Techno-economic investigation of an entirely solar-powered hybrid HDH/RO desalination plant for moderate water demand under various operating conditions

• A Hybrid solar energy-based HDH-RO desalination system was investigated. • An overall daily output of 535 L/day was achieved. • The daily GOR and recovery ratio of the hybrid system reached 11. 15 and 55. 73 %. • The estimated water price for the hybrid system was 0. 63 /m³. • The TDS of the output water did not exceed 425 mg/L. The study presented a scalable, entirely solar-powered hybrid desalination system suitable for moderate demand and valid for various water salinities. The system merged two desalination techniques: HDH (humidification-dehumidification) and RO (reverse osmosis). The required power for all components was obtained from a photovoltaic (PV) system. The experiments were conducted to evaluate the separate units' and hybrid system's performances under different conditions, including various sprayed hot water (to the HDH) temperatures, RO feed water temperatures, air velocities, and water salinities. Based on the recorded data, the techno-economic analyses were conducted to assess the gain output ratio (GOR), recovery ratio (RR), specific energy consumption (SEC), the total amount of dissolved solids (TDS), and production cost. As a result, the RO unit's productivity increased almost linearly with feed temperature, showing a maximum hourly yield of 60 L/m 2. In contrast, HDH productivity showed exponential growth with feed temperature, achieving a maximum hourly yield of 18 L/m 2. The SEC of the RO unit decreased from 1. 1 kWh/m³ to 0. 63 kWh/m³ when using the rejected HDH's hot brine. The hybrid system's accumulated productivity reached 535 L/m 2, significantly higher than the standalone HDH (58. 5 L/m 2) and standalone RO (368 L/m 2). Additionally, the hybrid system demonstrated substantial improvements in GOR and RR, with daily values of 11. 15 and 55. 73 %, respectively. Economically, the yielded water cost was significantly lower, at 0. 63 /m³ for the HDH/RO system compared to 3. 51 /m³ for the standalone HDH.