Pressure effect on an ocean-based humidification-dehumidification desalination process

A new humidification-dehumidification (HDH) desalination process is proposed and analyzed. Being ocean based, the process does not produce any brine. It is largely powered jointly by solar energy, wind energy, and various types of ocean energies in a nearly natural way. A vacuum pump is employed to drive the air circulation throughout the HDH process. It is the only unit that consumes electricity. The HDH process is analyzed under various conditions, including using a low pressure (as low as to 0.2 atm) for humidification and the ambient pressure for dehumidification, running the entire HDH process around a low pressure (as low as to 0.2 atm), and running it around the ambient pressure. The results from case studies show that applying different pressure levels to humidification and dehumidification would lead to a prohibitively high electric energy consumption of the vacuum pump. Being the most favorable operating condition, running the HDH process around the ambient pressure yields a freshwater production rate at the level of 4 to 11 l/h per HDH line, depending on the pipe sizing and weather conditions. The associated minimum electric energy consumption of the vacuum pump is at the level of 0.9 to 1.6 kWh/m(3)-water