RE: H2 on tap4 May 2020 11:43
What I am referring to is that by combining oxygen and hydrogen there is no gas exhausted. In fossil fuel engines of all kinds there is hot gas exhaust, mostly nitrogen. The often quoted figure is that the exhaust carries with it 39% of the energy (heat/LHV) from combustion. This heat is very difficult to recover, even in CHP because the exhaust stream is very corrosive and expensive heat exchangers are required to recover the heat into a useful form i.e steam, hot water, chp fluid etc. With a hydrogen engine using pure oxygen, rather than air, there need be no exhaust carrying away heat and the result of combustion, after using the heat, is hot water. The Allam cycle, which uses oxygen rather than air in power stations has been shown to be nearly 20% more efficient than using air, but it still has an exhaust stream containing co2, water etc making it too corrosive to commercially recover the exhaust heat.