THE GITARU hydro power station is located on the Tana river, about 160km north-east of the Kenyan capital, Nairobi. The Gitaru reservoir is relatively small, with long-term storage being provided by the upstream Kamburu and Masinga reservoirs.
Owned and operated by Kenya Electricity Generation Company Ltd. (KenGen), the plant with its two voith-siemens Hydro 72.5MW vertical Francis units, began commercial operation in 1978. In this initial phase, the civil design and construction had already made provisions for a third unit. Nevertheless, it was not until the second half of the 1990s, when Kenya’s electricity demand began to exceed supply, that the decision to install additional generating capacity was taken.
The Gitaru machines are among the largest hydro generating units in the Kenyan grid and, while the third machine would provide additional energy during the rainy season, it would give year-round peaking power and increase KenGen’s operational flexibility. Once the decision had been made, KenGen acted quickly to secure this additional capacity.
Time schedule and administration
When tender documents for international competitive bidding were issued in 1997, an ambitious time frame – outlining an implementation period of just 25 months – was proposed. Voith Siemens Hydro Power Generation accepted the tender and promised an even faster project implementation of just 22 months.
The generator housing outer diameter is 8m and the combined rotor/generator shaft weight is approximately 175t. A typical erection programme for machines of this size can take as long as 30 months to be completed. A period of 12 to 15 months for the design, manufacture and transportation is usually followed by an erection period of up to 18 months.
This was obviously not practical for the Gitaru unit installation. So, in order to allow sufficient time for manufacture and to fulfil the contracted schedule for completion, it was necessary to reduce the erection time to a period of 12 to 14 months, and to compress the design and manufacturing processes as much as possible. As a single main contractor, Voith Siemens Hydro was responsible for the timely and efficient management of all critical aspects of the project including design approvals, interfacing with existing station systems and relevant Kenyan regulatory authorities as well as customs clearances in the port of Mombasa.
To further minimise the time taken, simultaneous turbine and generator erection activities were optimised and the impact from the civil works minimised. A close management of all the activities and subcontractors involved was essential to the success of the project.
Flexible project management
Late into the project time line, it became clear that the civil works would be completed late. This allowed only five months for the completion of the remaining turbine and generator installations and all commissioning activities related to this equipment. In spite of these changed conditions, Voith Siemens Hydro was able to adapt its original programme accordingly and also cope with further delays from customs clearances. Dry commissioning of turbine and generator auxiliary equipment began in early October 1999. The unit was watered-up at the beginning of November 1999 and synchronised with the Kenyan grid on 11 November 1999. This was followed by unit load rejections on 13 November 1999. Commercial trial operation began in the same month – less than two years after contract award. This very significant achievement was made possible by the commitment of all parties involved.
Development based on hydro
The Kenyan government has been successfully implementing a programme of economic liberalisation since 1993. Deregulation has helped to boost most sectors of national economy and to attract private capital.Kenya’s energy programme is largely backed by foreign investment. However, electrical shortages remain a key barrier to development within the country.
At present, around 80% of power supplied in the country is generated from hydro power stations. Most hydro potential is found on the Tana and Turkwel rivers. It is estimated that the technically feasible hydro potential is 4710GWh/year, of which 62% has been developed. No new hydro plants are currently under construction, but existing facilities have potential for upgrades. On the other hand, there are several small, mini and micro hydro plants in operation, with a total capacity of around 14MW, being considered for development by private investors.
