
A Modest Proposal
Iceland turns geothermal energy into electricity in two ways: Venting 600°F steam from a mile underground through a turbine, and a more energetic method that pulls 390° water from deep wells and heats surface water, making steam to drive turbines. Harnessing a natural supply of supercritical water — water that's three times as hot and under enormous pressure — and turning it into electricity would be like switching from diesel to jet fuel. "If we succeed, we expect to increase power output by 5 to 10 times [above what a typical well can produce]," Fridleifsson says.
To appreciate the benefits of free supercritical water, it helps to understand that most coal plants and nuclear power plants make supercritical water before generating electricity. The plants transfer heat energy — produced by burning coal or by the radioactive decay of isotopes — to water in a pressurized tank to bring it to a supercritical state. The process allows the water to maintain the high-energy intermolecular hydrogen bonds of a liquid, yet flow through pipes with near-zero resistance like a gas. It then runs through heat exchangers to create even more steam, which drives turbines to make electricity.
The IDDP well will dip two and a half miles belowground into a pocket of water heated to 1,100° by a bubble of magma. Water normally exists as steam at this temperature, but the immense pressure of the rock above holds the water in a near-liquid state. Once the water squirts to the surface, it will retain nearly all the energy that heated and compressed it. It is virtually certain that engineers will have to redesign existing heat exchangers to handle the water's heat and potentially corrosive chemistry, but a plant running on naturally occurring supercritical water could churn out up to 500 megawatts, on par with a small nuclear reactor and half of what a large coal plant produces. Unlike these, though, the IDDP's zero-emissions power source will last as long as the Earth's core continues to heat rainwater.
Iceland's geothermal efforts are currently operating at 20 percent capacity. If it exploited the island's full reserves in only the conventional way, it could produce 20 terawatt-hours of electricity per year — about the same as three nuclear reactors. Tap into other supercritical reserves, or drill deeper into existing wells, and Iceland's electric output could be five times that of the U.S., the world's largest producer of geothermal electricity; Iceland is only the size of Kentucky.
In 2000, Fridleifsson recruited Wilfred Elders, a professor emeritus of geology at the University of California at Riverside, from retirement to co-lead the IDDP. Geological studies revealed that supercritical water does indeed flow under Iceland, and the six-mile-wide Krafla caldera was the place to go after it. They realized that all they have to do is tap the stuff — and hope that it doesn't destroy the drilling equipment in the process.

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I enjoyed this piece; it's informative and well written. I hope the project works out.
"If it exploited the island's full reserves in only the conventional way, it could produce 20 terawatt-hours of electricity per year" Big applauds for getting units right. It's so rare this days :)
"would be like switching from diesel to jet fuel" - This is about like switching from tap water to bottled. I would think that there would be an energy difference to illustrate here, and a reduction in purity.
The real big news in geothermal power is in exploiting ocean floor vents. Instead of drilling two miles, you can just install a pipe to feed a plant that dwarfs existing nukes. www.marshallsystem.com/
Bob Stuart
We can change anything.
But we can never change
just one thing.
Geothermal Power gives us great opportunities. Combined with some wind, some solar and some marine energy, like the Anaconda,it seems the right way to go.
http://tinyurl.com/ngsgat
@BobStuart
That looks rocking. Are there projects working already?
If not, why??
Going the write about it on my Blog
Milieunet Foundation is a non-profit organisation focused on awareness and change of behaviour by means of communication about waste, energy, sustainability, nature, environment, climate, human rights and international development cooperation.
Geez, this is a profoundly ignorant article. He completely misunderstands the nature of the HCl reactivity, assuming that is important, and implies some magical property to supercritical water which doesn't exist. The fact that the water is supercritical means exactly zero. The only reason it can supply energy is because it's at high T and high p, and that's it. Doesn't matter whether it's liquid, gas, supercritical, or anything else under the Sun.
I had to laugh at the ignorance on display in the comment that supercritical water was useful because it kept the "high-energy" H-bonding network intact. Gee, in that case, you'd expect plain water at 100C ("high energy" H-bonding network intact!) would give you more energy than steam at 100C. Which, of course, as anyone who's had the bad luck to come into contact with live steam can tell you, just ain't so. This guy could usefully look up the Wikipedia entry on "heat of vaporization."
But beyond that, he implies that somehow Iceland's experience drilling a hole in a volcano could somehow be a miracle for global energy needs. What kind of cluelessness is this? He's forgotten that geothermal power requires a very special set of circumstances, namely an active volcanic region with lots of water? Or does he think that people have bizarrely failed to map each and every one of those potential power sources over the past century or so? And that to the extent any of them are economically exploitable, they already are exploited?
I mean, next he's going to write a breathless article explaining how some ingenious person in country X has discovered that if you put a waterwheel in a swift-flowing stream, you can use it to generate power. Amazing! Who'd have thought? Imagine the possibilities! Feh.
I have to agree to some extent with Carl Pham's comments. The subject matter is quite interesting, but the technical details are in many cases inaccurate. I think "peer-to-peer" review was abandoned regarding this article. Someone mentioned "diesel to jet fuel", for example, a comparison of nearly 1 = 1.
And correction on the comments regarding power plants employing supercritical fluid technology. There are quite a few fossil fueled central stations employing supercritical technology in the US and a growing number in countries like China for example. The latter are all fossil fueled units, as well.
There are no nuclear units employing supercritical pressure/temperature conditions, period. In fact, the nuclear units generally operate at around 33% of critical presssure at around 1000 psi.
Geothermal energy (steam) used directly is difficult from a corrosion standpoint. In this example, a primary heat exchanger provides an interface between the thermal fluid and the steam side much like the configuration used in a pressurized water nuclear reactor. The corrosive elements that undoubtedly (in my view) will be present would be isolated from the steam cycle. I give these people a lot of credit for their efforts, but I wouldn't want to be anywhere near this site when it comes time to hook into that superhot, superhigh pressure source of around 700 degrees F and 3200 PSIA. This is an artisan well to exponential scale.
Good thing there is no EPA in Iceland. I'm sure they would never have gotten a permit to build something like this in the US (might disturb some Snaildarter or other obscure creature that no one cares about except some liberal tree-hugger).