One of the main obstacles faced by the correct operation of solar panels is overheating due to excess solar radiation and the high environmental temperatures that it faces, therefore, the performance of these will vary depending on the location where they settle. Overheating drastically reduces the efficiency of the panels . In this article we explain what is the optimal temperature to obtain the highest possible efficiency from solar panels .
Hybrid photovoltaic/thermal (PV/T) solar system is one of the most popular methods for cooling photovoltaic solar panels combined with a refrigeration system. The cooling agent, i.e. water or air, circulates around the photovoltaic panels to cool the solar cells, so that the hot water or air exhausted from the panels can be used for domestic applications such as heating.
The temperature of the water-cooled solar panels is reduced by up to 10⁰C , and therefore the electricity production of the cooled panels is increased by 15%-19%.
1.- Cooling systems
Various refrigeration systems exist today, one of which is a proprietary pipe with several very small holes, requiring special installation skills. The stored rainwater is transferred to a ramp at the edge of the panels and later, it flows over the surface of the modules and immediately lowers the temperature of these.
The pipes that are used are UV resistant and are pre-drilled with holes. The water only spreads over the glass surface of the panels and does not touch any plastic parts, such as the back sheets or other components of the PV panels.
The system is started by a temperature sensor that activates the dispersion of water when the ambient temperature exceeds 25⁰C. Although water can have some influence on the light absorption of photovoltaic modules , this is fully offset by the increase in energy yield that can be achieved by avoiding temperatures exceeding 30⁰C in such a way.
Cooling systems collect water from a rainwater reservoir and after use, it can be recycled, filtered and stored again .
Apart from this pipe cooling system, we can also find other strategies to cool our solar panels.
For example, solar panels can be cooled with fans, thereby reducing the temperature by around 15⁰C, leading to a significant increase in overall system output.
Another strategy is to cool the solar panels with water. This is the simplest and most common way to cool solar panels. This method can work for all types of solar modules, and is as simple as spraying cold, clean water onto the surface of the solar panels and then waiting for them to cool down. It is recommended for homes, but not for large-area installations where the cost of water would be considerable. Cooling solar panels with water can result in around a 50% increase in power output.
A great benefit of this method is that it also works to clean photovoltaic panels. There are improved water cooling designs that can collect hot water from solar panels and use it for other heating purposes in the house. One of the factors to take into account in this method is that the water must not be pressurized, the solar panels are delicate and could be destroyed by high pressure.
Another method of cooling is by ambient air from solar panels. Cooling by this method follows the principle of heat and mass transfer that occurs between the surface of the solar panels and the ambient air. A system can be designed around the solar modules with an ambient air inlet and outlet to transfer heat from the solar panels.
Air cooling solar panels mainly depend on weather conditions such as temperature, humidity, and airflow rate. If, for example, the temperature of the ambient air entering through the outlet is low, the temperature of the solar panels is reduced in the same proportion.
Air cooling’s dependence on weather conditions makes this method relatively less effective at cooling solar panels than other strategies. Although this solar panel cooling method can work as a stand-alone method, it works best when integrated with another cooling method. For example, it can be combined with water cooling to produce significant results.