This book describes how we can reduce the amount of water and electrical energy required to cool the solar panels, particularly in hot arid regions. How to develop a cooling system based on PV panel water spraying. A cooling model has been developed to determine how long it takes to cool down the PV panels to its normal operating temperature. It is found that the PV panels yield the highest output energy if cooling of the panels starts when the temperature of the PV panels reaches a maximum allowable temperature.