Water-based air-conditioning unit cools air without compressors

Researchers have developed a water-based air-conditioning system that cools air to as low as 18°C without energy-intensive compressors and chemical refrigerants.


Led by Associate Professor Ernest Chua from the Department of Mechanical Engineering at the National University of Singapore’s (NUS) Faculty of Engineering, the team’s air-conditioning system is claimed to be a cost-effective and sustainable solution to regulating ambient air conditions.

Chua said, “For buildings located in the tropics, more than 40 per cent of the building’s energy consumption is attributed to air-conditioning. We expect this rate to increase dramatically, adding an extra punch to global warming.”

According to NUS, the system consumes about 40 per cent less electricity than current compressor-based air-conditioners and negates the use of chemical refrigerants including chlorofluorocarbon and hydrochlorofluorocarbon for cooling. The system also generates drinking water while it cools ambient air.

Chua said, “First invented by Willis Carrier in 1902, vapour compression air-conditioning is the most widely used air-conditioning technology today. This approach is very energy-intensive and environmentally harmful. In contrast, our novel membrane and water-based cooling technology is very eco-friendly – it can provide cool and dry air without using a compressor and chemical refrigerants. This is a new starting point for the next generation of air-conditioners, and our technology has immense potential to disrupt how air-conditioning has traditionally been provided.”

Current air-conditioning systems require a large amount of energy to remove moisture and to cool the dehumidified air. By developing two systems to perform these two processes separately, the NUS Engineering team believe they can better control each process and achieve greater energy efficiency.

The new system first uses an innovative membrane technology to remove moisture from humid outdoor air. The dehumidified air is then cooled via a dew-point cooling system that uses water as the cooling medium instead of chemical refrigerants.

Unlike vapour compression air-conditioners, the system does not release hot air to the environment. Instead, a cool air stream that is comparatively less humid than environmental humidity is discharged – negating the effect of micro-climate. About 12 to 15 litres of drinking water can also be harvested after operating the air-conditioning system for a day.

“Our cooling technology can be easily tailored for all types of weather conditions, from humid climate in the tropics to arid climate in the deserts. While it can be used for indoor living and commercial spaces, it can also be easily scaled up to provide air-conditioning for clusters of buildings in an energy-efficient manner. This novel technology is also highly suitable for confined spaces,” said Chua.

The research team is currently refining the design of the air-conditioning system to further improve its user-friendliness. The NUS researchers are also working to incorporate features including pre-programmed thermal settings based on human occupancy and real-time tracking of its energy efficiency. The team hopes to work with industry partners to commercialise the technology.