Infrastructure Engineering - Research Publications
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ItemDevelopment and validation of a transient simulation model of a full-scale PCM embedded radiant chilled ceiling(TSINGHUA UNIV PRESS, 2023-06)Abstract The recent significant rise in space cooling energy demand due to the massive use of air-conditioning systems has adversely changed buildings’ energy use patterns globally. The updated energy technology perspectives highlight the need for innovative cooling systems to address this growing cooling demand. Phase change material embedded radiant chilled ceiling (PCM-RCC) has lately acquired popularity as they offer more efficient space cooling together with further demand-side flexibility. Recent advancements in PCM-RCC applications have increased the necessity for reliable simulation models to assist professionals in identifying improved designs and operating settings. In this study, a transient simulation model of PCM-RCC has been developed and validated using measured data in a full-scale test cabin equipped with newly developed PCM ceiling panels. This model, developed in the TRNSYS simulation studio, includes Type 399 that uses the Crank-Nicolson algorithm coupled with the enthalpy function to solve transient heat transfer in PCM ceiling panels. The developed model is validated in both free-running and active operation modes, and its quality is then evaluated using several validation metrics. The results obtained in multiple operating scenarios confirm that the model simulates the transient behaviour of the PCM-RCC system with an accuracy within ±10%. Aided by this validated model, which offers the user detailed flexibilities in the system design and its associated operating schemas, PCM-RCC’s potentials regarding peak load shifting, energy savings, and enhanced thermal comfort can be investigated more reliably.
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ItemComparing the life cycle costs of a traditional and a smart HVAC control system for Australian office buildings(Elsevier BV, 2024-08)Many smart technologies have been introduced in buildings with the aim to reduce the energy and GHG emissions associated with their operation, particularly through improved control systems for regulating heating, ventilation and air conditioning (HVAC) equipment. Despite their energy saving potential, only a few studies have comprehensively assessed the costs associated with their practical implementation from a life cycle perspective. Accordingly, this study quantifies and compares the life cycle costs of a smart HVAC control system with that of a traditional control system, in the context of an Australian office building. For both systems, the required hardware are specified based on the characteristics of these systems and the layout of the serviced spaces in the reference building. The costs incurred over the period of assessment are quantified using the net present cost (NPC) approach. To evaluate the effects of these control systems on the operational energy costs of the building HVAC system, the control logics of both these systems are modelled through building energy simulations. The results show that, over the period of assessment, the smart control system incurred a higher total cost compared to the traditional control system. However, the findings from the simulations show that the HVAC energy cost savings achieved through the specification of the smart control system offset the additional cost incurred to deploy this system over the traditional control system. The smart control system resulted in HVAC operational cost savings between 9 % and 10 % compared to the traditional control system. Sensitivity analyses indicated that the total life cycle costs varied between −27 % and +50 %, with the discount rate and energy price increase rate being the most influential parameters.
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ItemFifth-generation district heating and cooling systems: A review of recent advancements and implementation barriers(PERGAMON-ELSEVIER SCIENCE LTD, 2023-01)As global urbanisation levels continue to rise, supplying urban areas with low emissions energy becomes imperative in the fight against climate change. In areas with high demand density, district heating and cooling systems are generally a more efficient alternative compared to individual solutions, but current systems are mainly powered by fossil fuels and suffer from significant thermal losses due to high operating temperatures. Fifth-generation district heating and cooling systems (5GDHC) is a promising technology, able to address these drawbacks. 5GDHC systems operate at near ambient temperature, ensuring efficient integration of renewable energy sources and waste heat recovery potential. Their ability to provide simultaneous heating and cooling through the same pipeline and bidirectional energy flows allow for load balancing through the harvesting of demand synergies between different users. 5GDHC systems can play an important role in the energy transition but not much is known about their environmental performance over their life cycle and the novelty of the concept means that planning and design guidelines are scarcely present in the literature, hindering their development and further adoption. This study critically reviews recent advancements in the relevant literature as the 5GDHC technology transitions from research and development to the demonstration phase. Moreover, the paper addresses the design parameters and methodologies encountered in the literature for the modelling and operation of 5GDHC systems. Finally, the economic and environmental performance are discussed while presenting an overview of future developments and challenges related to full-scale deployment.
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ItemNo Preview AvailableIntegrating asset-specific flood vulnerability assessments with value-based preservation processes to develop the Heritage Building Flood Robustness Toolkit(ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER, 2024-03-01)
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ItemFifth-generation district heating and cooling: Opportunities and implementation challenges in a mild climate(Elsevier, 2024-01-01)Fifth-generation district heating and cooling (5GDHC) systems have the potential to provide simultaneous heating and cooling, allowing for energy exchange between users with different needs. However, their viability in mild climates with a higher share of cooling demand remains unclear. In this paper, we propose a framework for assessing the engineering, economic and environmental performance of a 5GDHC system compared to a state-of-the-art business-as-usual solution and demonstrate it through a practical case study for a university campus in Melbourne, Australia. When accessible heat sources and sinks are available, the 5GDHC system provides a cost-effective solution, with annual cost savings between 9 and 29 % and GHG emissions reduction between 25 and 58 % compared to an already advanced business-as-usual system. Additionally, by using peak off-peak tariffs and an hourly emission factor for the electricity consumed, we demonstrate the 5GDHC operational flexibility in pursuing different objectives, such as minimising cost or emissions, respectively. The results suggest that 5GDHC systems are an economically and environmentally viable solution in milder climates, and a successful implementation of 5GDHC in Australia can create new market opportunities and pave the way for its adoption in other countries with similar climatic conditions and no established history of district heating systems.
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ItemNo Preview AvailableOptimal design of micro pumped-storage plants in the heart of a city(ELSEVIER, 2024-02)
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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.