Infrastructure Engineering - Research Publications
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ItemEfficient HVAC system identification using Koopman operator and machine learning for thermal comfort optimisation(Elsevier BV, 2023-08-15)The aim of this article is to improve the efficiency of heating, ventilation, and air conditioning (HVAC) systems by using a linear control approach. Conventional HVAC systems use a wall thermostat and a simplified ON/OFF controller to condition the thermal environment, but this approach is not always efficient in meeting indoor heat loads. To address this issue, we propose using the Koopman operator combined with Machine Learning, a linear embedding method, to model the nonlinear behaviour of thermal comfort indices. Specifically, we use the Predictive Mean Vote (PMV) index, which has been a superior indicator of occupants’ thermal sensation. We apply Computational Fluid Dynamics to create high-dimensional training, testing, and validation datasets, and a deep autoencoder network framework to map the original nonlinear coordinates of the PMV index into a latent space where the system is behaving linearly. Our results show that the Koopman autoencoder can reproduce and predict data from the latent space, enabling offline system identification for the zone thermal conditions and this has the potential to improve HVAC feedback control systems.
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ItemThermal and energy performance evaluation of a full-scale test cabin equipped with PCM embedded radiant chilled ceiling(Elsevier BV, 2023-06-01)The escalating global demand for space cooling has led to the emergence of new cooling technologies, including the phase change material embedded radiant chilled ceiling (PCM-RCC) system. This technology improves energy efficiency and indoor environmental quality, while also offering demand-side flexibility. The present study experimentally evaluates the thermal efficiency and energy performance of a PCM-RCC system in a full-scale test cabin equipped with PCM panels. Here, the transient thermal behaviour of PCM ceiling panels besides the cooling energy delivered during charging-discharging cycles are examined. The indoor thermal comfort and peak electricity demand reduction enabled by the present PCM-RCC are also discussed. The results reveal that chilled water circulation for 4–5 h overnight was sufficient to fully recharge the PCM panels. Over 80% of the occupancy time was classified as “Class B″ thermal comfort according to ISO 7730. The system's daily electricity usage was mostly concentrated during off-peak hours, accounting for ∼70% of the total usage. While the controlling schedule used in this study responded to the transient thermal behaviour of the indoor space and PCM ceiling panels, a more dynamic, predictive schedule is necessary to improve the system's overall efficiency and further enhance indoor thermal comfort in response to the changing environmental conditions.
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ItemLessons Learned from PCM Embedded Radiant Chilled Ceiling Experiments in Melbourne(Elsevier, 2022-06)Buildings are responsible for over a third of energy consumption worldwide, particularly for the increasing demand of air-conditioners in response to the more extreme heat around the globe. It is imperative to move towards more energy-efficient space cooling alternatives. The integration of phase change material (PCM) with a radiant chilled ceiling (RCC) is a promising technology due to its benefits regarding energy efficiency and indoor environmental quality. This article presents a field study conducted on a newly-developed PCM embedded radiant chilled ceiling (PCM-RCC) installed in a stand-alone cabin located in Melbourne. The study evaluates the thermal and energy performance of the system through investigation of the transient thermal behaviour of PCM panels in charging-discharging cycles, the indoor comfort conditions, and the electricity peak demand. It was observed that the proposed PCM-RCC can provide satisfactory comfort conditions and contribute to load shifting if a refined operating strategy is applied. The efficiency of PCM recharge overnight depends on several factors that need to be carefully considered in design. The challenges related to the implementation of optimal operating dynamic schedules in response to the thermal behaviour of PCM-RCC, and accurate weather forecasting should be addressed to realise the full potential of this technology.
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ItemAlternative Heating and Cooling Systems for the Retrofit of Medium-Rise Residential Buildings in Greece(WILEY-V C H VERLAG GMBH, 2021-11)The European Union recently set the target of doubling building retrofit rates through the European Green Deal. Currently, more than half of the households’ energy consumption is accounted for space conditioning, with southern European countries experiencing increasing demand for cooling systems over the past decade. Herein, the performance of market‐available heating and cooling systems that can replace the existing low‐efficiency systems in multiresidential buildings in Greece is compared. The study's objectives are to minimize the operating greenhouse gas emissions and the life‐cycle cost. Results demonstrate that air‐to‐air heat pumps have the lowest life‐cycle cost. In areas where natural gas is not available, the replacement of the diesel‐oil boiler with a biomass boiler leads to a 48% to 73% decrease of the operating greenhouse gas emissions. In areas where natural gas is available, the gas absorption heat pump has the lowest operating greenhouse gas emissions, demonstrating a reduction between 40% and 54% when compared to a conventional gas boiler; however, it dramatically increases the life‐cycle cost, making it less attractive than heat pumps and condensing gas boilers. The findings are in line with the current residential space conditioning market, while indicating the potential of biomass boilers and gas absorption heat pumps.
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ItemA review of Net Zero Energy Buildings with reflections on the Australian context(Elsevier, 2018-01-01)A Net Zero Energy Building (NZEB) is a term, subject to ambiguity, that could be used to describe a building with characteristics such as equal energy generation to usage, significantly reduced energy demands, energy costs equalling zero or net zero greenhouse gas (GHG) emissions. Despite lacking an authoritative definition of NZEBs, this relatively new emerging concept in Australia provides significant opportunities to reduce GHG emissions, energy usage and operational energy costs for buildings owners. This paper aims to explore the existing NZEB models, assess the progression of NZEB literature, identify key policies encouraging NZEB development and recognise potential areas of NZEB research.