How Does Temperature Affect Solar Panels’ Efficiency?

How Does Temperature Affect Solar Panels’ Efficiency?

Las Vegas summers get crackling hot. How does temperature affect solar panels? Should you worry about the heat making them less efficient?

Find out how to keep them cool to maximize the value of your investment.

Solar panels can provide long-term savings on your utility bills.
Contact Bell Solar & Electrical Systems today for a residential solar panel installation!

How Hot Do Solar Panels Get?

It might surprise you, but too much sunlight is a bad thing for solar cells. Your roof absorbs tremendous amounts of heat energy throughout the day. As a result, rooftop solar panels are typically 20 degrees hotter than the air temperature. While this shouldn’t be a problem throughout most of the year, it can be during the intense heat of the Las Vegas summers.

How Does Heat Affect Solar Panels’ Efficiency?

The extreme Las Vegas heat can make your solar panels less efficient, but not enough to erase the economic advantages of installing them. Solar panels perform at peak efficiency between the temperatures of 59°F and 95°F, but for much of the year, the temperatures in Las Vegas are well above this range. The good news is that the decline in efficiency of your solar panels is easy to calculate with a mathematical formula.

How exactly does temperature affect solar cells? Most solar panels perform optimally in the laboratory at the Standard Test Condition (STC) temperature of 77°F. Their efficiency degrades significantly once they reach 149°F. The decline in solar panel performance past 77°F is easy to calculate, allowing you to create projections of their output at summer temperatures.

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How Does Shade Affect Solar Panels’ Efficiency?

Shade can significantly impair the performance of solar panels for homes or businesses. Each panel is connected to an inverter by a string or circuit. A string may include multiple solar panels and sometimes an entire array. When a shadow falls on one panel within a string, it acts as a crimp on the flow of energy, effectively shutting the entire string down.

Several technologies can mitigate the effects of shade. A string system with Maximum Power Point (MPP) Tracking will alter the voltage of the current so that shade doesn’t shut down the entire system. An alternative approach is to use a multi-string inverter system, which reduces the number of panels affected by shade. Mircoinverters and power optimizers can overcome the problem of strings altogether, as they convert the DC energy the panels produce into AC energy used by your home.

There are also a variety of low-tech solutions to shading that can provide a long-term defense against it. For one, your installer will carefully survey your roof to determine if parts of it fall under shade and plan your layout around them. This is especially important for complex roofs that receive inconsistent sunlight throughout the day. Also, if there are current or potential sources of shade nearby, such as trees, you can try to remove them or at least keep them from blocking your array in the future.  

How Do I Calculate Energy Loss and Efficiency 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

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 each degree change on either side of the STC impacts efficiency.

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 were 104°F, the average temperature in Las Vegas in July, your rooftop solar panels would be 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 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

Here are some steps you can take to keep your solar panels cool and 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) Install a thermometer to monitor your solar panels and alert you if they need to be cooled. The panels may need a substrate to diffuse heat or further elevation from the roof to facilitate greater air flow.

It’s important to take precautions to keep your solar panels cool and efficient. Solar projects in some areas have actually failed due to the tremendous amount of heat they absorb from the sun. However, you can enjoy long-term benefits from your solar panels by working with a professional installer. They can mitigate the amount of heat your solar panels be exposed to over the course of their working life.

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