As part of my present job, I am getting to mingle with people who have relatively deep backgrounds in the various facets of what is commonly called “renewable energy” in the United States nowadays. I am always eager to have my horizons expanded and my thinking challenged, so from time to time I talk with some of these people about their work.
A couple of Fridays ago I got to have coffee (for me it was actually herbal tea) with a geothermal engineer who holds advanced degrees. I was curious about geothermal energy, and was wondering as well about whether pursuing a post-baccalaureate education would actually be worth my time and effort. I learned a number of interesting things about geothermal energy.
First, the word “geothermal” has two common uses in the field of energy engineering. The first use, which more accurately reflects the classical definition, has to do with the energy, generated within the earth via radioactive decay, which is accessible via voids and discontinuities in the earth's crust that allow high-temperature matter to reach the earth's surface. Typically the high-temperature matter consists of steam, hot water, and high-temperature rock. The second use of the word has to do with the use of ground-source heat pumps to exchange heat between the earth (at shallow depths, typically less than 100') and a building which has spaces that must be conditioned (heated or cooled). (My geothermal engineer friend considers the reference of the word “geothermal” to ground-source heat exchange to be somewhat inaccurate.)
High-temperature geothermal energy resources are used for electricity generation and to supply heat for direct heating of spaces and for some industrial processes. My friend told me that in the United States, there is a strong bias toward using geothermal energy for electricity generation, and not nearly as much interest in using geothermal energy for direct heating applications, although there is a growing interest here in direct heat applications. I mentioned an article by Kris de Decker that I had recently read in Low Tech Magazine, in which Mr. de Decker stated that “Most of the talk about renewable energy is aimed at electricity production. However, most of the energy we need is heat...”
We discussed the bias toward electricity generation in the renewable industry in the U.S. and concluded that it must be due to the prejudices of the big economic players here who have sunk large amounts of capital in electric power plants and centralized schemes of electricity distribution. These players are only interested in a renewable source of energy to the extent that it can help them maintain and increase their profits via their current infrastructure and business model. Using a renewable resource for primary delivery of energy in a form other than electricity would undercut previous investments in electricity generation and distribution. (As an aside, my friend pointed out to me that non-electric uses of geothermal energy are very popular in Europe and elsewhere. China, for instance, has no geothermal electric plants, but has many applications of direct geothermal heating.)
We moved on to discuss how geothermal “resources” are discovered and exploited. I was interested in knowing whether the same methodology used for identifying potential oil and gas resources is used for identifying geothermal resources. My friend told me that historically geologists have used somewhat different methods for identifying geothermal resources, and that the oil and gas methodology is not altogether a good fit for identifying geothermal resources, due to the dynamic nature of heat flows within the earth's crust. A good (as in ethical, honest, accurate) geothermal geologist is therefore likely to include a much larger margin of error in his or her assessment of a potential geothermal resource than a petroleum geologist is in assessing a potential petroleum resource.
This puts a geothermal engineer in a bit of a bind, because the only true way to assess a potential geothermal resource is to drill a well, and wells require a lot of money up front. Therefore, venture capitalists and other lenders often demand that a geologist provide an unreasonable degree of certainty in identifying a resource prior to drilling. Of course, any geologist who identifies a resource with such certainty prior to drilling makes himself or herself professionally and financially liable if such an identification proves false. Typically, it is a petroleum industry service firm that drills a geothermal well, since such wells must be deep (at least 300 feet, and typically thousands of feet deep), and such firms normally collect hefty profits.
Although readily accessible geothermal resources in the U.S. are limited in availability, there are some good examples here of geothermal energy use. My friend told me of villages and towns in Alaska that are supplied with geothermal district heating. Also, there is the city of Klamath Falls in Oregon, which provides geothermal district heating to its populace, along with a geothermal heat and electricity plant at a state university campus in Klamath Falls.
One “take-away” point from our conversation is that geothermal energy is expensive due to high up-front capital and infrastructure costs. In a shrinking economy, this means a shrinking likelihood of expanding geothermal energy use. The American bias toward viewing renewable resources solely in terms of electricity generation is likely to have unpleasant consequences because of the age and increasing disrepair of our grid, along with the very high costs of an extensive grid overhaul and the rapidly appearing shortages of capital caused by our economic collapse.
What about ground-source heat exchange, then? We both agreed that it is a useful way to save energy. But here again, the up-front capital and infrastructure costs are high. Landlords and owners of large buildings would be far more likely to be able to afford the micro-tunneling needed to install a large heat exchanger in the ground next to a new building whose interior spaces were to be conditioned via ground-source heat pumps. Small landlords and homeowners would find the installation of ground source heat exchange to be quite “spendy,” to use an Oregonian term. Retrofitting an existing home – especially a home with a conventional joist floor – would be really spendy. (Think $30,000 or thereabouts.) This would be due to having to replace the floor with a concrete slab containing embedded heat exchanger pipes.
My conclusion at the end of our conversation was that exploiting geothermal energy or ground-source heat exchange is probably out of the reach of the vast majority of people in this country because of the high cost involved, and geothermal energy will therefore probably not be part of the toolkit of people looking to create resilient neighborhoods in this present time of energy and economic decline. Most of us will have to adopt low-tech strategies for getting our energy needs met. Geothermal energy has its place, but that place is limited.
And as far as me going back to school? I'll tell you all about that some other time...;)
P.S. Although I am an engineer, I am not a geologist. If any geologists read this, feel free to chip in your educated two cents...