Modelling Enhanced Air Conditioning System: Harnessing Waste Heat for Efficiency Optimization

Abstract

Air conditioning systems are among the most energy-intensive components in both residential and automotive applications, contributing substantially to electricity demand, fuel consumption, and greenhouse gas emissions. This study proposes and numerically evaluates an enhanced vapor compression cycle that integrates two waste heat recovery strategies: Hybrid Thermal Solar (HTS) panels for residential units and vehicle exhaust heat recovery for automotive systems. Thermodynamic models were developed in Engineering Equation Solver (EES) using R134a as the primary working fluid, with R600a used as a comparative reference. In the residential configuration, HTS panel assistance raised the cooling coefficient of performance (COP) from 6.03 to 7.31 at an ambient temperature of 25 degrees Celsius, representing an average compressor power reduction of 17.5% over the 25 to 35 degrees Celsius operating range. In heating mode, the same configuration improved COP from 4.829 to 5.089 at 2 degrees Celsius and achieved an average 10.20% reduction in compressor work. For the automotive system, direct integration of raw exhaust gas was found thermally infeasible due to refrigerant temperature exceedance; however, diluting exhaust heat to approximately 50 degrees Celsius via an intermediate heat exchanger yielded cooling COP values between 6.675 and 5.044 across the same ambient range, with average compressor work reduced by 8.46% relative to the conventional cycle. R600a consistently outperformed R134a across all configurations, with COP improvements of up to 46.25% in cooling and 50.44% in heating mode. These findings demonstrate that controlled integration of renewable and waste thermal sources into existing refrigeration infrastructure offers a viable pathway toward reduced energy consumption and lower carbon emissions in both sectors.