During the last few years operational experience with solar systems was gained in Germany from the "1000 Dacher Programm”, a government programme economically supporting the installation of solar equipment on the roofs of buildings. A number of reasons for system unavailability were discovered [1], as shown in Table 1, the main reason being component failures.

Table 1: Percentage of failure causes

Not only equipment failures were monitored, but also repair times and skill requirements for repair were recorded in [1] (cf. Figure 2). All of these aspects are addressed in the simulation procedure.

Not every failure directly leads to the unavailability of the energy supply system. Depending on the system configuration and timeliness of repair production may be maintained, as can be shown by simulation.