As the bus winds past the beautiful countryside in Tennessee and Alabama States in the U.S. and we enter a huge coal-fired electricity generating plant, a board announces, “Tennessee Valley Authority, Widows Creek Fossil Plant, Built for the people of the United States of America,1958-60.”
Widows Creek coal-fired power station has eight units — six that generate 125 MWe each and two of 500 MW each. The seventh unit of 500 MWe, nearly 50 years old and whose efficiency had dropped, is born anew today. Alstom Power, the world's leading power plant moderniser, has given it a retrofit, replacing the steam turbine section with a new bladed rotor and carrying out repairs in the stator to improve the machine's performance. The result is that unit seven's life will last not only another 20 years but it is generating 30 MWe more than before.
With many coal-fired and nuclear electricity generating stations in the U.S, Latin America and Europe approaching the end of their design-life of 30 to 40 years, Alstom Power has already captured a big slice of the market there to retrofit the turbines of these plants to increase their life, ramp up generation and cut down on carbon emissions. The company has won the contracts for retrofitting a nuclear power plant in Michigan, a coal-fired unit in Ohio, the Laguna Verde nuclear plant in Mexico, Huckingen, a coal-fired unit in Germany, two nuclear units at Koeberg Power Station in South Africa and units in Finland and Poland. As the efficiency of the power generation stations drop over a period of time, retrofitting their components such as boilers, turbines, rotors, casing and assemblies not only lead to more generation of electricity but increase the unit's life by about 20 years.
The reason why power utilities go increasingly for retrofitting is stricter carbon dioxide emission and nitrous oxide norms to slow down global warming, and difficulty in acquiring land to put up projects on green field sites. Besides, upgrading an operating plant is cheaper than building a new one. Since 1984, Alstom has retrofitted more than 825 steam turbine cylinders worldwide, more than any other company. About 360 of these retrofits were done on turbines made by other original equipment manufacturers (OEMs). Of these 825 steam turbines, about 600 were coal-fired or gas-fired. Alstom Power has also retrofitted more than 240 nuclear steam turbines worldwide, winning more than half of the global projects since 2005.
“Sixty per cent of the carbon emitted in 2030 will come from today's installed base,” Philippe Joubert, president, Alstom Power, told a group of visiting journalists at Chattanooga, a small town in Tennessee State. “Environment is the key driver” behind Alstom's philosophy of ‘Clean Air Today' and “our company provides the cleanest solution for new plants and the installed base,” Mr. Joubert said.
Journalists from India and France went round unit 7 of Widows Creek, whose turbine was retrofitted in the low pressure section in 48 days in March/April 2009.
Paul Elkovich, vice-president, Turbine Generator Service Operations, Alstom Power, explained how the retrofit was done: “We increased the efficiency of the plant by redesigning the blades in the turbine-generator.” Special tools, couplings and casing bolts were used in the operation. All valves, auxiliaries, bearings and steam seal systems were inspected and retrofitted. The components were brought in barges on the Tennessee river. “The TVA and Alstom Power worked as a team with aggressive project targets. The priorities were safety, quality and schedule,” Mr. Elkovich said.
Big market in India
In India, Alstom sees a big market for retrofitting, upgrading and life extension work, be it in coal-fired, gas-fired, hydro or nuclear electricity generating stations as their fleet gets aged. It has already done turbine rotor repairs for the Tamil Nadu Electricity Board, the Andhra Pradesh Power Generation Corporation, the National Thermal Power Corporation (NTPC) and the Maharashtra State Power Generation Corporation Company Limited, nuclear rotor repairs for the Nuclear Power Corporation of India Limited (NPCIL) and general excitor repair for the NTPC's 500 MWe unit at Rihand, Uttar Pradesh. It has performed boiler modernisation for the Indian Iron and Steel Company (IISCO) and mill upgrades for the Chhattisgarh State Electricity Board at Korba.