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A large amount of energy is consumed by heating and cooling systems to provide comfort conditions for commercial building occupants, which generally contribute to peak electricity demands. Thermal storage tanks in HVAC systems, which store heating/cooling energy in the off-peak period for use in the peak period, can be used to offset peak time energy demand. In this study, a theoretical investigation on stratified thermal storage systems is performed to determine the factors that significantly influence the thermal performance of these systems for both heating and cooling applications. Five fully-insulated storage tank geometries, using water as the storage medium, were simulated to determine the effects of water inlet velocity, tank aspect ratio and temperature difference between charging (inlet) and the tank water on mixing and thermocline formation. Results indicate that thermal stratification enhances with increased temperature difference, lower inlet velocities and higher aspect ratios. It was also found that mixing increased by 303% when the temperature difference between the tank and inlet water was reduced from 80 °C to 10 °C, while decreasing the aspect ratio from 3.8 to 1.0 increased mixing by 143%. On the other hand, increasing the inlet water velocity significantly increased the storage mixing. A new theoretical relationship between the inlet water velocity and thermocline formation has been developed. It was also found that inlet flow rates can be increased, without increasing the mixing, after the formation of the thermocline.

Managing thermal comfort, in both hot and cold climates, critically influences energy use in homes [1-4]. For low income households, who commonly live in thermally poor housing stock, maintaining thermal comfort can be costly relative to household income, leading to trade-offs between comfort, energy use and affordability. Comfort as a concept has been explored from many vantages, including as a physiological need [5,6]; a parameter for healthy housing [7]; as an energy efficiency building standard [4,8] and a cultural construct [9,10]. Yet, there is little research available that provides detailed insight into the relationship between thermal comfort and energy efficiency in existing housing stock or about the impact of support programs on these key indicators. This paper reviews measures of household thermal comfort as they relate to energy efficiency assessments in a project, Get Bill Smart (GBS), that worked with low income households in Tasmania, Australia. Thermal comfort and energy use data was collected over 15 months from 51 households, a sub-set of the 510 households participating overall. Longitudinal interviews and housing observations were also conducted. New thermal comfort and energy efficiency indicators were developed from this data. This paper demonstrates the application of these indicators by providing examples of findings in GBS. Suggestions are made for the refinement of measures discussed for use in future applications.

This paper presents the performance evaluation of an integrated photovoltaic thermal (PVT) collector-phased change material (PCM) thermal energy storage (TES) system. The PVT collectors can generate both electricity and low-grade thermal energy during the daytime, and the thermal energy generated can be temporarily stored in the PCM TES unit and used for space heating during the night-time. Taguchi method and analysis of variance are used for the simulation design and data analysis, respectively. The thermal performance of the proposed system was evaluated in terms of the useful energy stored in the TES system. The results showed that the outlet air temperature of the TES unit remained at least 2°C higher than the inlet air temperature during the discharging process in the selected test day. The PCM type and the PCM charging air flow rate were the most important factors influencing the useful energy stored in the TES system.

Building regulations in Australia and elsewhere are increasingly directed at reducing greenhouse gas emissions and achieving an efficient use of energy and water. These regulations significantly impact on aspirations with regard to the building design. Five case study houses recognized in awards from the Australian Institute of Architects are investigated for whether they met the aim and criteria of the relevant regulations for energy efficiency and greenhouse gas reductions. Qualitative and quantitative issues surrounding their environmental performance are examined, including occupants' comfort and energy consumption. The findings suggest that the assessment processes underpinning the regulations do not correlate well with measured environmental performance, the perceptions of occupiers, and how these houses are actually designed and operated. The regulatory concept of ‘meeting generic needs’ fails to account for the diversity of socio-cultural understandings, the inhabitants' expectations and their beh...

In designing an energy efficient impinging jet dryer, it is essential to match the energy demand for drying with the supply of heat by convection to avoid overheating and energy wastage. One way to achieve this is by intermittently supply heat to the drying chamber. By using computational fluid dynamics (CFD) approach, this study numerically investigates the possibility of energy saving by intermittency. First, inlet temperature intermittency is applied. This is conducted by alternately raise it to drying temperature and lowers it to the ambient temperature at certain period. Second, inlet velocity intermittency is applied which is conducted by alternately supplying the hot air to the several drying chamber. One, two, three and four chamber configurations are evaluated. In addition, the intermittency period of 10, 20 and 30 min were examined. The results reveal that the steady impinging jet offers faster drying rate as compared to intermittent impinging jet drying under the same inlet conditions. In addition it was found that drying rate goes down as the number of drying chamber increases. However, the intermittent impinging jet drying offers advantages in term of temperature uniformity and energy conservation. For the same energy usage, the production rate of single drying configuration is only one fourth of the four chamber configuration. This indicates the potential of multi chamber configuration in a real drying application.

Abstract This paper presents the development and performance evaluation of a novel ceiling ventilation system integrated with solar photovoltaic thermal (PVT) collectors and phase change materials (PCMs). The PVT collectors are used to generate electricity and provide low grade heating and cooling energy for buildings by using winter daytime solar radiation and summer night-time sky radiative cooling, respectively. The PCM is integrated into the building ceiling as a part of the ceiling insulation and at the same time, as a centralized thermal energy storage to temporally store low grade energy collected from the PVT collectors. The performance of the proposed system was numerically evaluated based on a Solar Decathlon house using TRNSYS. The results showed that, in winter conditions, the proposed PVT–PCM integrated ventilation system can significantly improve the indoor thermal comfort of passive buildings without using air-conditioning systems with a maximum air temperature rise of 23.1 °C from the PVT collectors. Compared with the system using PCM but without using PVT collectors, the coefficient of thermal comfort enhancement in the kitchen, dining room and living room of the case building studied using the proposed system improved from almost zero to 0.9823 while the coefficient of thermal comfort enhancement in the study room improved from 0.0060 to 0.9921. In summer conditions, the proposed system can also enhance indoor thermal comfort through night-time sky radiative cooling.

Pulsed laser polymerization experiments have been performed on the bulk polymerization of dimethyl itaconate over the temperature range 20–50 °C. The activation energy and frequency factor were calculated as 24.9 kJ/mol−1 and 2.15 × 105 L/mol−1s−1, respectively. The activation energy is comparable with the methacrylate series of monomers. The frequency factor is relatively small and reflects steric hindrance in the transition state caused by the bulky 1,1, disubstitution in the monomer (and consequently the radical). The Mark–Houwink–Kuhn–Sakurada constants were also determined for poly(dimethyl itaconate) in tetrahydrofuran, these are reported as 46 × 10−5 dL/g (K) and 0.51 (α). The influence of penultimate units (γ-substituents) on homopropagation reactions is discussed particularly for polymerizations leading to significant 1,3 interactions in the resultant polymer. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2192–2200, 2000

Double skin facades (DSFs) are often applied as energy reducing elements in modern buildings, but do experience overheating problems in warm seasons which may contribute to increase in cooling loads. There are currently various thermal management devices being used in DSF but have limitations such as secondary thermal transmittance and low energy storage capacity. In this paper, a novel laminated composite phase change material (PCM) blind system with high thermal energy storage capacity has been developed and evaluated in a typical DSF building. The results showed that the integrated PCM blind system was able to keep the average air temperature in the DSF below 35 o C during the monitored period in summer and showed no significant increase as compared with the ambient temperature. The surface temperature of the inner skin of the DSF was also reduced up to about 2.9 o C as compared with the external skin surface temperature thus reducing heat transfer into the building. By using validated numerical models, the PCM blind was found to perform thermally better than a conventional aluminium blind. Finally, design and operational parameters of the PCM