Delivering an Energy Efficient Air-conditioning System
01 November 2011
"The invention is based on decoupling the ventilation needs from the cooling needs. Ventilation (fresh) and cooling (recirculated) air are transferred separately. The novelty of our system lies in the twin objectives of providing better air quality and energy savings of 5 to 15 per cent."
Assoc Prof Chandra Sekhar, Department of Building, School of Design and Environment.
The innovative Single Coil Twin Fan system won the 2011 ASEAN Energy Award - Energy Efficiency Competition (Special Submissions category)
NUS researchers from the Department of Building, School of Design and Environment, have developed the Single Coil Twin Fan (SCTF) air-conditioning and air distribution system which provides "demand ventilation" and "demand cooling" by dynamically responding to the varying needs in the occupied zones of a building.
For this innovative system, their spin-off company, Enhanced Air Quality Pte Ltd (EAQPL), was awarded the 2011 ASEAN Energy Award - Energy Efficiency Competition (Special Submissions category). The ASEAN Energy Awards recognise efforts by innovative companies in ASEAN to promote and implement energy efficiency and renewable energy solutions.
Assoc Profs Tham Kwok Wai, David Cheong Kok Wai and Chandra Sekhar are the inventors of the SCTF system and Founding Directors of EAQPL which focuses on the design, manufacturing, installation, commissioning and maintenance of SCTF system.
"The invention is based on decoupling the ventilation needs from the cooling needs. Ventilation (fresh) and cooling (recirculated) air are transferred separately. The novelty of our system lies in the twin objectives of providing better air quality and energy savings of 5 to 15 per cent," said Assoc Prof Sekhar of the SCTF system which holds three US and several Patent Cooperation Treaty patents.
In contrast, a typical air-conditioning and air distribution system provides a mixture of cooling and ventilation air that needs to remove heat and provide ventilation. Since the recirculated air (taken from within the occupied zones of the building) is mixed with ventilation air and the mixed air is supplied back to the occupied zones in the building, it is generally not possible to optimise energy and air quality performance of such a system. When certain changes are made to the building, the system may not be able to respond, thereby reducing air flow and affecting ventilation or resulting in increased energy consumption to maintain air quality.
Assoc Prof Tham, who is also Head of the NUS Department of Building, said that the SCTF system allows for the customisation of ventilation in the work environment, be it on a zone or individual basis. "Once we have separated re-circulated air and fresh air, there are infinite possibilities. I can see that our direction and technology development will go along this line to support this evolution in the work paradigm. In fact, the user has a direct means of controlling his direct work space," said Assoc Prof Tham.
Assoc Prof David Cheong Kok Wai shared that the SCTF system has a distinctive feature which lessens contaminants in indoor environments that are originated indoors or outdoors. "When there is a haze, the fresh air from outside can be reduced and shut down as there are two fans in the system. One fan recirculates air within the building and the other fan delivers fresh air. The latter can be switched off so as not to bring contaminated outdoor air into the building," he said.
The potential applications of the SCTF technology include buildings with considerable load diversities such as commercial and office buildings as well as those with simultaneous and distinct "process" and "human" needs (e.g. laboratories, air-conditioned workshops).
The SCTF system has been installed as a demonstration project at Singapore's Building and Construction Authority's Zero Energy Building which resulted in total energy savings amounting to 14 per cent of conventional air-conditioning system. Previously, the SCTF system was also placed at the University Hall as part of a test-bedding project under a Technology Enterprise Commercialisation grant.