The ET 202 is a fully-functional demonstration model of a system for heating domestic water using radiation energy. A high-power lamp simulates natural sunlight. Therefore, the unit can also be used in closed rooms. The light is converted into heat in an absorber and transferred to a heat transfer medium, in this case water. A circulating pump delivers the heat transfer medium through a warm water reservoir. In the reservoir, the heat is transferred to the stored water by a heat exchanger. Additional heat can be dissipated using 2 tap water connections. The unit is equipped with sensors to record temperatures, illumination and flow rate. The measured values are indicated on displays. Using a data acquisition card, they can be transferred to a PC for further processing. The ET 202 can be used to investigate various angles of incidence and irradiances. To do this, the flat absorber can be set to different angles and the height of the lamp is continuously adjustable.