Geothermal energy set to power Africa's Rift Valley

A huge expansion of geothermal energy is planned in East Africa's Rift Valley after tests to assess the area's suitability for the technology proved hugely sccuessful, the UN Environment Programme announced last week.

Geothermal technologies typically work by harnessing the energy from hot rocks underneath the earth's surface to create steam that can be used to drive turbines to create electricity and heat water.

The UN estimates that not only could the technology provide the region with zero carbon energy, it would also prove more cost effective than conventional fossil fuel-based power stations. It estimates that a geothermal power plant capable of producing 70MW of energy would cost $75m less than a conventional plant of the same scale.

The research project, funded by the UN's Global Environment Facility (GEF) and involving the Kenyan power company KenGen, found a number of suitable steam wells, each of which could generate between four and five megawatts of electricity.

Achim Steiner, UN under-secretary general and UNEP executive director, said there were at least 4,000MW of electricity ready for harvesting along the Rift. "It is time to take this technology off the back burner in order to power livelihoods, fuel development and reduce dependence on polluting and unpredictable fossil fuels," he said. "From the place where human-kind took its first faltering steps is emerging one of the answers to its continued survival on this planet."

The main challenge to expansion in Kenya and elsewhere along the Rift has been the risk associated with drilling and the high costs if the steam wells are missed.

However, the UN claims that a $1m Joint Geophysical Imaging project headed by the GEF has helped overcame this challenge by more accurately pinpointing well locations. The project also used techniques known as Micro Seismic and Magneto Telluric surveys and studies for identifying promising new drilling sites.

One existing geothermal plant in Kenya generating 45MW has been operating for a quarter century. A second plant was brought on stream in 2000 with a capacity of 70 MW.

Two years ago the GEF Council approved the Africa Rift Valley Geothermal Development Facility (ARGeo) to expand use of geothermal technology, backed with close to $18m of funding. It will aim to harvest energy from at least 15 wells.

Kenya's current electricity capacity is around 1,000MW. The country relies heavily on hydro-electric plants that have suffered in recent years as a result of low rainfall and diminishing water supplies.

The country has set itself a goal of generating 1,200MW from geothermal sources by 2015.