A Superior Idea

At first glance, MIT’s Prof. Jefferson W. Tester was doubtful about the practicality of Atlantic Geothermal’s “heat canal” concept. Once Dr. Tester took a good look at the heat canal idea, however, his skepticism changed. Should the concept prove workable, Tester told Atlantic Geothermal’s founder, David Reynolds, the heat canal approach to enhanced geothermal energy development would offer real advantages to geothermal heat mining.

Let’s be clear on the importance of the Feb. 12 meeting between Tester* and Reynolds. An expression of geniune interest by one of the world’s foremost authorities on geothermal energy can go a long way toward bringing a good idea into the real world of analysis, conclusion and validation. This would be very good for Atlantic Geothermal, of course; but launching a superior geothermal energy production design would be enormously beneficial to a world in desperate need of clean energy sources. It would also, by the way, be very good for the U.S. economy, as well as the quality of the air we breathe, the food we eat and the water we drink.

Prof. Tester agreed that the heat canal looks good on paper. Rather than building multiple enhanced geothermal wells to pump water down into hot rock and extract steam to drive power-generating turbines at each site, the heat canal would draw from a much larger underground field for a much longer period of time — possibly measured in centuries rather than decades for the typical geothermal site. The heat canal, a horizontal bore 50 ft. wide and 80 to 100 miles long, 20,000 ft. below the surface and filled with sea water under pressure, with bore holes extending laterally 7500 ft. into hot rock, would generate an estimated 16 times the energy of the largest conventionally designed enhanced geothermal well, yet all that energy would be extracted from a single site. This design, Prof. Tester said, would significantly increase operating efficiency through a “synergy of systems.”

During their discussion, Tester and Reynolds identified two optional designs for the bore holes that could work with the required efficiency. One option would utilize fracturing of the hot rock area from which heat would be extracted. (Fracturing allows more heat to be extracted, but could multiply any tendency within the site toward geological instability.) The second option would involve drilling a lattice of bore holes and, while more expensive to install, would not require fracturing.

The next step is to have a mathematical analysis of for both options performed by GeothermEx, the big California-based geothermal exploration and development firm. Tester told Reynolds that he would be glad to verify mathematical calculations of heat extraction rates the geothermal canal model. While the sustainability of the heat canal design is being calculated, Atlantic Geothermal will be refining the design concept and trying to get a fix on projected costs. The immediate question is, how many billions of dollars are we talking about?

by Loren Jenks (lorenjenks@charter.net)

*Dr. Tester, the H. P. Meissner Professor of Chemical Engineering at MIT, directed the multidisciplinary task force that recently released its major report, “Future of Geothermal Energy: Impact of Enhanced Geothermal Systems (EGS) on tbe United States in the 21st Century.”