A novel motor-free solar-thermal vapor-pressure water pump: concept validation and thermal feasibility assessment

Electric motors account for a large share of global electricity consumption, particularly in water pumping applications for agriculture and urban infrastructure. Conventional solar water pump systems rely on electric motors and photovoltaic systems, which introduce mechanical and electrical losses and increase system complexity. This study proposes and evaluates a novel motor-free solar-thermal water pumping concept that converts concentrated solar energy directly into hydraulic work via vapor-pressure-driven piston motion. The system employs a parabolic solar concentrator to generate cyclic pressure through daytime heating and nighttime cooling. Technical feasibility was assessed through field measurements, laboratory-scale testing, and long-term thermal simulations. Field experiments demonstrated focal-point temperatures exceeding 600 °C for an 11.4 m 2 parabolic concentrator. Laboratory tests verified controlled piston-driven suction and discharge under alternating pressure conditions. Annual and seasonal simulations using TRNSYS predicted average piston tank temperatures of approximately 391 °C during peak irrigation months under Mediterranean climatic conditions. The results confirm that the thermal conditions required for vapor-driven piston operation can be achieved and sustained throughout the year. While hydraulic performance and economic analysis require full-scale prototype validation, the present study establishes the thermodynamic and mechanical feasibility of a motor-free solar-thermal pumping approach for off-grid water supply applications.