a common shaft in fig1 the power plant 10 is coupled to a heat pump 20 the latter has a compressor 21 an evaporator 22 an expansion valve 23 and a condenser 25 particularly advantageously on the one hand a mechanical power connection needs to be produced between the power plant 10 and the heat pump 20 in such a way that the generator 11 and the turbine 12 of the power plant 10 and the compressor 21 of the heat pump 20 are coupled on a common shaft w furthermore the power plant 10 and the heat pump 20 are interconnected via the first thermal store t 1 a heat store the latter is charged by waste heat of the condenser 15 and the evaporator 22 extracts the heat again from the thermal store t 1 the condenser 25 of the heat pump 20 is additionally connected to a second thermal store t 2 in turn a heat store which is charged to a significantly higher temperature level as a result of the thermal coupling to the condenser 25 of the heat pump 20 this is particularly suitable for being discharged via a district heating grid 30 the temperature level of the first thermal store t 1 is for example between 50 u00b0 c and 90 u00b0 c and the temperature level of the second thermal store t 2 is for example between 80 u00b0 c and.