What Factors Affect Solar Panel Efficiency?

When most people think about renewable energies, we conjure up images of solar panels dotting the roofs of homes across the nation, and for a good reason. Today, there are well over two million residential solar panel installations across the United States. Despite the impressive growth of the solar industry, most of the United States' renewable energy comes from hydropower and wind. Seventeen percent of US energy generation comes from renewables, and hydropower and wind account for about 80 percent of that energy. Why isn't solar energy more of a player in the renewable energy market?

Does Share Impact Solar Panel Efficiency?

If your home, rooftop, and yard receive a significant shade during the day, your solar panel system's efficiency will also suffer. Fortunately, micro-inverter technology can help avoid losses in efficiency if partial shade only affects a part of your solar setup. Without micro-inverters, even a small shadow on the corner of one panel would change the entire system.

Does Temperature Affect Solar Panel Efficiency?

Though it might confuse some homeowners, extremely high summer temperatures can reduce the efficiency of solar panels. When installing in an area with long, hot summers (think Phoenix), the right installer will ensure that the panels receive natural airflow for cooling.

Does The Age of the Panels Affect Solar Panel Efficiency?

As solar panels age, they also tend to lose efficiency. As a rule of thumb, most experts agree that even the best solar panels lose about 0.5 percent of their total potential power output each year. Make sure to check the guarantee on the solar panels you purchase. Many companies will guarantee a minimum power output (usually between 80 and 85 percent) over a 20 to 25 year period.

What Is The Highest Efficiency Solar Panel?

As research and development in the solar industry continue, photovoltaic panels' efficiency ratings should continue to rise. Today, the most efficient solar cell is called a multi-junction concentrator. This panel can convert an impressive 44 percent of solar energy into electricity. The problem is that these panels cost hundreds of thousands of dollars and are not commercially available. For the North American market, the most efficient solar panel currently being sold is the SunPower SPR-327NE-WHT-D. This 327-watt panel has a module efficiency of 20.1 percent, which is significantly higher than the average 17 to 18 percent of competing models.

How to Increase Solar Panel Efficiency

For homeowners who have already invested in a solar panel system, upgrading to a better system with slightly higher efficiency ratings is probably not a financial possibility. Fortunately, a few things can be done to improve the efficiency of your existing solar panel system. First, you can prune any trees or other vegetation on your property that create shade on your rooftop or wherever your panels are located. It might make sense to place your panels on a garage, shed, or some other building in some cases. While the distance from the house might nominally increase installation costs, a south-facing shed in a sunny part of your backyard will allow the panels to produce much more electricity than the shady, west-facing roof of your home.

You might consider upgrading to a micro-inverter system. String inverters or central inverters are generally only built to last between 5 and 10 years. In contrast, your solar panels will hopefully last for at least 25. If you do need to change your inverter, micro-inverters don't only last longer. Still, they can also increase the system's overall efficiency by reducing the adverse effects of partial shading on the system. 

What Decreases Solar Panel Efficiency?

The leading causes that decrease solar panel efficiency include:

• cloud cover,
• sun intensity,
• relative humidity,
• and heat buildup.

Heat buildup can lower solar panel efficiency because as the solar panel temperature rises, the output increases while the voltage output is linearly reduced. To avoid this decrease in efficiency, proper airflow and spacing can keep the panels cooler. Of course, cloud cover is an element affecting solar power efficiency that homeowners have no control over. According to some estimates, solar PV panels' efficiency can drop anywhere between 10 and 25 percent on cloudy days. Again, micro-inverters can play a significant role in increasing efficiency even during dark days.

Relative humidity can lower the efficiency of panels because water vapor can accumulate on the solar PV units. This excessive humidity reflects sunlight away from the solar cells. Similarly, improper maintenance can lead to dust buildup that also reduces efficiency due to obstruction of sunlight.

What Is the Theoretical Maximum Efficiency of a Solar Panel?

Physics dictates that we will never see 100 percent efficient solar panel technology. Even 50 percent efficiency is probably never going to happen. The Shockley–Queisser limit estimates that maximum solar conversion for a single p-n junction photovoltaic cell is around 33 percent. More recent findings have stated that the maximum possible efficiency might be closer to 44 percent for this solar cell type.