in basic form comprises an air compressor a turbine portion and a combustor although the turbine portion is only a single element of the entire assembly the entire assembly is commonly referred to as a gas turbine or gas turbine engines in operation of a simple single shaft gas turbine air is compressed in a compressor after which it enters a combustion chamber where the temperature is increased through the combustion of fuel while the pressure remains essentially constant the resulting high temperature air is then exhausted through the turbine portion where it performs work typically by causing turbine blades to rotate typically such turbines are used to drive electric power generators which convert the rotational energy of the turbine portion to electricity in accordance with the present invention the two gas turbines of fig1 are individually modified as follows the first gas turbine 10 is modified for use as a motor driven compressor thus forming a portion of the compression train of the preferred embodiment while the second gas turbine is modified for use as a turboexpander thus forming a portion of the expansion train of the preferred embodiment gas turbine 10 comprises a turbine element 15 and a compressor 40 connected to a shaft 30 clutch devices 45 50 are provided in gas turbine 10 for isolating compressor 40 turbine element 15 and a motor 35 advantageously motor 35 can be the original generator that was.