SPECO: A Systematic and General Methodology for Calculating Efficiencies and Costs in Thermal Systems

A systematic and general methodology for defining and calculating exergetic efficiencies and exergy related costs in thermal systems is proposed. The methodology is based on the Specific Exergy Costing (SPECO) approach, in which (a) the fuel and product of a component are defined by taking a systematic record of all exergy additions to and removals from all the exergy streams of the system, and (b) the costs are calculated by applying basic principles from business administration. Thus, a direct link between the definitions of fuel and product for a component and the corresponding costing equations is established. In particular, the paper shows how to obtain detailed definitions of exergetic efficiencies using separate forms of exergy (thermal, mechanical and chemical) and how, according to these definitions, to conduct an evaluation of costs associated with all the exergy streams entering and exiting a system component. For this case, the cost equations are presented in a general matrix form.