Exergoeconomic Assessment of a Compact Electricity-Cooling Cogeneration Unit

Abstract

This study applies the SPecific Exergy COsting (SPECO) methodology for the exergoeconomic assessment of a compact electricity-cooling cogeneration system. The system utilizes the exhaust gases from a 126 hp Otto-cycle internal combustion engine (ICE) to drive a 5 RT ammonia–water absorption refrigeration unit. Exergy destruction is higher in the ICE (67.88%), followed by the steam generator (14.46%). Considering the cost of destroyed exergy plus total cost rate of equipment, the highest values are found in the ICE, followed by the steam generator. Analysis of relative cost differences and exergoeconomic factors indicate that improvements should focus on the steam generator, evaporator, and absorber. The cost rate of the fuel consumed by the combustion engine is 12.84 USD/h, at a specific exergy cost of 25.76 USD/GJ. The engine produces power at a cost rate of 10.52 USD/h and specific exergy cost of 64.14 USD/GJ. Cooling refers to the chilled water from the evaporator at a cost rate of 0.85 USD/h and specific exergy cost of 84.74 USD/GJ. This study expands the knowledge base regarding the exergoeconomic assessment of compact combined cooling and power systems.

Keywords

• thermoeconomics
• combined cooling and power
• combustion engine
• absorption refrigeration
• SPECO