I’ve seen/heard a number of stories about hydrogen-powered vehicles from GM or Honda, etc. In all cases, the companies are being lauded for their plans to bring clean burning ‘green’ vehicles to the market by 2010 that can free us of dependence on ‘foreign oil’.
Did I sleep through a major technological breakthrough that suddenly makes the production of hydrogen a net gain? I always thought that it took more energy to produce the hydrogen than the vehicle will extract?
Silly example: Do you have to put 1.21 jigowatts of power into producing the hydrogen, which will only generate .80 jigowatts of power?
Maybe if we used solar/hydro, nuke or wind power to produce the hydrogen, I could see the benefit, because it is hard to take those power sources and use them to power a vehicle. Some loss would occur, but it’s not like I am buring coal and oil to produce hydrogen.
What’s the straight dope on hydrogen-powered vehicles?
Also, who wants to chime in on the environmental effect man will be making by pumping a whole heap load of water vapor into the atmosphere? :eek:
Yes, hydrogen is a net loss. Hydrogen isn’t a source of energy, it is a method of storing energy created by other methods. It takes more energy to create the hydrogen than you get when you burn the hydrogen.
The advantage would be that you can generate hydrogen using “green” power, like hydro, solar, wind, or whatever, and when you burn hydrogen the only waste product is water. The environmental consequences of releasing that water vapor into the atmosphere are comparable to watering your lawn.
Also the distribution network can be much more efficient. If each “gas station” has water and electricity it can make and store the hydrogen on site rather then shipping it around on tanker cars.
Realistically, most hydrogen produced is going to come from coal. Whether this is a good thing or not depends on your goals. Powering vehicles with coal would increase the amount of greenhouse gas emissions, since coal is almost pure carbon, while gasoline and other oil products are largely hydrogen, so in that sense, coal is worse. On the other hand, we have centuries worth of coal right here in the US, so it would reduce dependence on foreign suppliers, and postpone the time when fuel starts running low, so in that sense, it’s better.
A number of hydrogen vehicles being promoted are fuel-cell-electric. I understand that a fuel-cell-electric vehicle would apparently be more efficient than an internal-combustion vehicle of comparable output power, no matter what the fuel. But I believe that there have been some internal-combustion vehicles that run on hydrogen.
#2: hydrogen as an energy-transfer and energy-storage medium.
Breaking water apart into hydrogen and oxygen, then recombining them beck into water, always involves a net loss: producing the hydrogen and moving it to the destination takes more energy in total than you get back from recombining it.
The system of fuel source, fuel transport, and fuel use in a vehicle can presumably be mode more efficient as a whole using hydrogen and fuel-cell-electric vehicles than by using oil and IC engine vehicles. Offsetting this is the fact that gasoline is much denser an energy-storage medium than hydrogen at room temperature.
So people are looking at the whole fuel/vehicle system rather than just vehicles by themselves.
Chronos, how is the hydrogen going to be produced from coal? Do you mean simply producing it from water using power from coal-fired power plants?
My understanding is that most hydrogen these days comes from methane in natural gas.
Presumably carbon would be a byproduct of this process, possibly as carbon dioxide. But getting pure carbon out of the process might be good, because then we could start filling the coal mines back in.
(Which has me wondering. Could we take methane from the atmosphere, strip the hydrogen from it, and stockpile that carbon as well?)
Straight electrolysis of water is a horrible waste of energy, and electricity is currently an expensive source of energy as it is, and “green” sources of electricity are even more expensive. If a “hydrogen economy” must be based on electrolysis, it will never happen.
Reforming natural gas, or alcohol (either ethanol, or methanol) is a more efficient way to generate hydrogen, and may be viable.
It’s possible, without violating physical law, to construct a hypothetical scenario where burning fossil hydrocarbons to generate the power to make hydrogen would be more efficient than just powering vehicles on the hydrocarbons directly - it would look something like this:
-Technology for hydrocarbon-fueled engines small enough to power a vehicle has developed so as to give us functional, but not very efficient devices
-Bulk conversion of hydrocarbons to energy at powerplant scale is sophisticated and efficient
-Hydrogen technology for vehicles is sophisticated and efficient.
In that scenario, it would make sense to burn the hydrocarbons to make the hydrogen, then run the vehicles on that. the hypothetical scenario just doesn’t closely resemble the way things actually worked out in reality, is all - it’s not impossible - it just didn’t happen that way.
It sounds like one piece of the overall system comparison isn’t being included; doesn’t it also cost a lot of energy to create and deliver a gallon of gasoline? I’m thinking of the whole process of getting oil out of the ground, transporting, refining, more transport and probably more steps…
I’m not plugging for hydrogen or any other alternative fuel. It’s just that every time I hear a discusssion starting with “Doesn’t it cost energy to make hydrogen?” I don’t hear a comparable analysis of the energy required to create gasoline.
