Las Vegas summers can get crackling hot, so how does temperature affect solar panels? As air temperatures sail past 110°F and exposed surfaces get dangerously hot, do you have to worry about the heat damaging your solar cells or reducing their efficiency? While sunny days are ideal for solar energy, you do have to take precautions to guard rooftop solar panels against excessive heat. Find out how to keep your solar panels cool to maximize their efficiency and the value of your investment.
How Hot Do Solar Panels Get?
While you probably think that the more sunlight, the better your solar panels would work, there is a point at which it can negatively impact their performance. Your roof absorbs tremendous amounts of heat energy throughout the day, and if you install rooftop solar panels, they will take on the brunt of it. Rooftop solar panels are typically 20 degrees hotter than the air temperature. While this shouldn’t be a problem throughout most of the year, the intense heat of the Las Vegas summers could impede the performance of your solar panels if you don’t take the necessary precautions.
How Does Heat Affect Solar Panel Efficiencies?
How exactly does temperature affect solar panels? Most solar panels perform optimally at the Standard Test Condition (STC) temperature of 77°F, an industry-standard temperature for the laboratory testing of solar panels. Once solar panels begin to reach 149°F, their efficiency may degrade significantly. The decline in performance past 77°F is easy to calculate, allowing you to create projections of their output at summer temperatures.
How Do I Calculate Energy Loss in Solar Panels?
To calculate how efficient solar panels are at different temperatures, simply use the following formula:
Solar Panel Efficiency = (Maximum Current X Maximum Voltage) / Power from absorbed light
Want to find out how much your solar panels will decline in efficiency with higher temperatures? Solar panels have a normal operating cell temperature (NOCT) in the lab that is used to calibrate changes of efficiency. This value in rate of change is called the temperature coefficient of the maximum output power (Pmax). The Pmax Temperature Coefficient can be found on the solar panel’s datasheet and indicates how much its efficiency increases or decreases with each degree on either side of the STC.
To find out how much power your solar panels are losing to heat, multiply Pmax by the difference in the temperature of the solar panels. For example, if it was 104°F degrees out, the average temperature in Las Vegas in July, your rooftop solar panels could be around 124°F. By subtracting the STC of 77°F from 124°F then converting this to Celsius, the solar panels would be approximately 37.7778°C above the STC. Multiply this value, 37.7778°C, by the temperature coefficient of Pmax -0.44 %/°C to determine the amount of energy lost, or about 16.62%, then multiply the remaining energy, 83.38%, by 250W to determine the new output of 208.44 W.
How to Keep Solar Panels Cool
While solar panels can and will get hot, especially in Las Vegas, there are a number of steps you can take to keep them relatively cool and well within their safe range of operation.
1) Make sure your solar panels are properly elevated above the roof to create space and air flow.
2) Choose polycrystalline blue solar panels instead of black monocrystalline panels.
3) Keep a thermometer near your panels to monitor them and alert you if you need to cool them off. The panels may need a substrate attached underneath them to help diffuse heat or may need to be elevated further from the roof to allow for more air flow.
While solar panels are built to withstand high levels of heat, it’s important to take precautions to keep them cool and, thus, maximize their efficiency. Solar projects in some areas have actually failed due to the tremendous amount of heat they are exposed to from the abundant sunshine. However, you can enjoy long-term benefits from your solar panels by working with a professional installer, who can mitigate the amount of heat they’ll be exposed to over the course of their working life.