When severe drought conditions reduced the level of Lake Volta, Ghana, in 1998, Akasombo Hydro Electric Dam, which generates 80% of the country’s electrical power, was affected along with the water supply. The result was power rationing and outages lasting up to 12 hours a day.The Ghanaian government needed power urgently and decided to bring in diesel and gas turbine generators. Cummins Power Projects supplied the first 30MW of power within 24 weeks of receiving an order from the Ministry of Mines & Energy.
The scope of the £16m turnkey project was to design, manufacture and supply the generating sets, control systems, containers, transformer, and distribution switchgear, and operate and maintain the plant for two years. Cummins also organised the shipping, transportation to site, offloading and positioning of the equipment, and all civil works on site. This included the construction of two bulk storage tanks with a combined capacity of 1.5 m litres and the installation of 21 km of instrumentation and power cables.
Installed at Tema, approximately 20 miles from the capital Accra, the plant comprised 39 generating sets, each with a continuous prime power rating of 900 kW, 1125 kVA, 3300V. Each set was made up of a sixteen cylinder KTA50G3 diesel engine coupled to a Newage/Stamford brushless alternator and installed in a 6m ISO standard container. Synchronising and parallelling duties were handled by a digital PowerCommand control system, and remote networking facilities allowed for continuous monitoring of the sets’ performance locally and from Cummins’ factory in Ramsgate, Kent, some 4828 km away.
All 39 sets and three 12 m long control containers were on site within 16 weeks of the order confirmation. Installation of the fuel lines, control and power cables and transformers, and construction of the fuel storage tanks took another 8 weeks.
On to Kenya
Having served its purpose in Ghana, the entire power station was then relocated to Kenya in 12 weeks. Ordered on a six-month contract by the Kenya Power and Lighting Company (KPLC), the power station is operating 24 hours a day feeding into an existing sub-station at Embakasi in the Kenyan capital Nairobi.
The country, which generates about 60-65 per cent of its power from hydroelectricity, was experiencing a similar problem to Ghana. The rainy season had passed without any rain, and to make matters worse there had been droughts at the end of the previous year. The result was power rationing lasting 18 hours a day, even in Nairobi, affecting industry, business and domestic users, and costing KPLC several million dollars in lost revenue.
Funded by the World Bank, the Kenyan Government agreed to purchase a total of 105 MW of power from three separate suppliers. The project took Cummins less than 12 weeks to complete. This included the retrieval of virtually all the 21 km of cable and pipework, which had to be dug out of the ground, coiled or cut into manageable lengths and flown to Kenya in a chartered aircraft.
“We got permission from the Ghanaian Government to take the power station away on 21 August 2000, and demobilisation took about three weeks” said new business development manager John Oliver. Some equipment was flown to Nairobi on a charter flight. The remainder, 58 containers in total, were shipped around the Cape of Good Hope. Nine days after arriving in Mombassa, the equipment had been transported 500 km to Nairobi, installed and commissioned.
Across Africa
At the Sadiola Hill goldmine in Mali, Cummins replaced an existing 16 MW power station with 16 x 1MW sets. The operation was carried out stage by stage to ensure a smooth changeover with no loss of power. The company also has a seven-year maintenance contract and has guaranteed the sets will run to the minimum requirements of the mine.
More recently, Cummins Power Projects won a three year contract worth approximately US$3 million to supply a 20 MW power station to Societé Nationale d’Electricité in Senegal. To meet the demands of the contract, the company has installed the mini power station alongside the existing oil-fired Senega 1 power plant at Cap des Biches, 20 km from Dakar.
The plant comprises 20 generating sets, installed in a single plant room. Powered by KTA50G3 turbodiesel engines coupled to a Newage brushless alternator, each set has a continuous prime rating of 1005 kW, 1256 kVA, 415 V, 3-phase at 50 Hz. The units include their own exhaust silencers, control panels, fuel tanks and other accessories. Cummins also supplied the containerised switchgear and fuel system for the project. Power is delivered to the grid via 20 ring mains, one 11 kV step-up transformer per set and a single 11 kV/30 kV transformer.
“There is currently about 300 MW of installed power in Senegal, but much of it is produced by old and unreliable power stations that are past their peak operating efficiency” says John Oliver. ‘The problem reached a peak in 1999 when there were power losses 6 to 12 hours a day.” Senelec, who had £2 million to invest in power, placed the order with Cummins in May 2000. The equipment was shipped from the company’s factory in Ramsgate, UK, at the end of June and, despite unseasonally heavy rains in Senegal, the power station was built and commissioned by the end of December.
