The average energy per unit time per unit area that reaches the upper atmosphere of the earth from the sun, called the solar constant, is 1.35 kW/m². Because of absorption and reflection by the atmosphere, about 1 kW/m² reaches the surface of the earth on a clear day. How much energy is collected in 8 h of daylight by a solar panel 1 m by 2 m on a rotating mount that is always perpendicular to the sun's rays.