From: Debra Goldberg, ENN
Published December 13, 2013 03:45 PM

Carbon dioxide takes on geothermal energy

Geothermal energy originates from the original formation of the planet and from radioactive decay of minerals. In 2010, the United States led the world in geothermal electricity production with 3,086 MW of installed capacity from 77 power plants. Though geothermal power is cost effective, reliable, sustainable, and environmentally friendly, it has historically been limited to areas near tectonic plate boundaries, such as The Geysers in California. However, researchers from Lawrence Livermore National Laboratory (LLNL) are developing a new kind of geothermal plant that will use carbon dioxide to boost electric power generation by at least 10 times.

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The primary objectives of using carbon dioxide are to find a way to help make CO2 storage cost effective while expanding the use of geothermal energy. Additionally, the plant may have the capabilities to sequester as much as 15 million tons of CO2 per year, which is about the amount produced by three medium-sized coal-fired plants.

The new power plant design resembles a cross between a geothermal plant and the Large Hadron Collider. According to co-principal Jeffrey Bielicki, assistant professor of energy policy in the Department of Civil, Environmental and Geodetic Engineering at The Ohio State University, "Typical geothermal power plants tap into hot water that is deep underground, pull the heat off the hot water, use that heat to generate electricity and then return the cooler water back to the deep subsurface. Here the water is partly replaced with CO2 and/or another fluid."

CO2 mines heat from the subsurface more efficiently than water and "can be at least twice as efficient as conventional geothermal approaches, and expand the reach of geothermal energy in the United States to include most states west of the Mississippi River," he added.

During the past year, Tom Buscheck, earth scientist from LLNL, added nitrogen to the geothermal mix, resulting in "a design that his team believes will enable highly efficient energy storage at an unprecedented magnitude (at least hundreds of gigawatt hours) and unprecedented duration (days to months), provide operational flexibility, and lower the cost of renewable power generation."

According to Buscheck, "Nitrogen can be separated from air at lower cost than captured CO2, it's plentiful, it's not corrosive and will not react with the geologic formation in which it is being injected...What makes this concept transformational is that we can deliver renewable energy to customers when it is needed, rather than when the wind happens to be blowing, or when spring thaw causes the greatest runoff."

Increased geothermal energy efficiency and carbon-sequestration make this coal-burning alternative a powerful player in the future of renewable energy. Heat Mining Company, LLC, a startup spun off from the University of Minnesota, expects to have an operational project based on an earlier form of this new approach in 2016.

Read more from Lawrence Livermore National Laboratory

Geothermal power station image via Shutterstock. 

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