S’pore team develops water-based air conditioner

A TEAM from the National University of Singapore has developed a “green” air conditioning system that is the first of its kind in the world.

The system that harnesses water to cool the surrounding air could, in a couple of years, replace those that use chemical compounds which also deplete the ozone in the atmosphere.

This alternative also does not require a compressor. Together, the features make it a world first.

Researchers at the National University of Singapore have developed a bulky prototype. But they believe a compact version no larger than a conventional air-con will be ready in two to three years’ time.

Most notable about the system is that it does not use harmful chemical refrigerants such as chlorofluorocarbon and halogenated chlorofluorocarbon, part of the greenhouse gases that trap heat and lead to depletion of the ozone layer.

Tests done on the NUS campus, both indoors and outdoors, also show it consumes 40 percent less energy. This is largely because it does not need a compressor, said Associate Professor Ernest Chua, who led the research.

Conventional air-cons have a compressor, often placed on a balcony or a building’s external ledge, to expel the heat that has been absorbed by the chemical refrigerants. The process requires high pressure and this is the reason for the high consumption of energy, said professor Chua from the NUS Department of Mechanical Engineering.

Without the compressor, the system will not emit hot air which can adversely affect the microclimate of surrounding areas, he said.

The NUS system involves a two-step process. First, hot and humid air is blown into a dehumidifier, where paper-like membrane sheets absorb its moisture.

Next, the remaining air moves into an “evaporative cooler” where water absorbs the heat from it. The resulting cool and dry air is then released into the surrounding area.

Explaining the concept of evaporative cooling, Chua said it is similar to what happens when one steps out of a swimming pool.

“You feel cool when you step out because of evaporative cooling. The layer of water on your skin changes from liquid to vapour, taking heat away from your skin, causing you to experience a cooling effect.”