• Energy Research

The aim of this research was to evaluate the effectiveness of phase-change materials (PCMs) incorporated into the supply air duct of a hollow-core slab ventilation system. Both experimental and numerical approaches were adopted in this investigation. In the experimental work, the air was passed through a PCM-incorporated aluminum air duct, and the temperature at various points of the duct was recorded. Computational fluid dynamics models of the PCM-incorporated supply air duct and the hollow-core slab were developed and validated with the respective experimental data. The validated models were used to simulate the performance of PCM-incorporated hollow-core slabs during summer in Melbourne, Australia. The results showed that the reduction in temperature fluctuation varied with the way the PCM was incorporated inside the supply air duct. The temperature difference was maximum and was maintained for a longer period when the PCM was spread to all four internal surfaces of the supply air duct. The results also showed that the effectiveness of the combined PCM–air duct–hollow-core slab system in reducing the temperature fluctuation was lower than the individual performance of the PCM–air duct and hollow-core concrete slab for a given inlet temperature condition during the simulated period. This was because the integration of PCMs in the supply air duct resulted in a precooling effect which reduced the difference between the amplitude of slab inlet temperature swing and average slab temperature. As a result, the reduction in temperature fluctuation due to the thermal mass of the hollow-core slab was 21% lower in the presence of PCMs compared to the no-PCM case.

Cold spray additive manufacturing (CSAM) is generally used to repair worn components and build complex on-demand parts by depositing metal powder layer-wise using compressed air. Previous studies on CSAM were focused on printing parameters, materials properties, and printed part mechanical performance. However, the energy consumption and environmental impacts of CSAM processes have not yet been investigated, which are essential factors for sustainable manufacturing. This study aims to investigate the carbon footprint of the CSAM process and compare it with conventional machining processes and other additive manufacturing. The life cycle assessment methodology was followed to calculate the carbon footprint of a pipe flange, considering rod or tube as a feedstock. Results revealed that the machined flange from the tube had the lowest CO2-eq emissions of 31 kg CO2-eq due to low rough machining energy consumption and scrap production, compared to the machined flange from a rod and a printed flange from powder. Moreover, the life cycle carbon emissions increased by 8% and 19% in case of the printed and machined flanges, with uncertainties of 4% and 9%, respectively, when changing feedstock CO2 emissions. From a regional perspective, the CSAM process was responsible for the lowest CO2-eq emissions in Tasmania and South Australia.

Abstract The integration of Phase Change Materials (PCMs) in buildings as a potential method to improve indoor thermal comfort can be achieved via three different approaches: passive, active and free cooling. Previous studies on the thermal performance enhancement using these methods revealed that all three methods can improve the energy efficiency or indoor thermal comfort of a building significantly. However, there is no study available in the literature comparing the effectiveness of different PCM application methods. Such comparative analysis is important to understand which application method would be best for increasing the energy efficiency and thermal comfort of a particular building type. The aim of the present study is to compare and analyze the effectiveness of passive and free cooling application methods of PCM in a residential building in Melbourne, Australia. The passive application method utilizes a macro-encapsulated PCM, so-called BioPCM mats, installed in the ceilings of the building. In free cooling, outdoor air was supplied to the indoor after passing it through a PCM containing heat exchanger. The comparative study was carried out using validated numerical models for both application methods. The simulation models were developed using building simulation software EnergyPlus V8.3 and computational fluid dynamics (CFD) software ANSYS V15.1. The results showed that, for the studied building, free cooling application of PCM is more effective than the passive application in reducing the indoor zone temperature. During the studied period of seven days, passive application of 25 °C PCM resulted in up to 0.44 °C reduction in peak indoor zone temperature compared to 2.63 °C reduction in the free cooling application which is about six times of the reduction in passive case. Despite the use of several supporting strategies to improve the performance of passive PCM application, its effectiveness in reducing the peak zone temperature was always found to be lower than the free cooling method. Parametric studies showed that the optimum PCM temperature should be carefully chosen based on the application method as free cooling and passive cooling methods are influenced by outdoor air temperature and indoor zone temperature respectively.

Energy use in the building is responsible for one-third of total carbon dioxide (CO2) emissions globally. Nearly half of the energy loss occurs through the building envelope due to heat transfer to/for the surroundings. Therefore, there is a need to design an optimum building envelope to reduce energy use in buildings that depend on several parameters. This study aims to review different building parameters and provide a conceptual framework to optimize the building envelope. In total, 260 papers were reviewed, and the building envelope design consideration was categorized into: 1) Design Parameters (design and geometry), 2) environmental conditions (indoor and outdoor) and 3) performance criteria (energy, environment, economic, comfort). Energy use and CO2-emission in buildings increase with high thermal conductivity, low thermal mass, and low solar absorption of its envelope. Geometrically, building orientation impacts energy use more than the building shape factor. Changing set point temperature according to surrounding conditions has reduced energy use and CO2-emission by 30% and 56%, respectively. However, indoor air quality, velocity, and occupancy have meagerly affected building energy use. Energy and emission optimization criteria are directly related, but the emission-based optimized envelope is thicker than the energy one. Other criteria such as economy and comfort (thermal and visual) are inversely proportional to the energy-efficient building envelope. Based on the comprehensive review, this study proposed a conceptual framework to design a sustainable building envelope that includes life cycle assessment, occupant's satisfaction, and social benefits. Several future research recommendations were made, including 1) the use of switchable reflective materials to minimize heat transfer, 2) dynamic insulation material to control insulation value as needed, and 3) smart windows with tunable optical properties.

Abstract In this study, a novel thermal energy storage composite was developed by impregnating paraffin into hydrophobic coated expanded perlite (EPO) granules. A paraffin/uncoated expanded perlite (EPW) phase change composite was also prepared to study and compare the stability when integrated into cementitious composites. Paraffin/EPW, containing 35% by weight of paraffin, showed significant leakage of phase change material (PCM) during integration into concrete. However, no PCM leakage was observed for novel paraffin/EPO containing 50% by weight of paraffin in the composite. Microstructural and mechanical properties were studied for the compatibility of hydrophobic coated PCM composite in concrete. The thermal behaviour of a concrete panel incorporating PCM was studied and compared with the reference panel. The results revealed that incorporation of the developed PCM composite into concrete significantly improved the thermal inertia and thermal energy storage.

Abstract Climate change has led to an increase in the frequency and intensity of heatwaves as well as the risk of heat stress within buildings. To provide habitable indoor conditions without air-conditioning during heatwave, residential building energy efficiency need to be upgraded. The aim of this research is to investigate the possible correlation of building energy rating upgrading with heat-related health hazard during heatwave, with case data drawing from Melbourne, Australia. Using building simulations, indoor heat stress conditions of different energy rated houses were calculated using wet bulb globe temperature and discomfort index under the Melbourne 2009 heatwave conditions. The results showed that during three days heatwave period, residents of 0.9 star energy rated house were exposed to extreme heat stress conditions for almost 25 h compared to only 6 h experienced by the occupants of 5.4 star energy rated house. Several robust empirical relationships were proposed to predict deaths, ambulance calls, emergency department presentations and after hour doctor calls during heatwave. It was concluded that mortality rate from a Melbourne 2009 type, as well as, future more intense heatwave may reduce by 90% if entire existing lower energy star rated houses can be upgraded to minimum 5.4 star energy rating.

Abstract Knowledge of the barriers and coping strategies for retrofitting government buildings for energy efficiency is essential for the success of these types of complex retrofitting programs. This study utilised thematic findings from two focused groups consist of government employees from two States within Australia to create a comprehensive list of barriers to retrofitting public building stock for energy efficiency and associated strategies to address them. Thematic analysis revealed that a lack of political will, financing protocols, department/agency capability, industry capability, quality assurance and misaligned incentives, are the key barriers to public building energy efficiency retrofitting projects. To address such barriers, research revealed that a government championed top-down approach is required. A key strategy identified was enabling government departments and agencies to take on debt to fund retrofit initiatives that would derive returns, in terms of reduced energy utility costs, over the short-medium term. Other important strategies included having a mandatory energy efficiency retrofitting policy, dedicated financing mechanism, flexible procurement model, facilitation team and list of pre-qualified professionals.

This research investigated the real-world operational performance of five purposely designed and built net-zero-energy houses in Melbourne, Australia. The embodied energy and carbon emissions of these houses were calculated based on their architectural and engineering drawings, as well as the relevant databases of embodied energy and emission factors. Operational data, including solar production, consumption, end uses, battery usage, grid import, and grid export, were measured using the appropriate IoT devices from May 2023 to April 2024. The results showed that all the studied houses achieved net-zero energy and net-zero carbon status for operation, exporting between 3 to 37 times more energy than they consumed to the grid (except for house 2, where the consumption from the grid was zero). The embodied carbon of each case study house was calculated as 13.1 tons of CO2-e, which could be paid back within 4 to 9 years depending on the operational carbon. Achieving net-zero cost status, however, was found to be difficult due to the higher electricity purchase price, daily connection charge, and lower feed-in tariff. Only house 2 was close to achieving net zero cost with only AUD 37 out-of-pocket cost. Increasing the energy exported to the grid and storing the generated solar energy may help achieve net-zero cost. The installation of batteries did not affect the net-zero energy or emission status but had a significant impact on net-zero operational costs. However, the calculated payback period for the batteries installed in these five houses ranged from 43 to 112 years, making them impractical at this stage compared to the typical 10-year warranty period of the batteries. With rising electricity purchase prices, decreasing feed-in tariffs (potentially to zero in the future/already the case in some areas), and government incentives for battery installation, the payback period could be reduced, justifying their adoption. Moreover, the installed 13.5 kWh Tesla battery was too big for households with lower energy consumption like houses 2 and 5, which used only 25% of their total battery capacity most of the year. Therefore, selecting an appropriately sized battery based on household consumption could further help reduce the payback period.