The gas cooled solar tower powerplant with a hybrid solar-fossil heating system in the form given here represents a significant step towards the industrial use of solar energy. The transition from fossil fuels to solar energy can be facilitated for the power plant operators if the transition is gradual and if conventional technology is used. Using solar energy and with a turbine inlet temperature of 800/sup 0/C the GAST power plant reaches an output of approximately 20 MW and a thermal efficiency of approximately 40% reference to the heat supplied by the receiver. In the absence of solar radiation the plant can be operated exclusively on fossil fuel. Increasing the turbine inlet temperature to 1000/sup 0/C enables an efficiency of about 47% to be reached in the GUD cycle.