Plants absorb and convert sunlight into energy through the process of photosynthesis. Solar panels work similarly in that they also absorb and turn sunlight into energy. The key difference, however, is they convert it to electrical and not chemical energy.
Do Solar Panels Emit Heat?
Solar panels do emit heat when exposed to sunlight. Solar panels convert the sunlight they absorb into electrical energy through a photoelectric process. As with any conversion process, turning solar energy into electricity is not 100% efficient. There is some energy loss that happens. This energy loss comes in the form of heat.
If you know your basic physics then you will know that heat is a typical byproduct of any conversion process. Solar is not an exception.
How Does Temperature Affect a Solar Panel?
Solar panels, like any other electrical devices, work best in cooler temperatures. They have what is called a temperature coefficient. This is the optimum temperature at which a solar panel will efficiently convert sunlight into energy. The temperature coefficient of solar panels is 25°C.
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When the temperature of a solar panel rises above this, its efficiency decreases.
This means the hotter (over 25°C) a solar panel becomes, the less electrical energy it produces.
Does this mean solar panels will stop working when it gets extremely hot? The answer is no because solar panels are manufactured to withstand extreme heat. It is highly improbable they will get so hot they will stop working.
For more on this topic, check out our post titled “Do Solar Panels Overheat? Is it a Big Deal!“
How Much Heat Do Solar Panels Radiate? (Influential Factors)
Only 20% of incoming solar energy is converted into electricity. Most of the remaining energy is re-radiated as longwave sensible heat. A small proportion is either reflected into the surrounding air or absorbed and later radiated as latent heat.
Several factors determine how much heat a solar panel radiates. Here are some of the most important factors.
Solar insolation
Solar insolation is how much solar radiation is received at a certain point in the earth’s atmosphere. In simpler terms, it’s how much sunshine an area receives. The insolation of an area is a factor of the angle of the sun, height above sea level, and cloud cover. Places in lower altitudes and drier conditions have higher insolation. (Source)
Naturally, if there is a higher degree of insolation then there’s more heat to be radiated. In the US, California receives the most sunshine while states like New York receive the least.
| City | Insolation |
|---|---|
| California | 7.5 |
| Texas | 6 |
| Iowa | 5 |
| Washington | 4.5 |
| New York | 4 |
Solar panel material
Different components of the solar panel will absorb and radiate heat. This includes the surface of the solar panels. The amount of light absorbed is determined by the color of the surface and the back material of a solar panel. Darker surfaces like what you find with monocrystalline solar panels will absorb more.
The aluminum used in the back of most solar panels absorbs a high amount of the heat that comes from sunlight.
For more on this, check out our post : Why Solar Panels Are Blue Or Black? Alternatives & The Best Color To Use!
Low absorption of infrared light
Light reaches a solar panel at different wavelengths. The light that cannot be converted into energy will contribute to heating. Solar panels differ in terms of how efficient they are at converting the different wavelengths.
Monocrystalline solar panels do not convert infrared light as efficiently as thin-film solar panels for example.
Solar cells
The solar cells in a solar panel will produce more heat than any other part. The more densely packed the solar cells in a solar panel the more heat per unit area is generated.
Solar panel efficiency
Higher efficiency solar panels will convert more sunlight into electricity. This leaves less energy that is lost to heat generation. This means the more efficient a solar panel is, the less heat it will radiate.
Do Solar Panels Raise the Ambient Temperature?
Solar panels raise the ambient temperature of an environment. This is primarily due to the inefficiency of a solar panel in converting the solar energy it absorbs into electricity. Generally, solar panels are 2.2°C warmer than the ambient external air around them. They are designed to absorb the sun’s energy and have a maximum temperature threshold of 85°C.
The energy not converted into electricity has to go somewhere. This is the heat that the solar panel generates. Some of it is reflected in the sky. Some of it is absorbed by the solar panel frame while some is carried away into the surrounding air above and below the panel by convection currents.
Absorbing the sun’s heat makes them warmer. Absorption of heat is how you get what is known as a “heat island.”
The heat island effect
Energy from the sun is absorbed or reflected by the Earth’s surface. The heat island effect describes a phenomenon whereby more heat than normal is “trapped” by the glass and concrete of buildings in a city or other structures that absorb heat at scale.
Solar panels are thought to have this same trapping effect. In a study conducted at a large-scale solar power plant, the ambient temperatures around the plant were found to be 3-4°C higher than the surrounding areas. (Source)
Most of this heat dissipates at more than 100 feet away from the power plants and the effect is less than that caused by large urban cities and industrial areas.
Solar panels don’t only increase the ambient heat, however. They also have a minor cooling effect. Solar panels can cool the area beneath them by providing shade. This is why there needs to be a gap between solar panels and the surface they are installed on. To allow them space to remove excess heat.
This can contribute to cooling a home for example. Because roof shingles are typically dark and made of dull material, they absorb more heat. Solar panels are made from reflective silicon so they absorb less. The more solar panels there are on a roof the less heat the roof absorbs. (Source)