Geothermal energy accounts for half of Kenya’s total energy production. The majority of this energy is produced at the Olkaria geothermal power project in Naivasha. At the end of last year, Kenya ranked seventh in the list of the best countries for geothermal energy worldwide. Geothermal energy makes up 47% of the total energy production in the country – a percentage that is on the rise. The only other geothermal energy producer in Africa is Ethiopia, which started production in 1998 and has a capacity of 7.5 megawatts.
Why East Africa is a hotspot for geothermal energy
Globally, geothermal resources are often found at tectonic plate boundaries, such as around the Pacific Ring of Fire. In Africa, there are many geothermal resources where new boundaries are being formed: the East African Rift System. The beginning of the system is not clearly defined; it originates on the Arabian Peninsula before extending southward across the Red Sea and reaching Djibouti. As it progresses southward in Africa, the rift area forks into two arms: the eastern arm ends at the border between Kenya and Tanzania while the western arm goes further south, stretching 6,400 kilometers through over 10 countries before ending in Mozambique.
Over millions of years, the African plate has been pulled in two directions at a rate of a few centimeters per year. Eventually, Africa will split into two separate continents and two tectonic plates will emerge, the Nubian plate in the west and the Somali plate in the east.
The pulling process also causes magma to form at various points along the rift system. One of these places is Olkaria in Naivasha. Below the surface, molten rocks heat groundwater. Wells bring this hot water and steam to the surface. When used at high pressure to drive turbines, the steam generates electricity. The hot water is injected back into the ground to recharge the groundwater supply.
How to find geothermal energy resources
A team of experts is needed to determine the suitability of a site for exploring geothermal resources. At a minimum, it requires the presence of groundwater and high temperatures – often around or above 150 degrees Celsius – and permeable rocks that allow hot water and steam to flow into production wells, according to Mohamed Abdel Zaher, a geophysicist at the National Institute for Astronomical and Geophysical Research in Cairo.
Some surface visual characteristics may give an initial hint. Hot springs, hot mud pools, and steam rising from the ground are signs of geothermal activity. Another indicator is the presence of specific rocks, such as calcite, or mineral veins like quartz, which suggest that the rocks have been altered during interactions with hot water.
At Olkaria, the clue was the fact that the surrounding area is ring-shaped like a collapsed volcanic caldera. A series of smaller volcanic peaks appears to have been drawn into the caldera.
If the surface characteristics seem promising, geochemists will intervene to analyze fluid and gas samples to estimate the depth and temperature of the heat source and where the fluids are flowing. Seismic sensors may be deployed to infer the fragility of the subsurface rocks. It is important that the rocks are permeable but they need to be strong enough to withstand interactions with cold water heated by the magma below.
If all this data looks promising, drilling for exploration will begin, and if everything goes well, a production well will follow, and ultimately a full power station.
Zaher and his colleagues recently completed a project that could help experts across the continent identify potential geothermal energy targets before starting costly exploration on the ground. “It’s hard to predict the exact energy or electricity that can be produced for all of Africa,” he says. But his team integrated a variety of geological, seismic, and other geophysical data into a Geographic Information System to predict the most promising places for geothermal exploration. The team reported in a paper published last year in the Geothermal Energy journal that the resulting map identifies 14 areas with high geothermal potential.
Source:
https://www.sciencenews.org/article/geothermal-energy-africa-kenya-renewable-electricity
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