Olkaria Geothermal Project is situated within Hell’s Gate National Park 120KM from Nairobi and neighbours horticultural farms that produce some of the inest flowers in the world. The project is also adjacent to Lake Naivasha, which is a fresh water lake in the Kenya ift and a Ramsar site.
Location of Geothermal fields and prospects along the axial region of Kenyan rift.
Geothermal energy is the natural heat stored within the earth’s crust. The energy is manifested on the earth’s surface in the form of fumaroles, hot springs and hot-altered grounds. To extract this energy, wells are drilled to tap steam and water at high temperatures (250-350oC) and pressures (600-1200 PSI) at depths of 1-3KM. For electricity generation, the steam is piped to a turbine, which rotates a generator to produce electrical energy.
Geothermal Development in Kenya
Exploration for geothermal resources in Kenya started in 1950’s and gained momentum in the 1960’s, when two wells were drilled at Olkaria. From 1967, the United Nations Development Programme (UNDP) in collaboration with the Kenya Government and the then East African Power and Lighting Company Ltd., conducted geological and geophysical surveys in the area between Lake Bogoria and Olkaria. The studies identified Olkaria as the most prospective area leading to the construction of the first geothermal power station between 1981 and 1984.
Olkaria Geothermal System
The heat source of the geothermal system at Olkaria is due to intrusion of hot magma bodies to depths of less than 6 KM from the surface. Parts of the magma extruded to the surface to form the numerous hills and dome that dot the Olkaria landscape. The Ololbutot lava erupted about 200 years ago attesting to the youthfulness of the volcanic activity at Olkaria.
The geothermal system at Olkaria consists of a two-phase reservoir that is hosted within 0.9-1.65 million-year old fractured trachyte and rhyolite rocks at depths of between 600M and 3000M. At the Olkaria East, Olkaria Domes field and Olkaria North East Geothermal fields, wells with a nominal diameter of 8 inches are drilled into the reservoir and the upper 700M-1200M cased off to avoid cold fluid inflow into the bore. The wells produce 75% water and 25% steam. Separation of steam is done using cyclone separators from where dry steam is piped to the powerhouse and separated water injected back into the reservoir.
KenGen’s Geothermal Power Plants
KenGen owns five geothermal power stations; Olkaria I, Olkaria II, Olkaria IV, Olkaria I unit 4 & 5 and Olkaria V. In addition to the Power Stations, KenGen own fifteen wellheads generation plants one at Eburru and fourteen at Olkaria.
The Geothermal Power Plants have a combined generation capacity of 699 MW.
Olkaria I Power Station
Olkaria I Power Station was the first geothermal power plant in Africa. The 45 MW plant was commissioned in three phases and has three units each generating 15MW of electricity. The first unit was commissioned in June 1981, the second and third units in November 1982 and March 1985, respectively.
A total of 33 wells were drilled for the station. Thirty-one of these are currently connected to the power station while two of these are retired. One of which is currently being used for hot re-injection. The turbines are direct condensing 4-stage running with an inlet steam pressure of 5 bars at temperatures of 152oC and steam consumption of 9.2 t/h/MW. The plant has had an average availability factor of over 95 per cent from commissioning. The power generated is connected to the national grid via a 132KV-transmission line.
Olkaria II Power Station
Located in the North Eastern sector of the greater Olkaria Geothermal field and commissioned in 2003, Olkaria II Power Station generates 105 MW. Initially, the power plant generated 70 MW from two units of 35 MW each. Later a third 35 MW unit was added. Construction of the third unit commenced in 2009 and was completed in May 2010, bringing the total generation capacity to 105 MW.
Wells were drilled between 1986 and 1993 but construction of the power plant was delayed until the year 2000 when funds became available. The project was co-financed by the World Bank, the European Investment Bank, KfW of Germany and KenGen. Designed and constructed with an advantage of newer technology, this state- of- the- art plant is highly efficient in steam utilization. It works on single flash plant cycle with a steam consumption of 7.5 t/h/MW. The turbines are single flow six stage condensing with direct contact spray jet condenser.
The power generated is transmitted to the national grid via 220 KV double circuit line.
Olkaria II Power Plant
Olkaria I Unit 4 & 5 and Olkaria IV Power Stations
Olkaria IV and Olkaria I unit 4 & 5 each generating 140 MW were commissioned in December 2014 and February 2015 respectively. This is the country’s largest Geothermal Power Project. Olkaria I unit 4 & 5 is located at Olkaria East of the Olkaria geothermal field whereas Olkaria IV is at the Olkaria domes field. The projects were funded by KenGen and bilateral partners such as World Bank, Japan International Cooperation Agency (JICA), European Investment Agency (EIB), Africa Development Bank and KfW.
Olkaria V Power Station
Construction of the plant which is located in the North East of the field began in January 2017. H-Young Company (HY), Mitsubishi Corporation with its compatriot Mitsubishi Hitachi Power Systems were contracted to provide some of the parts needed to equip the steam plant.
The plant features two units with a capacity of 82.7 MW each with a total of 165.4 MW. The plant will be supplied by around 500 tonnes of dry steam per hour at temperatures of about 270 centigrades. The project is being funded by a loan from the Japan International Cooperation Agency (JICA).
KenGen Successfully synchronized the first unit to the national grid on Friday 26th July. The unit achieved the design full load of 86.6 MW which is above the rated capacity of 82.7 MW.
KenGen is gearing up to commission the Olkaria V geothermal Power Plant.
Olkaria Wellhead Generation Plants
The Company has installed fourteen wellhead generating units with a capacity of 81MW in the Olkaria Geothermal field. A pilot wellhead generating unit was commissioned in February 2012. The unit is installed at well OW-37A, which is located within the Olkaria East geothermal field.
Olkaria Wellhead Pilot Plant
Eburru Wellhead Generation Plant
The Company engaged a consultant and contractor for the construction of the Eburru Wellhead plant that has a generation capability of 2.44 MW. The plant will be upgraded to 25 MW. The Eburru geothermal field is estimated to have a potential of more than 50MW.