Found this....

http://www.hindawi.com/journals/ijce/2012/512803/

You type like you have a horse in the race....

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Perhaps more useful than imagining would be analysis/comparison?

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Comparing power density of various technologies might not be a bad place to start.

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I'm also curious about your '...something other than methane...' comment. What characteristic of methane leads you to recommend against it specifically?

If your imagined electric car was running today, what percentage of the electricity used to charge the batteries would come from coal? How do the emissions from that amount of coal compare to converting methane to hydrogen?

I don't think methane is being recommended against, it is being suggested that a different energy source would be more desirable since methane is a valuable fuel. Hydrogen as a fuel suffers from the need to produce the hydrogen (we can't pump it out of the ground like methane).

You type like you have a horse in the race....

I'm "imagining" a Nissan LEAF, which I don't own, but have driven. (Although, yes, I do have a different horse in the race, but try to refrain from advertising it here.) The LEAF works extremely well, and costs no more (even without subsidies) than a typical near-luxury car. (Fuel cell vehicles are a long way from dropping out of the $1,000,000-per-copy science fair project category.) Unlike fuel cell vehicles, there are thousands already on the road, and many are being charged by solar power.

Comparing power density of various technologies might not be a bad place to start

Gasoline and diesel are hard to beat in both power density and energy density, although the Tesla roadster demonstrates that a 250 hp electric motor can be much smaller and lighter than a comparable gas engine. Energy density in the Tesla is "workable" with the entire car being light enough to be fast and fun to drive, despite its 900 lb battery.

Fuel cell technology is awful in terms of power density, so fuel cell cars also carry batteries to enable high power bursts. Energy density is better than with a battery-only electric car, but far worse than a gasoline or diesel car.

I'm also curious about your '...something other than methane...' comment. What characteristic of methane leads you to recommend against it specifically?

Methane is already a good fuel, although it requires more costly and heavier tanks to store it in a vehicle than gasoline does. It can offer the same convenience that an electric car does -- you can buy a home filling station to fill up from the same line that feeds your furnace. So starting with a good fuel, and then adding energy to change it into hydrogen (a very hard-to-manage and costly fuel) does not make a lot of sense to me: just burn the methane. (Imagine trying to convince a homeowner that he should buy a methane-to-hydrogen reformer so that he could heat his house with hydrogen.) Reforming methane gives off CO2, so there is no advantage to commercial hydrogen in that respect. Hydrogen from electrolysis, with solar cells powering the process is cleaner, but so far, too costly to be competitive with methane reforming.

If your imagined electric car was running today, what percentage of the electricity used to charge the batteries would come from coal? How do the emissions from that amount of coal compare to converting methane to hydrogen?

The EPA fuel mileage site shows the carbon footprint for charging a LEAF in any zipcode. In New Hampshire, a LEAF is amazingly clean. In North Dakota, pretty poor, although even there, it's better than the carbon-per-mile of a typical small car (but slightly worse than a Prius). In the average state, the LEAF is better than any small car, including the Prius.

I don't have the GREET figures in front of me, but on a well-to-"tank" basis, I think that the "hydrogen from methane/compressing/freezing/transporting/fuel cell car" route is in the same ball park (in energy required and carbon emissions) as the average for creating electricity. The electric car then has an efficiency advantage in going from battery to wheels, vs hydrogen-through-fuel-cell-to-electricity-to-wheels.

About 5% of hydrogen is created by electrolysis. This is about as bad an environmental deal as you can imagine, if you assume that the electricity comes from the grid, which is 38% efficient on average, from all sources.

If hydrogen were easy to store, and if you could fit an amount of energy equal to a gas tank's worth, and if fuel cells were more efficient, and if batteries were not required, etc. etc., then hydrogen could become a viable fuel. Even if it existed in nature in free form, it would still be a tough sell, just as natural gas has been for powering cars. At least with natural gas, compression alone yields enough energy density to make tankage close to reasonable. But when liquification is required (meaning that the stuff boils off -- the BMW hydrogen car looses 50% of its fuel in 9 days) the whole process starts to look unattractive.

If one could dig a hole and get hydrogen out of the ground as a liquid (as we can with oil) then the story would be much different.

Thank you for clarifying. There isn't much I don't agree with in your well reasoned response. You are spot on, in your summary of power densities and maturity of various technologies.

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Hydrogen as you note has severe disadvantages both in the energy necessary to obtain it from whatever is being used as feedstock as well as in the difficulty of storing it. One area that hydrogen may yet prove useful in powering transportation is in making use of exhaust waste heat for steam reformation of methane. But this is just a small portion of fuel used in those vehicles alone. It is unlikely to experience significant use on the roads anytime soon.

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Albeit all the agreement, I believe a better near term focus would be building new cars and converting existing cars to run on methane/propane/natural gas, rather than focusing on new electric cars. Here are a few reasons I'd like to bring up for your consideration....

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- The electric grid has already experiencing capacity problems. If electric vehicles catch on quickly, the additional load to recharge the vehicles might present severe problems.

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- To meet the added demand from electric vehicles, more power must be produced. A significant part of the increased production is likely to come from coal fired power plants. I'm not so worried about the CO2.

The fact that worries me is that every year the average 1000MW coal fired plant releases around 12 tons of thorium, around 7 tons of uranium, along with massive amounts of lead, mercury, cadmium and other known toxins into the environment; much of it as fly ash.

Those contaminants are either not found or are at extremely low levels in things like gasoline, methane, propane, and natural gas.

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- Methane/propane/natural gas off the possibility of not only improvements in new vehicles, but also improvements by converting existing vehicles.

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- The metals used in batteries for electric vehicles present a significant future hazard.

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I don't want to give the impression I am against using wall power for vehicles. In fact I have converted my own car to what you might call a 'mild plug in hybrid'. Basically, I relieve the engine of around 15% to 20% of the load typically imposed by the alternator by carrying three large marine batteries which i recharge from wall power. I lack any regenerative braking, but along with a number of other modifications, I achieved by best ever tank mileage 733 miles on a little less than 12 gallons.

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Generating electricity on board via an alternator can be horribly inefficient. At around 12 cents per Kw-hr, wall power is far less expensive, even using very conservative estimates for the efficiency of the charger, battery charging and discharging, and added weight of the batteries. So it might make sense for many vehicles to convert to mild plug in hybrids, even without regenerative braking. While I still have concerns with the resulting increase in coal use, the amount of electricity needed is far less than a 100% electric vehicle.

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Thanks again for the thoughtful response.