• Energy Research

Abstract Solar chimney is a reliable renewable energy system that enhances the natural ventilation to reduce the energy consumption in buildings. Under the fact that previous optimization designs usually ignore the external wind, the impacts of external wind on the optimum designing parameters are then investigated. It is confirmed that external wind could affect its optimum designing parameters, which are different from those previously obtained value in the literature without considering the external wind. For the analysed wall solar chimney, it was known that previously obtained optimal cavity depth of 0.2–0.3 m is no longer applicable under the external wind, and the optimal value rises to 0.4–0.5 m, while the same applies to inlet height/area. Solar chimney performance is enhanced under the external wind, which is not only because of the incoming wind flow from the room opening but also the reduced air resistance. It was observed that increased solar intensity shows limited influences on the overall airflow characteristics. Solar chimney performance also presented a generally enhanced trend under a low external wind speed, but a strong wind could dominate its performance with limited fluctuation even though the wind angle is higher as 45°. It was known that the airflow rates through the solar chimney are largely hampered with a small cavity depth (i.e., smaller than 0.2 m) and inlet height under the external wind. And the airflow profiles are less affected when both of cavity depth and inlet height are bigger than 0.2 m. The obtained research outcomes could provide a technical guide on the optimization design of solar chimney in buildings.

This paper aims to explore the risks of applying energy efficient and renewable technologies (EERTs) in Australian green office buildings. An online questionnaire survey was conducted in several Australian states and territories to identify and evaluate the potential critical risks that may influence the implementation of EERTs. Consisting of architects, engineers, project managers, and contractors, participants of the survey were asked to evaluate the generic and some specific EERTs risks occurring in the implementation of a selected number of commonly used EERTs in Australian green office buildings. In addition, the participants were asked to pinpoint those stakeholders who were the most affected by the risks and the lifecycle stage of the technology or buildings at which these risks might mostly occur. The data analysis results shows that uncertain governmental policies were identified as the critical risk with the highest mean risk impact value, Lack of access to funds and Presence of system constraints were the most popular risks with influences on most of EERTs. It also identifies the EERTs owners as most affected stakeholders by EERTs risks and that the majority of these risks occur during the operation stage.

This study conducts a comprehensive life cycle assessment (LCA) on converting waste vehicle tyres into recycled crumb rubber (CR) granules as an alternative polymer for enhancing asphalt properties. The LCA study has been performed on acquired industrial primary data by incorporating CR at different proportions of binder in one ton (1-ton) of asphalt mix following the wet method. The uncertainty analysis of design variables identified a relatively strong positive relation of emissions with the equipment energy consumption (r = 0.98). Monte Carlo simulations evaluate the potential renewable sources (solar, hydro, and wind) in sequence over fossil fuels for the possible transition in the Australian grid by 2030 and 2050, as per the Paris Agreement. 71.91% reduction of CO2 emissions is achievable by recycling vehicle tyres into crumb rubber compared to landfill and incineration. Recycling by-products of CR production, such as steel and textile, significantly mitigates negative impacts. A decrease of 2.23% emissions was associated to the use of crumb rubber as a binder modifier in the asphalt mixture via the midpoint assessment. In endpoint LCA, a higher association of resource (US$) saving costs was observed than for other protective zones, i.e., human health and ecosystem damage. Recycling 466,000 tonnes of disposable waste tyres contributes to 16.1 million US$ worth of resource savings. An equitable industry-based LCA and uncertainty analysis of design parameters can assist in prioritizing suitable options to improve efficiency and future emission strategies on a global scale.

Abstract Solar chimney has been frequently adopted in buildings to save energy by enhancing the natural ventilation. Although its optimization studies have been frequently taken previously, most of them have focused on the configuration of solar chimney but ignored the air inlet, even though its significant influence has already been confirmed. The interaction between the air inlet and room openings (e.g. window and door) is critical to improving the solar chimney performance, but the related interaction mechanism is still not known. Interaction of room opening and air inlet on solar chimney performance was analysed under both natural ventilation and smoke exhaustion modes. Numerical results of 19 scenarios were first validated by reduced-scale experiment tests. Another 25 numerical scenarios for full-scale solar chimney room with different heights of air inlet (0.1–2.3 m) and window (0.6–1.8 m) were analysed. It was known from numerical results that the height of window shows limited influence on flow rate under natural ventilation mode but the obvious effect on both flow rate at the air inlet and the total flow rate (both window and air inlet) under smoke exhaustion mode, especially when the window centre is higher than wall centre. Scenario, when both the window and air inlet are at the vertical centre of the wall, shows the best performance of both natural ventilation and smoke exhaustion. An empirical model was also developed to predict the flow rate through the air inlet under smoke exhaustion. Critical conditions for air inlet to exhaust smoke were determined which happens when the neutral plane is almost no lower than the window centre.

Abstract Building construction incurs direct emissions from equipment operation and transportation. These emissions at a collective level seem to be high, which alerts contractors who are keen to explore reduction possibilities for emissions. Understanding emission contributions at the activity and equipment level are important to achieve this target. However, none of the past studies have conducted an in-depth analysis to identify direct emissions reduction prospects at the construction stage. This study aims to develop models and method to enable the estimation and analysis of emissions at project, activity and equipment levels in a building construction. A framework is then established to provide a systematic procedure to aid the decision making for reducing direct emissions at the construction stage. A case study of foundation construction in a commercial building is presented to validate and demonstrate the functions of the framework developed. The results show a GHG emission distribution of 77.13%, 13.53% and 9.34% for materials, equipment usage and transportation respectively at the project level. CO and NO x were the governing non-GHG emissions recorded. In-depth equipment level analysis concludes the importance of considering emission rates to compare and identify critical equipment for emission reduction. Activity level analysis ushers the identification of activities with significant emissions from transportation and equipment.

Abstract Green retrofit is an effective way of improving the performance of existing buildings to achieve low energy consumption and low carbon emission. To realize a successful building green retrofit, it is important to understand the barriers and to develop relevant policies for retrofitting existing buildings, especially in developing countries. As a typical developing country, China has a large number of aged buildings with high green retrofit potential. In terms of its government structure, economic development, and building stocks, China is unique in that it poses a unique set of barriers and policy strategies on the promotion of building green retrofit. Based on a critical review, existing retrofit policies in China were reviewed. Then, the barriers to building green retrofit within the context of China were identified. Based on the study of existing policies and barriers, relevant policies for addressing these barriers are recommended. The findings provide a valuable reference for policy makers in China to review current building green retrofit policies or to develop new policies that address the barriers. This study also provides a useful reference for other countries aiming to review their building green retrofit policies.

Circular economy (CE) is an emergent concept that promotes resource circularity in multiple product systems. Modular construction (MC), an evolving construction technique, which includes an off-site manufacturing environment, increasingly supports CE strategies such as reuse due to the elevated potential for design for disassembly (DfD). Design-stage environmental assessments are paramount in aiding the early decision making of modular construction projects to successfully plan and implement DfD strategies. Research on synergising modular construction, circular economy and environmental sustainability is rare in developing economies. Thus, the current study aims to conduct a design-stage life cycle assessment of a DfD and linear versions of a modular building unit in Sri Lanka to evaluate the potential environmental benefits. The life cycle assessment results highlight that the DfD strategy has the lowest environmental impacts in all categories, with a 63% reduction in global warming potential and an approximately 90% reduction in terms of human toxicity compared to the linear version. Further, it showed the elevated potential of reuse compared to recycling practices in improving the environmental performance. Sensitivity assessment revealed that steel was the most sensitive to the change in reuse percentage among main building materials. The analysis outcomes highlight the importance of long-term thinking, architectural design creativity and industrial and technology development to uptake the CE-driven MC in the Sri Lankan context. Finally, strategies are proposed to support the CE approach in MC in developing regions. Both quantitative and qualitative outcomes provide a basis for construction industry stakeholders, academia, and policy makers to explore further and promote modular construction practices to enhance the circularity of building materials and components in developing regions.

Natural ventilation is considered the first suggestion for COVID-19 prevention in buildings by the World Health Organization (WHO). Solar chimney's viability in aged care centers or similar facilities was analyzed numerically and theoretically. A new solar chimney design was proposed to reduce the cross-infection risk of COVID-19 based on an airflow path through window, ceiling vent, attic, and then chimney cavity. Solar chimney performance, quantified by the natural ventilation rate, presented power function with window area, ceiling vent area, cavity height, and solar radiation. The ceiling vent is suggested to be closer to the corridor to enhance the performance and ventilation coverage of the room. A cavity gap of 1.0 m is recommended to balance the ventilation performance and construction cost. A theoretical model was also developed for aged care centers with multiple rooms and a joint attic. Its predictions obey reasonably well with the numerical results. Solar chimney's viability in aged care center is confirmed as a 7.22 air change per hour (ACH) ventilation can be achieved even under a low solar radiation intensity of 200 W/m2, where its performance fulfills the minimal ventilation requirement (i.e., 6 ACH) suggested by the WHO for airborne infection isolation rooms. This study offers a new design and a guideline for the future implementation of solar chimney in aged care centers or similar facilities.

Emissions from equipment usage and transportation at the construction stage are classified as the direct emissions which include both greenhouse gas (GHG) and non-GHG emissions due to partial combustion of fuel. Unavailability of a reliable and complete inventory restricts an accurate emission evaluation on construction work. The study attempts to review emission factor standards readily available worldwide for estimating emissions from construction equipment. Emission factors published by United States Environmental Protection Agency (US EPA), Australian National Greenhouse Accounts (AUS NGA), Intergovernmental Panel on Climate Change (IPCC) and European Environmental Agency (EEA) are critically reviewed to identify their strengths and weaknesses. A selection process based on the availability and applicability is then developed to help identify the most suitable emission factor standards for estimating emissions from construction equipment in the Australian context. A case study indicates that a fuel based emission factor is more suitable for GHG emission estimation and a time based emission factor is more appropriate for estimation of non-GHG emissions. However, the selection of emission factor standards also depends on factors like the place of analysis (country of origin), data availability and the scope of analysis. Therefore, suitable modifications and assumptions should be incorporated in order to represent these factors.