Heat mining and power production
September 26, 2017 by Denis Pombriant
One power-generating solution that is both non-intermittent and nonpolluting involves mining (or extracting) heat from the Earth’s crust to generate electricity. According to “The Future of Geothermal Energy—Impact of Enhanced Geothermal Systems on the United States in the 21st Century,” a 2006 study from the Massachusetts Institute of Technology (MIT) sponsored by the U.S. Department of Energy, we can expect to generate many GW of base load power from mining the heat under the continental US, and this capacity would be available for hundreds of years.14
The study is an assessment carried out by an 18-member panel comprising some of the brightest minds in engineering and science, and energy-industry veterans. The purpose of the project was to estimate the obstacles to be overcome in bringing enhanced geothermal power generation from the blackboard to the marketplace and they set a benchmark of 100,000 or 100 GW of power production—at the time equal to 10 percent of US power consumption.
For comparison U.S. nuclear power plants have capacities between 500 and 1300 MW. So the analysis envisions generating capacity equal to between 100 and 200 nuclear power plants. 15 This is a lot, and it will be needed but it’s only a demonstration project at this level, heat mining can extend well beyond this. The report also concludes that in the next 15 to 25 years (from the publication date of the report) 50 GW of coal-fired capacity will need to be retired (some of it already has been) so there’s a significant need for this capacity and more.16
Where the heat is
As the report documents, there is a great deal of heat deep under our feet almost anywhere we step. But some places, such as locations near volcanoes that have erupted in the past million years or the Rocky Mountain states are better than others for heat mining. So the objective of 100 GW stated in the report represents a feasibility study, rather than a forecast of the total potential of heat mining.
According to the MIT study, the best places in the US for heat mining are the intermountain states, including Arizona, Colorado, Idaho, Montana, Nevada, New Mexico, Utah, and Wyoming. Also, California, Louisiana, Oregon, Texas, and Washington all have significant, high-grade heat resources that could be exploited using EGS. There’s heat underground in the eastern states, too, but not as much though the temperature gradient would still be sufficient for heating purposes if not for electricity generation.20 So, although it’s still possible to site heat mining capacity east of the Mississippi (in places like West Virginia and eastern Kentucky), the low-hanging fruit is in the Rocky Mountains and that’s where the MIT working group recommended that we start.
How much energy is down there?
The Earth’s crust represents the greatest potential energy source yet tapped. The energy is in the form of heat, not fossil fuels; using this resource would involve converting to a nearly all-electric energy infrastructure, and converting is assuredly worth the effort. According to the MIT study, “By almost any criteria, the accessible U.S. EGS resource base is enormous – greater than 13 million quads [or 13 million exajoules] or 130,000 times the current annual consumption of primary energy in the United States.”21
That’s enough energy to not only replace fossil fuels but also to provide energy to supplement ecosystem services, such as providing fresh water for agriculture and cities, for a very long time. With more fresh water, marginal land can be opened up to farming to feed the globe’s increasing population. With fresh water, you can stimulate a lot of green plant growth and the carbon absorption that goes with it.
This much additional energy can be used to drive chemical processes that are impractical now, but which are needed to ensure critical resource supplies like phosphorus. Currently, we get phosphorus from mines (but they are limited resources). Since it is an element, phosphorus isn’t destroyed but once used in farming it washes away in runoff and ends up in river deltas or it goes the same route as part of urban waste treatment. With an abundant supply of energy, natural-resources companies could profitably exploit river deltas for phosphorus and many other vital materials.
Of course, there’s a lot more to say. There are also two types of heat mining to be aware of Hydrothermal heat mining and Enhanced Geothermal Systems. Both are viable ways to make power. Hydrothermal heat mining is a bit easier to do and in fact, it’s already in use in the US and elsewhere xxx. Enhanced Geothermal Systems (EGS) is a term you’ll hear more about in the years ahead because it holds the greatest potential for replacing fossil fuels and putting the planet on course to clean up the environment and provide enhanced ecosystem services.