Re:How green is blue hydrogen?
by FabHK on Thursday August 12, 2021 @07:16PM
(#28162940)
Yes, also given that electric motors have an efficiency of 90%+ (or thereabouts) and internal combustion engines only of 20-30% IIRC.
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You're comparing apples and oranges. The around 40% efficiency modern ICEs have is thermal. The 90%+ going from battery to electric motor is not thermal. You're just converting high-exergy to high-exergy (kinetic) at that point. The interesting, potentially low-efficiency part happens before the battery, before charging it in the first place. Where does the electricity for that come from, at what efficiency? Perhaps there's a thermal engine involved, at said 40% thermal efficiency. Then you're at 0.4*0.9 total, and the EV looks pretty dull suddenly. (Just an extreme counter-example)
Your comparison reminds me of advertising for electric water kettles. 95%!! 97%!! Wow!! ... or not, because you're converting pure exergy (highest quality energy) in the form of electricity to heat. You're dissipating it (heat), using a resistor. That's child play and the efficiency is meaningless. The other way around is the interesting part.
Modern ICE are hitting 40%.
I don't know why you are being downvoted. You are correct, and some ICEs (large, maritime) are hitting 50% even. For a thermal engine, that's incredibly good (it's not about the gap to 100%, but the gap to Carnot efficiency).
There's a strong contingent here on HN that believes tha continued used of ICEs equates to the imminent death of the human race.
It's also a likely wealthy contingent that imports all of its food, flies everywhere, etc.
On what grounds do you draw that connection?
Previous threads, comments & votes.
Re:How green is blue hydrogen?
by AtlasBarfed on Friday August 13, 2021 @11:07AM
(#28169807)
... except the cost of the ICE drivetrain, certainly to hit 40% (that takes turbos and other complexities to the basic ICE, correct?) is about to lose to the cost of the EV drivetrain. It's basically at price parity based on what I see out of Tesla and what Lucid/Rivian/VW/GM are targeting. In three years? Less.
And a decade from now? EVs will probably be half the cost of an ICE.
Because of battery energy density, EVs still only work within a certain size&weight range.
ICE work in a much broader range of applications and at wider temperature extremes. They aren't going away.