Hydrogen as a motor fuel
Hydrogen can be used as a motor fuel, whereas neither nuclear nor solar energy can be used directly.Nuclear power requires heavy shielding to keep the neutrons away from people - too heavy for cars. It can be used in ships, and is used in American, British and Russian warships, especially submarines and aircraft carriers. The U.S. and Japan built commercial nuclear powered ships, one each (Savannah and Mutsu). (There were even proposals to use it in locomotives.) However, initial difficulties combined with anti-nuclear politics caused these projects to be abandoned and the ships mothballed. The Soviets built nuclear powered icebreakers, and these are in use. I think nuclear power will be revived for commercial ships when its political problems are overcome and the technology is further debugged.
Solar energy can't be used directly in cars except as a stunt. The current solar-powered cars are just religious exercises in the solar religion. The problem is that a solar array of a size that can be mounted on a car produces too little energy to give useful performance, and even that little isn't available at night or when it is very cloudy.
Hydrogen can be used as a fuel directly in an internal combustion engine not much different from the engines used with gasoline. The problem is that while hydrogen supplies three times the energy per pound of gasoline it has only one tenth the density when the hydrogen is in a liquid form and very much less when it is stored as a compressed gas. This means that hydrogen fuel tanks must be large.
Demonstrations of hydrogen powered vehicles have usually used compressed hydrogen gas. However, because of the low density, compressed hydrogen will not give a car as useful a range as gasoline. It may be even worse than using lead-acid batteries. Hydrogen can achieve a reasonable density adsorbed in metal hydrides, but then the weight of the metals makes the system very heavy.
The most practical way I know of using hydrogen as a motor fuel is to accept the difficulties of handling liquid hydrogen and solve them. There are three main problems.
- The low density. A hydrogen fuel tank will have three times the size of a gasoline tank. Also it must be insulated, and this will add to its bulk. This seems entirely bearable.
- Safety problems. Liquid hydrogen is cold enough to freeze air, and accidents have occured from pressure build-up following plugged valves. Some say these problems can't be overcome, but I side with those who think they can be overcome. In a collision the hydrogen tank may rupture, as can a gasoline tank. Limited accident experience suggests that the danger is somewhat less with hydrogen than with gasoline, because the hydrogen dissipates rapidly. The release of hydrogen into a confined space like a garage risks an explosion.
- Since the insulation can't be perfect, the hydrogen will gradually evaporate, typically 1.7 percent per day. This is too fast for a car to sit for months between uses. A tank of compressed hydrogen holding enough to get to a hydrogen station would solve this. If the engine is flexible enough to burn gasoline as well as hydrogen, a half gallon gasoline tank would suffice. Some automobile companies, e.g. BMW, have experimented with vehicles powered by liquid hydrogen. However, hydrogen cannot come into common use until the political obstacles to nuclear expansion are overcome or the technological obstacles to large scale solar energy are overcome. It is unlikely to be used as long as gasoline remains so cheap, i.e. as long as oil remains cheap and fear of global warming does not prevent its use. We hydrogen enthusiasts will just have to wait.
October 2000 note: The German automobile company BMW has just announced a car to be powered by liquid hydrogen and a plan to build a network of hydrogen refuelling stations in Germany. The car is named the 745 hdi and it is based on the BMW 745, a top-of-the-line model. A range of 350 km is promised. This is a bit small but may be tolerable. The car can also burn gasoline. BMW built a small fleet of these cars and has demonstrated them in various countries including the US, both in L.A. and Detroit.
Here's an article by BMW engineers. Oops, the link doesn't work directly as I have copied it, but the article and others can be found by Googling bmw+hydrogen.
2003 November note: Jay Keller of Sandia Laboratory presented Why hydrogen? - Building an infrastructure at the Stanford University Global Climate and Energy workshop on Hydrogen Production, Storage, and Utilization: Technical Barriers and Research Opportunities in 2003 April.
The large scale use of hydrogen for cars requires a very large investment in infrastructure. I suppose present gasoline stations can have hydrogen tanks and hydrogen pumps added, just as many gasoline stations also sell diesel fuel. Facilities for delivering hydrogen from the electrolysis plants to the users will be expensive. The transition to hydrogen will be triggered by one of two events. (1) The world will eventually run out of conventional motor fuel at reasonable prices. Opinions differ about when this will happen. Some pessimists predict a peak in world oil production in 2005. Other people think we won't run out in this century. I tend to the latter view considering that the oil sands in Alberta, Canada are being rapidly developed, produce oil profitably sellable at $12 per barrel and have resources greater than Saudi Arabia. (2) It may happen that increased CO2 causes real harm to the world and a crash program to stop emitting so much is required. There is not sufficient evidence of harm to convince governments to take drastic action in spite of the enthusiasm of the environmental community and its scientific supporters. [I can't take these proposals from these people seriously as long as they don't even mention nuclear energy. They are just playing with us.]
2003 September: A Republican draft of the energy bill includes $1.1 billion to build a nuclear reactor to produce hydrogen. That would be a big step in the right direction.
Energy and the hydrogen economy by Ulf Bossel and Baldur Eliasson analyzes the energy cost of a "hydrogen economy". The problem is that transporting energy as hydrogen uses much more energy than transporting it as oil or natural gas because of the low density of hydrogen, either as a liquid or as a compressed gas.
Bossel and Eliasson's rhetorical object seems partly to knock off the idea of a hydrogen economy in favor of their preferred methanol economy. However, they propose to get the carbon for their methanol economy from biomass. That would satisfy greenhouse objectives, whereas getting the carbon from coal would not. I'm doubtful about the biomass part, and they don't offer specific arguments for its feasibility.
New to me in their paper is the analysis of hydrogen transportation systems and their energy costs. The conclusion most interesting to me is that 2.12 times as much energy goes into generating and transporting liquid hydrogen by truck than you get into the fuel tank of the car. If their calculations are correct, the cost for the automobile user is regrettable but entirely bearable, because only a small part of the costs of operating a car are fuel costs.
An alternative to transporting liquid hydrogen long distances is to electrolyze water locally, perhaps in the fuel station itself.
Here's what Pimentel (1996, p. 211-212) has to say.In terms of energy contained, 9.5 kg of hydrogen is equivalent to 25kg of gasoline ( Peschka 1987). Storing 25 kg of gasoline requires a tank with a mass of 17 kg, whereas the storage of 9.5 kg of hydrogen requires 55kg, (Peschka 1987). Part of the reason for this difference is that the volume of hydrogen fuel is about 4 times greater for the same energy content of gasoline. Although the hydrogen storage vessel is large, hydrogen burns 1.33 times more efficiently than gasoline in automobiles ( Bockris and Wass 1988). In tests a BMW 745h liquid-hydrogen test vehicle with a 75 kg tank and the energy equivalent of 40 liters of gasoline had a cruising range in traffic of 400 km, or a fuel efficiency of 10 km per liter ( Winter 1986).
The references above are copied from Pimentel (1996, p. 211). I plan to look them up, and this may change what I say.At present, commercial hydrogen is more expensive than gasoline. Assuming $0.05 per kwh of electricity from a nuclear power plant during low demand, hydrogen would cost $0.09 per kwh ( Bockris and Wass 1988). This is the equivalent of $0.67 per liter of gasoline. Gasoline sells at the pump in the United States for about $0.30 per liter. However, estimates of the real cost of burning a liter of gasoline range from $1.06 to $1.32 when production, pollution, and other external costs are included (Worldwatch Institute 1989). Therefore, based on these calculations hydrogen fuel may eventually become competitive.
The above comparison between current costs of gasoline and hydrogen power for cars seems to be somewhat biased in favor of hydrogen. Taxes seem to be included in gasoline cost and not in hydrogen estimates, but roads will still have to be maintained when hydrogen is used as a fuel. Howover, I suspect the Worldwatch estimate of the "real cost" of burning a liter of gasoline is exaggerated.
For me the decisive point is that the costs of a automobile transportation system using hydrogen produced from water using nuclear energy are low enough so that people worldwide who use automobiles will not give up the freedom they provide, regardless of efforts to get people to settle for public transportation or low range and low performance cars of one kind or another. This doesn't say that adequate batteries won't be developed to make electric cars better than liquid-hydrogen internal combustion powered cars. Maybe they will, but we won't settle for less mobility than hydrogen can provide. See also my scheme for hydrogen powered Wankel engine cars. They are trying to get California to declare them zero emission with some prospect of success. However, if California chickens out of the zero emission demand (as it should and probably will), I'll bet the Mazda will not be offered for sale any time soon.
West Virginia University has a Hydrogen Review page. It mentions several ways of using hydrogen for motor vehicles. It would seem to me from their numbers that liquid hydrogen is the winner - as stated above. However, the page makes no comparisons at all.
The Department of Energy supports research on hydrogen. The value of this page seems to be somewhat limited. First, it only mentions what is currently being supported by DoE, and doesn't mention what other organizations are doing. Second, it is entirely politically correct as is apparent in the first paragraph. Nuclear energy isn't even mentioned as a possible source, not even to be dismissed. Nevertheless, there is useful information.
A check on the DoE site in 2002 February shows that there is still no mention of nuclear energy. The site still has the Clinton (or perhaps it's Gore) religion. During the California energy crisis Vice-President Cheney made a speech or two favoring nuclear energy, but the push evaporated when there turned out to be enough natural gas for the time being. I guess the Bush Administration has enough problems to occupy all its attention and has no energy left to make its Department of Energy stop ignoring a source of energy favored by the Administration. Of course, maybe it was just the Vice-President who favored it.
Some companies that supply hydrogen and related technology: Air Liquide(sells gases including hydrogen), Air Products and Chemicals, Inc., The BOC Group, Praxair. Air Products and Chemicals, Inc. has a page on a hydrogen fuel celled bus in Chicago that has a range of 250 miles - enough for a whole day. This may be good enough performance for cars.Let me reiterate that the point of this page is not to show that one particular way of powering automobiles is best but to show that there are enough ways of keeping individual mobility in the advanced countries and for the backward countries to achieve it. Cars powered by liquid hydrogen fueled internal combustion engines with the hydrogen produced by nuclear power plants electrolyzing water will suffice to preserve our mobility.
