The key component of a solar thermal system is the collector or the absorber, which converts solar energy into heat and transports it by means of a heat transfer medium via piping systems and heat exchangers to a storage tank. In systems for hot water supply, the storage tank compensates for fluctations in energy supplies and requirements at varying times of the day. In large solar systems which also greatly contribute to heating energy supplies, an underground seasonal storage tank is usually constructed in a local heating system to compensate for seasonal variations in irradiation and energy demand. These seasonal supply systems are currently at the trial stage and will not be considered further here. Where the solar energy is insufficient, an auxiliary heating system supplies the outstanding amount of energy to cover requirements.

A controller monitors the operational state of the solar system and ensures the most efficient use of the energy irradiated. If there is a temperature difference between the storage tank and the collector, it switches on the circulation pump in the collector loop, ensuring heat transport to the storage tank.