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Thermoeconomics applied to an air conditioning system with cogeneration

Abstract:

This paper indicates the method for applying a thermoeconomic analysis to a theoretical building services study, consisting of an air conditioning system using a single-stage absorption chiller driven by a cogeneration engine. The gas engine supplies heat to the absorption chiller and electricity to other HVAC plant, such as dry cooler fans, hot water, condenser and chilled water pumps, air handling units and fan-powered terminal units. The thermoeconomic model is used to optimise the specific cost of indoor environment cooling in terms of the absorption chiller variables, chilled water and condenser water temperatures. An improved design is obtained in two steps. First the design conditions are optimised, providing detailed exergy costing related to the plant investment and operating costs. Secondly, by analysing these, the most appropriate design modification of substituting dry coolers with a cooling tower is identified, and the system is again optimised, achieving 6% more cooling capacity while reducing the final specific cooling energy cost by 35%. This results in an improved thermal and economic design for the owner.