OVERVIEW OF GEOTHERMAL ENERGY IN KENYA
Kenya is one of the countries in sub-Saharan Africa with the fastest increases in electrification rates since 2013 whereby by 2018, 75% of the population had access to electricity access. Kenya is the leading producer of geothermal energy on the African continent and eighth in the world.
What is Geothermal Energy?
Geothermal energy is energy harnessed from the earth’s internal heat below the surface. There are two types of geothermal energy, shallow and deep well. Shallow well geothermal is in wide use throughout the world. It uses heat pump technology and wells drilled to a depth of 100 to 300 meters.
The extracted heat comes from heat primarily absorbed by the earth from sunlight. Deep well geothermal relies on wells drilled deep into or through the earths crust about 3km to 10 km, its source heat from the decay of atoms deep within the earth
Deep well geothermal energy is the heat derived within the sub-surface of the earth. Water or steam carries the geothermal energy to the earth surface whereby it can be used for heating and cooling purposes or be harnessed to generate clean electricity.
Geothermal power has the potential to provide reliable, cost-competitive, base load power with a small carbon footprint which is renewable. These factors coupled with massive potential for this renewable along the Great Rift Valley has placed Geothermal Energy at a prominent position in Kenya’s overarching energy development plans.
Kenya’s energy mix comprises of Hydro power, Fossil fuels, Geothermal, Solar, Wind and biofuels.
Kenya’s current effective installed/grid connected electricity capacity is about 1429 MW with about 725 MW of this being from geothermal.
Kenya Electricity and Generating Company PLC (KenGen) which is about 74% state owned is the leading electricity producing company. KenGen operates and owns five geothermal power stations; Olkaria I(45MW), Olkaria II(105MW), Olkaria IV(140MW ), Olkaria I unit 4 & 5(105MW) and Olkaria V( 170MW) . In addition to the Power Stations, KenGen also own fifteen wellheads generation plants one at Eburru and fourteen at Olkaria.
KenGen Olkaria Geothermal Project is situated within Hell’s Gate National Park 120KM North West from Nairobi.
Olkaria 1 Geothermal Power Station. Source: KenGen
Olkaria Wellhead Plant Source: KenGen
Exploration of Geothermal resource in Kenya started in 1950s around Lake Bogoria and Olkaria but it is until between 198 and 1984 when Olkaria 1 was constructed. This was the first geothermal power plant to be constructed in Africa.
Today, Kenya is eighth largest geothermal energy producer in the world as at the end of 2020 with an Installed capacity of 821 MW already ahead of Iceland and Japan.
Geothermal Energy power plant process.
There are three main type geothermal power plant cycles namely:
1. Dry steam cycle
2. Flash steam cycle
3. Binary cycle
1. Dry steam cycle.
This was the first type of cycle to be used for geothermal power production. In this cycle, steam directly from the ground is used to turn the turbine, which turns the generator to produce electricity. For this reason, geothermal well temperature has to be greater than 235oC. Steam is then re-injected into the reservoir for future use. However, the use of steam directly from the ground leads to fast wear of turbine blades hence it is now the least commonly used type of cycle.
2. Flash steam cycle.
This type of cycle is almost similar to dry steam, however, there is a separation unit to separate brine and steam before the steam reaches the turbine. This cycle is in practice in Kenya’s geothermal power plants operated by KenGen.
Kenya’s geothermal wells has a depth of 950m to 3.65km deep to tap steam underneath. Hot fluids are obtained from below the earth’s surface having been superheated from the core of the earth. These fluids are used to generate power in the form of electricity. The heated fluids are also used to heat water or other suitable fluids used to turn turbines. The turbine converts the heat energy to kinetic energy which is converted to electricity by the generator.
The geothermal fluid enters the cycle as shown in the schematic below. The reservoir is at a higher pressure than the surface and hence the geothermal fluid temperature increases and the fluid starts to boil. The hot fluid enters the separator where brine is removed at and pumped back to the reservoir. The dry steam from the separator then proceeds to the the turbine. In the turbine, steam will run the turbine then through the condenser to the cooling tower.
Flash cycle can either single flash or double flash.
Schematic diagram for single Flash cycle Geothermal Power Plant.
3. Binary Cycle.
Binary cycle power plants are closed-loop systems that use a second working fluid with a much lower boiling point than water to turn the turbine. The geothermal fluid obtained from the ground is used to heat the second working fluid but it does not come into contact with the second working fluid or the turbine. The geothermal fluid and working fluid pass through a heat exchanger, where the working fluid flashes to vapour and drives the turbine and subsequently, the generator. The geothermal fluid is normally of approximately 200oC and below. The most common working fluids used are hydrocarbons, such as iso-pentane and butane, and refrigerants. The Rankine cycle is the ideal form of binary power cycles.
The geothermal fluid from the source enters the well through station s1 at the inlet temperature. In most cases the geothermal fluid is usually water. When the pressure is kept high no gases will be separated from the fluid and hence no need for a gas extraction system. The fluid is cooled down in the vaporizer and then re-injected at station s2.
Olkaria III geothermal power plant, developed and operated by private actor Ormat Technologies which is the first privately funded and developed geothermal project in Africa, is a binary Geothermal Power plant. It was enabled by a phased development strategy, and a combination of public and private financing and risk mitigation instruments that ensured the viability of the project.
Olkaria III is a 110 MW binary geothermal power plant, whose resources were explored by the government before development was undertaken by private actor Ormat Technologies.
FUTURE OF GEORTHERMAL IN KENYA.
Geothermal Development Corporation- GDC was formed in 2008 as a Special Purpose Vehicle (SPV) to accelerate the development of geothermal resources in Kenya. GDC is tasked with developing steam fields and selling geothermal steam for electricity generation to Kenya Electricity Generating Company PLC (KenGen) and to private investors.
GDC is tasked with developing steam fields and selling geothermal steam for electricity generation to Kenya Electricity Generating Company PLC (KenGen) and private investors.
Since inception in 2008, GDC has acquired two high capacity drilling rigs in 2010. They have also continued geothermal exploration with construction of the Steam Gathering System in Menegai Geothermal Project in 2018.
Kenya Electricity Generating Company PLC (KenGen) which is the leading electric power generating company in Kenya has embarked on a diversification strategy, leveraging its expertise in geothermal energy by offering commercial drilling services, geothermal consulting and other energy-related services across Africa. KenGen has won various geothermal drilling contract in larger Eastern Africa region. . In February 2019, KenGen won yet another contract worth USD 76,801,344 for consultancy services and drilling geothermal wells. In October 2019, the company secured a Ksh 5.8 billion contract to drill 12 geothermal wells in Ethiopia. This contract with an independent power producer includes installing a water supply system and equipment. In February 2021 KenGen won yet another international contract to drill three geothermal wells in Djibouti, the contract signed with Office Djiboutien De Development De lenergie Geothermique (Djiboutian Office of Geothermal Energy Development) (ODDEG) is worth about USD 6,452,933.
Keep working ,impressive job!
Hello There. I found your blog the usage of msn. This is an extremely
neatly written article. I’ll make sure to bookmark it and come back to read
more of your useful info. Thanks for the post.
I will certainly comeback.
Thanks for your comment, I look forward to seeing you again