for rainwater to do the cleaning of the modules.

However, make no mistake, solar panels are still electronic devices that could get damaged if water enters into the module. The only reason why rainwater does not affect the performance of the solar panel is because the wiring and solar cells are protected by a set of components: glass, sealing glue, an aluminum frame, a backsheet made from polymer-based materials, and an encapsulant made of ethyl vinyl acetate (EVA) which is used to provide adhesion between the solar cells, the top and the rear surface of the PV module.

The figure below can better illustrate the structure and components of the solar panel.

explanation of all the components that make up a solar panel

Components of a solar panel (Source – IRENA Report)

All of these components protect the solar cells and wiring from getting wet, which allows us to practice maintenance procedures using wet sponges or even low-pressure water to clean the modules.

Without these seals, the cells would be exposed to the weather conditions and probably would not work anymore. In the odd and strange case that your solar panel’s seal is broken and water does enter into the module (resulting in damage), you must not worry because most manufacturers product warranties cover that.

Nevertheless, rainwater can become a problem when is mixed with dirt on the surface of the module. Generally, when rain falls, the glass of the module gets clean, but the corners and borders of the frame could accumulate mud. This is undesirable because it can lead to the presence of moisture and therefore increase the probabilities of leakage currents and a reduction in performance.

Top and new solar panel models take this into account and avoid the presence of corners or borders where mud could get accumulated. Water drainage systems like the HIT modules from Panasonic allow water to flow continuously through the surface of the solar panel, avoiding the accumulation of water in corners or borders.

If you still have doubts about the water resistance of solar panels, we can understand it, after all, they generate electricity and electrical power and water do not mix well. However, believe it or not, there are some solar panels that, unlike the traditional ones, they are constantly covered in water or surrounded by water. There are multiple examples of this such as solar bird baths, solar fountain pumps or even solar powered pool cleaners.

hit solar panel drainage system

HIT solar panel drainage (Source – RENVU)

Don’t Forget Your Roof!

It seems like solar panels are protected against water, however, there is something else in your PV system that needs protection from rainwater, your roof.

In a rooftop PV array, the mounting system requires to penetrate the surface of the roof and the flashings (aluminum supports of the rails) need to be installed over rafters or trusses that will effectively resist the weight of the solar panels and the mounting system.

Once the perforation is done, many solar installers include waterproofing sealants (applied under the flashing, around the bolt hole) in their installations to avoid any possible water leakages. Despite the fact that this is common practice, it has been verified that after 10-15 years these sealants could get broken due to the excess of solar radiation, contraction, and expansion of the material. This is due to changes in temperature, and it’s even due to oxidation. Therefore, the sealant by itself has short-term reliability.

image of how the change in temperature and weather has broken the seal of the mounting system

Broken seal of the mounting system (Source – Elemental Energy)

Once the seal is broken, rainwater can flow through small leaks, leading in time to rotten rafters and sheathing. This will translate into a costly removal and remounting of the PV array, along with the probability of adding a new roof (between $500 and $1000 ). Remounting your PV system could cost you around 50 c/watt, which if you think about a typical 4kW, could be around $2,000. As you can see, this is something that you do not want to happen.

This is the reason why it is advisable to use code-complying flashing methods like asphaltic roofing cement with reinforcing mesh, or single-ply membranes like PVC, EPDM, and TPO to install the mounting system on the roof.

Quick Mount PV, a roof mounting system manufacturer, focused on solving this problem by installing an aluminum flute to the top of the bolt hole, elevating the waterproofing sealant above the flood line and protecting it with a stainless fused aluminum instead of rubber. For more details, you can check this video.

Since the PV system should work effectively throughout a 25-year period, then your roof should be strong enough as to resist that extra weight from solar panels over the entire period. Based on this approach, the best recommendation that a good solar installer should give you is to replace/upgrade your roof (or at least the section where the PV array would be installed) if it is older than 10 years.

As you can see, there is more to say about waterproofing your roof than the solar panels themselves. Solar panels are designed to be waterproof and it’s very rare that they fail due to water leakages. However, a bad rooftop installation can lead to important damage in the support of the PV array, putting your investment in danger.

We hope you liked this article. Please rate it or leave us a comment.

Average rating 5 / 5. Vote count: 7

No votes so far! Be the first to rate this post.

broken solar panels

Can Solar Panels be Damaged by Hail?

Can Solar Panels be Damaged By Hail?

Carlos

Written by qualified solar engineer Carlos. Last updated:

Solar Panels can be damaged by a heavy hailstorm, but it is not statistically probable. Manufacturers use quality tests that simulate the impact of hailstones to PV modules in order to ensure that solar panels will be able to resist hailstorms.

In order to approach this topic properly, let’s take a look at the procedure for these tests. This will give you a reference of the kind of hailstorms that solar panels are designed to endure, and it will tell you a very impressive story that occurred in one of the facilities of the National Renewable Energy Laboratory. But first, let’s see some of the locations in the US where you should be most careful with hailstorms.

Hailstorms – A Costly Environmental Phenomenon

Hailstorms are one the most unpleasant weather conditions in nature. Large ice blocks that fall from the sky causing damage to cars, windows, roofs and more. Hailstorms can damage property, but they also can injure or even kill people if the size of the block is too big. Therefore, they are a pressing matter and problem — especially in some regions of the US.

Historical cities for hailstorms inside the U.S. are Denver, Dallas, Minneapolis, St. Louis, San Antonio, Oklahoma City, and Phoenix. This phenomenon can be predicted, and is important to pay attention to weather forecasts especially if you are located in the cities mentioned above. To check hailstorm forecasts across the US, you can go to hail.org.

The most costly hailstorm in US history fell in Phoenix, Arizona back in 2010, when up to baseball-size ice-blocks fell off the sky leading to almost $2.8 billion losses attributed to damages. San Antonio also had a bad time in 2016 with hailstones of grapefruits size that cost around 1.4 billion dollars. And recently in 2017, Minneapolis had a really bad week with a consistent storm with heavy hail that fell in the Metropolitan region costing up to $2.5 billion.

As you can see, hailstorms can be costly, and the solar panels located in these regions are exposed to falling hailstones that could strike upon them and break them, right?

Quality Tests on Solar Panels

Since outdoor conditions for solar panels can be harsh, solar panel manufacturers must submit their modules to quality tests that ensure solar panels perform well over a 25-year period, even at harsh environmental conditions.

According to the jurisdiction and test center, several or different tests may be applied. However, in the US, the general references on this topic are the IEC 61215 and 61730 Standards, which specify the design qualification standards for module durability.

These standards include the requirements and procedures for several tests related to:

  • Ultraviolet exposure using xenon lamps.
  • Thermal Cycling (-40°C to 50°C, 50 cycles) in a climate chamber.
  • Humidity freeze cycling.
  • Damp heat (1000 hours at 85°C with 90% relative humidity).
  • Twist test for torque resistance.
  • Pressure tests considering snow, wind and other mechanical loads.
  • Hot spot tests.
  • Corrosion tests.
  • Hail impact tests.
  • PID resistance related to electrical isolation.

One of them is particularly interesting for our approach: the hail impact test. The purpose of this test is to precisely ensure that the glass of the solar panel will not crack against estimated or regular size hailstones.

Hail Test

The typical hail test involves using 25 mm ice balls thrown at 23 m/s against the solar panel to 11 different spots. The path from the pneumatic cannon to the module can be modified as horizontal, vertical, or any other angle.

Generally, the procedure involves storing these ice balls in a freezer at -10°C  5°C, then the solar panel is put in place to adapt it to cold temperature conditions of the climate room. An ice ball is measured in a balance to determine the mass with an accuracy of  2% along with another instrument to measure the speed of the ball with an accuracy of . Then, the ball is thrown and the module is checked with a slow-motion camera to verify if there was any detachment of the glass.

This same procedure is repeated to shoot several ice-balls to the same module according to the following impact locations:

  • Shot 1: Any corner of the module window, not more than 50 mm from the aluminum frame.
  • Shot 2: An edge of the module, not more than 50 mm from the aluminum frame.
  • Shots 3 and 4: Near an electrical joint and over the edges of cells.
  • Shots 5 and 6: Over points of minimum spacing between cells.
  • Shots 7 and 8: On module window, less than 12 mm from one of the points at which the module is fixed to the supporting structure.
  • Shots 9 and 10: At points as farthest as possible from the points named above.
  • Shot 11: Any other point that may seem sensible to hail impact.

explanation of the hail test and how it affected the solar panel when tested

Impact Locations of the Hail Test (Source – Saudi Arabian Standard IEC 61215)

The hail test can also take into account other ice-ball masses and speeds that can guarantee the module to be more durable against hailstorms.

table with the hail test variations with different speeds and ice-ball masses

Hail Test variations with different speeds and ice-ball masses (Source – Saudi Arabian Standard IEC 61215)

In order to pass the test, the module must not show any evidence of visual defects after the impacts, the degradation of maximum power output cannot exceed 5% of the value measured before the test, and the insulation resistance must meet the same requirements as for the initial measurements.

If you like to see how hail tests are performed, you can take a look at an outstanding hail test at 100 mph (twice as international standard requirements) from the new Tesla solar roof, and at quality tests on solar panels from SolarWorld.

The NREL Experience Against Hailstorms

We have seen the tests that solar panels need to endure under lab test experiments, but how do they behave against real-world conditions?

This question remained unanswered until 2017 when a massive hailstorm fell upon Denver, Colorado with hailstones up to 2.75 inches (similar to the size of a big egg). This hailstorm turned out to be the costliest in the State’s history and one of the costliest in US history, reaching $2.3 billion in damages.

hailstone sizes of denver’s hailstorm in 2017

Hailstone sizes of Denver’s hailstorm in 2017 (Source – CBS)

The National Renewable Energy Laboratory (NREL) has a Research Support Facility in Denver, Colorado with up to 3,168 solar panels installed between the roofs of the facility and the ground of the property, reaching to a 2.5 MW power plant. Amazingly, when the hailstorm passed, only a single solar module was damaged! A true real-world test of the endurance of solar panels against hailstones!

The only damaged module of the installation was believed to be hit by several hailstones in the exact same spot. This created a network of micro-cracks in the glass from above 36 hits.

damaged solar panel from hailstones in the nrel’s facility

Damaged Solar Panel from Hailstones in the NREL’s Facility (Source – NREL)

Can My Solar Panel Get Damaged by Hailstones?

Yes, solar panels could get damaged by hailstones, especially if their sizes are greater than 2 inches or if they are very small PV cells just like those found in solar LED lamp posts. However, solar panels are designed and tested to endure severe hailstorms and other weather conditions that will not allow solar panels to break easily. This post has more information about whether solar panels are waterproof or not.

The greatest proof of that is the NREL solar power plant, therefore, it is highly improbable that your solar panel with be damaged in a hailstorm. In any case, in the unlikely event that you wake up in the morning and one solar panel’s glass is broken, don’t worry, your home insurance will cover that.

We hope you liked this article. Please rate it or leave us a comment.

Average rating 3.6 / 5. Vote count: 5

No votes so far! Be the first to rate this post.

artificial light from lightbulb shining on solar panels

Can Solar Panels Work with Artificial Light?

Can Solar Panels Work with Artificial Light?

Carlos

Written by qualified solar engineer Carlos. Last updated:

Solar panels can work with artificial light. However, their performance and energy outputs will never be as high as if they were exposed to sunlight. The energy output of the solar panel will also vary depending on the type of bulb, the type of light (warm or cold), intensity, and the wavelength of the artificial light.

Let’s analyze some of these facts in order to give you a good reference of the impact of artificial light on solar power performance. First, we must approach some technical factors.

Solar Radiation and Light Spectrum

Solar radiation is the main source of energy used by solar panels to generate electricity. We can describe it as the transference of energy from the Sun through a set of electromagnetic radiations that are distributed in a light spectrum that goes from ultraviolet to infrared radiation.

The solar radiation spectrum can be divided into several regions according to the wavelengths of the electromagnetic waves that reach the Earth, as you can see in the figure below:

solar radiation spectrum

Source: Geolycafe

From the figure above, we can notice that the highest irradiance values can be obtained in the region of visible light. This region contains all the colors of the rainbow and includes wavelengths that go from 400 to 700 nm. After the 700nm wavelength, there is no longer more visible light but infrared wavelengths. This section of the solar spectrum provides the heat in the Earth and is the radiation spectrum that a solar powered pool heater or a solar pool blanket would use to warm up the pool water in a household.

Based on this approach, most solar panel manufacturers focus on maximizing the absorption of light within the visible region. However, solar panels can also be designed to absorb light in wider wavelengths. As we can see below, some of the most common solar panel technologies, like monocrystalline and polycrystalline modules, are able to cover a higher range of wavelengths including visible light. They can also include wavelengths in the near infrared region (up to 1200 nm). Other popular thin-film technologies such as CIGS and CdTe can also cover these regions, although with less efficiency. Amorphous (a-Si), Gallium Arsenide (GaAs), Dye-sensitized (DSSC) and Organic Solar Cells are mainly restricted to the visible region of light.

efficiency vs. wavelengths of different solar panel technologies

Source: A proposal for typical artificial light sources for the characterization of indoor photovoltaic applications – B.Minnaer and P.Veelaert, Ghent, University

As you can see, there are other wavelengths of light that can also be used by large, commercially available technologies like silicon modules to harness electricity. Therefore, we can ask ourselves, is it possible that solar panels can harness electricity from other sources of light, like incandescent or fluorescent bulbs?

Artificial Light

An incandescent lamp is composed of a balloon of glass in which a filament is heated to high temperatures (2,000 to 3,000 K) and is generally defined within a spectrum of 300 -830 nm wavelengths, having its peak on the infrared region of light. Therefore, if solar panels can extract power from wavelengths as low as 300 nm to 1,200 nm, then it is logical to think that solar panels could extract some energy from this source.

the spectrum of incandescent light

Source: Comsol

On the other hand, fluorescent lights were defined and designed to be located inside the visible region of light. There are many types of fluorescent lamps (around 12) that are designed using different technologies. However, most of them use gases that are electrically charged, like mercury, to create a path for a current to flow. In turn, this will lead a phosphor to fluoresce and create visible light. This technology focuses on the lower band of the visible light spectrum which produces low ultraviolet light.

LED and metal halide technologies are also other common artificial sources of light. Metal halide lamps are high-pressure discharge lamps that use an electric arc in a gaseous mixture of vaporized mercury and metal halide to produce light in a broad spectrum. On the other hand, Light Emitting Diodes (LED) are solid-state lamps that use the electroluminescence of a bandgap (a barrier that limits electrons inside a material) to emit light. They can be divided into cool and warm technologies.

According to a research study done at the Ghent University in Belgium, we can visualize the typical wavelength ranges of all artificial light technologies scaled to 500 lux.

chart to explain the spectrum irradiance vs. wavelength ranges of light in different fluorescent lamps

Spectrum irradiance vs. wavelength ranges of light in different fluorescent lamps. F2: Cool fluorescent lamp of a correlated color temperature (CCT) of 4230 K. F7: Broad-band fluorescent lamp (CCT=6500 K). F11: Narrow tri-band fluorescent lamp (CCT=4000 K)

Source: A proposal for typical artificial light sources for the characterization of indoor photovoltaic applications – B.Minnaer and P.Veelaert, Ghent, University

chart to explain spectrum irradiance vs. wavelength ranges of light in different led and metal halide lamps

Spectrum irradiance vs. wavelength ranges of light in different LED and Metal Halide lamps

Source: A proposal for typical artificial light sources for the characterization of indoor photovoltaic applications – B.Minnaer and P.Veelaert, Ghent, University

Solar Panels Tested Under Artificial Light Conditions

Ben Minnaert and Peter Veelaert from the Ghent University asked themselves the same question that we wondered ourselves. So, to find the truth, they put all of the artificial lights into different categories: incandescent, fluorescent, LED, and metal halide lamps.

Then, they used different solar panel technologies like monocrystalline, polycrystalline, Cadmium Tellurium, CIGS, and others to quantify the power outputs of these modules under indoor conditions at 500 luxes (typical measure of the intensity of light in sq. meters inside offices) from the mentioned artificial sources of light. 

Amazingly, they found that it was indeed possible to harness electricity from artificial light through solar panels. However, efficiency values were nowhere close to what would be expected in outdoor daylight conditions.

They found that the monocrystalline technology and incandescent light were the best possible combination to obtain electricity from artificial light, followed by polycrystalline and CIGS technologies combined with incandescent light. Nevertheless, taking into account a 500 lux illumination, it was possible to obtain only 6 W/m2, too low for Standard Test Conditions.

Other sources of light like fluorescent, LED and metal halide were not as efficient with silicon cells, but instead with GaAs and CdTe solar panels. However, these technologies were not suitable at all since they were able to produce more than 1 W/m2.

Conclusion

There is a lot of speculation about how solar panels work in different scenarios. For example, whether solar panels work through glass or work when using artificial light are among the most speculated.

Maybe the reason why you wanted to know about this was to be able to use your cell phone solar charger while at home, or maybe to evaluate commercial security applications where you can install pwireless solar security cameras while placing the module inside to harvest the artificial light.

Whatever the reason is, based on this research we can conclude that solar panels can work with artificial light, but the efficiency obtained from using this source of light is so negligible that is not worth it to be considered as electrical supply.

Moreover, if we compare the spectrum of irradiance from fluorescent sources of light with the solar radiation spectrum, we can notice great differences.

Solar radiation spectrum curve follows a smooth and continuous shape that maximizes the conversion of light into electricity. We can notice that by multiplying the wavelength in nm. with the spectral irradiance in W/m2, we can theoretically obtain values of 1000 W/m2.

However, when we compare it with the fluorescent, LED, or metal halide spectral irradiance, we can notice that many of them have irregular spikes that do not allow a smooth absorption of light. Besides, these values are in mW/m2 rated at 500 luxes. When we multiply them with the wavelengths in nm., we obtain values lower than 30 W/m2. The difference is just astronomic.

For applications inside commercial buildings related to BIPV, illuminance values can increase, however, they will not be as attractive as to consider installing solar panels to take advantage of artificial light. As a reference, a UEFA Champions League Stadium can have an average illuminance of 2,000 luxes, and if you multiply the estimated 30W/m2 at 500 luxes by four (to achieve approximately 2,000 luxes), then you would only be obtaining around 120W/m2 irradiance values, which is still very low.

We hope you liked this article. Please rate it or leave us a comment.

Average rating 4.6 / 5. Vote count: 38

No votes so far! Be the first to rate this post.

sun shining through window glass

Will Solar Panels Work Through Glass?

Will Solar Panels Work Through Glass?

Carlos

Written by qualified solar engineer Carlos. Last updated:

Solar panels will continue to work even when sunlight passes through glass, but their efficiency and power outputs are nowhere close to their nominal values. Therefore, they will work but their device performance will be reduced. The reason stands behind a basic physics law called the Fresnel Law.

Those who are thinking about off-grid applications may find this answer quite interesting. For example, you may find yourself going on a camping trip, and you might be thinking of charging your mini solar power bank for your mobile devices while it is facing the windshield. Maybe you just want to make sure your solar rechargeable flashlight has enough energy before you make it to your destination. Or maybe you just want to know if installing some small solar panels inside the house would be useful if they’re facing a skylight. Or perhaps you were just curious about it.

Whatever the reason, you had to ask yourself these questions below. Here you will find the explanation as to why solar technologies can work through glass.

Will My Solar Panel Produce Electricity Behind Glass?

To understand the reasons behind it, we must first learn all the different ways, range, and design in which glass can affect the sunlight and the product. Let’s analyze them!

Fresnel Laws

Light can be described as a wave, as a particle (photon), or as both, depending on the type of experiment that evaluates it. When the ray of light travels from the Sun to the Earth, it has a specific speed and direction. If the ray of light reaches another surface, then part of the ray can be reflected back to the air, and another part of the ray can be refracted inside the surface.

This physical phenomenon occurs according to the Fresnel Law, based on the Snell Law . Simply put, these laws establish that when light reaches another media, like water or glass, then part of that light will be reflected and the other part will be refracted inside the surface, but with a different angle and speed.

The variation of the angle and speed will depend on a coefficient known as the refraction index of the media, which can vary according to the type of glass.

diagram explaining the snell law

(Source – The Theory Behind Optica Tweezers)

So, how does all of this affect our solar panel?

The amount of photons that reach the solar panel are not the same because some of them will be reflected by the glass. All of that sunlight, that is reflected by the glass, will be lost. The solar panel won’t be able to generate as much electricity as it should. Losses will change depending on the reflection factor of the glass, but in any case, they will reduce the energy output of the solar panel radically.

Orientation and Sun’s Position

As in any PV system, the orientation towards the Sun is essential to optimize the energy yields of the solar panels. Placing the solar panels inside a house or inside a car is a terrible idea from this point of view.

Solar panels need to be placed towards the South (US case) in order to maximize energy yields. If you are moving in a car there is nothing you can do about it because the orientation will change constantly, so you will simply obtain different power outputs across the day.

If you are inside a building or house, you will need to find a window or normal glass that faces South in order to maximize the application of your power output. Placing a solar panel behind a window or sheets of glass, that is facing North would be equal to not having a solar panel.

Second, placing solar panels inside a building or behind a car tinted glass window also has a bad effect. The solar irradiance will be at its maximum value when the Sun is in its highest position, meaning midday. Since the roof of the car, house, or the office building will be blocked from the direct incoming light path of sunlight at this time, then your solar panel won’t be able to take advantage of one of the best moments to generate solar energy and to reduce energy production. The only production at this moment will be from DHI.

DNI and DHI

Solar irradiance is generally described as the combination of two types of irradiance.

On one hand, Direct Normal Irradiance (DNI), related to the incident sunlight that impacts in a perpendicular angle directly to the solar panel without reflection, refraction, or loss of any kind.

On the other hand, there is the Diffuse Horizontal Irradiance (DHI), associated with all of that solar radiation, that is reflected or refracted by the atmosphere, clouds, mountains, lakes, or the ground. This component is referred to as the solar irradiance that indirectly impacts the surface of the solar panel.

By placing a solar panel behind a glass window, or safety glass, you are eliminating the DNI component of solar radiation that would directly impact the solar panel. Meaning that, your solar panel would be working mostly with DHI components, related to the reflection of sunlight from other sources.

Shadings and Thermal Losses

Another disadvantage of placing solar panels behind a window is that shadings created by frames or bars of the window will also reduce the power output and its power conversion efficiency.

Moreover, you might think to park your car under the Sun and leave your solar panel technology inside to obtain maximum energy yields. However, as heat concentrates inside your car without air conditioning, the solar panel will get hotter due to the generation of electricity and the hot temperature conditions inside the car. This will induce thermal losses and could even damage the solar cells if the heat is too intense. Therefore, it is not the best idea.

Is It Worth It to Install Solar Panels Behind Glass?

As you can see, there are many reasons why you shouldn’t install a solar panel behind a window. That doesn’t mean that the solar panel won’t work, it just means that the performance won’t be the one you paid for. Therefore, it is worth it to purchase solar panels but it is not recommended to place the solar panels behind glass. You can take a look at a solar fan video here to check the losses in the performance of a small solar panel located behind a window.

We hope you liked this article. Please rate it or leave us a comment.

Average rating 4.5 / 5. Vote count: 38

No votes so far! Be the first to rate this post.

small solar panel outside of a home

Will Solar Panels Get Smaller?

Will Solar Panels Get Smaller?

Carlos

Written by qualified solar engineer Carlos. Last updated:

Solar panels will have higher output capacities and smaller dimensions according to the recent trends in 96-cell technologies. By involving new manufacturing and design technologies, manufacturers such as Panasonic have been able to reduce or maintain solar panel dimensions while increasing power output.

This trend will be very valuable in the near future as solar panels spread across the world, since the cost of land is one of the main capital costs in commercial and utility scale projects. This fact will also be important for you as a residential customer, since this will determine how many solar panels you need for your home or property.

However, there are many aspects to consider on this topic before jumping to conclusions. Not too long ago, the trend was actually pointing towards increasing dimensions with 72-cell technology. Let’s analyze some of the factors that influence the size of solar panels.

What Factors Influence Solar Panels’ Size?

Number of Solar Cells

The conversion of sunlight into electricity occurs inside every single solar cell. The PV cells are the single unit of the photovoltaic world and they can be manufactured in different sizes, some as small as those that fit within solar digital watches. However, as you can imagine, the power that a single photovoltaic cell can generate is not too much since these devices can only produce a maximum of 0.5 V per cell. However, if we wire multiple solar cells in a series, we will obtain higher voltages and therefore higher power outputs. 

Solar panels are simply an assembly of multiple solar cells that are wired in parallel and series to increase current and voltage levels (therefore power outputs) to commercially scale values.

Commercially available solar panels generally have 36 cells, 60 cells, 72 cells, or 96 cells. The number of cells will increase the size of the solar panel either in width or length (or maybe both).

Efficiency

Efficiency is a factor that deeply affects the power output and the size of a solar panel. Actually, efficiency can be described according to this expression:

efficiency explained in a expression

Where:

Pmp: Maximum power point

Im: Incident insolation on the module

Am: Module area.

From the expression above we can realize that increasing the efficiency of the solar panel will reduce the amount of area (and therefore size) needed to obtain the same power output Pmp.

Efficiency values depend on the type of technology applied. Top commercially available monocrystalline solar panels can reach efficiency values between 20% (Panasonic and LG) and 22% (Sunpower), while top polycrystalline technologies can generally reach 17%-18% efficiency. Therefore, power outputs and sizes might change depending on the model and technology as well.

Single P-N junction silicon cells have a maximum theoretical efficiency value known as the Shockley-Queisser limit, which establishes that due to thermodynamic reasons, the maximum efficiency cannot surpass 33.7%. This would establish a limit related to how much we can reduce single P-N junction solar panel sizes.

However, this value has already been exceeded in laboratory tests using multi-junction solar cells that have allowed to reach efficiency values close to 50%.

The main issue with these technologies is that they cannot be commercially available yet because the additional cost to manufacture these solar cells on the market is still too high. Most applications for these technologies are related to aerospace applications, where the extra price for efficiency is totally worth it.

diagram of the manufacturing cost of solar cells

(Source – National Renewable Energy Laboratory)

The Market Trend

Just to be clear, small solar technology already exists in our world. We have solar LED outdoor lights with panels that can fit within a backpack, we have modern solar path lights with cells that fit within your hand, and you can even have a solar weather radio with a PV cell that measures just a few inches. As you can see, making the solar cells smaller (even very small) is not an issue. The thing is to make the sizes of solar panels small enough at the commercial industry scale while keeping their high energy production so that they can save space and serve not only for side applications as the ones mentioned above, but also to power your home.

The number of cells and the efficiency are indeed the main factors that influence the size of the solar panels. All other related factors such as power output, technology, or manufacturer may slightly change the length or width of the solar panel, but the changes are not radical.

When we evaluate the progress of the PV industry, we realize that the development has come from the off-grid market towards the grid-tied market. In the beginning, solar panels were mainly used for simple off-grid applications like charging a 12 V battery.

Nevertheless, when the solar industry started innovating in the grid-tied sectors, the 60-cell solar panels appeared in the market. Then, 72-cells appeared as the revolution of the solar industry, which allowed the achievement of higher power outputs. With these two technologies, the application for PV projects became much more attractive to investors (as costs per watt kept going down).

All of this development increased the size of the modules, but as efficiency values were increasing, the relation between space, power outputs, and costs started to make sense.

Generally, 72-cell modules have dimensions close to 1000 mm in width and 1960 mm in length and can achieve power outputs close to 400 W. On the other hand, 60-cell modules are generally 1000 mm in width and 1650 mm in length and can reach power outputs close to 300W. That’s 300 mm extra in length. If we compared that with original 36 cell solar panels, the difference is greater.

Therefore, the trend seemed like solar panels were actually getting bigger, not smaller.  If you think about it, makes sense.  For project developers, it is more attractive to install fewer solar panels that have a higher power output and efficiency (despite they may be bigger) than installing smaller solar panels that will not produce as much power. Costs related to wiring, labor, mounting systems, and electronics like microinverters or DC power optimizers would be bigger and unattractive with smaller solar panels.

It is important to notice the relation between size and efficiency, which can be confusing. Efficiency values are indeed increasing, but the progress has been slow and the increase of power outputs in the PV market has been greater and faster, therefore the dimensions of the solar panels must increase. After all, according to the expression above, if the power output and efficiency do not increase proportionally, then the area of the module must increase.

However, latest trends in the industry from remarkable solar panel manufacturers such as Panasonic and Sunpower have brought to the market the 96-cell product, with higher efficiency values and power outputs between 340 W and 370 W. These products have a width close to 1050 mm and a length of 1550 mm.

In other words, despite the fact that these solar panels have more cells, the dimensions can be smaller in length than their 72-cell module counterparts, and similar in size to 60-cell solar panels. This means that the solar cells from these two brands are smaller, more efficient, and can produce the same amount of power with less area.

It is not a coincidence that these two brands are in the top 3 of the most efficient solar panel manufacturers. The truth is that as efficiency values keep rising, we might see similar results in other brands as well, maximizing power outputs and reducing dimensions. Maybe we are reaching the point where power outputs are finally stabilizing, efficiency values are going up, and sizes are getting smaller.  Only time will tell if the trend changes or if these are isolated cases.

References

  1. Research cell Efficiency Records – Department of Energy
  2. Solar Panels: 60 vs. 72 Cells – altE Store

We hope you liked this article. Please rate it or leave us a comment.

Average rating 5 / 5. Vote count: 5

No votes so far! Be the first to rate this post.

solar panels out in the shade

Will Solar Panels Work in the Shade?

Will Solar Panels Work in the Shade?

Carlos

Written by qualified solar engineer Carlos. Last updated:

Solar panels will still work producing electricity even when they are partially shaded. If they are completely blocked by an object, however, then the solar panel will stop producing electricity. Sometimes, even if the shade does not completely block the solar panel, it can make electricity production stop.

To understand how this works, we must dig further into the impact of shadings on solar power production, the components of the solar panels, and how they work when shades are present.

Shadings and Solar Irradiance

Solar radiation is generally expressed as the sum of two components. The first is called Direct Normal Irradiance (DNI) and represents the irradiance (power that can be obtained from solar energy by square meter) on a surface perpendicular to the Sun. In other words, is related to the solar radiation that directly impacts the solar panels

The second component is known as Diffused Horizontal Irradiance (DHI). This concept is related to all the solar radiation that was reflected by clouds, lakes, or mountains  that indirectly impact the solar panels.

The image below can better express how these two factors reach the solar panel.

diagram explanation of how shading impacts solar radiation(Source – A.Walker. “Solar Energy: Technologies and Project Delivery for Buildings”)

There are two main types of shadings. One type is called far-shadings and the other type is called near-shadings.

Far-shadings (also called horizon shadings)  refer to the losses in solar radiation due to shadings caused by large objects like mountains, valleys or high buildings. Far-shadings are quantified as losses in DHI.

Near shadings are nearby objects such as trees, walls, chimneys, antennas, houses, or  other modules that cause shadings on the solar panel. These are quantified as losses in DNI and are the most significant ones.

Will My Solar Panels Produce Electricity on Cloudy Days?

The short answer to this question is yes.

Clouds reduce the amount of sunlight, but they specifically reduce the direct component of solar radiation. Based on the concepts that we described before, they radically reduce the amount of DNI that reaches your solar panels.

However, despite the cloudy day, we can still see sunlight, right?

That is because the DHI component is still present on cloudy days. Therefore, your solar panels will still produce electricity using the DHI component of solar radiation. The only difference is that they will indeed produce less electricity than on sunny days.

The Effect of Near Shadings in Solar Panels

Once an object causes shades in a solar panel, the effect reduces the power output of the whole string (set of solar panels configured in series) because the obstruction reduces the amount of photons that can be absorbed by the module.

At the same time, if a solar panel is partially shaded then the current is reduced. Now, if we have a string of modules and one of them is partially shaded, then the whole string must reduce its current or power output because they are configured in series. That is a physics law that unfortunately cannot be avoided.

Now, what exactly happens when a module is shaded?

Bypass Diodes and Solar Panels

In order to maximize the energy output in the presence of shades, solar panel manufacturers decided to include bypass diodes in the junction box (located in the rear side of the module). Bypass diodes are electronic devices that will act whenever there are partial shadings in a module.

With the bypass diodes included, the partially shaded module will still produce electricity, just in a lower amount. Since bypass diodes can be expensive, solar panel manufacturers tend to group a set of cells to a single bypass diode and place three bypass diodes on the junction box of the panel.

diagram of bypass diodes within solar panels(Source – A.Luque y S.Hegedus. “Handbook of Photovoltaic Science and Engineering”.)

That way, whenever a corner or sector of the module is shaded, the corresponding bypass diode will block the production of that sector of cells, but it will still allow the electricity production from the other two bypass diodes. To understand  this effect better you can take a look at this video

On the other hand, if one solar panel in a string of modules is partially shaded, then the bypass diodes will act to allow the current flow from the other modules according to the maximum current that the shaded module can produce. Moreover, bypass diodes also help to avoid the presence of hot spots that can severely damage the solar panels.

Diagram explanation of how to avoid hot spot damage on solar panels

(Source – A.Luque y S.Hegedus. “Handbook of Photovoltaic Science and Engineering”.)

Bypass diodes mitigate the impact of near-shadings on solar panels and allow them to keep producing electricity in the presence of shades. However, near-shadings are still completely undesirable for the performance of a PV system.

That is why your solar installer must design the system appropriately to reduce the impact of shadings, and he/she must quantify the shading losses to be lower than 10% annually in simulation programs.

Remarkable Solutions in the Industry to Mitigate the Impact of Shadings

To fight against scenarios where shadings cannot be avoided, the industry has come out with several solutions:

MLPE

The first and maybe most reliable ones for shading scenarios are the module-level power electronics (MLPE) such as microinverters from EnphaseDC power optimizers from SolarEdge, or Tigo Energy where power optimization in every module is independent. In other words, shadings on one panel do not affect the others.

String or Central Inverters

Another factor that must be taken into account when shadings are present on the solar array is the maximum power point (MPP) tracking.

When solar panels are shaded, the I/V curve of the string loses its regular shape and two maximum power points appear in the curve: Global MPP and Local MPP.

graph chart of how the shade affects the power of the solar panel(Source – SMA OptiTrac Global Peak.)

As you can see on the graph above, LMPP is lower than GMPP.

Regular inverters could choose the LMPP as the maximum operating point of the curve because their search range is limited. However, remarkable solutions from inverter companies like SMA and Fronius maximize the power output of the array in the presence of shades by selecting the operation point at GMPP, thanks to the SMA OptiTrac Global Peak feature and the Dynamic Peak Manager form Fronius.

Solar Panel Innovation

Another interesting solution that allows maximizing energy production in the presence of shades is the solar panel design from Panasonic.

The Panasonic HIT N330/N325 modules are the only ones in the industry that incorporate 4 bypass diodes. This allows reducing the number of solar cells that could unnecessarily lose production in the presence of shades, and it also maximizes the energy that the other non-shaded modules can produce as well.

explanation of how the panasonic hit n330/n325 maxamises performance with 4 bypass diodes(Source – Panasonic HIT N330-N325 Brochure)

References

We hope you liked this article. Please rate it or leave us a comment.

Average rating 5 / 5. Vote count: 5

No votes so far! Be the first to rate this post.

Scroll to Top

Get Free Personal Solar Pricing

Progress 20%

Do you own your home?

Progress 40%

How much is your average monthly electric bill?

Progress 60%

How much sun does your roof get?

Progress 80%

Would you like to schedule a contact time? (optional)

Progress 99%

Where will the free pricing information be sent to?

By clicking the “SUBMIT” button I agree ecotality.com can contact me by email, text or phone only at the number I have provided, including through automated and/or pre-recorded calls and texts even if your number on any federal, state, or local do not call list. Your consent to this agreement is not required to make a purchase. I also agree to the ecotality.com terms of use and privacy policy. We respect your privacy.

🔒Your information is secure.

Progress 100%

Thank you!

Your form has been submitted. We'll send you a reply after we look over your info.

Error message goes here