THERMO- ECONOMIC ANALYSIS OF GAS TURBINE -ABSORPTION REFRIGERATION COGENERATION SYSTEMS

Abstract

Energy consumption rationalization is one of the fundamental demands for development in Egypt. In order to sustain an adequate supply of electric energy necessary for development projects, energy losses must be reduced as much as possible in domestic as well as in industrial and public applications. Cogeneration is one of the major techniques for energy conservation.

The present work provided a feasibility study for a cogeneration system, which utilizes the heat energy available in a gas turbine exhaust to be the heat source for an absorption air conditioning unit. The exhaust gases are used to produce steam in a waste heat boiler, which is then supplied to the generator of the absorption unit.

The system components were studied separately to determine the factors affecting their performance. Simple cycle gas turbine was applied being the most suitable type for cogeneration, the variations of exhaust gases mass flow rate and temperature were studied for a wide range of pressure ratios , maximum cycle temperature and turbine power output. Simple waste heat recovery application of an unfired waste heat boiler was applied. The boiler performance was analyzed for different suitable operating pressures. Practical ranges of application were determined, considering the critical pinch point temperature difference which affects the steam generator and system design. Water- Lithium Bromide absorption unit equipped with solution heat exchanger was applied and analyzed, to determine the factors affecting its coefficient of performance and refrigeration capacity.

The system components were linked together to form an integrated cogeneration system , which was analyzed thermally and economically and compared to separate production systems for power generation and air conditioning. The study concluded that the cogeneration system is highly feasible and economically advantageous. Cogeneration increased the fuel energy utilization by more than 100% in comparison with the turbine thermal efficiency, and decreased the total annual cost by 30% to 400/o in comparison with separate production systems, for medium power ranges.