Steam generator e.g for driving gas turbine

A steam generator has a container with a light source within the steam drum at a minimum design temperature of 500 degrees C and a minimum design pressure of 50 bar. The inside of the container is evacuated and is partly filled with material. The design pressure and temperature of the container are at least 15 % higher than those of the steam drum. When a minimum temperature is reached, the light source is switched off whereupon the material releases heat and loses weight. There is a pipe with air locks passing through the drum to the container for feeding in the material. The drum has entry pipes for water and an exit pipe for the steam.