State-owned power utility 
Eskom’s research into 
renewable energy has predominantly focused on biomass energy, ocean energy, wind 
energy and solar energy, but, this year, the power parastatal has 
included geothermal energy as part of its project research portfolio.

Last year, Eskom began assessing large-scale geothermal energy as a renewable resource of energy that may be worth exploring for electricity generation. “We have a list of sites and are going to begin prefeasibility studies to determine if the identified sites can produce large-scale power generation,” says Eskom renewables manager Terence Govender.

Eskom’s research and innovation department is busy compiling a scope of work for the detailed resource assessment. 
“This will allow us to determine the sort of potential there is that can be transferred into large-scale power generation, hopefully, leading to the conceptual design stage next year or so,” notes Govender.

The high-level resource 
assessment will include studies to determine the type of rock as well as the temperatures gradient below the surface areas. 
“We are looking for temperatures in excess of 90 ºC to 100 ºC, 
and between 500 m and 3 km below the surface. Any temperatures below this would provide low-efficiency geothermal power generation,” adds Govender.

The World Energy Council (WEC) reports that electricity has been commercially generated by geothermal steam since 1913 and has been used on a scale of hundreds of megawatts, for five decades.

Geothermal energy was, until recently, only considered economically viable in areas where thermal water or steam is found concentrated at depths of 
less than 3 km in restricted 
volumes. 
This has changed in the past two decades. Developments in the application of ground-source heat pumps which use the earth as a heat source for heating or as a heat sink for cooling, depending on the season, make it possible for all countries to use the heat of the earth for heating and 
cooling.

“One of the benefits of geothermal energy is that it is not influenced by weather conditions like solar, wind, or hydroenergy 
applications. 
“Geothermal energy also has a storage capacity that can be used for baseload and peak power plants,” concludes Govender.

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