« on: 06/02/2022 14:38:51 »
Going back a few posts, I note that hydrogen has been declared by an expert consensus uneconomic and unfeasible for domestic heating and urban transport. Precisely the uses for which it was put in every city 200 years ago, and currently in Orkney, respectively.
The right economic comparison is between making heat by burning hydrogen generated by electrolysis using carbon-free electricity, and using the electricity directly to make heat. From a systems cost point of view, hydrogen loses in this comparison. First, electrolysis is at best about 75% efficient in capturing the energy content of electricity. So you need a lot more green electricity sources to make up for that loss. Second, you need an essentially duplicative energy distribution grid to get the hydrogen to where the heat is needed. The cost of that network raises again the cost of hydrogen relative to electricity. Finally, hydrogen is substantially less efficient as a source of heat in a home or building. A hydrogen fueled furnace is at best about 95% efficient in delivering the energy content of its fuel as heat; in all but the coldest climates, an electrically driven air-source heat pump can easily deliver 300% annualized efficiency (and in climates where there is any demand for summer cooling, the equipment for heating and cooling are essentially the same, so there is additional advantage there).
Over all, hydrogen from electrolysis loses the economic equation horribly as a domestic heat source.
Fixed distance between termini means that you can start with just one or two refueling points, say London and Birmingham, with minimal environmental impact and speeds of 200+ mph. Hydrogen power offers a compromise between the fuel weight of a diesel generator and the cost and engineering limitations of overhead power lines.
I agree on the value of high speed intercity trains. Far superior to air travel for most, and maybe all travel on the island of Britain and in most of Europe. When you figure in the ability of trains to move people city-center to city-center, I think the advantage is there for distances well over 200 miles. I have no opinion on air-levitated trains, although the idea makes sense. But trains, of all forms of transportation, most readily lend themselves to battery-electricity power. Refueling is a matter of switching discharged battery trucks off the train, and full charged ones on, or for that matter, if you're building an air levitated system, building induction recharging coils into select track runs. (In other words, I think the need for friction-contact overhead electrical lines is soon to pass). The mass disadvantage of batteries for transport that you've assiduously plugged here simply are not present in "rail" based transport options.
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