Quote:
Originally Posted by diablo2112
This idea is perhaps the single stupidest piece of automotive engineering I've read about from a major auto company in 40 years.
Hydrogen is fine. It's a clean power source. We'll eventually figure out production, distribution, and on-vehicle storage options for it. That's not the problem.
The problem is burning hydrogen in an ICE. This is monumentally stupid. ICE technology is the production of useful, mechanical work by use of a heat cycle. More than 150 years ago, Victorian-era engineers figured out the efficiency of heat cycles. The best you can do - ever - is called the Carnot Efficiency. And amazingly, this depends only on temperatures. The hottest you can get your engine, and the coldness to which you expel heat. You're never going to get an ICE to exceed about 40% efficiency because of this, given limitations on materials and achievable temperatures.
So what's the alternative? Extraction of the energy in H-H bonds via electrochemical cells. This isn't new. It's been done for 100 years as well. It's the way nearly every manned spacecraft is powered, including the Apollo missions and the Space shuttle. Hydrogen is the perfect input to these "fuel cells". You avoid a heat cycle completely, and the strangling aspects of the Carnot efficiency. The amount of useful, electrical power you can pull from a fuel cell is well over 90% of the energy available in the hydrogen fuel. And the only emission is water. Water clean enough to drink; this is how water is made during space missions.
Fuel cells are so attractive for automotive use, that the only real issue is fueling them. You can burn carbon-containing fuels in a fuel cell, but the presence of that carbon leads to reaction products (carbonates) that clog the delicate membranes in these cells, quickly rendering them inoperative. The engineer that solves that particular materials problem will become the richest man on earth, btw.
For now, we're stuck with burning hydrogen in fuel cells. The limiting problem deploying this on vehicles is getting enough hydrogen onboard to be useful. Some groups have been working on "onboard reforming" technology that would convert gasoline (stored on the vehicle) into hydrogen with a small, onboard chemical reactor. This has the advantage of using existing infrastructure for fuel.
The other option is to store the hydrogen directly as either a high pressure gas, liquified, or (probably the best option) as a metal hydride, which releases hydogen upon heating. Uranium works great here, but it's heavy. The weight of a uranium hydride bed with useful quantities of hydrogen storage exceeds the mass of long-range Lithium battery packs. And it's violently pyrophoric, another slight problem for vehicle use...
Anyway, Toyota's decision to produce a hydrogen-burning ICE is just catastrophically, insanely bad engineering. Hydrogen is great. It's so great, that we should develop an infrastructure for it. The reason it's great is that when used with fuel cells, it solves most of the problems of batteries and EVs, and avoids the terrible efficiency penalty from using heat engines. Burning that hydrogen in an ICE as opposed to a fuel cell really is that monumentally dumb.
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Agree with all you said, but BMW built the Hydrogen 7 about 15 years ago. Seems most the the Bimmerheads here forgot?
The idea of on-board gasoline-to-hydrogen conversion is the correct path except some don't like carbon in the conversion process.