Geothermal Energy: The Power Beneath Us

by Michael Grimm, September 7, 2011

Ever thought of harnessing the power of a volcano? Geothermal energy systems tap the Earth’s inner heat and could soon provide a significant chunk of global electricity production.

It was the biggest explosion of the 20th century. When Mount St. Helens erupted in 1980 it released 24 megatons of thermal energy—equivalent to 1,600 Hiroshimas.

Yet this was only a hiccup, a mere hint of the colossal forces below. The Earth’s smouldering interior continuously generates temperatures up to 6000 degrees Celsius, a furnace created by heat left over from the planet’s fiery birth and the slow decay of radioactive particles.

That’s an immense energy reservoir that is largely untapped, a renewable energy frontier seldom explored.

That will change, according to a new report from the International Energy Agency (IEA). Global production of heat and electricity from geothermal energy between now and 2050 could increase tenfold, it says, reaching up to 3.5 percent of annual global electricity production.

But how do we get to that energy source, several kilometres underground?

Up to now, we have let it come to us, tapping the water heated by the Earth that finds its way close to the surface, for example in the form of geysers, often in volcanic areas such as the Pacific ‘Ring of Fire’.

The world’s largest geothermal power plant, The Geysers in the Mayacamas Mountains close to San Francisco, draws on a steam reservoir tapped by more than 350 wells - some more than two miles deep. On average, the plant produces energy of 955 MW, enough to provide electricity to 1.1 million people.

In 2010, 24 countries used geothermal power plants to generate electricity—the leaders being the US (3.1 GW capacity), the Philippines (1.9 GW) and Indonesia (1.2 GW), says the Renewable Energy Network’s latest Global Status Report. Iceland gets 27 percent of its power from geothermal energy. Meanwhile, at least 78 countries use geothermal energy to provide heating.

Basically, engineers are using water and air as giant energy storage spaces. Once the heat energy rises to the surface – as it does naturally in tectonic active areas like in Iceland - heat pumps extract the energy from its sources. The pumps work in a similar way to fridges – only they produce heat not cooling.

As for power production, the steam harnessed at The Geysers, for example, is put to work spinning turbines to generate electricity.

Future Development

Although development slowed in 2010 compared to 2009, the IEA report expects “a significant acceleration in the rate of deployment as advanced technologies allow for development in new countries” such as Kenya.

Why Kenya? The country is traversed by Africa’s Great Rift Valley, like the Ring of Fire a very seismically active region. And so the UN Environment Programme (UNEP) is supporting a project in six East African countries to explore the Rift Valley’s geothermal potential.

Meanwhile in Indonesia, geothermal is a key alternative to fossil fuels. The government wants to add 9.5 GW of geothermal capacity by 2025, equal to about 33 percent of Indonesia’s electricity demand, according to Bloomberg New Energy Finance. The World Bank and several international power companies are about to invest billions of dollars, prompting Al Gore to call Indonesia the first potential “geothermal superpower.”

Indonesia sits on tectonic plate boundaries which makes geothermal energy easily accessible. Nature does most of the work. But what if you want to extract Earth’s energy from non-volcanic places?

Most of that energy within reach—up to 5 kilometers below the surface—is contained within dry, impermeable rock, says the IEA. Geothermal engineers want to extract that energy using the hot-dry-rock (HDR) process. The first pilot projects, like the one in France close to Soultz-sous-Forêts in Alsace, look promising.

Drill, baby, drill?

Engineers drill a well into 200-degree-hot rocks. Water is then injected into the fracture, capturing the heat of the rocks, and then it is pumped out of a second well as hot water. Then a heat exchanger extracts the energy out of the water either for generating power or for heating.

HDR is still very costly, but enhanced geothermal systems are being developed that could expand global geothermal exploration more economically. One way to reduce costs could be to combine geothermal with more established power plants.

The world’s first solar-geothermal power plant is in development, industry leaders announced at the 2011 National Clean Energy Summit in Las Vegas. The facility will combine 80,000 solar PV modules with traditional hydrothermal technology and is expected to feed 24 MW of electricity into the national power grid.

There is a spirit of optimism in the air. The IEA estimates are echoed by experts who see geothermal energy potential against the backdrop of rising fossil fuel prices and climate change mitigation targets.

"High prices and climate change are definitely creating a renaissance in geothermal interest, particularly on a state and local level," said Karl Gawell, executive director of the Geothermal Energy Association, in The Telegraph online.

This renaissance is very likely to spread to Europe too, the birthplace of geothermal energy production back in 1904, when the Larderello steam power plant in Italy started operating.

Geothermal energy feeds volcanoes and triggers earthquakes. It also paved the way for the first life on Earth. Billions of years later, could our planet’s hot heart help us towards a better life? Could the slogan “drill, baby, drill” even turn into a rallying cry for green energy?

Source: Allianze SE

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