Background to Geothermal Energy
Geothermal energy is heat from within the earth. This heat is continuously being produced by processes in the subsurface and stored in rocks. When cold water comes into contact with these hot rocks, geothermal reservoirs are formed which when drilled into and fluids brought to the surface can be used to produce electricity, heat buildings and greenhouses and for other purposes. The most active geothermal resources are usually found along major plate boundaries where earthquakes and volcanoes are concentrated. The East African Rift Valley that runs through Eritrea, Djibouti Ethiopia, Kenya, Uganda, Tanzania, Rwanda, Burundi, Malawi, Zambia and Mozambique is endowed with enormous amounts of geothermal resources as manifested by volcanic eruptions and geothermal manifestations (hot springs, fumaroles, geysers). This indicates the presence of a remarkable geothermal potential in the region and therefore presents an opportunity for major geothermal power developments in these countries.
A good number of these East African countries have taken keen interest in the development of geothermal energy. Kenya is leading in the region in the development of this indigenous resource, largely due to government commitment and well trained workers. In fact, it is among the 1st ten countries in the world that generates electrical power from geothermal resources, currently standing at about 273 MWe against an estimated total potential of over10,000 MWe. Olkaria geothermal field is so far the largest potential site with current installed capacity of 269 MWe from three power plants owned by Kenya Electricity Generating Company (155 MWe) and Orpower4 (110 MWe) and Oseria (4 MWe). Production drilling is currently taking place at the Menengai geothermal field for 125 MWe power developments. Detailed exploration and drilling are planned for prospects in Suswa, Longonot, Baringo, Korosi, Paka and Silali volcanic fields.
Apart from electricity generation, geothermal resources are also being used directly. Some of the projects on direct use include the Oserian flower farm which has a 50-acre cut flowers farm under geothermal heated greenhouses using 18MWth. Other direct uses of geothermal energy in Kenya include a spa and swimming pool at Olkaria geothermal project and at Lake Bogoria. Other minor uses are for drying pyrethrum at Eburru and water harvesting at Eburru and Suswa.
Ethiopia follows Kenya in development of this resource. A 7.2 MWe net capacity pilot plant was installed in the country which operated for a short while before encountering operational difficulties that were essentially due to lack of appropriate field and plant management skills. In the last couple of years interest has again picked up. The Aluto Langano Power plant is being refurbished, more wells being drilled in this geothermal field and elsewhere in the country’s rift valley.
Zambia has had a mini geothermal pilot binary power plant of 200 KW capacity since the 1970’s which was installed on the basis of limited exploration work. The plant, however, never became operational due to lack of trained manpower. Plans are now in place to restore the plant and make it operational.
Djibouti has drilled about six exploratory wells in the Assal geothermal field and intercepted a very high temperature system. However, due to the high salinity of the encountered fluids, the resource development has been delayed, till funds are available to apply proposed technical solutions to the salinity problem.
Other countries in the region have carried various but limited reconnaissance surveys. The geo-scientific studies have resulted in identification of viable prospects in each of the countries which have been given priority for exploratory drilling. Rwanda is currently drilling its first exploration wells.