Effects of Heat on Solar PV Modules

A photovoltaic system (PV system) converts the sun’s energy into usable electricity. The solar PV modules vary in different sizes, from small house rooftop panels to massive utility scale generation plants. Since solar panels convert light into electricity, it is easy for people to assume that more sunlight results in better performance, but that’s not always true. Your solar panel will perform great if it gets a lot of light, but as it gets hotter its performance degrades. Let’s see how high temperature affects the effectiveness of solar panels.

Solar PV modules are usually quoted for 25°C (meaning their best performance is at or around this temperature), and the problem is most solar panels’ power output starts to degrade if the temperature of the panel goes over 25°C. Basically, if the temperature outside is 25°C, the solar panel on top of your roof will be closer to 50°C. So if you want to know how much power you will be losing on a 25°C day, you need to know the "Max Power Temperature Coefficient", which is on the solar panel’s specification sheet.

A typical range for this is 0.4% per °C, which means that for every degree that the solar panel is above 25°C the power will fall 0.4%. So on a cool 25°C day where the panel is cooking at 50°C, you will be losing 10% of your solar power. And on days when the mercury breaks 40°C you could be losing close to 20% of your max solar power! Which is why you can often find that on the hottest days those solar panels on your roof are actually producing less solar power than usual.

Some solar PV modules respond to temperature changes better than others. Amorphous Silicon does a bit better. The Sanyo HIT hybrid cells and bifacial cells, which consist of a layer of monocrystalline silicon covered with a thin coating of amorphous silicon have a lower temperature coefficient of –0.34% - making them a good choice for people looking for high efficiency solar panels.

Cadmium Telluride panels are the best in dealing with high temperatures – with a temperature coefficient of –0.25%. While they are good with dealing with temperature changes, they aren’t as efficient at converting sunlight into electricity. Newer technologies such as CIGS and some of the 4th gen solar technologies being developed seem to be better at dealing with temperatures. There is promise, but it’s too early to tell yet.

Regardless of which solar PV module you decide to use, there will always be some energy output loss due to heat. However, there are several ways to mitigate the effects of hot temperatures on solar panels. After the module technology is selected for installation, here are some ways to minimize the negative effects of high temperatures:

• Use a thermally conductive substrate to house panels, which helps direct heat away from the glass layers
• Use light-colored materials to reflect heat and reduce heat absorption
• Move components like inverters and combiners into the shaded area behind the array
• Keep some space between the panels and the roof so air flow can cool the panels.

Solar installers customize their system designs to meet the specific needs of each individual property, which includes the temperatures a roof might expect to see throughout the year. However, if you are considering installing solar panels on your roof, finding the installer that’s the right fit for your home may take a little browsing around. Companies like Mahindra Susten and others make the process easy, from start to finish.

I work at a solar Epc company as a project executive.