A comprehensive review of water distillation technologies for green hydrogen production

Abstract

The use of low-carbon hydrogen is called to be one of the key vectors for the decarbonization of the energy sector and industry. In that regard, green hydrogen, which is produced through the electrolysis of water using renewable sources of electricity, is the process that offers the most advantages. In order to operate efficiently, water electrolysis technologies require a water source of near-ultrapure quality. To achieve this, a preceding water treatment stage is necessary, and reverse osmosis technology is currently the most widely used. This pressure-driven technology has reached maturity, but it still has certain technological limitations and energy consumption to be considered. This paper presents a comprehensive literature review of water distillation technologies currently available for obtaining the water quality required by green hydrogen electrolyzers. The comparison between mature and innovative water distillation processes showed that membrane distillation is one of the most promising technologies and that it has proved its effectiveness in the desalination sectors, but it has yet to be exploited to produce green hydrogen. This technology uses hydrophobic membranes and can be powered by a low-temperature heat source (between 40 °C and 90 °C), which provides opportunities to use alternative sources of heat, such as solar, geothermal, and even low-quality waste heat. This presents a great opportunity for energy integration with water electrolysis processes, as they generate a low-temperature waste heat flow (around 80 °C) during operation, which is compatible in quality and quantity with membrane distillation process requirements.