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LETTER TO THE BOOKSHELF

George Bush and the Hydrogen Car: A One-Act Play

Dramatis Personae
KC: Knowledgeable Citizen
CE: Chemical Engineer

KC: I see that President Bush has committed $1.2 billion to the development of a hydrogen car. What are the chances for success?

CE: We most certainly will be able to develop a vehicle that will operate on hydrogen. The real questions are these: Will anyone buy it? Will it help our current balance of payment problems, reduce air pollution, extend the limits on fossil fuels, soften political problems in the Middle East, and so forth? The manufacture, transport, and storage of hydrogen is very expensive.

KC: I thought that hydrogen was the most abundant element in the universe and that fuel cells (devices that turn hydrogen into electricity) were a mature technology.

CE: "Yes" on both counts. The trouble is that the hydrogen is locked in compounds like water and is difficult to separate. At the moment fuel cells are very expensive.

KC: So how do we get the hydrogen?

CE: We know a lot about this. About 10 million tons of hydrogen are manufactured each year in the United States. A typical plant will process 1.1 million cubic meters of natural gas per day and deliver about 2.8 million cubic meters of hydrogen.

KC: That sounds like a good deal: One gets you two.

CE: Not really. The energy in a cubic meter of hydrogen is about 10,000 Btu, whereas the energy in a cubic meter of natural gas is about 30,000 Btu. There is energy loss in the process. The overall efficiency is about 80 percent.

KC: Why would anyone build a plant that loses energy?

CE: Ah, but hydrogen is a very important chemical. It can increase the yield of gasoline from a barrel of crude oil and can be used to manufacture fertilizer, make detergents, and so on. Hydrogen is a feed stock for a great variety of chemical processes.

KC: Is there enough natural gas to feed all these chemical processes and, at the same time, provide hydrogen for the fuel cells to keep our cars on the road?

CE: We use a lot of natural gas: 24 quads per year. A quad is short for quadrillion Btu—that's fifteen zeros. It’s 24 trillion cubic feet or 700 billion cubic meters. Most of this natural gas is used for residential, commercial and industrial heating along with the generation of electricity. One quad in the 24 is used to make hydrogen, as I said before.

KC: I thought we would be discussing energy, but with numbers this large I feel like we are discussing the national debt.

CE: As soon as we start to talk about energy in the transportation sector, the numbers really get large. The transportation sector uses about 30 quads, almost all as gasoline or diesel oil. Let's assume that hydrogen in a fuel cell is so efficient that we can supply the future transportation sector not with the present 30 quads, but with only 10 quads. That will require 12 quads of natural gas. We already import considerable natural gas in the form of liquefied natural gas. Hydrogen from natural gas does not solve our dependence on foreign sources of energy, greenhouse gas emissions, or, in the long run, our dependence on fossil fuel.

KC: Are there other ways to make hydrogen?

CE: Yes. Electricity can break water down into hydrogen and oxygen. It takes about five kWh of electric energy to make one cubic meter of hydrogen. This is very expensive. Very little hydrogen is manufactured by electrolysis. About two units of electric energy are required to produce one unit of hydrogen energy. And it is worse than that. In the United States, most of our electricity is generated using coal. It takes three units of coal energy to produce one unit of electric energy; hence the coal-to-hydrogen ratio would be six to one. Not a good deal. But coal can generate hydrogen in a much more energy-efficient way. If coal is retorted with steam and oxygen, one ton of coal can produce 10,000 cubic meters of hydrogen. This is an energy ratio of about two-to-one: Two units of coal energy will produce one unit of hydrogen energy. But a lot of stuff comes out of the retort other than hydrogen. To make use of these byproducts and prevent pollution would be a major issue.

KC: Can nuclear energy play a role?

CE: Yes. The electricity needed to separate hydrogen from oxygen (water electrolysis) depends upon the water (steam) temperature. The nuclear reactor can do both—heat the steam to high temperature, then generate the electricity for the separation of hydrogen.

KC: But that which is technically feasible may not be politically possible. I have read books by Lester Brown and publications of the World Watch Institute that claim that hydrogen can be made from renewable energy—sun, wind and the like.

CE: Let's look. The best wind machines in the very best locations can produce about 1,000 kWh per year for each square meter of wind disc. The largest machines, with blades that are 370 feet in diameter and a disc area of 10,000 square meters, can generate about 10 million kWh per year. If the conversion from electric energy to hydrogen is 100 percent efficient, 300,000 of these incredibly large wind machines would be required to generate the electricity needed to supply the ten quads of hydrogen energy. But it is worse than that. Good wind resources are not found in areas with large populations and high energy use. The pipelines, compressors, storage and so forth that would be required boggles the mind.

KC: What about biomass?

CE: Sure. A small (20 megawatt) electric plant will consume 700 tons of biomass per day. Biomass can be retorted to generate hydrogen in much the same way coal is retorted. But the logistics of material handling is foreboding.

KC: What you say is most discouraging. But I understand that Iceland is dedicated to a hydrogen transportation system.

CE: That's right. Their population is small (about the size of Albany, New York) and they do not have a large transportation sector. They do have much excess hydropower. They will use that excess hydropower to drive the electrolysis of water.

KC: What are we going to do? Things look grim.

CE: I agree. But this is a complicated business with many options. There are two documents that cover our energy posture in great detail: World Energy Assessment United Nation Development Programme. (This has 500 pages, 100 authors—a document that leaves no option unturned.) A document of similar size, On the Road in 2020, was published by the Energy Lab at MIT. In neither case is there a proposed "breakthrough" technology.

KC: I am sorry I brought up the subject.

Richard C. Hill
Old Town, Maine

 

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