I get the increased efficiency but what about the ease of turning braking and/or downhill travel back into useable energy? Doesn' t seem like the increased efficiency would be worth it if that is lost (particularly for city driving).
Quoting: "Fuels containing hydrogen are hydrocarbon based. The resulting amount of carbon freed from the H2 bonds would be identical to that released in an ICE engine."
The amount of CO2 released only makes sense as it compares with the amount of engine horsepower created by a given volume of fuel. An engine that's twice as efficient as the one you're comparing it to will produce half as much volume of CO2 as the less efficient engine.
The other piece of the puzzle is the car's efficiency, leaving aside the engine's efficiency. A heavy car requires more energy to get to speed than a light car does. True, with electric cars you get some of that energy back when braking. And an aerodynamic car requires less power to maintain any given speed than a blocky car. Much less.
For instance, an efficiently designed car only needs around 12 to 14 HP to maintain a steady 50 mph. A pig like an SUV or full size truck easily needs twice that, if not more than twice. And that waste increases as speed increases, which is why the top speed of SUVs and trucks is so pathetic, compared to that of cars with far smaller engines.
>>I put my hopes on separating the H2 from a fuel, stored in the car, in a regular fuel tank. The entire process should easily be twice as efficient as internal combustion engines are, and more efficient than that at low power levels, such as city driving. So that's how you cut the CO2 emissions.<< Fuels containing hydrogen are hydrocarbon based. The resulting amount of carbon freed from the H2 bonds would be identical to that released in an ICE engine...and a distributued large scale carbon sequester technology does not currently exist. Waaay back in the 70's I worked on a university research program to employ liberated hydrogen in powering vehicles with H2 from a variety of sources CH4, H20, diesel, turns-out that this is really difficult to without either encountering a net energy loss or creating pollution in the process.
The URL says it all. The basic point being, creating electricity out of solar power, in large scale, comes at a price. For one, worn out solar panels create toxic waste. Extracting natural gas comes at a price. Nuclear comes at a price. Spent batteries themselves create pollution. So the main point is, CO2 emissions alone is just one small piece of the puzzle.
Here are the numbers on efficiency. Reformer efficieny varies, depending on the fuel the H2 is extracted from. Reformers which use natural gas as fuel are about 80 percent efficient.
Fuel cell cars which run on pure H2, when you take into account the fuel cell efficiency and the efficiency of electric motors, are roughly 65 perecent efficient or so. Although fuel cells are less efficient at their highest output. Still, something over 60 percent overall is the figure.
So the entire process is right about 50 percent efficiency. Could be somewhat less than that at max power output, however, althoug of course max power diving is something we don;t often do.
Compare this with the practical efficiency of ICE cars, which runs anywhere from 18 percent to a theoretical best of about 30 percent, where 30 percent is only at very high power levels.
Junko, I too am puzzled why the trade press only covers battery electrics. Their range claims are usually way optimistic, their "refueling" times are way too long for practical general purpose use, the rate of technolgical improvement is slow as molasses, they weigh a huge amount, battery swap technology is impractical to say the least, requiring a whole lot more machinery than pumping gas.
It usually pays to look for the most elegant solution, when trying to decipher what the future brings.
I think the auto industry is doing it's best to hedge its bets.As with other things, it's ultimately about money.
The industry has been steadily consolidating to get economies of scale and cut costs. The problem is that fuel cell vehicles require expensive R&D. Where does the money come from? And once you have the production challenges resolved, what will such cars cost to build, and what will you have to charge for them?
The issues I recall seeing back when were just how you safely stored the hydroge you were going to use as fuel, and that's still an open question.
One thing I expect to see in the US, at least, is more use of natural gas rather than gasoline. NYC already has natural gas powered busses in the MTA'a fleet, and I'd be surprised if the progam wasn't expanded, because the US has plentiful supplies of natural gas.
Like anything else, the form of energy used will be the cheapest available. Until economic factors make EVs and hydrogen powered vehicles cost competitive to buy and run with fossil fueled cars, I expect conventional fossil fueled vehicles to be with us for a while yet.
"From coal-fired electric plants, they pollute at least as much as ICE cars."
Well, at least in California, we get very little of our power from coal plants (and it is rapidly approaching zero). More than half of our power comes from natural gas.
We could burn natural gas to generate energy to create hydrogen, then burn the hydrogen in our cars. Or we could just burn natural gas in the car directly. Why aren't these car companies pushing natural gas cars? We already have the delivery infrastructure--natural gas is piped all over the state. Most people use it for heating.
As for hydrogen fuel cell cars, the Honda FCX Clarity has been available for lease in the US for years. I think there are about 50 in the US. So it clearly has been a small-scale experiment. Has the economics really changed so much so all these car companies think it will now take off? It makes me wonder if there's something else they know that they aren't telling us--like some new lower-power way to create hydrogen.
reading through all comments, I agree that the technology is still in its infancy comparing to gas powered cars, however, I belive that's the way of teh future as both gas and electricity are coming from fossil fuels and they will end sooner or later, however, 2/3 of our earth is still water which hopefully one day could be used as a source to generate cheap Hydrogen.
I personally belive that auto industry is not too eager to switch from gasolin engines to other sources simply becuse its a proven technology with a vast support network built over 100 years, and it's teh most profitable type of car they can make today.
however, I am glad to see that they are willing to invest in other type of technologies such as EV and Fuel Cell, so when the time comes they are ready.