Hot and Cold Mining
(This 829th Buffalo Sunday News column was first published on February 18, 2007.)
Geothermal Power Plants in Geysers, California
In late January an important report was issued by an MIT interdisciplinary panel entitled The Future of Geothermal Energy (web address: geothermal.inel.gov). It paints a rosy future for "mining" the Earth's heat to meet by mid-century a substantial portion of our country's energy needs economically, safely, with high national security and without harming our environment.
For a federal research investment over the next 15 years of less than the cost of a single modern coal power plant, the report projects private and public development of 100 gigawatt capacity by 2050, supplying 10% of our base-load electricity by that date. (For comparison the Niagara Power Project delivers less than 15 gigawatts.)
This report reminded me of an experience I had when I was a youngster living in Rochester. An inventive neighbor, Mr. Bullock, constructed his own summer cooling system. His home was already fitted for hot water baseboard heating just like mine here in Amherst today.
He had workmen dig a series of six foot deep trenches through his backyard, then run what must have been at least a hundred feet of pipe back and forth through those trenches. They then connected the pipes with those that ran around the baseboards of his home interior. Instead of circulating heated water through his house as his system did in winter, by changing to these summer connections his new arrangement circulated water cooled by flowing underground through his backyard.
If your heating bills have risen as fast as mine, you will probably feel that this is not a time to be talking about cooling our homes. But I tell it because Mr. Bullock's story is reversed by geothermal energy technology.
In thinking about the ground beneath our feet, we are misdirected not only by Mr. Bullock's episode, but also by our usual thoughts about people buried in the cold ground of the cemetery. What we need to realize is that the ground is really a source of warmth. In Mr. Bullock's case the warmth of the ground was in summer less than that of the ambient air above it. In winter, of course, that situation is reversed as animals like woodchucks and bears know well.
The total amount of the Earth's warmth is in fact quite remarkable. Penn State professor of geosciences Chris Marone states this in prosaic terms. He tells us that enough heat emanates from the interior of the planet to make 200 cups of hot coffee per hour for each of Earth's 6.2 billion inhabitants.
There is a problem, however. In most places, tapping that heat source requires holes far deeper than those dug by Mr. Bullock.
There are exceptions to this. In particular I recall being impressed by Yellowstone Park springs: clear pools with pastel colored water into which you could see down many feet. In some you could boil an egg.
In places like Yellowstone or Iceland you can indeed heat your home or swimming pool simply by drawing on the heat so close to the surface. Here in western New York, however, the holes would have to be many hundreds of feet deep just to obtain heat that would provide enough warmth.
Scientists today are very interested in the Earth as a heat source, not just for heating buildings by a modification of Mr. Bullock's method as some greenhouses and office buildings are today, but even more important by digging deeper to obtain steam to drive turbines and produce electricity.
The concept is straightforward. Pipe water down into the mantle two to four miles. There it is heated by the molten rock. The resulting superheated steam is then piped back up separately to work for you.
While the concept is simple, the application faces several engineering problems. Heat mining is already being done in California, but further advances are needed to make geothermal energy production economically attractive to investors.
I found one document especially interesting. A map showed the advantageous regions that have heat near the Earth's surface, but a caption notes: "Area Suitable for Geothermal Heat-Pumps (Entire U.S.)" And a nearby table shows how the geothermal energy resource base far outweighs world oil reserves.
As the MIT report underscores: This is an important resource that has too long been ignored.-- Gerry Rising