H2, or not H2: That is the question

[unixronin]

radarrider found this article on hydrogen-fueled cars, which led me to the following response:

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I hate the common misrepresentation of hydrogen as an "clean, non-polluting energy source".  It isn't.

Sure, it burns cleanly, producing nothing but water vapor when burned in pure oxygen.  But it's not an energy source, it's an energy storage medium, and not a highly efficient one -- it takes around 20% more energy overall to produce hydrogen than you get back by burning that same hydrogen even in a fuel cell, let alone an internal-combustion engine.  Neither is it non-polluting; it merely relocates the pollution to the generation site of the power you use to produce the hydrogen.  It sweeps it under the rug, so to speak, and then you hope no-one notices and wonders why that particular patch of the rug is sorta lumpy.  And storage is a major headache; either you need a pressurized tank refrigerated to cryogenic temperatures to keep your hydrogen liquid, or you need a metal-hydride absorbtion tank that requires a heater to release the hydrogen.  Either way, still more energy loss.  (Room-temperature storage of pressurized hydrogen gas, to the best of my knowledge, has been written off as infeasible; I saw an analysis of a proposed bus fuelled by gaseous hydrogen, and the analysis pointed out that to give the bus sufficient range to make it commercially operable, it'd have to have a hydrogen tank as big as the bus.)

To get an idea of the realism of this idea, you need look no further than the numbers.  "It is time for the people to make a move, the vehicles they say they want to run on hydrogen are available now," says Tai Robinson.  Yeah, sure.  How many of "the people" can afford to spend $150,000 on their next vehicle?  Especially when they can then, to all practical purposes, only drive that vehicle in California -- and be restricted to a few California cities at that, and pay up to $20 per kilo of fuel for the privilege?  Come on, guys, you CANNOT be serious.  No-one's going to be taking that two-week camping vacation in the Sierras driving a vehicle with an unrefuelled range of 80 miles.

Sooner or later, we have to move away from the IC engine.  That's pretty much a given.  Unfortunately, we don't have a better solution yet.  In the meantime, there's a lot that can be done to reduce pollution and fuel use.  Stratified-charge engines, for instance; or direct-injection turbodiesels, which are increasingly popular in Europe but have never made a big impression on the US market because -- frankly -- Detroit can't build a decent diesel engine to save its life.  No, not even Cummins.  You want to learn how to build automotive diesels, ask, say, Mercedes-Benz.  Diesel exhaust can be cleaned, too, if you have low-sulfur fuel.  Europe has it.  US oil companies complain about the refining cost.

My guess is that in the longer term, we'll actually be moving to electric vehicles, and they'll probably be powered by fuel cells.  But the fuel cells probably won't be burning hydrogen.  Sure, hydrogen is sexy, hydrogen is modern, hydrogen is so 21st-century .... it's also a bastard to work with.  However, with a suitable reformer, you can just as well run a fuel cell on methanol or ethanol, both of which can be refined cheaply and easily from vegetable sources as biofuels, and both of which are much easier to store than hydrogen.  You can even modify an IC engine to run on ethanol or methanol in the meantime -- and you can push compression ratios to the stratosphere, because alcohol-fueled IC engines don't suffer from detonation like gasoline-fueled ones do.  Drag racers burning pure nitromethane run compression ratios as high as 20:1 -- that's diesel territory.  Bio-alcohols are renewable, and they aren't net producers of greenhouse gases because what you produce burning one batch, you consume again growing the feedstock for the next batch.

The unfortunate truth of most of this, though, is that ultimately what you can buy in the showroom is not driven by what's the best technology available, nor by what does least harm to the environment, but by what makes the most money in Houston and Detroit.  This will not change significantly as long as our government is in the pocket of industry, and specifically the oil companies.

Comments

[unixronin.livejournal.com]

Well, there are several drawbacks to the IC engine. For one, there's definite limits to the thermodynamic efficiency it's possible to attain with one, plus the higher the operating temperature (and the more efficient the engine), the more nitrogen oxides are produced. (Historically, this was the rationale behind Detroit using exhaust gas recirculation to lower cylinder temperatures, which has to be one of the more stupid engine-design ideas ANYONE has ever come up with.) As long as you're going to burn organic fuel to power a Carnot engine, one of the most efficient (and least polluting) ways to do it is actually a Stirling-cycle engine, but so far we have yet to figure out a way to produce a Stirling engine for vehicle applications that Westerners raised on internal-combustion engines will accept. Another option that is capable of offering very high efficiency would be a high-temperature ceramic turbine, but despite several efforts, there has again yet to be a commercially-viable model developed.

I'm not sure that high-temperature-depolymerized fuel is going to be enough cleaner to make a big difference in this regard; the main arguments in favor of it are (1) it's renewable, (2) it'll let us turn landfills into usable resources, (3) it can make the US energy-independent.

If we can achieve a move to fuel cells, especially powering room-temperature superconducting motors, that's going to make a huge difference to both energy expenditures and pollution. A fuel cell/superconducting motor combo has the potential to be on the order of twice as efficient, iirc, as any possible IC engine, and can be made to all practical purposes entirely non-polluting.

[technoshaman.livejournal.com]

Here's a silly question: What ARE we going to do with all those turkey guts, if we don't make'em into clean fuel? Efficiency is fine, but sometimes there's a point where we need to leave well enough alone. See also farming efficiency... (I'll spare the rant unless the remark prompts a double-take...)

And you've also go the question of what do you do with the 40 years' worth of IC-engined cars you've got running around. Now, if you can come up with a fuel suitable for both IC and fuel cells, I think you've got a winner, but we can't just flip overnight....

The flip side of that is that the turkey guts gas is by its nature a "designer" fuel; we can pretty much tune it to suit our needs.

Hey, this is kinda crazy: Reckon how small one of those HTDF factories can be made? and how cheaply? I know a biodiesel plant can fit in the corner of your garage, and can be kit-built for a couple hundred... if one could put one of these in every town, say, next to the landfill... can you say, transportation cost savings? You'll have to retrain folks a bit to use separate bins for organic and non-organic waste, but the whole recycling thingy already has the groundwork laid, and composters know this too...

Meh. It's not like either of us is enough of a ChemE to figure all this out... but 'tis fun to think about anyway, kinda like a warp drive :)

[unixronin.livejournal.com]

Here's a silly question: What ARE we going to do with all those turkey guts, if we don't make'em into clean fuel?

On, absolutely. Not questioning that for a second. Even if we could go over to fuel-cell cars overnight, we should still be going with the HTDF process, not only for all the applications we can't use fuel cells for, but to turn all that crap in landfills to productive use and to stop our dependence on Middle East oil.

HTDF plant in every town? Absolutely. The oil companies, of course, will hate it. Tough. They've had their hands around our throats for long enough. They had plenty of opportunity to sponsor research into things like this themselves against the day when the oil runs out, and instead the guys at the top of the pile just sat back and said, "I'll be dead by then, it's not my problem. I want my money, and I want it now." Fuck'em.

As for fuel cells, I'm sure it's possible to come up with a reformer to get hydrogen out of turkey-guts oil. Or as an intermediate measure until fuel cells become practical, crack the oil right down to, say, propane and run IC engines on liquified propane. It's still an alkane, sure, but the smaller the alkanes, the cleaner they burn. Chrysler's already shown off a 400HP LPG-powered V8 for their Charger R/T concept car of 2002 (which, I understand, they have finally decided once and for all not to build, although they haven't offered any explanation as to why).

[technoshaman.livejournal.com]

Right spot on...

one wonders if one wouldn't get a whiff of Vast Olgarchical Conspiracy Theory if one got too close to where they locked up the LPG-powered Hemi...

[unixronin.livejournal.com]

Oh, it was only the show car that was LPG powered. They said that the LPG V8 "probably" would not see production. All the same, it served to illustrate that it was perfectly feasible to produce an LPG powertrain with high power output and package it into a passenger car that people would want to buy.

(I still don't really understand why they decided not to build it in the end. It would have given DaimlerChrysler a domestic sporty sedan that could compete on even ground with the Mustang while having room to tote four or five adults around in LHS-like comfort, and they'd probably have been able to sell gobs of them to police departments. My best guess is that they figured they'd take a bath under CAFE standards.)