Solar and renewable/waste energy powered turbine with two stage heating and graphite body heat exchanger

A process for operating a turbine driven from renewable or waste energy sources wherein a working fluid which drives the turbine is passed around a working fluid circuit and heated in a two stage heating process using a first heating apparatus using a renewable or waste energy source and a second heating apparatus comprising a graphite body heated by concentrated solar energy the graphite body containing an embedded heat exchanger comprising at least one heat exchanger tube embedded in and in contact with the graphite body, the process, comprising:

• heating the working fluid using the renewable or waste source to generate a stream of working fluid heated to an intermediate temperature;
• heating the graphite body using the concentrated solar energy to store heat within the graphite body;
• delivering the stream of heated working fluid into the heat exchanger which is embedded in the graphite body whereby the graphite body releases stored heat to heat the working fluid to provide a continuous stream of the working fluid heated to a working temperature for input to the turbine;
• and
• wherein, a relationship exists between an outer surface area of the embedded heat exchanger tube and a mass of graphite in the graphite body whereby there is from 0.60 m2 to 20 m2 of outer surface area of embedded heat exchanger tube per tonne of graphite in the graphite body.