Hydrogen is a unique fuel. When burned, it produces no carbon dioxide. The exhaust from hydrogen combustion is water vapor. From each of the internal combustion engines or gas turbines, the exhaust is run through a condenser capturing and cooling the water vapor which changes its state back to water to be used again and producing hydrogen, thus The Hydrogen Cycle.
The plant sizes can vary dramatically which necessitates the use of different types of energy generation. Very small plants where energy generation is 1 to 2 kW would use fuel cells. These have a limited use based on the slow rate of energy production and a much higher per kilowatt hour cost of operation but they are a good solution for very small energy projects.
Plants in sizes from 15 kW to 50 MW would use a variety of internal combustion engines. Smaller plants in the KWH range would use internal combustion engines similar to those in your automobile. Plants sized in the megawatt range would use diesel generators comparable to engines for heavy equipment up to extremely large maritime diesel engines. In larger plants where maritime diesel engines are used, it will be possible to use a co-gen Rankin Cycle low-temperature turbine to increase energy output and efficiency.
The Rankin Cycle generator is similar to home air conditioner. It uses a low temperature boiling solution in a closed system. The solution is heated by the exhaust from the diesel generators causing it to boil and produce steam energy. That steam energy is then used to turn a turban generating electricity. The gas is then condensed back into liquid form which starts the cycle over again.
Very large plants in the hundred-megawatt range use jet turbines similar to those offered by Siemens. Siemens has successfully in recent years engineered several models of their jet turbines to run successfully on pure hydrogen. The volume of gas emitted by the jet turban and the high temperatures makes it very conducive to use Rankin Cycle in a co-gen position to increase production plant efficiency.