SINGAPORE: A team of researchers from the National University of Singapore (NUS) has invented hybrid air-conditioners that reduce electricity consumption. 

The technology uses solar heat as an energy source, increasing the efficiency of the hybrid air-con as the weather gets hotter, NUS said.

The team, from the Department of Mechanical Engineering at the NUS Faculty of Engineering, worked with industry collaborator Ecoline Solar to develop the "next generation of hybrid solar-thermal air-conditioners" to reduce energy consumption and carbon footprint. 

Companies such as NCS, Starhub, and Singtel have recently installed the cooling systems in their buildings. 

The technology has also provided cooling solutions to Singapore's "vertical farms", and to several condominiums and hotels.

The air-cons have electrical compression machines that use heat from the sun and surroundings to ease the electrical load of compressors by up to 55 percent.

“As the global temperature rises, fuelled by urbanization and exacerbated by climate change, so does the global demand for fuel to run energy-hungry air-conditioning," said Associate Professor Ernest Chua Kian Jon, who led the NUS team.

Assoc Prof Chua explained that conventional air-cons require high electrical energy and also produce a high volume of heat which is released into the environment, creating "undesirable heat zones". 

“The NUS and Ecoline innovative hybrid system leverage solar thermal technology to markedly reduce energy consumption and cut the volume of heat dissipated to the environment through our specially designed condensing unit,” he said.

The jointly developed technology uses a solar thermal collector comprising of vacuum tubes filled with a novel medium specially designed and engineered by the NUS team to absorb more solar energy and ambient heat. 

The energy collected is then recycled to assist in the superheating of the refrigerant in the system, converting it from low pressure, low-temperature gas to high pressure, high-temperature gas. 

This reduces the system's reliance on the compressor that pumps the refrigerant through the system, which reduces the system's overall electricity consumption and greenhouse emissions released. 

The team believes the solar thermal air-conditioning technology may help improve the energy efficiency of buildings and is a potentially effective way for businesses and households to reduce their operating cost and carbon footprint, while "becoming an integral part of the global warming solution", NUS said. 

Actual usage data has shown the hybrid system has consistently reduced energy usage, which also cut down utility bills by 30 to 55 percent, depending on usage. 

The project was also awarded the Prestigious Engineering Award by the Institute of Engineers Singapore and the ASEAN Outstanding Engineering Award by the ASEAN Federation of Engineering Organisations in 2019.

The NUS team and Ecoline Solar are now working to incorporate NUS’ patented membrane dehumidification technology to the thermal-based air-con to yield even higher energy savings.

Mr. Colin Chia, Director of Ecoline Solar, who led the collaboration project said the hybrid system is a "game-changer in the air-conditioning industry".

“The hotter the sun and the warmer the surrounding environment, the more efficient our hybrid air-conditioner system becomes," he said.  

"For consumers, this translates to greater savings in electricity consumption even when compared to the best conventional and inverter air-conditioning systems in the market."

The hybrid solar thermal air-conditioner is now available in Singapore, NUS said.

Although it costs 20 percent more than an inverter air-con, the cost difference can be offset by electrical cost savings in under two years.

"In the long run, this would be a more cost-effective cooling option," NUS added.

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