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Building System and Diagnostics Pte Ltd has developed and commercialised a hybrid cooling system, VARC, that aims to provide thermal comfort for occupants under higher temperature conditions to reduce cooling demands and energy consumption. VARC is a patented technology that will provide radiant cooling. Instead of the typical supply & return chilled water circulation from a central cooling plant in the entire ceiling or floor, VARC utilizes lower temperature of water under lower pressure conditions in a vacuum cavity in modular panels. The vacuum pump maintains lower pressure in a cavity of panel to avoid the condensation issue on the surface of cooling panel. This will be the first radiant cooling system in tropical countries, which can provide thermal comfort in higher temperature space condition without any condensation issue. VARC is 50% more energy efficient than the typical air-conditioning system while enjoying satisfied thermal comfort.

This cooling system could be used for semi-outdoor or outdoor condition such as canteen, café, restaurant, public outdoor space etc. under naturally ventilated condition to support the better thermal comfort to assist the ceiling fan. This system can improve the thermal comfort of outdoors in tropical countries.

The cooling performance and energy efficiency for the proposed system was testbedded in actual site at Soilbuild office building. Four scenarios were tested:

(1) closed window condition with 10 degree C of supply temp,

(2) open window condition with 10 degree C of supply temp,

(3) closed window condition with 12 degree C of supply temp, and

(4) open window condition with 12 degree C of supply temp.

Temp, RH, MRT (Mean Radiant Temp), air flow for indoor, and temp & RT were measured for corridor and outdoor. In addition to the measurement of indoor and outdoor condition, thermal comfort survey was conducted for the users of the space on their feedback on thermal comfort of the proposed system.

As the project outcome, when outdoor air temp was varied from 29 degree C to 33 degree C, indoor temp was maintained at 26 degree C under 10 degree C of supply chilled water temp and at 26.5 degree C under 12 degree C of supply chilled water temp. Based on thermal comfort survey with total 19 persons with 10 degree C supply chilled water temp, 55% of persons under closed window and 67% of persons under opened window answered that it is neutral for thermal comfort and 48% of persons under closed window and 22% under opened window answered that it is quite cool.  Total 16 persons (of total 19 persons) would like to consider using this cooling system instead of typical air-conditioning system if energy savings can be achieved at around 50%.

Based on the measurement of the energy consumption, the proposed system achieved total energy savings at 41.5% at 10 degree C of supply chilled water temp and 50.2% at 12 degree C of supply chilled water. It is mainly from the cooling load reduction.