• Energy Research

Abstract While the energy saving performance of an active phase change materials (PCMs) system in buildings has been widely investigated using prototype-scale experiments and numerical assessments, their performance during the operational phase of a real building has been less understood. This study assessed the energy-saving performance of an active PCM system installed in an eleven storey building in Melbourne. Macro-encapsulated PCM with the phase transition temperature of 15 °C was installed in a large PCM tank. Water was used as the heat transfer fluid (HTF) to extract and store cooling energy from the PCM tank. The performance of the active PCM system was monitored for 25 consecutive months, and the results were analyzed on a seasonal basis. Building design documents and the maintenance manuals were studied to understand the difference between design intent and actual operation. The analyzed results revealed that the active PCM system reduced cooling load on the chiller by 12–37% only during colder months, but, remained dormant during the summer. Even in the case of maximum effectiveness, the PCM tank only utilized 15% of its available heat storage capacity to reduce the cooling load. The factors that contributed to the underperformance of active PCM system include mismatch between designed and actual operation of the PCM system, inefficient operation logic of the system, poor material quality, and limited knowledge of maintenance staffs during the operation stage. The lessons learned from the operation of this active PCM system in this multi-storey building were reported and discussed.

Abstract While the energy saving performance of an active phase change materials (PCMs) system in buildings has been widely investigated using prototype-scale experiments and numerical assessments, their performance during the operational phase of a real building has been less understood. This study assessed the energy-saving performance of an active PCM system installed in an eleven storey building in Melbourne. Macro-encapsulated PCM with the phase transition temperature of 15 °C was installed in a large PCM tank. Water was used as the heat transfer fluid (HTF) to extract and store cooling energy from the PCM tank. The performance of the active PCM system was monitored for 25 consecutive months, and the results were analyzed on a seasonal basis. Building design documents and the maintenance manuals were studied to understand the difference between design intent and actual operation. The analyzed results revealed that the active PCM system reduced cooling load on the chiller by 12–37% only during colder months, but, remained dormant during the summer. Even in the case of maximum effectiveness, the PCM tank only utilized 15% of its available heat storage capacity to reduce the cooling load. The factors that contributed to the underperformance of active PCM system include mismatch between designed and actual operation of the PCM system, inefficient operation logic of the system, poor material quality, and limited knowledge of maintenance staffs during the operation stage. The lessons learned from the operation of this active PCM system in this multi-storey building were reported and discussed.

Abstract Occupant behavior is viewed as a main source causing the building energy performance gap between the predicted and the actual consumption. The nature of occupants’ energy behavior research requires a combination of social science and natural science, which indicates that a mixed methods design would be useful. However, researchers often do not know when and how mixed methods approach should be used. To fill this gap, this paper first reviewed the research methods adopted in 230 relevant articles published in the past decade. The results show that 83.48% of articles applied quantitative methods, followed by mixed methods (5.22%) and qualitative methods (0.87%) with rest being pure review or conceptual papers. This shows that researchers in the field of occupant behavior mainly adopt the objectivist philosophical position. Subsequently, an in-depth analysis of research methodologies was conducted in relation to worldviews and philosophical assumptions, and the advantages and disadvantages of qualitative and quantitative methods were discussed. Finally, a mixed methods research design framework was proposed as a point of departure for researchers to gain a comprehensive understanding of mixed methods design. It is expected that this framework could help researchers develop a proper mixed methods research design according to the nature of their research problem.

Abstract Occupant behavior is viewed as a main source causing the building energy performance gap between the predicted and the actual consumption. The nature of occupants’ energy behavior research requires a combination of social science and natural science, which indicates that a mixed methods design would be useful. However, researchers often do not know when and how mixed methods approach should be used. To fill this gap, this paper first reviewed the research methods adopted in 230 relevant articles published in the past decade. The results show that 83.48% of articles applied quantitative methods, followed by mixed methods (5.22%) and qualitative methods (0.87%) with rest being pure review or conceptual papers. This shows that researchers in the field of occupant behavior mainly adopt the objectivist philosophical position. Subsequently, an in-depth analysis of research methodologies was conducted in relation to worldviews and philosophical assumptions, and the advantages and disadvantages of qualitative and quantitative methods were discussed. Finally, a mixed methods research design framework was proposed as a point of departure for researchers to gain a comprehensive understanding of mixed methods design. It is expected that this framework could help researchers develop a proper mixed methods research design according to the nature of their research problem.

The agenda for improving China’s building energy efficiency is not progressing smoothly, mainly due to many risks associated in the China’s building energy efficiency market mechanism. This paper employs a system dynamics methodology to analyse these risks, by dividing the risks in the building energy efficiency market into six subsystems: laws and regulations; standards and specifications; economy; technology; policy and education. The paper further analyses the relationship between these subsystems and their relationships with the overall system (building energy efficiency market) by establishing and drawing the causal relationships and feedback loops. Through a qualitative analysis on the positive and negative feedback loops of the system, potential risks were ascertained, and new perspectives established for the implementation and monitoring of risk tackling strategies. It is expected that the results presented in this paper will help decision makers to identify the risk factors and their interdependent relationship in a complex context system involving law, economy, policy, market, education and technology issues.

The agenda for improving China’s building energy efficiency is not progressing smoothly, mainly due to many risks associated in the China’s building energy efficiency market mechanism. This paper employs a system dynamics methodology to analyse these risks, by dividing the risks in the building energy efficiency market into six subsystems: laws and regulations; standards and specifications; economy; technology; policy and education. The paper further analyses the relationship between these subsystems and their relationships with the overall system (building energy efficiency market) by establishing and drawing the causal relationships and feedback loops. Through a qualitative analysis on the positive and negative feedback loops of the system, potential risks were ascertained, and new perspectives established for the implementation and monitoring of risk tackling strategies. It is expected that the results presented in this paper will help decision makers to identify the risk factors and their interdependent relationship in a complex context system involving law, economy, policy, market, education and technology issues.

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.

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.

Abstract In Australia, the government spending on public buildings’ energy and water consumption is considerable; however the building energy and water retrofit market potential has been diminished by a number of barriers, especially financial. In contrast, in other advanced economies there are several reported financing strategies that have been shown to accelerate retrofit projects implementation. In this study, a coupled Bayesian Network – System Dynamics model was developed with the core aim to assess the likely influence of those novel financing options and procurement procedures on public building retrofit outcomes scenarios in the Australian context. A particular case-study focusing on Australian public hospitals was showcased as an example in this paper. Stakeholder engagement was utilised to estimate likely preferences and to conceptualise causal relationships of model parameters. The scenario modelling showed that a revolving loan fund supporting an energy performance contracting procurement procedure was preferred. Subsequently, the specific features of this preferred framework were optimised to yield the greatest number of viable retrofit projects over the long term. The results indicated that such a financing scheme would lead to substantial abatement of energy and water consumption, as well as carbon emissions. The strategic scenario analysis approach developed herein provides evidence-based support to policy-makers advocating novel financing and procurement models for addressing a government’s sustainability agenda in a financially responsible and net-positive manner.