Humidification-dehumidification desalination system based on solar air and water heaters

Abstract

Low-cost, low-grade solar-thermal humidification/dehumidification (STHDH) desalination system is viewed as a highly promising solution for small to medium-scale freshwater production. Key components influencing the productivity of STHDH systems include the heat source and packing material. This study focuses on the development of an STHDH desalination system, incorporating a novel solar water heater, a solar air heater, a humidifier using coconut fibre as packing material, and an evaporative cooler-based dehumidifier. The solar air and water heaters achieve average temperature differences of 68 °C for air and 11.1 °C for seawater, with respective flow rates of 100 kg/h and 0.028 kg/s. In the humidifier, coconut fibre provides sufficient surface area and ensures uniform distribution of air and seawater, resulting in a 48 %-126 % increase in the air’s humidity ratio. Results show that increasing both air and seawater flow rates significantly boosts system productivity and efficiency. The system produces between 3.78–5.34 L/h of freshwater with a thermal efficiency of 33.2 %-46.8 %. Additionally, it reduces 312.19 tons of CO₂ emissions and offers freshwater at a cost of $0.011-$0.015 per litre. Water quality tests reveal that the system effectively removes 99.6 % of TDS, 99.7 % of total hardness, and 99.9 % of chlorides from seawater.