Monday, November 29, 2004

Hydrogen Production Method Could Bolster Fuel Supplies

You hear a lot of talk about the "hydrogen economy". I think this is misleading and many people are under the impression that instead of drilling for oil, we just drill for hydrogen. But you don't just collect hydrogren, you have to produce it from some other energy source. Hydrogen should be thought of as a battery, a way to transport and store energy. And how is hydrogen as a store of energy?

Experts cite three big roadblocks to a hydrogen economy: manufacturing hydrogen cleanly and at low cost, finding a way to ship it and store it on the vehicles that use it, and reducing the astronomical price of fuel cells.
Pretty crappy. So instead of thinking of the "hydrogen economy" we should be thinking of the "renewable energy economy". We need to replace coal and oil with solar, wind and nuclear. We need to find a way to store and transport the renewable energy. If Hydrogen is the most economic and technically feasible way to do it great. If another gas like methane, a fluid like methanol or some sort of solid salt is better fine use that.
The heart of the plan is an improvement on the most convenient way to make hydrogen, which is to run electric current through water, splitting the H2O molecule into hydrogen and oxygen. This process, called electrolysis, now has a drawback: if the electricity comes from coal, which is the biggest source of power in this country, then the energy value of the ingredients - the amount of energy given off when the fuel is burned - is three and a half to four times larger than the energy value of the product. Also, carbon dioxide and nitrogen oxide emissions increase when the additional coal is burned.
Nothing quite like getting your clean hydrogen from dirty coal and loosing 80% of the energy in the transfer.
The idea is to build a nuclear reactor that would heat the cooling medium in the nuclear core, in this case helium gas, to about 1,000 degrees Celsius, or more than 1,800 degrees Fahrenheit. The existing generation of reactors, used exclusively for electric generation, use water for cooling and heat it to only about 300 degrees Celsius.

The hot gas would be used two ways. It would spin a turbine to make electricity, which could be run through the water being separated. And it would heat that water, to 800 degrees Celsius. But if electricity demand on the power grid ran extremely high, the hydrogen production could easily be shut down for a few hours, and all of the energy could be converted to electricity, designers say.

The goal is to create a reactor that could produce about 300 megawatts of electricity for the grid, enough to run about 300,000 window air-conditioners, or produce about 2.5 kilos of hydrogen per second. When burned, a kilo of hydrogen has about the same energy value as a gallon of unleaded regular gasoline. But fuel cells, which work without burning, get about twice as much work out of each unit of fuel. So if used in automotive fuel cells, the reactor might replace more than 400,000 gallons of gasoline per day.
The Chinese are working on such a nuclear reactor as this Wired article explains. If we can create hydrogen from a nuclear plant at an economic price, this sounds like a good way to go.
Another problem is that the United States has no infrastructure for shipping large volumes of hydrogen. Currently, most hydrogen is produced at the point where it is used, mostly in oil refineries. Hydrogen is used to draw the sulfur out of crude oil, and to break up hydrocarbon molecules that are too big for use in liquid fuel, and change the carbon-hydrogen ratio to one more favorable for vehicle fuel.

Mr. Herring suggested another use, however: recovering usable fuel from the Athabasca Tar Sands in Alberta, Canada. The reserves there may hold the largest oil deposits in the world, but extracting them and converting them into a gasoline substitute requires copious amounts of steam and hydrogen, both products of the reactor.
Interesting idea to use the hydrogen not directly, but to hydro-crack petroluem tars to create gasoline. You could put one of these mini-nuke plants next to a tar-sand refinery in Alberta and get gasoline out.

via New York Times

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