Thermodynamic,economic And Environmental Evolution Of A Cooling System Driven By Solar Energy And Mechanical Work In Cold Storages

Cold chain becomes increasingly popular owning to societal development and improvements in living standards.The issue of high energy consumption in cold storages,which is a key in the cold chain,has been brought to public attention.The cooling system driven by solar energy and mechanical work in cold storages reduce energy consumption significantly,but these systems in previous studies are hard to be in practical applications because of poor economic performance.Absorption-subcooled compression hybrid cooling system can be driven by low-grade energy and has high coefficient of performance.Therefore,the new system driven by solar energy and mechanical power is proposed to meet the cooling demand of cold storages.Thermodynamics,economic and environmental evolution model of the system is built to analyze the working process of the system and the influence of design parameters.And then cool energy storage tank is supplemented to improve performance.Finally,the genetic algorithm is utilized to optimize the design parameters of the system.Compared with the traditional vapor compression refrigeration system,the optimal absorption-subcooled compression hybrid cooling system driven by solar energy and mechanical work in cold storage reduces 6.7% compression work(the annual energy saving is189.6 MWh).The payback period and the net present value are 5.8 years and 1.369 million CNY,respectively.However,the mismatch of absorption subsystems cooling capacity and subcooler heat capacity limits the increase of energy saving.The energy saving has potential for improvement.To solve the problem that the energy saving of the absorption-subcooled compression hybrid cooling system driven by solar energy and mechanical power is significantly lower than the upper limit,the cool energy storage is supplemented to match the heat capacity of the cool energy storage and the cooling capacity of the absorption subsystem.The optimal annual energy saving and net present value of the system increase 70.1% than the absorption-subcooled compression hybrid cooling system and that is 11.4% lower than vapor compression refrigeration system(the annual energy saving is 322.5 MWh),respectively.The payback period is 4.2 years.In addition,the solar cooling energy of the off-valley operation strategy reduces because the thermal efficiency of the collector and the COP of the absorption subsystem come down.Therefore,the thermodynamics and economic performance of the solution with the off-valley operation strategy is lower than that of the solution with the normal operation strategy.Based on the comparison of the life cycle analysis,the vapor compression refrigeration system with photovoltaic panels has the shortest carbon dioxide emission payback period(1.85 years),and the hybrid cooling system with evacuated tube collector has the shortest energy payback period(0.73 years)and investment payback period(6.5 years).The hybrid refrigeration system with photovoltaic/thermal collectors has the maximum annual energy saving(640 MWh)and the energy saving of life cycle(11280 MWh).In this paper,the thermodynamics,economic and environmental evolution of a cooling system driven by solar energy and mechanical work in cold storage is carried out and this work provides a support of theory and data support for the use of solar energy to reduce the power consumption of cooling system in cold storages.