Energy, economic and environmental assessments for gas-turbine integration into an existing coal-fired power plant

The concept of repowering existing power plants has been recently revalued, in the light of the increasing energy needs, combined with the cost and the difficulty in developing new generating capacity. Among technologies for existing steam power plants, feedwater repowering is considered one of the less-intrusive and cost-effective option to expand capacity, improve efficiency and reduce the pollutants emissions. This paper aims to evaluate the effects of feedwater repowering operating conditions on energy, environmental and economic system performances. Considering a 600 MW coal fired power plant as a study case, two feedwater repowering configurations are investigated. In the first case, a simple throttling of high pressure regenerative steam extractions is operated; in the second configuration, the feedwater upstream the boiler inlet is partially preheated using the waste heat of an additional gas turbine. In both cases, a characteristic plane is introduced for comparing energy, economic and environmental performances of feedwater repowering options, at different condenser overloads and fossil boiler modes of operation. (C) 2013 The Authors. Published by Elsevier Open access under CC BY-NC-ND license.