Nomenclatures

• \(H_{t}^{extra}\): extraterrestrial radiation for day \(t\). It is the theoretical radiation outside the atmosphere.

• \(C_{t}^{clearsky}\): clear sky radiation for day \(t\). It refers to the amount of solar irradiation that would be received at the Earth’s surface under cloud-free conditions.

• \(GHI_{t}\): global horizontal irradiance for day \(t\). It is the radiation that is able to reach the ground.