Membrane distillation uses hydrothermal, solar

KIST develops membrane distillation methods using hydrothermal and solar energy. The goal is to maximize system efficiency through customized membrane distillation technologies for regional climate characteristics

KIST has developed membrane distillation methods using hydrothermal and solar energy. The goal is to maximize system efficiency through customized membrane distillation technologies for regional climate characteristics.

Clean water is essential for human survival. However, less than 3% of freshwater can be used as drinking water. According to a report by the World Meteorological Organization, drinking water is scarce for approximately 1 billion people worldwide. This is expected to rise to 1.4 billion by 2050.

Seawater desalination technology, which produces fresh water from seawater, could solve the problem of water scarcity. At the Korea Institute of Science and Technology (KIST, President: Seok-Jin Yoon), a research team led by Dr Kyung Guen Song from the Center for Water Cycle Research has developed a hybrid membrane distillation module. It combines solar energy with hydrothermal heat pumps to reduce thermal energy consumption during desalination.

Reverse osmosis and evaporation methods are relatively common seawater desalination processes. However, these methods can operate only at high pressures and temperatures. In comparison, the membrane distillation method produces freshwater by utilizing the vapour pressure generated by the temperature difference between the flowing raw water and treated water separated by a membrane.

This approach has the advantage of low energy consumption. Fresh water can be generated at pressures of 0.2–0.8 bar, lower than atmospheric pressure, and temperatures of 50–60℃. However, large-scale operation requires more thermal energy. Thus, research studies are needed to reduce the use of thermal energy for commercial operation.

Benefits of membrane distillation

The membrane distillation involves simultaneous mass and heat (energy) transfer. It is divided into a direct contact membrane distillation (DCMD) and an air gap membrane distillation (AGMD). They are based on the modes applied to the treated water side of the membrane to generate vapour pressure differences, which are the driving force. For high energy supply, producing water by direct contact with raw water of high temperature and treated water of low temperature to the membrane surface (i.e., DCMD) is beneficial.

In contrast, for low energy supply, the efficiency is greater if the heat transmitted (heat loss) is reduced by air gaps rather than direct contact between raw water and processed water. Thus, the mode that generates water by condensing over a cold surface and maintaining air gaps between the membrane and the condensation surface (i.e., AGMD) are preferred.

The KIST Research Team developed a hybrid desalination technology by conducting on-site tests for 1 month. It was an opportunity to compare the system performance and economy using solar energy and hydrothermal heat pumps. When the system operated in parallel with solar energy, production increased by 9.6 per cent and energy usage was reduced by 30 per cent compared to the membrane distillation method using only hydrothermal heat pumps. Comparison of the consumption of thermal energy depending on the presence of solar energy showed that the efficiency of the membrane distillation plant process increased by up to 17.5 per cent when solar energy was used as an additional heat source.

Future of membrane distillation

According to Dr. Song, “The hybrid desalination technology we developed could be a method to supply water to some industrial complexes and island areas facing water scarcity as it can reduce the energy consumption required to generate fresh water. We expect this technology to be applied to significant water supply facilities in the Middle East and Southeast Asia where the annual solar radiation quantity is 1.5 times that in Korea.”

He added, “Membrane distillation is not significantly affected by raw water quality. It will be possible to supply drinking water to areas where raw water quality became heavily contaminated due to water pollution and areas where heavy metal detection is high.”

KIST was established in 1966. It was the first government-funded research institute in Korea to establish a national development strategy based on science and technology. KIST sought to disseminate various industrial technologies to promote the development of major industries. KIST is now elevating the status of Korean science and technology through the pursuit of world-leading innovative research and development. For more information, please visit KIST’s website at

This research was supported by the Ministry of Science and ICT. It was conducted as a BRIDGE Fusion Research Development Program, which is part of the STEAM Research Project. The results have been published in “Energy Conversion and Management”, an international journal in the mechanics field.

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