Geothermal electricity: The next hot thing?

Michael Richardson, The Straits Times 12 Oct 09;

ENVIRONMENTAL activists have an above-ground and a below-ground view of the world.

Energy sources harnessed on or very close to the surface, such as wind, tidal, solar and hydro power, are good. These sources are renewable and do not emit carbon dioxide, the main greenhouse gas warming the planet.

However, energy sources found under the ground - such as coal, oil and natural gas, as well as uranium for nuclear power - are bad. Fossil fuels are major greenhouse gas emitters while nuclear power, though it produces almost no global warming emissions, is still regarded by many environmentalists as too much of a safety and proliferation risk.

But there is another form of underground energy that gets an environmental seal of approval: geothermal heat. What comes out of the ground with this form of energy are hot water and steam, and almost no pollution.

Advocates point out that geothermal is the only form of renewable energy that provides a near-constant supply of base- load electricity to commercial grids in the same way that plants powered by coal, oil, gas and nuclear fuel do. Other types of renewable energy generate electricity intermittently, depending on the strength of the sun, wind, waves and tides.

South-east Asia is a world leader in exploiting the first wave of geothermal power, although it could do even more with the right incentives. Of some 10,000 MW of geothermal power installed around the world, nearly one-third is in the Philippines and Indonesia, the two largest generators of electricity using underground heat, after the United States.

This is only a tiny fraction of global electricity supply. But installed geothermal capacity is expected to reach 13,500 MW next year, with the number of countries producing power from underground heat rising to 46, from 21 a decade ago.

This power system is currently limited to areas where volcanic activity produces very hot underground water in reservoirs, which may be as large as 50 sq km and can be tapped to drive steam turbines installed in power plants on the surface.

Among places with the richest volcanic resources are those on the so-called Ring of Fire that circles the Pacific. They include New Zealand, Indonesia, the Philippines, Japan, Russia's Kamchatka Peninsula, the west coasts of the US and Canada, Central America, and the west coast of South America.

The Ring of Fire is a zone where tectonic plates collide to create the earthquakes and tsunamis so much in the news in recent days. But these same forces also create subterranean heat reservoirs that can easily be reached with current oil and gas drilling technology.

But volcanic geothermal power exploits less than 5 per cent of the very hot underground water resources that could be exploited worldwide, according to the International Energy Agency. Advanced drilling technology in geologically stable parts of the world has opened up a big underground heat source for future power generation. This has unleashed a wave of exploration and development activity in Australia, Europe, the US, China and India.

Known as Enhanced Geothermal System (EGS) or 'hot rock' technology, it focuses on high heat-producing granite typically found between 3km and 5km below the surface. In this zone, which draws heat from the molten core of the earth and the decay of radioactive elements in the crust, the temperature can reach 300 deg C. By some calculations, the heat energy content in the upper 10 km of the earth's crust is 50,000 times greater than the energy content of all known oil and gas resources.

Exploiting this power - by drilling down, fracturing the rock with water pumped in under high pressure and then drawing very hot water from the resultant reservoir up a separate well - poses major technical and financial challenges. Since 2006, two EGS projects in Europe, both near urban centres, have been halted amid concerns that the underground rock fracturing had caused earth tremors. However, this appears to be a manageable problem.

Geoscience Australia, a government agency, calculates that extracting just 1 per cent of the energy from rocks hotter than 150 deg C (the minimum for generating electricity) and less than 5 km below the surface would yield about 26,000 times Australia's primary power usage in 2005.

A report last year commissioned by the Australian Geothermal Energy Association concluded that geothermal power could provide 2,200 MW of baseload capacity by 2020, about a third of the new generating capacity the country would likely need by then.

But this will require investment of at least A$12 billion (S$15 billion). The cost of geothermal electricity will also have to fall. The industry reckons this will happen as commercial-scale generation results in improved efficiency and climate change concerns impose added costs on fossil fuel power.

The writer is a visiting senior research fellow at the Institute of Southeast Asian Studies.