In this brief we focus on geothermal as source of energy, shading some perspectives on what it is, the potential and why it may be an attractive source of energy but also point out the downside factors that may limit its exploitation in East Africa.
By Moses Kulaba, Governance and Economic Policy Centre
Globally, there is an increasing focus on mitigating climate change by gradually transiting to clean energy sources. With its location along the equator and various volcanic plates, Africa is considered as a sleeping giant of renewable energy sources. Despite this abundancy, Africa lags behind in energy access and investment in renewables generally. If deliberate efforts are not taken, Africa will remain perpetually in Energy poverty. The disparity in East Africa is even worse, with countries facing significant energy shortages and a very small investments in Geothermal power.
According to scientists, geothermal energy is largely heat flowing from the core of the earth’s crust to the top surface, which is trapped and transformed into energy.
The Earth is generally a block of solid rock and molten surfaces. At about 3000km deep into the earth there is a transition from solid rock to an inner molten core comprising of liquid iron, nickel and a mixture of other substances. The amount of heat within 10,000 meters of the earth’s surface contains 50,000 times more energy than all the oil and natural gas resources in the world.
At this depth, the temperatures raise up to around 5700 Kelvins, which is almost the same on the sun. These temperatures ordinary do not reach to the surface of the earth because the solid rock between the earth’s surface and its molten core are heat conductors.
However, the molten rock can escape to the earth surface through an eruption and the heat can reach the earth surface through fissures or cracks. This is trapped and harnessed to generate power as illustrated below:
Where does the heat come from?
Geothermal comes from the Greek word, where ‘Geo’ refers to Earth, and ‘Therme’ refers to Heat. The heat comes from beneath the earth’s crust. Generally, it is found distantly far below the earth’s burning molten rock ‘Magma’ and stored in the rocks and vapour in the earth’s centre. The heat comes from two major sources.
- Residual heat, which is heat left over largely when the earth formed during the gravitation aggregation phase when the solar system formed. Small bodied such as asteroids which existed before and collided to form the earth and cooled still exits and emit the heat from their bodies
- Decay process of radioactive elements in the earth’s mantle. It is estimated that since the earth formed over 4.5billion years ago, there are significant radio active materials, largely radium, radioactive potassium and others in tiny quantities but the decay of these generated enough materials to keep the earth warm
Geothermal energy resource at the surface is therefore the rate of heat flowing through the earth’s surface at any given location.
The rate of this heat flow is to surface is highly variable and depends on the local geological settings and on the types of rocks directly beneath the surface at any given location.
The heat generated from the earth’s surface is measured in the same way as we measure solar energy (Watts per Meter Square). The hottest points on the earth’s surface are ironically the deep ocean basins where magma is always welling up and creating an undersea chain of volcanic mountains.
These actually create new crusts in the ocean basins. Continents are relatively cool although there are hot spots on the margins such as in the North America where there are occasional heat flows with rates ranging between 20 milliwatts per square meter to 50,000 milliwatts per hour.
Key Features of Geothermal Power
The key feature of geothermal power is (electricity generation) is the rate at which temperatures increases with depth, which is the Local Geothermal gradient. i.e How far deep you have to reach the rocks that is hot enough to create steam.
An average gradient in the crust is about 25 degrees centigrade per km. i.e if you dig by 1 km deep the temperature at that point will be 25 degrees Celsius and constantly at that rate as you go deep and deeper.
The local gradient and thermal conductivity of the rocks the surface determine the local heat. In the mountain areas where the rocks are relatively recently formed the temperatures are hotter and well suited for geothermal.
Geothermal gradients are important because they determine how deep one has to dig to reach to a rock hot enough to produce steam by exposing water to the hot surface. Even in areas with low gradients, geothermal systems can be used for residential and commercial heating and cooling.
Geothermal power basics
To date geothermal power is still a very small tinny part of the overall electricity generating capacity of the world. The total geothermal capacity was approximately around 15 GW by 2018 and was projected to increase to 18 GW by 2021, compared to 600GW of solar and 400 GW of hydro. Asia had the largest installed capacity of around 4.8GW closely followed by the United States with around 3.5GW.
Types of Geothermal systems
There are largely two types of geothermal systems. The Hydrothermal systems (Hot wet rock) and the Enhanced Geothermal Systems (EGS).
The Hydrothermal systems account for nearly all installed and commercial systems. These are systems where natural ground water or injected water is heated at a depth. It is either its natural depth or deep boreholes and circulated through an exchange system to create steam to drive a conventional steam turbine. Hydrothermal systems must have enough natural permeability of rocks to support enough water circulation without high pressure pumping or fracturing of the rocks.
The Enhanced Geothermal System (EGS) is also referred to as the dry rock system, whereby water is circulated through a hot dry rock so the rock itself is hot but doesn’t naturally have water present because it is largely impermeable.
EGS are considered quite revolutionary in the geothermal energy sector as they can be easily installed in multiple places around the world through available engineering methods. Practically, everywhere around the world it is possible to drill and reach enough depth to generate an Engineered Geothermal System.
Why it is attractive
Geothermal has the lowest carbon foot print of any energy system types and the cheapest in dollar terms per megawatt hour produced and therefore quite competitive compared to other sources. Moreover, it can operate at high capacities of around 70% capacity compared to 20% to 30% for solar and wind respectively. Geothermal systems can also easily support other associated economic activities such as tourism in the hot water springs and spurs.
East Africa’s Geothermal potential
Kenya
In East Africa so far Kenya has the largest geothermal energy systems network located within the Rift Valley with an estimated potential of between 7,000 MW to 10,000 MW spread over 14 prospective sites. Kenya generates at least 47% of its energy geothermal with a substantive portion of this being generated from the expansive Olkaria station in Naivasha, generating up to 800MW of Kenya’s geothermal power.
Figure 2: Olkaria Geothermal Project in Kenya, Courtesy Photo of Shutterstock
According to Kenya power, so far, the Country sources up to 91% of its energy from renewables with 47% geothermal, 30% hydro, 12% wind and 2% solar. Kenya hopes to transition fully to renewables by 2030, with KenGen saying the country has the potential to increase its capacity to as much as 10,000MW of geothermal energy.
A report by the Geothermal Energy Association noted Kenya as “one of the fasted growing geothermal markets in the world.” The country is fortunate to have great geothermal energy potential, offering a cost-effective alternative to expensive fossil fuel power. In 2017, installed geothermal capacity in Kenya stood around 660 megawatts (MW); the government has established a target of 5,000 MW by 2030[1].
With more than 14 high temperature potential sites occurring along the Rift Valley, Kenya has an estimated potential of more than 10,000 MWe. Other locations include Chyulu, Homa Hills in Nyanza, Mwananyamala at the Coast and Nyambene Ridges which have equally good potential for additional geothermal generation.
As a result, it is predicted that “Kenya will lead the world with substantial additions to their geothermal infrastructure over the next decade and become a center of geothermal technology on the African continent.”
Geothermal has numerous advantages over other sources of power. It is not affected by drought and climatic variability, has the highest availability (capacity factor) at over 95 %, is green energy with no adverse effects on the environment, and is indigenous and readily available in Kenya, unlike most thermal energy that relies on imported fuel. This makes geothermal a very suitable source for baseload electricity generation in the country[2], putting Kenya in clean energy terms, a step ahead of the others in the region.
Tanzania
Tanzania is endowed with a huge geothermal potential which has not yet been used, and has only been explored to a limited extend. According to Tanzania Geothermal Development Company Limited (TGDC), a 100% subsidiary company of Tanzania Electric Supply Company Limited (TANESCO), in 2013 Tanzania had a geothermal power potential of 650 Mw. However given its location along the East African Great rift valley system, it is likely that these figures are conservative and geothermal potential could be higher with some estimates putting it up to the range of 5000 MW.
Most of the identified geothermal resources occur in three regions: in SW Tanzania in the Rungwe volcanic field, where the project site Songwe-Ngozi, is located, in northern Tanzania at the southern end of the eastern branch of the East African Rift system and in eastern Tanzania (e.g. Rufiji Basin) along the Proterozoic mobile belt around the Tanzanian Craton.
The Deputy Prime Minister and Minister for Energy, Dr Dotto Biteko said Tanzania would start drilling by April 2024. This was to be a major first step in establishing the resource potential before starting energy production.
However, to date, very limited information is available on the progress of these projects and the actual dates when geothermal power could flow into Tanzania’s energy system are uncertain.
Geothermal power is a reliable, low-cost, environmentally friendly, alternative energy supply and an indigenous, renewable energy source, suitable for electricity generation. With an increasing demand for power amidst outages and uncertain future of the LNG gas to power projects, investment and development of geothermal, could be a major boost to Tanzania’s power needs.
Uganda
The main geothermal areas are Katwe-Kikorongo (Katwe), Buranga, Kibiro and Panyimur located in Kasese, Bundibugyo, Hoima and Pakwach districts respectively. According to available data Uganda geothermal resources are estimated at about 1,500 MW[3]. Currently, the government has ambition to develop up to 100 MW in geothermal power generation capacity in the country, as reported by Afrik21[4].
Uganda’s geothermal potential lies primarily within the western part of the country, with the most prominent prospects found in the Panyimur and Kibiro regions. Geological studies indicate that the East African Rift System, which traverses through Uganda, provides favorable conditions for geothermal reservoirs. The estimated geothermal capacity in the country is substantial, and tapping into these resources could significantly contribute to the nation’s energy mix.
The main geothermal resources of Uganda are centered around Lake Albert and Lake Edward in the districts of Kasese, Hoima, Bundibugyo and Nebbi. This area lies along the Western Branch of the East African Rift System (EARS)[5]
But despite the considered geothermal potential, challenges remain in the development and utilisation of the resources. Uganda’s geological complexity poses challenges for geothermal drilling operations. However, advancements in drilling technologies, such as slim-hole drilling and directional drilling, have the potential to overcome these obstacles. Investing in research and development specific to Ugandan conditions is considered a major factor that will improve drilling efficiency and reduce costs[6].
Obstacles to peaking of Geothermal in East Africa
Despite being the cleanest and most efficient energy source, scaling up geothermal generation in East Africa faces significant obstacles.
- The resources are site specific. Globally, hydrothermal systems with wet hot rocks are rare in the world and can only be found in very special locations. Similarly in East Africa these resources are located largely along the Great Rift Valley belt such as Western Uganda, Along the Rift Valley in Kenya and Tanzania
- Relatively long lead time of between 5-7 years from conception to production of electricity. Heavy investment in transmission and other support infrastructure due to long distances to existing load centers.
- High upfront investment costs. In East Africa, the initial investment costs in geothermal is still expensive compared to other forms such as hydro. According to published data indicate that installation costs range between 2.5 to 6.5 million US$ per MWe. Kenya average installation cost is about 3.6 million US$ per MWe[7]. Geothermal exploration demands money upfront – one well costs about 500 million USD[8]. With a few private investors so far, the governments have to borrow expensive loans to build geothermal power plants.
- High resource exploration and development risks. In East Africa there is limited updated knowledge of the geology and geodata about the resource potential. Most of the data was collected in the 1970s and 80s and has been upgraded slowly. For example, McNitt (1982) estimated resource potential for Kenya at 1,700 MW, whereas the latest estimates have revised the potential to 7,000-10,000 MW and similarly in Tanzania the latest resource estimate is about 5000 MW, up from 650 MW in 1982.
- Inadequate geothermal expertise. Unlike other power options, it requires highly skilled technicians. In a developing country such as in East Africa, geothermal training programs are hard to come by and local experts are limited.
- Land use conflicts. Geothermal power stations require substantive large chunks of free land to develop. In this process there can be potential risks for land conflicts between the government or investors and local residents.
- Risks for natural disasters. EGS systems have to deal with induced seismicity, or fracturing of rocks to high depth of about 10km or deeper, which risks induced earth quakes due to injected fluids through fracturing. This technology despite being revolutionary in nature is yet to become readily and cheaply available in East Africa.
Key policy recommendations
- Conduct and update the existing geodata on the resource potential and feasibility. Experts confirm the only way forward for scaling up geothermal might be for the “government to carry out feasibility studies and exploration to attract private sector development. Once areas with geothermal energy capacity are well mapped out, (…) it will be easier to attract investment in this sphere.”
- Scale up investment in existing geothermal projects. Given its huge initial investment costs, the government can reduce this burden by developing projects through Private Partnerships (PPPs) structured investments. Moreover, the government must continue to support and fund geothermal resource assessment and development so as to manage the geothermal exploration risk and attract investors.
- Reduce administrative barriers and corruption in the energy sector, by among others, adequate financing of dedicated Geothermal departments, streamlining licensing and allocation of geothermal blocks with incentives and sanctions in order to accelerate geothermal development.
- Promote research, development and capacity building for geothermal development by providing fiscal and other incentives. Investment in training can reduce on the current specialized skills gap required for Geothermal development and operations.
- Increase marketing of East Africa’s Geothermal potential and its value as a clean energy source. This can be further ramped up by the government packaging and offering multiple incentives through attractive pricing to promote and encourage direct uses of geothermal resources such as utilization of heat, water, gases and minerals. In other words, investment in Geothermal is not only an investment in the energy sector but also in associated productive ecosystem around it, including tourism. A good example is the Olkaria hot spur in Naivasha.
- Promote early geothermal generation through implementation of efficient modular geothermal technologies. This is essential in cutting back on the long lead time from conception to production by more than half.
- Enforce proper compliance to mitigate possible occurrence of disasters such as man induced earth quakes from fracturing for geothermal power with the regulatory requirement to utilize the best available technologies that optimize the resource and conserve the reservoir.
[1] https://ndcpartnership.org/knowledge-portal/good-practice-database/geothermal-energy-powering-kenyas-future-menengai-geothermal-field-development#:~:text=The%20country%20is%20fortunate%20to,of%205%2C000%20MW%20by%202030.
[2] https://renewableenergy.go.ke/technologies/geothermal-energy/
[3] https://www.thinkgeoenergy.com/uganda-targets-geothermal-development-of-up-to-100-mw-by-2025/
[4] https://www.thinkgeoenergy.com/uganda-targets-geothermal-development-of-up-to-100-mw-by-2025/
[5] https://www.carbon-counts.com/uganda-geothermal-resources
[6] https://www.linkedin.com/pulse/geothermal-energy-engineering-uganda-harnessing-earths-enyutu-elia/
[7] https://rafhladan.is/bitstream/handle/10802/6070/UNU-GTP-SC-17-1201.pdf?sequence=1#:~:text=The%20installation%20cost%20is%20also,3.6%20million%20US%24%20per%20MWe.
[8] https://www.euronews.com/business/2022/11/14/cheap-and-eco-friendly-the-huge-potential-of-geothermal-power