According to the standard ISO 9459-2, test procedures for characterizing the performance of solar domestic water heating systems operated without auxiliary boosting are established. A “black box” approach is adopted which involves no assumptions about the type of system under test; the procedures are therefore suitable for testing all types of systems, including forced circulation, thermosiphon, freon-charged and integrated collector-storage systems. The test system is applicable only to systems of 0.6 m3 of solar storage capacity or less.

The structure and flow charts of solar water heating test system is shown in the figure 1. The main components of test system include units as shown below, constant temperature tank, return tank, water heaters, cooling systems, water distributor, water collector, pumps, solenoid valves and other components. The instrumentations coincided with measurement requirements of ISO 9459-2 contain pyranometers, diffuse pyranometers, anemometers, flowmeters, PT-100 thermal resistance and data recorders. Pipe system in test system of solenoid valves and non return valves to control the direction of flow can be achieved with the open-cycle and closed cycle. And so, solar water heating test system can separately test daily system performance, the degree of mixing in the storage vessel during draw­off and the storage tank heat losses.

After repeated testing determined in design, now the test system is completed. Solar water heating test system is presented in Figure 2 as follows.