This note explains the very high cost of electricity generated by burning green hydrogen instead of natural gas in turbines.
Background. There is worldwide enthusiasm for producing ‘green’ hydrogen by electrolysis of water using electricity generated by wind and solar farms. This does not generated CO2, unlike the current commercial methods that extracts hydrogen using coal or gas.
The objective is to use hydrogen as a form of green energy storage.
One of the end uses is to generate electricity in gas turbines using hydrogen as the fuel instead of natural gas.
Critical Issues. The major issue is the cost of production. All the plans for green hydrogen at present are hopes and wishes that depend on major technological advances and practically unlimited supplies of very cheap wind and solar power.
The Facts of the Matter. The paper below uses current data to provide a realistic estimate of the cost of producing green hydrogen and then using it to generate electricity.
The process is wasteful due to the number of stages in the process to convert wind and solar energy into hydrogen gas and then back into electricity.
The most important figures in the calculation are:
The efficiency of the electrolysis (this indicates the amount of energy lost at that stage of the process).
The efficiency of conversion of the energy in the hydrogen to electricity from the generator.
The anticipated selling price of the hydrogen compared with the price of natural gas (the alternative fuel).
Electrolyser efficiency - 55.25%
Hydrogen fuelled system efficiency - 33.26%
Minimum selling price of hydrogen - $39.34/GJ
Cost of natural gas - $11.30/GJ.
There is clearly a significant price difference which, in turn, will result in higher electricity prices fed back to the NEM grid.
It is also evident that the hydrogen fuelled system efficiency of 33.26% compared with a natural gas fuelled gas turbine efficiency of 60.2% (combined cycle mode) is wasteful of energy.
Conclusion. Unless there is a dramatic reduction in the cost of renewable electrical energy and the capital and O&M costs for electrolysers, green hydrogen is not competitive with natural gas as a fuel for gas turbines.