Hydrogen may hold key to storing wind power - A system that could make renewable sources of power more reliable has begun operating in Germany, marking a milestone for a new energy storage system, the companies involved say.
Number 1: Hydrogen has a high BTU value per pound but a low BTU value per cubic foot. It takes a lot more pipeline diameter (or pressure) to deliver a given number of BTU of hydrogen than natural gas. Hydrogen is not energy dense from a pipeline point of view.
Number 2: Hydrogen has a gross heating value of 325 BTU/scf and a net heating value of 275. The ratio of LHV to HHV is about 84.6%. Natural gas typically has a ratio of LHV to HHV of 91%. Turbines, boilers, and engines utilize the LHV not HHV because they do not condense the water out of the exhaust gas in the process of doing work. So, not only does it take many more cubic feet of hydrogen but there is less useful energy extracted from the gas.
Number 3: Battery storage units typically return some 90% plus of their stored energy as electricity. To do the hydrogen thing, one must convert electrical energy to hydrogen, then burn the hydrogen in a process that is at best (gas turbine combined cycle), 60% efficient. There are losses in converting electricity to hydrogen so the overall process is maybe 55% efficient compared to 90%.