NOVELTY - The system has a solar collector (12) and a non-cylindrical water storage tank containing a heat transfer medium (3) i.e. water-propylene glycol solution, included in a single construction of parallelepiped shape and connected to each other with hydraulic interconnection (8, 9). A photovoltaic generator (13) is in electrical connection (10) with an electric pump (6) and placed on the solar collector. The generator is unable to produce electric current when sunlight is not adequate or during night such that the pump immediately stops operation to avoid aimless recirculation of the medium.    USE - Solar thermal system for providing hot water for domestic use.    ADVANTAGE - The water storage tank is of rectangular parallelepiped and not cylindrical shape and specially designed to be resistant to the operating pressure, which occurs due to circulation of the heat transfer medium such that the water storage tank occupies less space, so that transportation and storage of the system becomes easier and more economical. The domestic water storage tank is seamless and specially designed so as to assure material homogeneity all over the body, so that initial mechanical properties of the material remain the same and tolerance pressure is increased. The design of the system avoids accumulation of mineral deposit or other corrosion products, so that the domestic water is absolutely drinkable and domestic water does not stagnate in the water storage tank, mixed with deposits and corrosion products, and flows within the domestic water tank, which acts as a heat exchanger, to supply the mains with water when required. The water storage tank and the solar collector are arranged together with all other components needed, thus making installation extremely easy without any specialized technicians. The special design of the tank with static water eliminates the need of maintenance such that all components and the overall equipment, which is included in the tank are protected from mineral deposits. The system does not require many components such as differential thermostat, regulator, non-return valves, temperature sensors, expansion tank or safety valve for operation, such that maintenance or regulation works are not required, so that the system is extremely simple and economical. The photovoltaic generator produces volume of current needed, and the pump operates recirculating the heat transfer medium between the storage tank and the solar collector when sunlight is not adequate such that the system avoids delay phenomena, so that the heat is exchanged from the collector and stored in the tank, and the content of the tank is fully homogenized. The photovoltaic generator and the electrical pump avoid requiring any maintenance or regulation, and are constructed in a way that can operate constantly and efficiently for many decades.    DESCRIPTION OF DRAWING(S) - The drawing shows a perspective view of multi-level sections of a solar thermal system.    Heat transfer medium (3)    Electric pump (6)    Hydraulic interconnection (8, 9)    Electrical connection (10)    Solar collector (12)    Photovoltaic generator (13)