Solving Africa’s Energy Poverty Problem, Part 5 Geothermal

Geothermal Power can help solve Africa’s energy poverty
The East African Rift Valley Geothermal Resources Source: Alan Hoffman at lapsedphysicist.org

Geothermal power generation is possible in broad seismically active regions of Africa such as the Rift Valley and near some volcanoes. There are 157 active volcanoes in Africa that may offer potential for geothermal energy generation (see map). Most of them are in East Africa along the Rift Valley, but some occur in North and West Africa. The Rift Valley has an estimated potential of 4,000 MW of energy, but less than 600 MW have been developed, largely in Kenya with 586 MW currently available. Ethiopia has a small 7.3 MW facility. Surface surveys and exploration are underway in several other countries. Much of the funding for these projects comes through the World Bank and Geothermal Risk Mitigation Facility (GRMF) fund, a multinational organization, which is administered by the African Union (AU).[1] GRMF has eleven-member countries: Ethiopia, Kenya, Tanzania, Rwanda, Uganda, Burundi, Comoros Islands, Eritrea, Democratic Republic of Congo, Djibouti and Zambia.

For comparison, the “Geological Survey of India has identified 350 geothermal energy locations in the country. The most promising of these is in Puga valley of Ladakh. The estimated potential for geothermal energy in India is about 10,000 MW.”[2] None have been developed to generate electricity at this time. Surveying, exploring and evaluating potentials continues.

Source: India Energy Portal at http://www.indiaenergyportal.org/
Geothermal Electric Power Details

Wells are drilled into thermally active areas and hot water or steam is pumped out, often under their own pressure, to turn turbines connected to electrical generators before being condensed and returned through injection wells to replenish the reservoir. Water heated above the boiling point turns to steam as the pressure is relieved while being pumped to the surface. There are several types of plants depending on the temperature of the geothermal energy available.

  • For vapor dominated systems at the highest temperatures, 464 to 572°F (240 to 300°C), steam is forced directly from wells under its own power to turn turbines/generators.
  • For liquid dominated systems at temperatures, greater than 360°F (182°C), superheated water under pressure pushes toward the surface and, as pressure is reduced in transit, part of it boils and produces steam for turning turbines/generators.
  • For binary systems at temperatures in the range of 248º to 392ºF, (120º–200ºC), hot water pushes is pumped out of the wells, which then heats a lower boiling secondary fluid to produce “steam,” a.k.a. gas, to turn turbines/generators.

In all of these cases the water is condensed and returned through an injection well although some of it may be recycled in binary systems for further heat extraction. The secondary fluid of binary systems, usually a lower boiling hydrocarbon, is completely condensed and recycled in a closed-loop system (see diagrams below).[4]

Figure 13: Schematic diagram of a typical steam or hot water to steam geothermal power plant [5]
Schematic diagram of a binary cycle geothermal power plant

By 2020 Kenya hopes to be the first sub-Saharan African nation to reach “universal access” to electricity with 95 percent of homes having access to electricity, an increase from 2016 when 55 percent of homes had access. Over 60 percent of Kenya’s electrical power is provided by hydroelectric and geothermal power plants. Kenya plans to increase geothermal power output ten-fold to 5,000 MW by 2030, which is 26 percent of its total geothermal capacity.

[1] Waruru, Maina, “More African Countries Embrace Geothermal Power, Receive $37M in Funding,” Renewable Energy World magazine, June 23, 2016, http://www.renewableenergyworld.com/articles/2016/06/more-african-countries-embrace-geothermal-power-receive-37m-in-funding.html.

[2] India Energy Portal at http://www.indiaenergyportal.org/

[3] India Energy Portal at http://www.indiaenergyportal.org/

[4] India Energy Portal at http://www.indiaenergyportal.org/subthemes_link.php?text=geothermal&themeid=1 Original source is World Energy Council, 2001 Survey of World Energy Resources at https://www.worldenergy.org/publications/2001/world-energy-resources-2001.

[5] World Energy Council, 2001 Survey of World Energy Resources at https://www.worldenergy.org/publications/2001/world-energy-resources-2001/ Original Source: Geothermal Energy, 1998, University of Utah).

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