Geothermal energy remains the poor cousin in our current stable of renewable resources, in spite of offering enormous benefits. That’s Jefferson Tester’s inescapable conclusion, after participating in a Department of Energy investigation into the technical and economic viability of tapping into this potentially vast energy pool. He describes the findings of the DOE report to a live and online MIT Museum audience.

The 18-member research team accepted as givens the fact that U.S. will demand ever more power, having just passed the one million megawatt milestone. But there are threats to the supply system, with increasing prices for natural gas and difficulties expanding coal production, not to mention issues around electric transmission lines and energy storage. Renewables like solar and wind won’t make much of a dent in the next 20 years, researchers believe, and nuclear power continues to meet public resistance.

Meanwhile, for the last 30 years, geothermal systems have been successfully demonstrating their capacity to generate electricity. Some areas of the world are blessed with steam or hot water located fairly close to the surface (think of Yellowstone’s Old Faithful geyser). In Iceland and locations in the U.S. west, says Tester, “instead of mining minerals from the ground, we’re mining heat.” Right now, the U.S. produces 3000 megawatts of geothermal electricity. But “not all the earth is so blessed” with hot springs, says Tester, so the trick is “to replicate what nature has done.”

In several critical demonstrations around the globe, researchers are working on such enhanced/engineered geothermal systems (EEGS). They drill down to depths of 5 kilometers and beyond, deep enough to reach hot rock. Then they circulate water into these underground heat reservoirs, where it warms up enough to generate electric power. The work shows great promise, Tester believes.

Tester’s report assumed that if geothermal were “going to be anything more than a minor curiosity,” it would have to supply energy at the level of nuclear or hydropower in the U.S. today – 100 thousand megawatts. EEGS could become such an energy player by 2050, if in the next 15 years, government and industry kicked in for a handful of field demonstrations -- first in some shallow, high grade sites in the West, which would quickly and economically start producing energy, and then eventually in some sites requiring more expensive mining at depths greater than six kilometers -- such as in the eastern U.S. The total investment of $600-800 million would be less than the cost of a single clean coal plant, notes Tester. Currently, unlike other renewable energy projects, “geothermal has no money in the budget.” Comments Tester, “If I look to the future of my children, and my grandchildren, I’d want to make sure we’re looking at all the options.”