Three types of systems are investigated in this work. A large solar water heating system suitable for a block of 10 flats or similar use, a solar heating system for a house and an industrial process heat system. A generic schematic diagram of the systems considered is shown in Fig. 1. The same basic system applies to all cases with the options concerning location of auxiliary and house heating as shown.

Fig. 1 Schematic diagram of the solar hot water and space heating system

1.1 Large hot water system

The system consists from a collector array, a storage tank, solar pump and auxiliary. A differential thermostat is used to compare the temperature at the exit of the collectors and the storage tank and give a signal to switch on the pump. The auxiliary energy considered in this case is diesel. The specifications of the system are shown in Table 1. Such a system can supply hot water to blocks of 10 flats or to any other similar size system.

1.2 Solar heating system

This is very similar to the hot water system with the difference that the hot water is supplied to the house radiators circuit. The specifications of the system are shown in Table

2.