Energetic, exergetic and economic analysis of a trans-critical solar hybrid CCHP system

Abstract

A solar hybrid CCHP (combination of cooling, heating and power) system was proposed to organically integrate the Brayton and reverse Carnot cycle by trans-critical CO2 working medium. The transient thermal storage in a solar hybrid CCHP system (SCCHP) was designed to overcome the energy coupling challenges in regions rich in solar and gas resources. Moreover, the incorporation of an optimally efficient throttling expander in cooling cycle was designed to enhance energy utilization efficiency. The thermodynamic performance of the SCCHP system was systematically evaluated by comparing with the ejector hybrid CCHP system from energetic, exergetic, and economic perspectives. The results suggest that elevating the intake pressure of both the high-pressure compressor from 5.2 kW to 6.4 kW and turbine from 7.3 kW to 7.8 kW, led to an enhancement in the COP of the SCCHP system. Moreover, raising the turbine intake temperatures from 483.15 K to 503.15 K yielded a significant improvement in system energy efficiency from 0.66 to 0.71 and COP from 1.58 to 1.72. Furthermore, in contrast to the ECHP system, the components in the SCCHP system demonstrated not only less exergy efficiency variation to the influence of ambient temperature but also lower hourly economic costs. The SCCHP has an average hourly investment cost that is 5.70 USD (kgh)−1 lower than ECHP, and its economic efficiency improves with higher ambient temperatures.