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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ItemNo Preview AvailableExperimental evaluation of PCM embedded radiant chilled ceiling for efficient space cooling(Department of the Built Environment, 2023)Because of climate change, together with rapid urbanisation and continuous population growth, the global demand for space cooling is increasing dramatically. Under a business-as-usual trajectory, there will be a more than threefold rise in the number of in-use air conditioners worldwide by 2050. A radical shift to innovative space cooling technologies is therefore essential, ones that can sustainably meet the growing requirements. Phase change material embedded radiant chilled ceiling, called PCM-RCC, offers an emerging alternative for more sustainable space cooling provision. This system provides a range of benefits to endusers, in terms of efficiency and indoor environmental quality, together with demand-side flexibility. PCM-RCC, however, is still under development, and further research is needed to realise its full capabilities. The present work experimentally analyses the thermal-energy performance of a PCM-RCC system using a full-scale test cabin equipped with PCM ceiling panels. Here, the transient thermal behaviour of the panels besides the cooling energy delivered in charging-discharging cycles are examined. Additionally, the indoor thermal comfort and peak energy demand reduction enabled by the present PCM-RCC are discussed. Based on the results, typically 4–5 hours of chilled water circulation overnight could sufficiently be able to fully recharge the panels in the morning. Over 80% of the occupancy time was found within Class B thermal comfort defined in ISO 7730. About 70% of the system’s daily electricity usage time was during off-peak hours. The significance of implementing optimal predictive operating schedules was also highlighted to fully utilise PCM-RCC’s potentials.
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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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ItemNo Preview AvailableA multi-layered energy resilience framework and metrics for energy master planning of communities: A university campus case study(Society of Risk Analysis, 2021-12-05)
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ItemNo Preview Available
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ItemLessons Learned from PCM Embedded Radiant Chilled Ceiling Experiments in Melbourne(Instituto Superior de Engenharia do Porto, 2021-09-14)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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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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ItemNo Preview AvailableDataset on validation of double U-tube borehole and seasonal solar thermal energy storage system TRNSYS models( 2021-08-09)This dataset includes data from the validation of double U-tube borehole and seasonal solar thermal energy storage system TRNSYS models. The simulated transient temperatures at various points of the systems were compared with the measured ones. To quantify the agreement between each simulated and measured temperature of interest, mean bias error (MBE), root mean square error (RMSE) and correlation coefficient (CC) were applied.
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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.