Geothermal energy is heat derived within the sub-surface of the earth. Water and/or steam carry the geothermal energy to the Earth’s surface. Depending on its characteristics, geothermal energy can be used for heating purposes or be harnessed to generate clean electricity. Globally, geothermal energy is a $4.6bn (£3.3bn) industry, with more than 500 power plants electrifying millions of households across South-east Asia, North America, Europe and beyond. Geothermal is, after all, the second most abundant source of energy in the world behind solar.
But it in terms of how much we tap this source of power, geothermal lags well behind. In 2016, the energy the world harvested from geothermal was just 4% that from solar, despite geothermal having some important advantages. Wind turbines are useless on a still day, and solar panels’ energy falls when the sun is covered by clouds and at night. Meanwhile, no matter the time of day, the Earth below us is steadily releasing vast quantities of heat, whatever the weather.
Currently the nine countries that produce most geothermal power are: The USA, Indonesia, Philippines, Turkey, New Zealand, Mexico, Italy, Iceland and Kenya. Kenya has got a really good resource and that’s the Rift Valley. You’ve got this incredible heat that’s so near the surface.” In other parts of the world, you’d have to drill several kilometers or more to find equivalent temperatures. Harnessing this energy for electricity is very simple, says Karingithi. “The way we do it at Olkaria, you separate the water from the steam. The steam you take to the turbine, which rotates and generates electricity.”
When you drive along the dusty dirt road that winds through Kenya’s Hell’s Gate National park, past the zebra, gazelles and giraffes, you will see a plume of steam shooting skyward in the distance. Vehicles must sometimes swerve to avoid running over warthogs as they enter a vast valley dotted with dozens of steam vents – a factory of clouds. Blasts of steam billow loudly, releasing heat from deep within the Earth. But even more powerful is the steam you don’t see: that which twists through miles of tubes to push past turbines, generating a type of clean energy that won’t run out for millions of years.
Atop this infernal labyrinth of tubes is Kenya’s Olkaria Geothermal Project, where a new addition to the power plant is about to go online. “When Olkaria VI is complete, it will be the largest single geothermal plant in the world,” according to Cyrus Karingithi, who leads infrastructure and resource development for Olkaria. At 86 megawatts, the Olkaria VI expansion will push the project’s total production to 791.5 megawatts. That’s about 27% of all the energy in Kenya, according to KenGen, the parastatal company that operates Olkaria. Already, Kenya relies on geothermal steam for 38% of its power – a greater proportion than any other nation and its network continues to expand. This should be great news, as geothermal steam is an unlimited natural source of energy, however harvesting this energy is not without risks.
Once you identify a strong location, “you need investors not to be faint-hearted”, says Karingithi. “Drilling a well costs six million. And if you miss, you’re sunk.” That is the major disadvantage of geothermal, he says. “The capital investment is very high and it puts off many people.” For many geothermal engineers, the most exciting moment comes when you drill a new well – and strike steam. “When you drill a well they open the valve and let the fluid discharge into the atmosphere, the noise and the shaking is incredible – it’s just absolutely amazing,” says Newson, of what’s called a vertical discharge test. “The power that comes out of that well – for 20 years – that’s so exciting!” As the steam powers the turbines, the water gets injected back into the ground, to make sure the steam wells never run dry. With time it will reheat and return once more as steam.
At Olkaria, wells are tested for about two months to measure their flow rate. Then, the steam is directed either into an on-site mini plant, or through tubes to a larger plant such as Olkaria VI. The small plants that sit upon the wells are less than a football pitch in size and can be dismantled and moved from one well to another when more powerful steam sources are found. The small satellite wells tend to be two to three kilometers deep, each producing about 5 megawatts of energy – enough to power 50,000 Kenyan homes. “That is a major advantage of geothermal – it requires a very small footprint,” says Karingithi. Geothermal requires significantly less land than wind, solar or coal.
That said, a single geothermal well may be tiny, but 300 of them spread across a valley crisscrossed by tubes and transmission lines, access roads and injection pools, makes Olkaria a behemoth. Because Hell’s Gate is home to a lot of wildlife, in some places the steam pipes must be lifted several meters above the ground to allow giraffes and other wildlife to pass safely. The geothermal well also pose a problem for the pastoralist Maasai who have grazed their cattle across this land on and off for centuries. To make way for Olkaria’s expansions, Kengen relocated 1,181 Maasai from 155 households to a 1,700 acre stretch of land outfitted with houses, churches and schools. “We hope to get the next generation of scientists and engineers from that same, Maasai community,” says Karingithi.
So far, Olkaria employs 1,250 people but only about 50 are Maasai, and only 20 hail from the community that was displaced. Not many Kenyans have the opportunity to attend university, least of all rural pastoralists. Now, some of the 500 Maasai families who live around Suswa crater to Olkaria’s south worry they’ll soon be forced out, too. Another geothermal company has begun scouting for geothermal potential around the crater, formed by a now inactive volcano. The company believes the Suswa crater has the potential to generate 750 megawatts of geothermal electricity – as much as Olkaria produces today. “In Olkaria, those people have been chased away,” says Kiano Sempui, a Maasai man and father of three who lives and grazes goats, sheep and cows at Suswa. “We are very sure that when the company comes here, sooner or later, the same will happen to us.”
What’s more, Sempui fears that geothermal would disrupt the small tourism industry he’s worked so hard to create. On weekends, dozens of Kenyan and foreign tourists head up the crater to visit a labyrinth of natural caves, hike along the crater rim for stunning views of the forest below them where leopards live, and to camp under the stars at the edge of a cliff. The conservancy’s tourism revenue pays teachers’ salaries, hospital bills and repairs roads.
“When the geothermal comes up, the conservancy will be destroyed, because there aren’t many tourists who will want to put up with all that noise,” says Sempui, in reference to the mind-shattering billowing of steam that erupts from geothermal wells when they are being tested or undergoing maintenance. But maybe there is hope. If all effort is applied o use the geothermal energy in the most sustainable way, then you could actually invite tourism to witness this process. The organization Tomorrow’s Air is already offering educational touristic tours that visit carbon offset plants. When well performed, in Kenya it might be possible to organize conservation tours that include wildlife spotting and visiting a geothermal energy plant. A good example of sustainable integration is GeoParks, the Colline Metallifere in Tuscany, Italy. Besides boosting Italy’s energy supply in a sustainable way, this geothermal plant and its surrounding also boost tourism in the region. GeoParks, the Colline Metallifer is therefore recognized by UNESCO as both a geothermal nature reserve and a sustainable geothermal energy plant.
Another challenge is how to handle the CO2 released by the geothermal fluids and that can occur naturally in hot springs and steam vents. The amount of carbon released by geothermal varies widely from one project to the next, but overall it is still miniscule compared with burning fossil fuels – just 2.7% as much as burning coal, or 5% as much as natural gas. Some plants, such as projects in Iceland, capture the carbon and inject it back underground, where it mineralizes and becomes harmless. A project in Iceland, called Carbfix, has been researching this for the last 10 years, and now a large proportion of CO2 from the large Hellisheidi Geothermal Power Station is re-injected deep into the basalt rocks where it forms new minerals which become part of the rocks.
More problematic than the CO, can be the reinjection of water deep into the rocks to replenish the steam. The water re-injected “has high concentrations of silica and salts [relative to cold groundwater], and sometimes toxic elements, such as arsenic, lithium, antimony, mercury, sulfur, and many others,” says Newson. In most cases, the water is injected deep enough that it doesn’t interfere with aquifers, but if done wrong it has the potential to pollute sources of drinking water.
And then there is the fact that through fracturing rocks, geothermal engineering can, and regularly does, cause seismic activity. On rare occasions, “you can feel the earthquakes. And people don’t like that,” says Newson. “That generates a lot of distrust and a lot of ‘not in my backyard,’ for which you can’t blame people.” Although infrequent, sometimes the earthquakes are more serious. In November 2017, a geothermal plant caused a 5.5 magnitude earthquake in Pohang, South Korea that left 1,700 people displaced when water injections fractured a previously unknown fault line. Better monitoring and risk management could help avoid large earthquakes like this in the future.
As governments and foreign investors spend billions of dollars to connect more of East Africa to the grid, concern for about wildlife and rural pastoralists’ land are some of several challenges that will need to be addressed as people turn to geothermal to meet the energy demands. Worldwide it will be interesting to follow and learn from their experiences, so geothermal energy can be used in the most sustainable way possible for us humans and the environment. More tips about Geoenergy you can find at Think Geoenergy.