Category Archives: geothermal

Geothermal energy, the little-known resource

In Iceland and a few other countries, geothermal energy delivers a large part of the energy used for heating or cooling through geothermal heat pumps. But you may be surprised to learn that there are hundreds and thousands of buildings in the U.S. that are also hooked up to such systems. Geothermal energy is also applied at larger scales for electricity generation in various countries and, faced with rising energy demand, there has been renewed interest in developing this sustainable resource more aggressively.

But what is geothermal energy and how is it developed? Professor Roland Horne, who leads the geothermal institute at Stanford University, gives a lecture on existing and future geothermal energy systems in this Woods Institute Energy Seminar from 2007. While some of the statistics he cites are a few years out of date, his discussion remains relevant and provides an introduction to this potentially important future energy source.

Stanford researcher determines global clean energy is within reach

Mark Z. JacobsonStanford News Service is reporting that a new study – co-authored by Stanford researcher Mark Z. Jacobson and UC-Davis researcher Mark A. Delucchi – analyzed what is needed to convert the world’s energy supplies to clean and sustainable sources and determined that it can be done with today’s technology at costs roughly comparable to conventional energy.

“Based on our findings, there are no technological or economic barriers to converting the entire world to clean, renewable energy sources,” said Jacobson, a professor of civil and environmental engineering. “It is a question of whether we have the societal and political will.”

The world they envision would run largely on electricity. Their plan calls for using wind, water and solar energy to generate power, with wind and solar power contributing 90 percent of the needed energy.

Geothermal and hydroelectric sources would each contribute about 4 percent in their plan (70 percent of the hydroelectric is already in place), with the remaining 2 percent from wave and tidal power.

“This really involves a large scale transformation,” Jacobsen said. “It would require an effort comparable to the Apollo moon project or constructing the interstate highway system.”

“But it is possible, without even having to go to new technologies,” he said.  “We really need to just decide collectively that this is the direction we want to head as a society.”

You can read the full article and see a related video on the Stanford News Service website.

Old/new ways of life unite in New Zealand’s geothermal production

New Zealand, one of my favorite countries in the world, is very determined to reduce its energy dependency. No surprise for an island nation that pays a hefty premium on imported energy because of its remote location. Luckily, New Zealand is blessed …with large natural renewable resources. It is particularly rich in geothermal energy and keen to expand its production. Many of the geothermal sites are owned by the Maori, the indigeneous people of New Zealand. The Maori have a very strong relationship to the land: they are keepers and guardians that put utmost importance on ensuring that land resources will be available for future generations to come. The exploration of geothermal energy therefore requires a careful synergy of indigenous knowledge and practices and modern day science and engineering. New Zealand is not the only country where this fascinating merge of the old and new ways of life is taking place. The Big Island of Hawaii, for example, is going through a similar process in its exploration of geothermal energy.

We talk to Dan Hikuroa, an earth scientist and Maori who is heavily involved with the geothermal energy expansion in New Zealand, about the challenges in implementing indigenous beliefs in contemporary settings.

The Future of Geothermal Energy in the US: what a little report can do…

Two years ago, the future of geothermal energy in the US did not look all that exciting. Although heatpumps (used for heating and cooling of buildings) and natural geothermal energy were certainly not uncommon, very large scale geothermal, which draws heat energy from deep down in the earth’s crust, seemed far in the future.

But then, MIT (Massachusetts Institute of Technology) published an exciting report titled “The Future of Geothermal Energy” with subtitle “Impact of Enhanced Geothermal Systems (EGS) on the United States in the 21st Century”. This changed the scene. The report got the intention of policy makers as well as investors, EGS received enough capital to start several new projects, and suddenly it became a potentially important future energy source. I wished that more scientific reports had such a positive outcome! The report itself can be found at .

To date there are 18 natural geothermal resources in the United States in California, Nevada, Hawaii and Utah. In total, they supply around 2,700 megawatts (MW) of electricity. A decent amount when viewed by itself. 1 MW can be seen to supply electricity to about 1000 homes, so this delivers enough energy for 2,7 million households. It is not that much as compared to the total capacity of the US which is around 1,100,000 MW. However, in California, geothermal energy supplies 5% of total electricity demand and 7% of that in Northern California, which boasts the site of the largest geothermal plant (the Geysers, 620 MW) in the world. Apart from these 18 geothermal plants, the USA has more than 1 million geothermal heatpumps, supplying an additional 3700 MW for heating and cooling.
Geothermal energy is not completely clean. Subsurface water, which is brought to the surface, can contain some carbon dioxide, for example, but it is a minor problem. It is estimated that a geothermal plants emits about 1/200 of the carbon dioxide of an equivalent coal-fired power plant.

The geothermal story gets much more interesting when we look at geothermal heat contained between 3 and 10 kilometer depth, which EGS taps into. The total energy in this layer is staggering. Just producing 1% of this energy would supply 1400 times the total energy that the USA needs per year! So, how can we tap into this resource? The idea is simple: we drill down to a depth at which the rocks are sufficiently hot (say 150-250 degrees centigrade). It is not a simple task to drill through hard granite to a depth of 20,000 feet, say, but in the oil industry we do this on a regular basis and so the technology exists. Then, we fracture the rock over a reasonable large area. We drill another well a bit removed from the first. This second well will serve as our production well. The first is used to pump water, or another liquid, into the rocks under high pressure. It will start moving through the fractures to the producing well under a pressure gradient. As it moves, it picks up heat from the surrounding rock. We then pump it back to the surface, extract the heat, and reinject the new cool liquid again. Sounds easy enough, and it certainly sounds like a great idea to tap into that huge heat reservoir down below.

EGS is not without its complications, of course. It is not trivial to create a good fracture system down below. We need to have a very large network of fractures so that the water that flows through this network touches a lot of the rock for better and prolonged heat transfer. Also, to make this economic, an EGS well must pump through at a rate of, say, 80 liters per second, the equivalent of 50,000 barrels per day. This has not yet been achieved in pilot tests.

However, EGS is certainly a promising technique. Estimates are that if it can be done at the high rate mentioned, then within 5-10 years a typical EGS project can be cost competitive in the current energy market of around 5 US cents per kilowatthour of energy. Not bad, huh! With sufficient investments, experts claim that we could produce around 30 times as much geothermal energy by 2030 as we do now, supplying around 5-10% of the electricity needs of the US in 2030. A substantial contribution. I think we should go for it. And I’m delighted that this MIT report established so much. It has pushed this energy technology forward at a much faster rate than I thought possible.

OK, so let’s now write a report on “The Future of Wind Energy” and “The Future of Solar Energy”. Maybe not by MIT, maybe by Stanford. Yep, we should be able to do that too, don’t you think?

See also this KQED show of November 18, 2008 on geothermal energy.


Geothermal Energy in the Washington Post

The Washington Post last week had an interesting article about geothermal energy in the Philippines and beyond, featuring Stanford’s Roland Horne.

Energy down under: A look at New Zealand

Having lived in New Zealand for five years, I much enjoyed talking to Dr. Jonathan Leaver, engineering research manager at Unitec, one of the universities in Auckland. Jonathan has played a major role in New Zealand’s energy systems for over 20 years. He paints an interesting picture: New Zealand’s isolated geographical location has lead to an energy portfolio that contains a large renewable energy mix. Electricity is generated mostly from hydro and geothermal energy. Wind is a growing energy resource. For transport, New Zealand relies on oil imports. No wonder that the New Zealanders are interested in exploring electric or fuel cell vehicles, with the electricity and hydrogen generated in New Zealand in an environmentally friendly way.