Olkaria VI, Kenya: Inside the world's largest single-turbine geothermal plant

An exclusive interview with KenGen's, Frank D. Ochieng, reveals all there is to know about the African giant leading geothermal energy globally.
Sade Agard
Olkaria VI Geothermal Power Station
Olkaria VI Geothermal Power Station

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  • One of the largest geothermal power plants in the world, Olkaria, which is situated in Kenya, is now generating more geothermal power than some of the world's top geothermal producers, including Italy, Japan, and Iceland, by drawing energy from the Earth's core.
  • With new geothermal drilling contracts, including one in Aluto-Langano, Ethiopia, KenGen has its sights set on helping other countries that, like Olkaria, are along the East African Great Rift where tectonic plates are moving apart.
  • Other than electric power generation, the Olkaria geothermal field has showcased to the world other direct-use applications of geothermal steam, such as balneotherapeutic bathing and supplying energy to flower farms.

Right under our feet is the future of clean, renewable energy.

The temperature of the Earth's core, which is what we're referring to, is approximately 5,200° Celsius (9,392° Fahrenheit), making it about as hot as the sun's surface. If we could harness this heat, we could turn it into a source of unimaginable amounts of renewable energy — if we drill down far enough. However, some of that heat also travels upward through the Earth's thick mantle, to the surface.

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There is no better location to observe the potential of this heat than Hell's Gate National Park, which is situated around 120 kilometers (75 miles) northwest of Nairobi, the capital of Kenya. Here, steam plumes litter the dirt roads and off-grid valleys, spewing heat from the Earth's interior.

Olkaria, one of the world's largest geothermal power plants, is tapping into this heat and is already generating more geothermal energy than some of the world's largest geothermal producers, such as Italy, Japan, and Iceland.

Now, as the world prepares for an African CoP (the UN Climate Change Conference) set to start in Egypt on November 6, Interesting Engineering (IE) interviewed chief communications officer, Frank D. Ochieng, at KenGen - the parastatal company operating the Olkaria facility - to learn all there is to know.

Olkaria VI, Kenya: Inside the world's largest single-turbine geothermal plant
A geothermal steam plume amid red-pigmented rocks

Olkaria lies in the volcanic Great Rift Valley of East Africa- where tectonic forces are tearing the continent apart

Olkaria VI, Kenya: Inside the world's largest single-turbine geothermal plant
In the Great Rift Valley: A chain of volcanoes exist on the border between Kenya and Tanzania

The Olkaria geothermal area is located within the Kenya Rift System (KRS). This is part of the greater East African Rift System (EARS). This tectonically-active valley runs for around 7,000 kilometers (4,350 miles) across the continent's eastern side. Here, the continent is literally tearing itself apart, as two tectonic plates separate.

According to a BBC article, Anna Mwangi, a geophysicist for KenGen, explained, "This is an active process that will go on for several millions of years to come. In some millions of years, if you come here, this will be an ocean."

Still, while this is happening, Olkaria can exploit the energy released during tectonic movement.[This location] is quite unique in its potential as a geothermal resource," shared Frank D. Ochieng.

"Due to the thinned crust caused by lithospheric extension of the Nubian and Somali plates, there is high heat flux to the shallower levels of the crust, where it is easily mined through [the] drilling of geothermal wells."

Olkaria VI, Kenya: Inside the world's largest single-turbine geothermal plant
A steeply sloping ridge of the Great Rift Valley southwest of Nairobi, Kenya, East Africa

Technology that separates the steam from the water is the key to using geothermal energy for electricity

The Olkaria geothermal plant currently has six units, which are known as Olkaria I, II, lll, IV, V, and VI, with a seventh (Olkaria VII) currently under tender (i.e has yet to be constructed).

In general, geothermal power plants generate energy using steam. The steam comes from the geothermal reservoir and is mined by sinking a geothermal well to greater depths. In Olkaria's case, this is 3,000 meters below the ground surface.

Ochieng described to IE that the geothermal reservoir in Olkaria is two-phased, i.e., it has both steam and water (brine) phases. First, a steam separator isolates the steam from the water.

"The separated steam (which is 99 percent dry) is directed to the power plant via steam lines and rotates the turbine at 3,000 revolutions per minute. The turbine is coupled to a generator which converts the geothermal energy to electrical energy," revealed Ochieng.

On the other hand, water, the concentrated liquid left over after heat and steam are extracted, known as the 'geothermal brine,' is re-injected back into the ground via re-injection wells to ensure reservoir sustainability.

Olkaria VI, Kenya: Inside the world's largest single-turbine geothermal plant
The Olkaria power plant works by separating water and steam

Massai community roots: a geothermal energy resource that has served cooked eggs since the 19th century

Olkaria VI, Kenya: Inside the world's largest single-turbine geothermal plant
Olkaria roots: The Maasai community has used the geothermal energy since the 19th century.

As mentioned earlier, the Olkaria geothermal site is located inside Hell's Gate National Park. This area is home to a wide variety of wildlife, including warthogs, zebras, and giraffes. It's also home to members of the pastoralist ('cattle farming') Maasai community, who have been using the heat since the 19th century.

"The natural heat that flows from underground is critical to their nomadic way of life," explained Ochieng. "The Maasai community are known to have used hot springs in Olkaria for bathing as early as the 19th century."

IE is informed that the community views the geothermal springs as essential to their way of life. From cooking eggs, washing, and bathing to providing a location to heal illnesses or for performing traditional rites, the heat continues to serve them in various ways.

'The name Olkaria is derived from the "red ochre," a natural clay earth pigment'

Olkaria VI, Kenya: Inside the world's largest single-turbine geothermal plant
Olkaria roots: Red 'ochre pigment has been used since prehistoric times for cave art.

Additionally, "The name Olkaria is derived from the "red ochre," a natural clay earth pigment composed of iron oxide, clay, and sand," explained Frank D. Ochieng. The olkaria is dug up by locals in Maasai communities and brought back to the community to be used as paint in various Maasai celebrations, particularly among warriors and women. Subsequently, it is seen as a source of pride for the community.

Civilizations across the continent have also used the red pigment for hundreds of years to make insect repellent, provide protection from the sun, and for cave art.

From Olkaria's '1950s' failures to being the second-largest geothermal plant in the world

Olkaria VI, Kenya: Inside the world's largest single-turbine geothermal plant
Olkaria Unit II Power Plant

"It was not until the 1950s when the [Kenyan] Government ventured into large-scale tapping of the geothermal steam to change the country's fortune through electricity generation," said Ochieng.

While the year 1952 saw the successful drilling of the first geothermal well, many decades of successes- and failures- occurred before Olkaria's first power plant (Olkaria I) was commissioned in 1981. The original generation capacity of which was a humble 15 Megawatts (MW).

Since then, five more power plants have been put into operation at the site, along with several refurbishments. The most recent addition is 'Unit 6' (Olkaria VI), which came online in June 2022. Olkaria VI shares the title of the world's biggest largest single-turbine power geothermal plant with Rotokawa II- which is located in the northeast of Taupo in New Zealand.

"Presently, the Olkaria geothermal site has installed capacity to produce about 799MW of cost-effective, baseload power to the national grid," said Ochieng, making Olkaria the second-largest geothermal plant in the world.

KenGen estimates that the facility generates around 27 percent of all the energy in Kenya. The nation already relies on geothermal steam for 38 percent of its power- a higher percentage than any other country.

Addressing a misconception: Does geothermal heat contribute to global warming?

IE learned that there are two common misconceptions about geothermal heat: that it contributes to global warming, and that geothermal heat is not a renewable form of energy.

In reality, "geothermal energy, which is basically the heat generated and stored within the Earth, does not emit greenhouse gases (GHG) as compared to conventional energy sources such as the burning of coal or fossil fuels," said Ochieng. "As such, it helps mitigate the impacts of global warming and climate change."

"Also, many believe that geothermal plants produce smoke. This is not true, he said. "What is seen as smoke is actually steam, therefore clean.

Equally, geothermal heat is a renewable source of energy. This is because the heat is continuously produced from the decay of radioactive substances in the Earth's interior."

Further, well-managed geothermal reservoirs, through controlled and robust re-injection strategies, can produce energy indefinitely. The natural water cycle also ensures that the reservoir replenishes with time.

The future of Olkaria is heading towards an estimated potential of 10,000 MW

Olkaria VI, Kenya: Inside the world's largest single-turbine geothermal plant
Geothermal infrastructures in Hell's Gate National Park

"The exploitation of the geothermal resource potential of the Olkaria geothermal plant has only begun," said Ochieng, who also claimed the site has an estimated potential to produce 10,000 MW of energy. The plan is to fully exploit this potential in line with the Kenyan government's mandate of doubling the facility's generation capacity by 2030 in order to provide reliable, affordable, clean, and sustainable power to the country.

Several geothermal expansion projects are also in KenGen's pipeline. This includes refurbishment of the aging Olkaria I power plant to increase the plant's installed capacity from its current 45 MW to 60 MW.

The company also plans to further the development of Olkaria VI and VII power plants, with a capacity to generate 140 MW each. It will also continue its geothermal exploration program in Olkaria to evaluate its geothermal resource potential. A seventh plant - Olkaria VII - is currently under tender, with a proposed generation capacity ranging from 83 megawatts to 140 megawatts.

Furthermore, KenGen completed plans to set up an energy industrial park at the Olkaria geothermal power site. The industrial park will allow the company to sell electricity directly to the businesses that will set up there, allowing Kenya to take advantage of its competitively priced geothermal steam and electricity as critical economic drivers of production.

Other than electric power generation, Olkaria showcases other direct-use applications of geothermal steam

"Today, the Olkaria geothermal field places Kenya as the seventh largest geothermal producing country in the world, trailing behind USA, Philippines, Indonesia, Turkey, New Zealand, and Mexico," explained Ochieng.

"Other than electric power generation, the Olkaria geothermal field has showcased to the world other direct-use applications of geothermal steam, such as bathing for balneotherapeutic effects." The Olkaria Geothermal Spa and Demonstration Centre, the only all-natural spa in Africa, demonstrates this, which continues to attract significant domestic and foreign tourism.

Additionally, the field is also used for heating purposes in flower farms.

Olkaria VI, Kenya: Inside the world's largest single-turbine geothermal plant
Oklaria's geothermal steam will be used to grow flowers at scale

Geothermal is a renewable energy source that can power the planet

Olkaria VI, Kenya: Inside the world's largest single-turbine geothermal plant
KenGen's geothermal drilling in Aluto-Langano, Ethiopia.

However, even though Kenya is the continent's leader in harnessing geothermal energy, what about the half a dozen other nations up and down the East African Great Rift? Well, KenGen has it's eyes set on them as well, as seen with its ambitious 'Diversification Strategy' which includes a geothermal drilling contract in Aluto-Langano, Ethiopia. The company has also built up a service business to support geothermal development in other countries in Eastern Africa through drilling.

It's only a matter of time before when other nations will start tapping into the heat too.

With this is mind, geothermal is already powering more than 500 power plants worldwide. The renewable resource provides electricity to millions of homes in Southeast Asia, North America, Europe, and other regions. It is already one of the most common renewable energy sources in the world.

We know geothermal power opportunities exist wherever tectonism and volcanism have pushed magma closer to the surface. In light of this, we look forward to discovering how the 4.6 billion dollar industry will inspire upcoming efforts to harness the enormous potential of the Earth's heat.