One of the key factors in the efficiency of a solar installationthat is, if it produces energy optimally, it is the temperature to which the solar panels are exposed throughout the year.
The temperature directly affects performance of a solar installation. High temperatures above 30°C can reduce the efficiency of solar panels by 10%. However, a low temperature does not decrease the efficiency of the plates. The ideal temperature for optimal energy production is between 20 and 25 °C.
Here, especially in areas with a continental climate, solar panels suffer large temperature variations throughout the year. Depending on the geographical area where the installation is located, these variations can affect the efficiency of the installation to a greater or lesser extent.
The correct efficiency obtained in the winter months is diminished by the lower number of hours of sunshine per day and cloudy days. While in summer, solar panels suffer a decrease in their efficiency due to high temperatures, but in turn they are irradiated by more hours of sun per day.
Temperature factors affecting the energy production of a photovoltaic installation
As we just discussed, temperature has a direct effect on the efficiency and final output of solar panels. For this reason it is essential to control certain aspects that can reduce efficiency of solar panels. Here are three fundamental elements:
- Ambient temperature. Although cold temperatures are good for solar panels, the winter months have fewer hours of sunshine and more cloudy days. In the summer months the efficiency is lower due to the high temperatures, but at the same time they enjoy more hours of sunlight.
- Panel temperature coefficient. Solar panel manufacturers have marked 25º C as the ideal temperature at which they achieve the best performance. Most panels have a coefficient between
-0.2%/Cº and -0.5%/Cº. A temperature coefficient is better the closer it is to 0. This means that solar panels are more efficient as temperatures vary throughout the year. - Installed system temperature. Because solar panels are usually located on rooftops, they tend to experience higher temperatures. The panels not only take heat from the sun, but also from the roof they are attached to. However, there are photovoltaic installations that raise the roof panel with a structure that allows air to circulate between the panel and the surface, generating a cooling effect.
Calculation of efficiency deterioration of solar panels
Knowing the data we have just exposed will help us make a better decision about what type of solar panel to purchase for our installation, because if we live in a very hot area, it will be convenient that the type of panel selected be one that does not greatly reduce its efficiency at high temperatures.
For this reason the first thing we must consider before deciding of one type of panel or another, it is the temperature coefficient of each solar panel. This appears in the panel specifications along with the temperature at which it was tested.
Let\’s see below a example:
- Panel temperature: 27ºC.
- Temperature coefficient: -0.4%/ºC.
- The temperature at which the panel was tested: 25ºC.
- Structure and roof temperature: 32ºC.
- In this case the panel is at: 27º + 32ºC= 59ºC temperature.
- The temperature at which it was tested or the test temperature was 59º-25ºC = 34ºC.
- Finally, the test temperature is multiplied by the coefficient: 34ºC x 0.4 = 13.60% efficiency loss.
With this simple calculation we will be able to see the difference between the various solar panels to choose the one that will give the best result according to the temperature variation.
How to reduce the effect of heat
Being a stationary installation, it is quite difficult for us to reduce the heat effect on the solar panels. However, there are some actions we can take to reduce the impact of heat about panels:
- Install the panels above the ceiling. In this way, a space is left between the two so that the air can flow and a cooling effect is obtained.
- Light colors in building materials, roofing and panel components. Thus, heat absorption is lower.
- Installation of inverters and monitors in the shade. To prevent system overheating.
- Installation of panels with refrigeration systems. This type of panel captures the rain and stores it in the side frames of the panel. When temperatures rise, the system distributes the water through the sheets and cools it. This helps improve efficiency by 20%.
- distribution boards. An innovative technique that helps to better distribute the radiation captured by the panels, while distributing the temperature to achieve greater efficiency.
