KenGen has pioneered a new technology in geothermal power generation by installing two wellhead generator units at Olkaria and Eburru. The wellhead units generate 5MW and 2.5MW of electricity respectively.
This technology involves tapping steam from wells, which are undergoing tests, or are awaiting connection to permanent plants so as to benefit from early generation.
This move by KenGen comes at a time the country is experiencing an increased demand for electricity. Rapid Economic growth and industrialization has created the need to accelerate the drilling of geothermal wells in order to tap geothermal power potential and avoid over-reliance on the erratic hydroelectric power.
Long drought has slashed the capacity of main darns, forcing shutdowns and leading to reliance on costly diesel-powered generators, which have in turn pushed up energy bills.
With the success of the Olkaria and Eburru wellhead power generating units, KenGen now intends to install more units with an expected yield of70MW.Other geothermal areas targeted for this new technology include; Menengai, and Longonot.
Through this move, KenGen has gone on record as the first company in Africa to embrace this new technology and therefore moved a step away from traditional methods to achieve the same results.
Permanent power plants take between 24 to 36 months to construct and commission. The well head power plant on the other hand takes 6 months hence a quick return on investment
The planning of geothermal development comprises the following stages:
a) Review of existing information of a prospect
b) Detailed surface exploration
c) Exploration drilling and well testing
d) Appraisal drilling and well testing;
e) Feasibility studies
f) Production drilling, power plant design and environmental impact assessment
g) Power station construction and commissioning
h) Reservoir management and further development
i) Shutdown and abandonment
The development program from Project identification to Power station commissioning is about 8 years but can be reduced to 5 years if finances are readily available. From the experience of development at Olkaria, it has been learnt that:
Timely financing of the projects is very critical;
Good wells recover quickly and within one month they develop enough wellhead pressure to discharge on their own. Other wells may require to be assisted to start discharge by compressing and releasing several times. Discharge tests takes a minimum of three months and a maximum of 1 year to determine the full characteristic and long-term behaviour of the well.
During discharge tests, steam and brine measurements are made to determine the amount of steam available. Chemical analysis data of steam and brine is useful during exploitation and also for defining the reservoir characteristics.
The current method is to pass the geothermal fluid through a pipe, measure the total flow and direct the fluid to a wellhead separator to separate the steam from the water. The water fraction is measured and the difference between the total mass flow and the water gives the steam fraction.
Normal well testing in its entirety wastes resources. In most cases, wells are discharged over long periods to assess their response to exploitation as the resource is drawn down without tangible production.
KenGen Pioneers Wellhead Power Generation Systems
Through use of this new technology, KenGen will test the wells while routing the steam through the generators, which will supply power to the grid. Using this approach the country's energy demand will be achieved within as short a time as 70 days of commencing well drilling.
Eburru is located approximately 2 hours outside of the capital, Nairobi, in Kenya's Great Rift Valley. The Eburru geothermal field is on the flanks of the OlDoinyo Eburru Volcano and is situated 11 km northwest of Lake Naivasha."
The project is unique because, for the first time, KenGen engineers carried out implementation work without the assistance of external consultants. Civicon served as the General Contractor, responsible for construction of the plant.
During the month of January 2015, GDA engineers worked closely with KenGen engineers and operators and Civicon construction crews to complete the commissioning and performance testing. The plant was first synchronized to the grid on January 23rd. The performance testing was completed just six days later on January 29th.
GDA designed the plant and the steam field, and supplied all of the major equipment. This included an Elliott GYR steam turbine, Kato generator, Lufkin gearbox, Graham condenser and vacuum pump, Goulds cooling water pumps, and a Cooling Tower Depot single-cell fiberglass tower. GDA also manufactured auxiliary equipment in-house to minimize installation time, including the lube oil system, turbine control valve assembly, compressed air system, fire pump skid, emergency power system, and plant control system. The equipment and materials were shipped from the US to Kenya in 11 shipping containers one month ahead of schedule.
Olkaria 4.7MW power plant
KenGen has partnered with the Green Energy Group (GEG) in constructing the 5MW Olkaria geothermal wellhead power plant. The highly experienced executive team at GEG has assembled a team commanding a wealth of experience within the design, engineering, project management and operation of geothermal plants and is supported by a Board of Directors drawn from both investment banking and the engineering sector.
This technology has proved sustainable and KenGen has now commanded the lead into the next phase of power generation in line with the country's vision 2030. It has indeed embarked on an ambitious 70MWe project, which has already kicked off at the Olkaria Geothermal field with the second wellhead plant at 75% completion. This project will be guided by construction of sixteen wellhead power plants. It is notable that this is the first project of its kind in the world.
Below are photos showing the characteristic long steam lines associated with the conventional power station.
Long steam lines are characteristic of the conventional power plant unlike the case of the portable wellhead power plant.
Power Station Construction and Commissioning
A 50 – 70 MW geothermal power plant takes about 2 years to construct and commission. Remember that two years is the time for construction of the power plant only. On average at the figure of 5mw per well, we would require approximately 14 drilled wells each drilled for 3months therefore 52 months in total i.e. about 4 1/2yrs. This means that it will roughly take eight years to have the plant up and running considering delays in procurement.
The construction of the power plant includes;
Transmission lines can be an issue particularly if the wayleave acquisition is not handled in good time and professionally. This is because transmission lines can be fairly long and traverse very many land ownerships. Land compensation may be required in some parts while in others outright purchase may be the solution. Power lines, just like power stations require an environmental impact assessment to be conducted.