The study of a seasonal solar CCHP system based on evacuated flat-plate collectors and organic Rankine cycle

The demands of cooling, heating and electricity in residential buildings are varied with seasons. This article presented a seasonal solar combined cooling heating and power (CCHP) system based on evacuated flat-plate collectors and organic Rankine cycle. The heat collected by evacuated flat-plate collectors is used to drive the organic Rankine cycle unit in spring, autumn and winter, and drive the double-effect lithium bromide absorption chiller in summer. The organic Rankine cycle condensation heat is used to yield hot water in spring and autumn, whereas supply heating in winter. The system thermodynamic performance was analyzed. The results show that the system thermal efficiency in spring, autumn and winter, ηsys,I, increases as organic Rankine cycle evaporation temperature, T6, and evacuated flat-plate collectors outlet temperature, T2, decrease. The maximum ηsys,I of 67.0% is achieved when T6 = 80 °C and T2 =100 °C. In summer, the system thermal efficiency, ηsys,II, increases first and then decreases with the increment of T2. The maximum ηsys,II of 69.9% is obtained at T2 =136 °C. The system output performance in Beijing and Lanzhou is better than that in Hefei. The average output power, heating capacity, hot water and cooling capacity are 50-72 kWh per day, 989-1514 kWh per day, 49-57 ton per day and 1812-2311 kWh per day, respectively. The system exergy efficiency increases from 17.8-40.8% after integrating the organic Rankine cycle unit.