| Energy issues have always been one of the important challenges faced by society’s development,especially with the exponential growth of the global population,which has led to increased energy consumption.According to statistics,the carbon emissions produced in the building sector account for 19.5%of the national energy carbon emissions,of which heating,ventilation,and air conditioning systems account for over 50%of the building’s energy consumption.How to reduce energy consumption in buildings has become a widely discussed topic,and as such,many scholars have proposed that temperature and humidity independent control air conditioning systems based on desiccant technology have significant potential for reducing energy consumption and improving indoor environments.To reduce the energy consumption of desiccant air conditioning systems and achieve efficient regeneration of dilute solutions,this paper proposes a highly efficient vacuum membrane distillation solution regeneration system based on solar-heat pump coupling.This system greatly reduces the energy consumption of the solution regeneration process and has significant implications for the development of desiccant air conditioning systems and the reduction of carbon emissions in building air conditioning systems.Initially,a solar-heat pump coupled vacuum membrane distillation solution regeneration system was constructed,in which mathematical models were established for key system components including the vacuum membrane distillation module,solar collector,heat pump unit,and stratified heat storage tank.The accuracy of the vacuum membrane distillation model was verified by comparing it with experimental data.The system model was then utilized to analyze the steady-state and transient-coupled characteristics as well as the performance under various working conditions,investigating the influencing factors and their variation patterns on the overall system performance.The results showed that the system’s coefficient of performance（COP）was most sensitive to temperature fluctuations,which varied between 3.53 and 21.98.Meanwhile,the specific total exergy consumption（STEC）and specific exergy efficiency of condenser（SEEC）were most sensitive to the volumetric flow rate,with STEC varying between 3480.19 and 9241.36k W/m3,and SEEC varying between 167.14 and 1148.51 k W/m3.Secondly,based on the second law of thermodynamics,the exergy model of the constructed system was established to analyze the influence of the inlet temperature and volume flow rate of the solution,as well as the solar radiation intensity on the exergy loss and efficiency of the system and its components.It was found that the exergy losses of the solar collector and stratified thermal storage tank accounted for more than 80%,while that of the membrane distillation component was only 5.45%,and those of other components were below 2%.Comparing the exergy efficiencies of the components under different operating conditions,the solar collector exhibited the lowest exergy efficiency,fluctuating between 8%and 11%.Furthermore,in order to explore the optimal operating conditions of the system,a genetic algorithm was used to optimize the system and component performance based on seven decision variables,including solution inlet temperature,volume flow rate,concentration,regeneration vacuum,solar radiation intensity,collector tilt angle,and initial temperature difference of the stratified thermal storage tank.The results showed that the single-objective optimal values of the membrane distillation module were membrane flux of 8.96 kg/m2·h and regeneration thermal efficiency of 89.60%;the single-objective optimal value of the solar collector efficiency was51.19%;the single-objective optimal value of the thermal storage efficiency of the stratified thermal storage tank was 77.41%;and the single-objective optimal values of the COP,STEC,and SEEC were 29.49,3053.60 k W·h/m3,and 142.22 k W·h/m3,respectively.The membrane flux Pareto front of vacuum membrane distillation unit is between 3.07～14.82kg/m2·h,and the thermal efficiency Pareto front is between 84.88～89.28%.COP ranges from 14.61 to 31.09,and SEEC ranges from 138.78 to 166.02k W·h/m3.Based on the Pareto optimal solution set,the TOPSIS decision method was used for sorting.The optimal solution of the membrane distillation module was sorted into the same ideal point under three weights,while the optimal solution of the system was sorted into three ideal points under three weights.Finally,considering the trade-off between productivity and energy efficiency,the system was analyzed for economic performance by varying solution flow rate,concentration,solar irradiance,and exchange rate.The initial investment cost and net income（NET）and net present value（NPV）under different operating conditions were evaluated based on literature review and peer review.Environmental impact analysis was conducted based on the annual emissions and reduction of pollutants.The annual emissions of CO2,CO,NOx,and PM were 5726.25kg,5.69kg,12.55kg,and 75.51 kg,respectively,while the annual reduction of these pollutants were 4249.61 kg,4.23kg,9.32 kg,and 56.04 kg. |
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