What are Bifacial Solar Panels?
Bifacial solar panels are panels that can capture sunlight on either side. Since they’re made to be completely transparent, they are usually made of glass. They tend to have higher efficiency compared to monofacial panels since they can capture light on two surfaces.
Bifacial solar panels perform best when they’re mounted near reflective surfaces, such as swimming pools, glass, or areas where the ground is reflective. That way the solar panel can capture energy from above and below. Sandy and snowy areas are high-performing environments for bifacial solar panels. They also do well when mounted on pergolas and open walkways, and can be a great aesthetic choice to help create a shady overhang.
How do they work?
Bifacial solar panels work just like normal solar panels. They use the same semiconductor material which generates power by converting light energy into electricity. When sunlight hits the bifacial panel, a portion of the sun’s light is absorbed by the solar cells and converted into electrical energy. Some of the light is caught in the glass and is reflected throughout the interior of the panel until it strikes a solar cell and gets absorbed. Some of the light passes right through the glass panel and strikes the ground. Assuming the ground has a high reflectance, this light then bounces back toward the panel and is converted into electricity.
Since they are made to capture energy on both sides, they are constructed differently. They don’t have the metal gridlines that are seen on a normal panel. Instead, the solar cells are held in place by the glass structure. They also don’t require a metal frame. The tempered glass helps make them more durable and weather resistant and the lack of a frame reduces corrosion and efficiency losses due to potential induced degradation, also called PID.
Solar cells in bifacial solar panels are exactly the same as in monofacial solar panels. The only real difference is that the solar cells are made to be two-sided, so the silicon p & n layers are exposed on the backside. Depending on the configuration, extra conductors may be added to the backside of the panel.
Pros & Cons of Bifacial Solar Panels
Bifacial solar panels are becoming increasingly popular, and have been rapidly gaining market share as they become more affordable and efficient. More homes and businesses have been choosing to install bifacial over monofacial panels to take advantage of the benefits. But do the benefits outweigh the costs?
- Increased efficiency
- Lower costs over time
- Less space per watt
- Aesthetically pleasing
- Reduced PID
- UV resistant
- Don’t need grounding
- Work well in diffuse light
- Durable and weather-resistant
- Longer warranties
Bifacial solar panels are more efficient than monofacial, simply because they collect sunlight on either side. Many bifacial solar panel manufacturers claim between 20% and 30% more power output from their bifacial panels compared to monofacial panels. They also perform better in diffuse light because the extra surface area allows bifacial panels to capture more light. This means that the long-term costs are lower than monofacial panels. The higher efficiency also translates into less space per watt, so homeowners can install fewer panels to meet their needs.
The tempered glass frame brings some added benefits as well. Since they don’t have metal frames, the solar cells are less likely to suffer from PID, where electrical currents stray from their intended path and corrode the solar module. That also means that bifacial solar panels don’t need to be grounded, as there are no metal contacts on the exterior. The tempered glass is weather-resistant and can withstand high temperatures and strong winds. The lack of plastic laminate also means that the panel is resistant to UV degradation. Many see the glass frame as more aesthetically pleasing compared to monofacial solar panels.
Due to their durability and resistance to weather and various types of degradation, bifacial solar panels are expected to have longer lifespans, and so they tend to have longer warranties. Whereas a typical warranty for a monofacial solar panel is about 25 years, bifacial solar panels are often sold with 30-year warranties.
- Higher cost per module
- Higher installation costs
- Very heavy
- Must be mounted properly to take advantage of ground albedo
Due to the manufacturing process, bifacial solar panels are expensive. They can cost up to 10% more than monofacial solar panels, which translates to an extra 20 cents per watt. Then there are the installation costs. Bifacial panels are pretty heavy compared to their single-sided counterparts, meaning they cost more to install due to the extra labor. To take full advantage of the benefits, they need to be mounted on specialized equipment, which is meant to reduce the shadow and maximize the albedo of the ground around the solar panel. Though this equipment is easy to obtain as it’s provided by the manufacturers, the costs are higher.
Types of Bifacial Panels
Being made completely of glass, bifacial solar panels are limited in terms of variance. So far, commercially available bifacial solar cells are exclusively monocrystalline (mono-Si) panels, though a few polycrystalline (poly-Si) panels do exist. The emphasis on mono-Si panels means that bifacial panels have an overall higher efficiency than monofacial panels.
A few companies have made flexible bifacial panels. These are usually quite small and are mainly used in recreation. They are usually made of monocrystalline solar cells encased in a transparent cloth or plastic. Flexible bifacial modules are especially useful for boating, where they can be hung on the masts and can collect energy directly from the sun as well as reflected light from the ocean’s surface.
Mounting Bifacial Solar Panels
To get the biggest benefit from bifacial solar cells, they have to be mounted correctly. They can’t be installed against a roof like a monofacial panel, or else there’s limited benefit from the reflectance. Those who install bifacial solar panels are tasked with being a bit more creative. There are still several different ways to orient your bifacial solar panels, so don’t fret if you were planning to put them directly on the roof of your home.
Bifacial solar arrays are often installed on the ground. Ground-based arrays can take advantage of the ground’s reflectance if installed over the ground with a high albedo, or reflectance. White tile, white sand, or brightly colored gravel are all good choices to maximize the ground’s reflectance. Bad floor choices for ground-based systems would be dark materials that absorb more light than they reflect. Dark-colored dirt, grass, or rocks would minimize the reflected sunlight and lower the efficiency of the solar panel.
Ground-based arrays can get a boost in efficiency in snowy areas. Snow has a high albedo, so if the ground is covered in snow, the bifacial solar panel will capture the reflected sunlight. This can make up for the fewer hours of daytime in the winter months.
The key to installing bifacial solar panels is to minimize any potential shading and shadows. For this reason, special mounting clamps are usually provided by the manufacturers or installers and are made specifically for your brand. The mounting brackets and clamps are usually thinner than those on monofacial panels and are designed to minimize the casting of shadows.
As with monofacial solar panels, one must ensure the right tilt panel orientation to get the maximum power output from your array. The tilt angle differs by latitude, so make sure you know the optimal tilt for your location.
The best roofs for bifacial solar panels are white or highly reflective roofs that are flat and lack any significant slope. White roofs are among the best surfaces for bifacial solar panels as they usually have the highest albedo, being comparable to snow. It’s not recommended to install the solar panels directly on the roof lying flat, as that defeats the purpose of having two sides. Like ground-based arrays, roof-mounted bifacial panels should be tilted at an angle that corresponds to the latitude. Many of the same rules as ground-based systems apply, though it’s wise to remember that bifacial solar panels are much heavier than monofacial, so you should make sure that your roof can handle the weight.
Vertically installed bifacial panels are usually installed east to west. This allows them to capture electricity both in the early morning and late afternoon. During midday, the panels capture sunlight that is reflected off the ground and surroundings, since it isn’t getting direct sunlight when the sun is directly overhead.
Horizontal setups for bifacial panels are great for installing on the side of a home or building, where the solar panel can add to the aesthetics and provide partial shade for the inhabitants underneath. Horizontal setups can capture energy directly from the sun during the day and still collect reflected light from the ground, which can bring added benefits in the snow. Horizontal installations are best installed over a pool, deck, or front porch. They can also serve as a transparent roof on a pergola or open walkway.
Height & Altitude
Bifacial solar panels perform better when they’re installed high above the ground. This is because their shadow is minimized, so the panel can catch more of the light that is reflected from the ground and surrounding areas.
Like all solar panels, bifacial panels reach higher efficiencies at high altitudes. This is because there is less atmospheric interference between the sun and the panel.
Bifacial vs. Normal Solar Panels
Bifacial panels have their ups and downs, but choosing between two-sided and single-sided panels comes down to your needs. Monofacial panels may be better when you’re on a budget, and would rather pay a lower initial cost. But if you have the money, and want to make a better investment for the long-term, the bifacial panels are definitely worth the price. Here are a few other things to keep in mind when deciding between double and single-sided panels.
Location, Location, Location
The extra efficiency from having bifacial panels is tied to your latitude. If you live above 65 degrees latitude, bifacial solar panels see massive benefits, which are multiplied when it snows.
All solar panels are negatively affected by cloudy and rainy weather, but bifacial modules have the added benefit of a second side, which gives it more surface area to collect energy. This picks up the slack during cloudy weather, helping to maintain higher overall power output.
Future of Bifacial Panels
Though bifacial panels are costly, they are becoming more affordable as time goes on. Some lower-end bifacials are beginning to equalize in price with monofacial modules. The added efficiency will make them competitive as the cost per watt decreases. Bifacial modules also last longer and are more durable, making them the better choice in the long haul. Already, we are seeing increases in the market share of bifacial solar panels which directly correlate to decreases in price. In 2017, bifacial solar panels held less than 5% of the c-Si market share. In 2020, that number increased to 15%. By the end of the decade, bifacial solar panels are set to compose at least half of the market share for crystalline silicon panels.
Bifacial solar panels may very well be the future. For now, they are a costly luxury, but the price is well worth it. They have double the surface area that monofacial modules do, and pick up residual reflected light that single-sided panels can’t, giving bifacials an edge on efficiency. Double-sided panels do great in high latitude and snowy climates, where they can capture reflected sunlight. They also can perform quite well under cloudy conditions. The all-glass frame means that you won’t have to worry about losses in efficiency from PID and UV rays, nor do they have to be grounded. The aesthetics are also a big selling point. The all-glass design and two-sided setup mean that they can be used in your home as overhangs, awnings, and transparent roofs, adding a technological touch to sustainable and biophilic design concepts.
Bifacial solar panels are modules that are double-sided. They can capture sunlight and generate electricity from both sides. The increased surface area gives them a higher efficiency compared to single-sided panels, as they capture diffused and reflected sunlight.
Bifacial solar panels can see efficiency increases between 20% and 30% compared to monofacial modules. They can collect sunlight that reflects from the ground, and do well in snowy and cloudy conditions. They also last longer than monofacial panels, as the tempered glass makes them more durable.
Bifacial panels are more expensive. Expect to pay an extra 20 cents per watt for the modules alone. The installation costs are also quite high, thanks to the heavier weight compared to single-sided panels, and they also require specialized mounting equipment which can be more expensive.
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