In recent years, many people wrote that as oil reserves are diminishing, we should use hydrogen to power our cars. Before going further, it is important to remember that hydrogen is not itself a source of energy, but a carrier of the energy produced by fuel cells. And if we want a greener world, all this hydrogen needs to be produced by renewable sources of energy. In "Hydrogen economy looks out of reach," an article which invites controversy, Nature mentions the paper of two UK authors, a professor of economy and an energy consultant. They say that to convert all cars and trucks in the UK to use hydrogen would require 100,000 wind turbines or 100 nuclear stations. And these numbers would have to be multiplied by 10 for the U.S.: one million wind turbines or 1,000 nuclear plants. By looking at their calculations, I have the feeling that the authors forgot that technology evolves at a rapid pace. Wind turbines will be more powerful and more efficient twenty years from now. This should significantly reduce the above numbers. Also, the two authors didn't take a look at other alternative energies. So, even if an hydrogen economy is not for tomorrow, it will not be necessary to spoil our landscapes with huge wind farms. Read more...
Here are the opening paragraphs of the article from Nature.
Converting every vehicle in the United States to hydrogen power would demand so much electricity that the country would need enough wind turbines to cover half of California or 1,000 extra nuclear power stations.
So concludes a British economist, whose calculation is intended to highlight the difficulties of achieving a truly green hydrogen economy.
"This calculation is useful to make people realize what an enormous problem we face," says Andrew Oswald, an economist from the University of Warwick.
How did they reach their conclusions? The details of their calculations appear in a paper called "The Arithmetic of Renewable Energy" (PDF format, 5 pages, 18 KB).
They took the UK annual consumption of transport energy as a basis, with 54 (MTOE) Million Tons Oil Equivalent, and considered that the process of releasing power from hydrogen was only 50% efficient. So we need to produce 108 MTOE. Assuming some conversion coefficients and 3 MW wind turbines, they reach a number of around 48,000 turbines.
Finally, considering that the wind doesn't always blow, they multiply the number of wind turbines by two to reach the number of 100,000 wind turbines.
Then the authors look at where to put all these turbines. Giving a reasonable spacing, they conclude that it would need a band of wind turbines 18 deep all around the coasts. "This represents slightly less than an approximately 10 km deep strip of wind turbines around the periphery of the UK."
And if these wind turbines were put on land, this would need the entire area of Wales, or 20,000 square km.
As I said above, I think the authors didn't take into account that technology is moving fast. The efficiency of wind turbines will probably be multiplied by a factor of 2 or more by 2020. And the average wind turbine will probably have a power of 10 MW or more at the same time. So my best guess is if hydrogen would only be produced using electricity from wind turbines, the numbers they reached should be divided by an order of magnitude.
The same is true for other kinds of alternative energies, which all will be more efficient in twenty years. And there will probably other efficient ways to produce hydrogen by that time.
What do you think of the Oswalds' numbers?
Sources: Mark Peplow, Nature, October 7, 2004; University of Warwick website
6:12:08 PM
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