Re:Water Out of the Tailpipe: A New Class of Electric Car Ga...
by dredmorbius on Sunday July 24, 2016 @03:39AM
(#12152628)
The two Achilles heels of fuel-cell automobiles have been the cost of the fuel cell itself, and sourcing the hydrogen needed to fuel it.
Fuel cells typically use a lot of highly-expensive catalyst, with full costs on the order of a million dollars each. Odds are good the sales price of these vehicles (just under $60k) represents a small fraction of the manufactuer's actual costs. This is a test pilot for real-world experience.
Hydrogen is the other problem, both in sourcing it and in distributing and dispensing it. Hydrogen is an energy carrier, not an energy source[1], but an energy carrier. You need some other source of energy to provide hydrogen, usually via hydrolysis, or from some hydrogen feedstock, usually natural gas.
In the case of hydrolysis, your problem is the energy cost of electrolysis, which costs you about 40% of the input energy. The bad news is you get much less hydrogen energy out than electrical energy in, the good news is that you can store the hydrogen, while electricity doesn't bank well.
In the case of natural gas, you've got the sitation that your vehicle is still ultimately consuming fossil fuels, though methane (CH4) emits far less CO2 than petrol (about a C8H18) -- roughly half as much. Since you're pre-processing the methane into hydrogen, there's the option of sequestering the carbon for other uses.
Hydrogen also has extensive problems with storage and handling -- it doesn't like to be contained, will literally leak out between the atoms of containers, embrittles metals, etc., etc.
Another alternative, one I'm interested in, though 50 years of serious research[2] has yet to result in a working large-scale prototype, is Fischer-Tropsch fuel synthesis. Effectively it creates hydrocarbon fuels using electricity. The most promising model I'm aware of sources both hydrogen and carbon from seawater, hence seawater-based Fischer-Tropsch fuel synthesis. Penciling out the studies I'm aware of, it actually could scale up to current US and forseable global levels of production, without literally paving the world with solar panels and/or synthesis plants[3]. E.g., not patentently impossible. The fact that the research hasn't proceeded further makes me question its ultimate practicality.
If, however, it is possible, then we end up with a fuel that is an exact chemical analog of existing hydrocarbon fuels, is infinitely miscable with them in the fuel processing, dispensing, and utilisation chain, and is carbon neutral.
And if you're generating hydrogen, you're already about 90% of the way to creating synthetic hydrocarbon fuels which avoid most or all of hydrogen's storage, transport, dispensing, handling, embrittlement, and energy conversion issues.
As I mentioned, I've looked into this in several posts, you might want to start with the historical overview here:
1. Technically, so are petroleum, coal, and natural gas. Though the source energy was supplied hundreds of millions of years ago, on average, in the form of sunlight converted to plant matter. Given this, at the rate of roughly 5 million years of ancient primary production per year of current consumption, you could make a reasonable argument that the fully realised solar energy cost (what's called "emergy") of petroleum is about 5 million per single unit of energy delivered. At the very least, we're spending 5 million years of accumulation per year. Something you might want to reflect on.
2. Brookhaven National Lab, M.I.T., and the US Naval Research Lab. Generally serious outfits.
3. For a counterexample, see schemes for biofuels. At best, present US fuel consumption would require plausibility-stretching levels of development, if not quite literally multiples of total US landmass. E.g., quite patently and evidently batshit impossible.
Fuel cells typically use a lot of highly-expensive catalyst, with full costs on the order of a million dollars each. Odds are good the sales price of these vehicles (just under $60k) represents a small fraction of the manufactuer's actual costs. This is a test pilot for real-world experience.
Hydrogen is the other problem, both in sourcing it and in distributing and dispensing it. Hydrogen is an energy carrier, not an energy source[1], but an energy carrier. You need some other source of energy to provide hydrogen, usually via hydrolysis, or from some hydrogen feedstock, usually natural gas.
In the case of hydrolysis, your problem is the energy cost of electrolysis, which costs you about 40% of the input energy. The bad news is you get much less hydrogen energy out than electrical energy in, the good news is that you can store the hydrogen, while electricity doesn't bank well.
In the case of natural gas, you've got the sitation that your vehicle is still ultimately consuming fossil fuels, though methane (CH4) emits far less CO2 than petrol (about a C8H18) -- roughly half as much. Since you're pre-processing the methane into hydrogen, there's the option of sequestering the carbon for other uses.
Hydrogen also has extensive problems with storage and handling -- it doesn't like to be contained, will literally leak out between the atoms of containers, embrittles metals, etc., etc.
Another alternative, one I'm interested in, though 50 years of serious research[2] has yet to result in a working large-scale prototype, is Fischer-Tropsch fuel synthesis. Effectively it creates hydrocarbon fuels using electricity. The most promising model I'm aware of sources both hydrogen and carbon from seawater, hence seawater-based Fischer-Tropsch fuel synthesis. Penciling out the studies I'm aware of, it actually could scale up to current US and forseable global levels of production, without literally paving the world with solar panels and/or synthesis plants[3]. E.g., not patentently impossible. The fact that the research hasn't proceeded further makes me question its ultimate practicality.
If, however, it is possible, then we end up with a fuel that is an exact chemical analog of existing hydrocarbon fuels, is infinitely miscable with them in the fuel processing, dispensing, and utilisation chain, and is carbon neutral.
And if you're generating hydrogen, you're already about 90% of the way to creating synthetic hydrocarbon fuels which avoid most or all of hydrogen's storage, transport, dispensing, handling, embrittlement, and energy conversion issues.
As I mentioned, I've looked into this in several posts, you might want to start with the historical overview here:
https://www.reddit.com/r/dredmorbius/comments/28nqoz/electri...
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Notes:
1. Technically, so are petroleum, coal, and natural gas. Though the source energy was supplied hundreds of millions of years ago, on average, in the form of sunlight converted to plant matter. Given this, at the rate of roughly 5 million years of ancient primary production per year of current consumption, you could make a reasonable argument that the fully realised solar energy cost (what's called "emergy") of petroleum is about 5 million per single unit of energy delivered. At the very least, we're spending 5 million years of accumulation per year. Something you might want to reflect on.
2. Brookhaven National Lab, M.I.T., and the US Naval Research Lab. Generally serious outfits.
3. For a counterexample, see schemes for biofuels. At best, present US fuel consumption would require plausibility-stretching levels of development, if not quite literally multiples of total US landmass. E.g., quite patently and evidently batshit impossible.