MIT Study on Geothermal Electricity

MIT has released a landmark study on the opportunity for making electricity from geothermal resources in the US.

The study concludes that the US could install 100,000 MW of capacity, enough to supply 10% of their electricity, by 2050, and at a cost competitive with other forms of electricity.

Ten percent is a large amount of electricty. It would similar to the amount that the US obtains from waterpower today, and half of what is obtained from nuclear.

Interestingly, it is the oil and natural gas business that is opening up this enormous opportunity, because of their skills at drilling very deep wells. To make geothermal electricity, you typically drill two wells. You force pressurized fluid (usually water) down one well, and the water flows through the hot rocks, absorbing the heat, and then back up the other well. Some rocks are naturally porous and permeable. If not, then horizontal drilling, and fracturing of the rock may be necessary. These processes are widely used in enhancing oil recovery, and in coal bed methane production.

The hot fluid is then used to make steam, which can be used to run a generator.

The study points out that we already produce a lot of electricity from geothermal. There are over 10,000 MW of installed plant in the world today. But most plants use relatively shallow heat resources. Use of deeper resources is the part that the oil industry is opening up, and that will dramatically expand the possibilities. This is not bleeding edge technology – it is tried and proven. But it can be improved, and more widespread, with the use of the deep drilling techniques.

The most accessible geothermal resources are in the western US. No doubt the same is true of Canada. But the maps show high temperatures in all regions if you drill deep enough. Under Toronto, for example, the temperature of the rock at 6500 m is estimated at 100 degrees C.

Of course geothermal energy can also be used for heat – you don’t have to make electricity. Downtown Toronto has a district heating system, where heat is produced centrally, and distributed by pipeline to a number of building. They burn natural gas to make the heat. I wonder if they should consider drilling deep well, and get rid of their gas bill?

I have always considered that the principal renewable energy resources were waterpower, windpower, biomass, and solar, with wave and tidal in their infancy. But clearly, geothermal needs to be on the list.

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