: Vetter, M.; Wittwer, C.

Abstract
Natural gas driven fuel cell power stations for the domestic supply are presently promoted as one of the most efficient solutions to reduce the IKJML -emissions of private households. These small systems including a gas reformer, a fuel cell stack and an auxiliary burner are dimensioned to fulfill the heating and warm water demands of a building by hundred percent in the winter case. Considering the electric efficiency, the thermal load, the dimensions of the storage and the user behavior nearly the same can be said for the accumulated electric load of a building. Energy supply companies recognize this way of cogeneration as an opportunity to open up the heat market. "Virtual power plants" as a result of these distributed power stations are seen as an important part in the future grid structure. The resulting question deals with the role of renewable energy techniques in this scenario. In this paper the consequences for the solar thermal systems are discussed. Analogical to[OTTI-01] a 'Low Energy Consumption House' [EnBW-1] is considered. Predictive controlling strategies which optimize the running costs and/or the primary energy balance are developed for a supply system including a fuel cell power station, a solar thermal system, an auxiliary burner and a stratified storage. Based on simulation results of one year the expected difficulties are quantified and one possible answer of the headlined question is given.