First of its kind in Hong Kong - innovative reuse of treated effluent and enhanced energy efficiency for air-conditioning systems

In Hong Kong, air-conditioning (A/C) systems are major consumers of electricity. Although water-cooled air-conditioning systems (WACSs) are more energy efficient, the need for water towers, water treatment and other operation and maintenance (O&M) demands restrain their application in most buildings. This paper reviews a pilot application of treated effluent from sewage treatment works as a cooling medium for the Direct Expansion type of A/C system within the treatment Plant. The Drainage Services Department (DSD) installed a WACS with a self-assembled effluent-cooled condenser to study the energy efficiency, cooling performance and actual O&M requirements of the new system over a one-year pilot. It revealed that an energy saving of up to 27.6% per year could be achieved when compared with a conventional air-cooled air-conditioning system (AACS). This innovative effluent cooling A/C system achieves innovative reuse of treated effluent as well as reduction in carbon footprint as a result of higher energy efficiency for sustainable development.