Cooling system for photovoltaic panels

A method for controlling a cooling system for photovoltaic panels, the cooling system comprising:

• an air cooling assembly adapted to produce an air flow directed against an upper surface of a photovoltaic panel, exposed to solar light, or against a lower surface of the photovoltaic panel, opposite to the upper surface, said air cooling assembly comprising a fan driven by a first electric motor,
• a water cooling assembly adapted to produce a cooling water flow wetting said upper surface of the photovoltaic panel exposed to the solar light, said water cooling assembly comprising a pump driven by a second electric motor, and
• measuring means comprising a produced power meter adapted to measure electric power Pout produced as output by the photovoltaic panel, a first absorbed power meter adapted to measure electric power P1in absorbed as input by the first electric motor, and a second absorbed power meter adapted to measure electric power P2in absorbed as input by the second electric motor,
• wherein the method comprises the steps of:
• a) switching on the fan,
• b) calculating a difference ΔP1 between the electric power Pout produced as output by the photovoltaic panel and the electric power P1in absorbed as input by the first electric motor, hereinafter a first power difference, based on signals received from the produced power meter and from the first absorbed power meter,
• c) keeping the fan in operation during a first time interval Δt1 after the fan has been switched on, during which said first power difference is negative,
• d) in a second time interval Δt2 following the first time interval Δt1, after said first power difference has transitioned from a negative first power difference to a positive first power difference, keeping the fan in operation until said first power difference is positive,
• e) when the first power difference drops to zero from said positive first power difference, switching off the fan and switching on the pump,
• f) calculating a difference ΔP2 between the electric power Pout produced as output by the photovoltaic panel and the electric power P2 in absorbed as input by the second electric motor, hereinafter second power difference, based on signals received from the produced power meter and from the second absorbed power meter,
• g) keeping the pump in operation during a first time interval ΔT1 after the pump has been switched on, during which said second power difference is negative,
• h) in a second time interval ΔT2 following the first time interval ΔT1, after said second power difference has transitioned from said negative second power difference to said positive second power difference, keeping the pump in operation until said second power difference is positive, and
• i) when the second power difference drops to zero from said positive second power difference, switching off the pump and switching on the fan.