performance evaluation of repowering options using combined cycle technology

Most of the fossil units in the United States under 300 MWe that were built after 1950 are approaching the end of their design life as the year 2000 nears. Faced with continued demand growth and compliance with stringent requirements of the Clean Air Act, the utility industry may choose to build new units or extend the life of existing units through repowering. Repowering is an attractive alternative that incorporates state-of-the-art technology into an existing unit to achieve equal or better performance in thermal efficiency and emissions. Combined cycle technology has become very desireable for repowering existing plants due to its high thermal efficiency, low emissions, low installed cost, low operation and maintenance cost, short installation time, high reliability/availability, excellent cycling capability, and operating flexibility. Various options are available for repowering existing plants with contined cycle technology. The options considered are: hot windbox repowering, feedwater heater repowering, and combustion turbine/heat recovery steam generator repowering. The paper examines the performance benefits of these combined cycle repowering options and evaluates the associated capital costs.