Experimental investigation of vapor injection‐enhanced R290 solar‐assisted heat pump desalination system: Energy, exergy, economic and environmental performance

Freshwater scarcity and the high energy demand of conventional desalination technologies have intensified the need for sustainable freshwater production systems. Although solar‐assisted heat pump desalination has demonstrated considerable potential, the integration of vapor injection technology with the environmentally friendly refrigerant R290 has received limited experimental attention. This study experimentally investigates a photovoltaic‐powered direct expansion solar‐assisted heat pump desalination system operating with R290 under conventional heat pump (CHP) and vapor injection heat pump (VIHP) modes. Four operating conditions corresponding to injection ratios (IR) of 0.00, 0.10, 0.15, and 0.20 were evaluated through comprehensive energy, exergy, economic, and environmental analyses. The results show that vapor injection significantly enhanced the thermodynamic performance of the system. At the optimum injection ratio of 0.15, the coefficient of performance increased from 3.75 to 4.36, while the condenser heating capacity improved from 4.80 to 6.95 kW. Consequently, the maximum basin water temperature increased from 66°C to 74°C, resulting in a 49.3% increase in daily freshwater productivity from 30.55 to 45.60 kg/day. Moreover, the thermal efficiency and exergy efficiency improved from 41.8% to 58.7% and from 16.2% to 23.8%, respectively. The freshwater production cost decreased from INR 4.85/kg to INR 3.36/kg, while the annual CO 2 emission reduction increased from 1180 kg CO 2 /year to 1680 kg CO 2 /year. The findings demonstrate that integrating vapor injection with an R290 solar‐assisted heat pump provides an effective approach for improving thermodynamic performance, reducing freshwater production cost, and promoting low‐carbon, decentralized desalination systems for sustainable water production.