The Importance of Geothermal Power

Guest post by John Malone

John Malone, a VP/Senior Analyst with John S. Herold, an energy investment research firm in Connecticut, is a Truman National Security Project fellow.

In the world of renewables, most of the attention is on the wind and the sun. Geothermal power just hasn’t gotten the same respect. That could be changing, as both the Obama Administration and Silicon Valley are considering the heat under the ground as a potentially huge source of clean, domestic U.S. energy, but recent setbacks are calling into question how much geothermal can contribute. Given the potential benefits, we should be doubling our efforts to make geothermal a viable power source for the U.S.

Some background: All thermal power plants use the same basic process. A heat source (burning coal or gas, uranium, concentrated solar energy) is used to turn water into steam, and the energy released turns a turbine that produces electricity. What sets geothermal apart is that the steam comes directly from the ground. Water percolates down through cracks in the ground and is heated to the boiling point by hot rocks underground (in some cases coming back up as a geyser — think Old Faithful), and the resulting steam is drawn up via a well to a turbine.

This makes for, in principle, the ideal alternative energy source. Geothermal power releases virtually no CO2 or pollutants. Crucially, geothermal provides baseload power — wind and solar power are better suited as peaking technologies, as they are dependent on energy sources that wax and wane over the course of a day. Geothermal power is on 24 hours a day, 365 days a year (geothermal power plants can have utilization rates up to 98%). And from a national security angle, the promise of geothermal is obvious: There is no more domestic source of energy than the actual ground underneath us.

There’s one problem, though. There are only a few places in the U.S. where you can find shallow groundwater hot enough to get steam directly from the ground. Engineers and geologists are therefore looking at a new way to tap underground heat. Enhanced Geothermal Systems (EGS) make use of the fact that, if you drill deep enough, any bedrock in the world gets hot enough to boil water. Basically, EGS involves drilling a well into deep, hot, dry rock; drilling a second well nearby to the same depth; fracturing the rock between those two wells enough to allow water to pass between them; and then pumping water down the first well and allowing it to percolate through the hot fractured area to the second well, where it will come back to the surface as superheated steam. The potential for EGS in the U.S. is enormous. A 2006 MIT report concluded it could provide 100,000 MW of power by 2050.

EGS is not without its drawbacks. Cost is the main hurdle. Oil and gas companies now measure well depths in miles, but these are wells drilled through relatively soft rock, not the hard granites that are best suited for EGS. If not managed properly, rocks could lose their heat — eventually, pumping water through a hot rock system could bring the heat gradient down to the point that new wells need to be drilled. There has also been some concern about earthquakes. In 2006, an EGS pilot project in Switzerland set off a 3.4 magnitude quake.

That said, these hurdles are all surmountable, and given the huge benefits it could bring, there is already a surge in investment — both public and private — in EGS. Google laid down an $11 million investment for early-stage research. Perhaps most encouraging is the interest shown in EGS by our Nobel Laureate Secretary of Energy, Steven Chu. Obama’s stimulus plan set aside $400 million for pure geothermal R&D. And it’s looking like EGS wouldn’t need too much more of an investment. A recent NYU study found that as little as $3 billion in R&D development could make EGS cost-competitive with fossil fuel plants.

The widespread application of EGS is still a ways off. But geothermal, whether traditional or EGS, should be used alongside technologies like wind and solar to diversify our renewable base. There is no silver bullet in renewable energy. It’s better to think in terms of silver buckshot, where a collection of solutions add up to a big impact. We should do our best to make sure that one of those solutions is the one right under our feet.

(Cross-posted from Operation FREE.)

Author: Guest Voice

9 Comments

  1. “The potential for EGS in the U.S. is enormous. A 2006 MIT report concluded it could provide 100,000 MW of power by 2050.”

    The US currently consumes about 4 Trillion watts as of 2008. So even if this hypothetical value does get reached by 2050 and our consumption stays the same, your looking at an answer to 2.5% of our power needs. Geothermal is clean, and it certainly should be used where it can be, but overall it is not an answer to our needs. There just aren't enough locations to provide enough energy to make it one. The same can be said of tidal energy. Both solutions are side dishes to the clean energy problem, not the main course.

  2. Slamfu,

    Check your units. That's 100,000 MW of capacity, not generation. The U.S. consumes about 3.6 trillion kWh according to EIA. 100,000 MW of capacity running at 95% capacity factor would generate ~ 832.2 billion kWh, or roughly 20% of US consumption. That's roughly the current share of nuclear power, which operates a little over 100,000 MW of capacity in the US.

  3. “Geothermal is clean, and it certainly should be used where it can be, but overall it is not an answer to our needs. There just aren't enough locations to provide enough energy to make it one. The same can be said of tidal energy.”

    These problems are shared as well by wind (which, also, is intermittent, another defect) and hydro.

  4. As a side note, there's some geothermal power being generated on the Big Island of Hawaii currently. There's talk naturally about expanding it, but it runs into controversy with some native Hawaiian groups who consider it an attack on Pele. When I first heard the notion, to be honest, I was somewhat… taken aback, let's say. But then I realized it's sort of like saying, “we want to drill in Arlington National Cemetery,” or “there's an energy source in Cathedral Notre Dame.”

    No great implications to this story; just an interesting tidbit from out here in the pacific.

  5. I think there may be a different term for geothermal that uses the earth's thermal mass for heating and cooling, but it's contribution could be even greater than centralized geothermal and it is available everywhere. A friend of mine has built a net zero energy home that uses a geothermal exchange to preheat and precool incoming outside air through 260 ft of 6″ pipe 6-8 ft down. When it's 4 degrees outside, incoming air is 40 degrees, fairly easy to heat.

    http://www.ecofuturesbuilding.com/taxonomy_menu

  6. There is poor discrimination between the techniques, normally “heat pump” is added to the temperature control system (although it also helps cool, so just having heat in there is a misnomer).

  7. I know it's possible to use thermal mass coupled with a heat pump, which in our climate helps when you're trying to absorb heat from frigid air. Much easier to use the warmer earth to draw heat from.

    In this case, though, it's simply a pair of pipes, one intake and one exhaust, going through a heat exchanger, for 95% heat recovery. Take a look at the poster (PDF) for more detail. Very clever:
    http://www.ecofuturesbuilding.com/files/active/

  8. For a while, underground housing was in vogue — I recall literature that now can be found on used book store shelves (I think here in Detroit and definitely in DC metro). (I kept this in mind when I envisioned the hypothetical relocation of the federal government to Oklahoma City, likely close to the 2100 mean center of population, and in the heart of the tornado and hail zone.)

    Now consider an underground building (whose temperature the Earth moderates) with geothermal temperature control (heating and climate control system) added. That's real geothermal living!

  9. I'm not an engineer or anything, but I have spent quite a bit of time researching various renewable energy alternatives, including geothermal. Unfortunately, I haven't kept up for the last several months (I've been too busy), so my information could be a bit dated. But it's a fascinating story, and one is hard pressed not to be optimistic if for no other reason than the potential is dramatic. Anyone who hasn't read that 2006 MIT report should (that 100 GW by 2050 figure only scratches the surface of what could eventually be available).

    The progress that has been made over the last few years in developing “closed loop” geothermal resources (i.e., re-injecting recovered water back into the circuit), and employing dual cycle systems to operate at relatively low temperatures is very impressive. Add to that the fact that many of the recent advances in the natural gas industry that has led to a dramatic increase in provable, recoverable gas resources (e.g., horizontal drilling, artificial site stimulation, coatings and composites necessary to withstand highly corrosive environments) are at least theoretically applicable to geothermal applications as well. That's the good news. The bad news is that, as far as I know, the ability to identify productive sites with a high likelihood of success is still in its infancy. That is partially counter-acted by the fact that the oil and gas industries have provided enough information over the years to render many thus far un-tapped sites more or less no-brainers — particularly in places like CA, NV, ID, UT, and AZ. So there's an obvious trajectory available for production, not to mention further research, at a reasonable cost. Nonetheless, drilling into those fields is still risky — drilling a well is always an expensive proposition, and if it comes up dry, well, it's money down the drain (so to speak). And of course there's the possibility that stimulating a site will cause tectonic instability. But to my mind, if all it takes is stimulating a well-head to cause an earthquake, that earthquake was going to happen in relatively short order anyway. Think of the stresses involved as a constantly expanding balloon: the balloon will pop eventually, whether or not a pin (i.e., a stimulated well-head) is inserted in it beforehand. The difference, of course, is that the “pin” has a considerable amount of political fall-out associated it, lol!

    At any rate, my impression is that it's still too early to tell how much of a contribution hot rock geothermal could make to the overall energy picture. It could be huge or it could be a niche. But either way, IMO, it's worth spending a reasonable amount of money to find out. I think Steven Chu has it exactly right.

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