Abstract
This work focuses on developing a Low-cost, low-grade electrical-thermal solar humidification system, as a promising solution for freshwater production. To increase the air humidity ratio at the humidifier exit, a designed and instrumented solar humidifier harnesses solar radiation and receives both a forced hot air stream from a solar air collector and water droplets falling onto its absorber plate, where the droplets evaporate. The solar humidifier dimensions were 330 × 50 × 1000 mm. PV panels supplied electrical power to circulate water and air for preheating by a flat-plate and an air solar collector. Key factors influencing air’s relative humidity (RH) are air flow rates (0.5 m3/min to 1.5 m3/min), water drip rate (4 to 10 drops/s), and the solar humidifier’s absorber surface geometry (flat or dimpled). Tests were extended from 8:00 to 17:00 to evaluate air RH and temperature on clear-sky days in Baghdad, Iraq. Results showed that the highest outlet air RH was 61.2%, 72.4%, and 69.9% for water dripping rates of 4, 7, and 10 drops/s, corresponding to 0.167, 0.297, and 0.423 g/s, respectively, with a constant airflow rate of 0.5 m3/min. The best dripping rate was 7 drops/s. The outlet air RH from the humidifier was 72.4% and 85.6% for flat and dimpled absorbers, respectively, at an airflow rate of 0.5 m3/min and 7 water drops/s (0.297 g/s). The humidifier’s effectiveness was 85% and 70%, respectively. It is concluded that the dimpled absorber achieves significantly better humidification performance than the flat-plate absorber across all airflow rates. The humidifier pressure drops increases from 0.13 Pa to 0.36 Pa for the flat plate and dimpled plate, respectively, at solar noon, for a flow rate of 0.5 m3/min.