Extract

INTRODUCTION:
The energy usage of buildings in Australia is growing rapidly [1]. They account for 19% of Australia energy consumption and 23% of carbon emission [2]. Meanwhile, office buildings account for 60% energy usage for Australian building sector [1]. About 39% of the energy is used for heating, cooling, air-conditioning and ventilation (HVAC) systems in an Australian office building [3]. A typical HVAC system usually utilizes convective heat transfer which is “thermodynamically irrational” while neglecting the mean radiant temperature (MRT) [4]. Among three mechanisms of heat transfer between a human body and the environment, radiant is associated with MRT and contributes to nearly 50% of our body conditioning [4]. This means radiant conditioning systems should be prioritized over convective HVAC systems.

Perimeter zones are the areas near the building envelope with a depth of typically 4-5m. Office buildings usually have large glazing façades on the envelope for better visual comfort but also allow heavy solar penetration and dramatically increase MRT at the perimeter zones [5]. Also, large glazing areas with high U-value and SHGC might add to the problem [6]. This results in a high level of thermal discomfort within the perimeter zone [6]. However, occupants of the perimeter zones are often satisfied with their visual comfort despite the thermal discomfort caused by the constant changing conditions [5]. Therefore, a responsive and environmentally friendly solution for perimeter zone conditioning is sought.

METHODS:
This research will investigate the effectiveness of MRT changes to the perimeter zone via thermal comfort assessment. In doing so, the ISO 7730 thermal comfort model is applied. Simulation programs and instrumental measurement will provide comfort analysis. This will assist in the development of an experimental method. Comparative energy and comfort analysis will be made between HVAC (convective) and the proposed radiant system conditioning.

EXPECTED RESULTS:
The exploration into a highly responsive and quick conditioning system can be provided through the relatively new capillary hydronic conditioning systems. These hydronic mats offer a change to MRT within their applied ceiling, floor, or wall, within minutes, changing the comfort level. Furthermore, they apply a conditioning temperature often 10-15 C above or below desired setpoints. This low-temperature heating and high-temperature cooling principle allows this system to be more energy-efficient and offer better thermal performance than traditional HVAC systems [7].

EXPECTED CONCLUSIONS:
This research can provide an environmentally friendly solution to solve the thermal problem for perimeter zones. It is essential to acquire conditioning systems that are quick and responsive to the dynamic changes within perimeter zones. Further to this type of response or condition might be an instantaneous change to mean radiant temperature (MRT), requiring a balance within the perimeter zone environment. This MRT control can be efficiently provided by a thermal dynamic and energy efficient capillary hydronic radiant system. The proposed radiant system can also work alongside other systems such as improved glazing and/or shading systems.

REFERENCES:
[1] Allouhi, A., et al., Energy consumption and efficiency in buildings: current status and future trends. Journal of Cleaner production, 2015. 109: p. 118-130.
[2] Science, A., et al., Energy for Australia in the 21st Century: The central role of electricity. 2016.
[3] Residovic, C., The new NABERS indoor environment tool–the next frontier for Australian buildings. Procedia Engineering, 2017. 180: p. 303-310.
[4] Moe, K., Thermally Active Surfaces in Architecture. 2010: Princeton Architectural Press.
[5] Chaloeytoy, K., M. Ichinose, and R. Sasaki. Comparing the occupants’ comfort between perimeter zone and interior zone in Asian office. in IOP Conference Series: Earth and Environmental Science. 2019. IOP Publishing.
[6] Anderson, T. and M. Luther, Designing for thermal comfort near a glazed exterior wall. Architectural Science Review, 2012. 55(3): p. 186-195.
[7] Rhee, K.-N. and K.W. Kim, A 50 year review of basic and applied research in radiant heating and cooling systems for the built environment. Building and Environment, 2015. 91: p. 166-190.

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