FEASIBILITY STUDY OF CHILLED CEILING TECHNOLOGY IN SINGAPORE THROUGH SIMULATION AND VERIFICATION Bharath Seshadri 1 , Majid Bin Haji Sapar 1 , Zhou Jian 1 , Matthieu Neth 2 , Benedict Wu 2 and Dwayne Ng 2 1 Energy Research Institute, Nanyang Technological University, Singapore 2 SGL Group, Wiesbaden, Germany ABSTRACT Due to the hot and humid weather conditions in Singapore, air conditioning is widely used in buildings. The high cooling demands, met by conventional air-conditioning technology, result in very high energy consumption of buildings. Radiant Cooling technology, which has so far been widely limited to buildings in temperate climates, is a more energy efficient alternative. In this paper, we investigate the performance and comfort level of a certain type of radiant cooling system – Chilled Ceilings; and compare it with a conventional air- conditioning system in Singapore. The results of this study, concluded through energy modelling simulations, test bedding and verification (through sub-metering), show a significant decrease in energy consumption of the chilled ceiling system compared to a conventional air-based system, while maintaining ideal thermal comfort for the building’s occupants. This paper also aims to highlight the importance and relevance of building simulations to design and optimize buildings. INTRODUCTION In most buildings in Singapore, the air conditioning system makes up 50% of a building’s total electricity consumption. Figure 1 represents the energy consumption ‘break-down’ of commercial buildings in Singapore. One of the biggest challenges in achieving energy efficiency in buildings is to achieve a good indoor comfort level, while reducing the amount of energy consumed by air conditioning. Hence, there is a lot of interest to test innovative and more energy efficient air-conditioning systems that could replace current technology in Singapore and other tropical regions. Fig 1: Breakdown of Energy Consumption within commercial buildings in Singapore [National Environmental Agency Singapore, 2010] Conventional air-based air conditioning systems, such as Variable Air Volume (VAV) systems, which are widely used in buildings in Singapore, involve cooling, de-humidifying and distributing the air inside a building. These systems rely on large supply and exhaust air fans to move air through a distribution network of ducts within the building to supply large volumes of fresh and recirculated air for treatment at Air Handling Units (AHUs). Figure 2 is a schematic representation of a VAV system. Fig 2: Schematic of a typical VAV system used in Singapore A more energy efficient alternative to conventional air-conditioning systems is cooling via radiation or ‘radiant cooling’. Radiant cooling systems cool the ceiling surfaces through a network of pipes carrying chilled water that acts as a heat sink to cool the building space via radiation and natural convective air movement. Distribution of chilled water directly to the air-conditioned space is more efficient than centralized treatment of the fresh and recirculated air because water has a much higher heat capacity (4.187 kJ/kg.K) compared to air (1.006 kJ/kg.K). Consequently, the volume of water needed to achieve the same cooling demand and comfort level is significantly smaller than the volume of air needed by the traditional air-based VAV system. CHILLED CEILING TECHNOLOGY A chilled ceiling system refers to a type of low energy-high temperature cooling system that uses radiant cooling to cool a building space. A Chilled Ceiling is a ‘drop-down’ ceiling comprising of water- carrying pipes embedded in thin, conductive slabs and mounted on a metal ceiling plate. This system cools the occupants in the room through radiation and natural convection using the chilled ceiling as a heat sink for the heat load in the building. Figure 3 describes the radiant cooling and natural convection mechanisms in a chilled ceiling operation.