The effect of temperature on photovoltaic panels

A veces tenemos el concepto erroneo de que cuanto mas calor haga mayor sera la energia producida por los paneles pero dejeme decirle que esto no es asi y le explico por que. Los paneles solares funcionan con luz solar no con calor, cuando la temperatura sube por encima de los 25 ° grados la eficiencia de conversion empieza a disminuir.

The effect of temperature on photovoltaic panels

One of the  key factors in the efficiency of a solar installation , that is, if it is producing energy optimally, is  the temperature to which the solar panels are exposed throughout the year. 

Temperature  directly affects the performance  of a solar installation. High temperatures of more than 30º 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 optimum energy production is between  20 and 25º C.

In our country, especially in continental climate zones, solar panels suffer  significant temperature variations throughout the year . Depending on the geographical area in which the installation is located, these variations may affect the efficiency of the installation to a greater or lesser extent.

The correct efficiency obtained in the winter months is diminished by the fewer hours of sunshine per day and by cloudy days. While during the summer, solar panels suffer a decrease in their efficiency due to high temperatures, but in turn they are irradiated by more hours of sunshine per day.

Temperature factors that affect the energy production of a photovoltaic installation

As we have just commented,  temperature has a direct effect on the efficiency and final production of solar panels.  For this reason it is essential that we control certain  aspects that can reduce the efficiency  of solar panels. Here are three basic ones:

• Environmental temperature.  Although solar panels benefit from cold temperatures, in the winter months there are 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 more hours of sunlight are enjoyed.
• Panel temperature coefficient . Solar panel manufacturers have marked 25º C as the ideal temperature at which they reach their most optimal performance. Most panels have a coefficient between
  -0.2%/Cº and -0.5%/Cº. A temperature coefficient is better the closer to 0 it is. This means that solar panels are more efficient with the variation of temperatures throughout the year.
• Installed system temperature . As 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 to which they are attached. However, there are photovoltaic installations that raise the roof panel with a structure, which makes the air flow between the panel and the surface, generating a cooling effect.

Calculation of efficiency deterioration of solar panels

Knowing the data that we have just exposed will help us make a better decision about what type of solar panel to acquire for our installation, since if we live in a very hot area it will be convenient for the type of panel selected to be one that does not greatly reduce its efficiency at high temperatures.

For this reason, the first thing  we must take into account before deciding  on one type of panel or another 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 an  example below :

• Panel temperature: 27ºC.
• Temperature coefficient: -0.4%/ºC.
• Temperature at which the panel was tested: 25ºC.
• Structure and roof temperature: 32ºC.
• In this case the panel is at: 27º + 32ºC= 59ºC of temperature.

• The temperature at which it was tested, or test temperature, was 59º-25ºC = 34ºC.
• Finally, the test temperature is multiplied by the coefficient: 34ºC x 0.4 = 13.60% loss of efficiency.

With this simple calculation we will be able to observe the difference between various solar panels to choose the one that will provide the best result based on the variation in temperature.

How to reduce the effect of heat

As it is a stationary installation, it is quite difficult for us to reduce the effect of heat on the solar panels. However, there are some  actions that we can carry out and that allow us to reduce the impact of heat  on the panels:

• Install the panels above the ceiling.  In this way, a space is left between the two so that air can flow and a cooling effect is achieved.
• Light colors  in building materials, roof and panel components. Thus the absorption of heat is less.
• Installation of inverters and monitors in the shade . To prevent overheating of the system.
• Installation of panels with cooling 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 sheets . A novel technique that helps to better distribute the radiation captured by the panels, while distributing the temperature to achieve greater efficiency.