Exergo-environmental cost optimization and thermodynamic analysis for a solar-driven combined heating and power system

Abstract

Reasonable pricing of each product in a combined heating and power system is essential to improve the economic benefits of the system. However, the whole life cycle pollutant emissions cost of the system and energy level in the conventional exergo-economic method are ignored, leading to irrational pricing of each product. Hence, an exergo-environmental cost optimization methodology that considers the whole life cycle pollutant emissions cost and energy level is developed. The compressor discharge pressure of the transcritical carbon dioxide heat pump is employed as the optimization variable to obtain the lowest unit exergo-environmental cost of the system. The unit exergo-environmental cost is converted to the unit energy-environmental cost to determine the price of each product. Optimization results show that the lowest unit exergo-environmental cost of the system is 0.387 $/kWh when the compressor discharge pressure is 10.15 MPa, the unit exergo-environmental costs of the electricity and space heating water are 0.199 $/kWh and 0.989 $/kWh, respectively. The corresponding unit energy-environmental costs of the space heating water and electricity are 0.047 $/kWh and 0.199 $/kWh, respectively. Compared with the conventional exergo-economic method, the unit exergo-environmental costs of the electricity and space heating water are improved by 16.37 % and 11.37 %, respectively, Furthermore, under optimal configuration, the exergy, energy, and solar to electricity efficiencies of the system are 16.28 %, 88.09 %, and 13.79 %, respectively. The above results prove that the developed exergo-environmental cost analysis and optimization methodology can reasonably determine the price of each product of the building energy system.