Until now, assessments of real energy savings achieved by individual solar thermal systems are very scarce, especially for solar combisystems. This is an obstacle for a good global evaluation of the impact of such systems in national or European energy policies. Methodology based on a common European and /or international agreement is still lacking.

In order to increase the quality of solar combisystems, one major item is to build up a test method that is able to produce test results representative of the yearly energy savings gained by a solar combisystem.

In principle the thermal performance or the primary energy savings respectively, can be determined with two methods.

One is the so-called CTSS method [5] (Component Testing — System Simulation) which is based on a separate test of the major components followed by a simulation of the system performance. First, the collector, the store and the controller are tested separately. With the parameters determined for the single components the thermal performance of the whole system can be calculated with an appropriate simulation programme. On this basis, a prediction of the thermal system performance for reference conditions and variable boundary conditions (e. g. different

meteorology and load profiles) is possible. This method is preliminary standardised in ENV 12977 part 1 to 3.

The other test method is the so-called AC/DC and/or CCT test method [1-4, 8]. This method is based on a test of the complete system (except the collector array). In order to determine the system performance, the system is operated during several days according to specified test sequences and the energy consumed and delivered by the system is recorded.

Three systems will be tested in different institutes: two of them will be both tested by CTSS method and one of the black box approaches in order to verify that results are quite the same, and the third one, that can not be tested by the CTSS method will be tested only by a black box approach.

The consortium will take care that the tested systems will also be monitored in order to compare test results to monitoring results.

A round robin test will be performed between the different laboratories involved in this project.