A brief consideration of Sun structure and solar spectrum at the top of the atmosphere and at sea level is made. Blackbody radiation law with respect to short-wave solar radiation and Earth thermal radiation is also considered. It is noted that the worldwide implementation of alternative energy with increasing rates is the key moment, which is necessary to achieve the set climate goals and improve the environmental situation in the world. At the same time, the cleanest and accessible almost everywhere solar energy should play a leading role. There are two main factors affecting the gained solar energy: PV efficiency and solar panel direction. Here, the new method for the determination of the optimal location and direction of solar panels is presented. This method is based on a mathematical model of solar radiation, which determines the amount of solar energy for any instant of time and any point taking into account shadowing of the Sun caused by surrounding relief. The optimal direction of the solar panel is determined as a solution of the derived system of equations. For the chosen site, the results of calculations and measurements are compared and the adequacy of the method is shown. This method can be very useful for the quick determination of optimal direction and installation of panels, especially in mountain regions with high touristic potential.