Transient simulation has been carried out to investigate the effects of varying the remuneration tariff in terms of value and time distribution in comparison to the current situation where the bonus is not seasonally dependent. In that way, the interactions between all system components of the heating system with either the rCHP, or the solar thermal system can be considered in a detailed fashion.

Control algorithms have been especially developed for rCHP. One of them, the control algorithm developed in [Vetter u. Wittwer 2002] offers the possibility to operate the rCHP while minimising primary energy consumption or energy cost (i. e. cost-driven control but limited by the maximal heat capacity of the storage unit).

The heating system based on a PEMFC (proton-exchange membrane fuel-cell) has been modelled considering all stages for the natural gas processing (reforming, CO shifting, preferential oxidation, …, see Fig. 1) and the performance of the PEM stack, the inverter, the various heat exchangers and the balance of plant. This model enables the description of dynamic processes (starts, stops and load variation) and the interactions between the various system components (i. e. the influence of the storage temperature on the thermal performance of the rCHP).

180 m2. The rCHP is of the PEMFC type with a nominal electric power output of 2 kW (see Fig. 2). The building model picks up data for the space and domestic hot water (DHW) heat load computation from a database. The yield of an optional solar thermal system is calculated with a dedicated model that has been parameterised with 5 m2 of solar absorber area. The thermal storage tank has a volume of 750 litres. Simulation results are depicted on a monthly basis in Fig. 3.

In the case of energy cost optimisation, several CHP bonus patterns as well as several remuneration approaches have been investigated (i. e. constant remuneration or varying with the price fluctuation at the Leipzig power stock exchange).