Geothermal technology

November 20, 2017 by Denis Pombriant

Everyday I receive automated search results for the term geothermal. It’s a rather geeky idea that few people bother with but it is also the stealth candidate for disruptive innovation in the 21st century in my humble opinion.

Briefly, geothermal is about capturing heat from the earth’s crust, condensing it, and applying the resulting energy to various uses including heating and power generation.

Geothermal energy for heating is an ancient idea. People used hot springs before recorded history—the oldest known spa fed by a hot spring goes back to China’s Qin Dynasty (3rd century BCE). Geothermal’s first use, beyond baths, was for heating and the oldest geothermal district-heating system has been operating in Chaudes-Aigues France, since the 14th century. Also, in the first century CE, the Romans conquered Britain, and Bath, in what is now Somerset, got its name from the hot springs that the Romans used to feed public baths as well as for heating.

Modern uses for generating electricity from hydrothermal heat mining go back at least 100 years on every continent. Today there are publicly traded utilities that make at least some of their electricity from hot springs. For instance Calpine has over 600 megawatts of generating capacity, based in Sonoma Valley, which it supplies to San Francisco.

There are several approaches to capturing geothermal energy and all involve drilling wells into hot spots and extracting very hot water, which, these days, gets run through steam turbines to generate electric power. Earth’s crust is quite warm naturally due to its molten radioactive core as well as radioactivity in the mantle and crust. The planet has been “cooling” for about 4.5 billion years and the minute quantity of heat extracted isn’t enough to accelerate that process.

So geothermal is like finding a present under the tree, or finding a large denomination bill in your favorite jeans that you’d completely forgotten about, and we’ve discovered it just in time. A 2006 study lead by MIT, “The Future of Geothermal Energy—Impact of Enhanced Geothermal Systems on the United States in the 21st Century,” describes the uses of geothermal as well as the investments needed to commercialize it.

In the years since publication free market entrepreneurs have been deploying the first generation of modern geothermal systems, hence the results of the Google search in my inbox every day.

Geothermal is useful for multiple reasons. First, it’s non-polluting; it doesn’t rely on burning anything and the 4.5 billion year-old planet has plenty. The MIT study suggests that the intermountain western states sit atop thousands of years worth of energy. Second, geothermal power plants, like their coal cousins, can operate 24/7 except for some scheduled maintenance. This gets us around the limitations of intermittency with wind and solar. Third, geothermal power is pretty cheap. Think of a common coal plant without the pollution and you’ve got a fair idea of the overhead.

Fourth, and very important, geothermal, despite its unfamiliarity in many quarters, is not exotic. Nuclear power with its radiation hazard and long cooling off period for spent nuclear fuel, is exotic and expensive. Hydro dams plug up rivers and change their ecosystems making life tough for salmon and other species. But also there are very few rivers in the US that haven’t been dammed already making it hard to expand further. There’s also the expense of maintaining a dam.

Geothermal is a good solution for clean electric power generation where the right geological conditions are found. Hawaii and Iceland each have active volcanoes and each generates some power from geothermal wells; Calpine relies on thermal vents near fault lines.

But the greatest opportunity for geothermal generation may be in places where it’s plenty hot below the surface but where there’s no water. Enhanced geothermal approaches (EGS) call for drilling wells and forcing water into fractured rock below the surface. The forced water heats up and is then retrieved from a second well.

With its many positive attributes, geothermal energy generation appears to be one of a small cluster of innovations that will replace the existing energy paradigm as supplies of fossil fuels decline and demand rises in the years ahead. Providing abundant and cheap energy is the first part of a strategy that provisions adequate resources for a growing planet in the 21st century. Our population base is consuming natural resources faster than nature can make them and new energy sources are a critical first step to dealing with a series of related challenges.



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