Gas Turbines in District heating combined heat and power systems: influence of performance on heating costs and emissions

Much work is currently focussed on identifying economically and environmentally optimal strategies for increasing gas turbine based combined heat and power (CHP). In many such studies, only a few ®xed parameters are used to describe the CHP plant. These are typically total and electrical e ciencies, investment and running costs, minimum and maximum acceptable size, and minimum acceptable part- load. However, for gas turbine based systems these characteristics are clearly functions of the operating conditions, especially for part-load operation. This study examines the e ects of varying performance of the gas turbine on the overall heat production costs and CO2 emissions of a medium sized community district heating plant. Both single and double-shaft engines are considered in the study. The results show that the assumption of constant e ciencies for all operating conditions leads to an overestimation of the optimal CHP plant size, thereby underestimating the heat production costs and overestimating the CO2 emissions of the plant. The results also show marked di erences according to the type of gas turbine used and part-load operating strategy adopted. In particular, the paper discusses the part-load operating di culties for CHP plants running gas turbines equipped with low emissions burners. 7 2000 Elsevier Science Ltd. All rights reserved.