Latent heat thermal energy storage is an attractive technique as it can provide higher energy storage density than conventional heat energy storage systems and has the capability to store heat of fusion at a constant (or a near constant) temperature corresponding to the phase transition temperature of the phase change material (PCM). This paper provides a state-of-theart review on phase change materials (PCMs) and their applications for heating, cooling and electricity generation according to their working temperature ranges from (-20℃ to +200℃). Four working temperature ranges are considered in this review: 1) the low temperature range from (-20℃ to +5℃) where the PCMs are typically used for domestic and commercial refrigeration; 2) the medium low temperature range from (+5℃ to +40℃) where the PCMs are typically applied for heating and cooling applications in buildings; 3) the medium temperature range for solar based heating, hot water and electronic applications from (+40℃ to +80℃); and 4) the high temperature range from (+80℃ to +200℃) for absorption cooling, waste heat recovery and electricity generation. Different types of phase change materials applied to each temperature range are reviewed and discussed, in terms of the performance, heat transfer enhancement technique, environmental impact and economic analysis. The review shows that, energy saving of up to 12% can be achieved and a reduction of cooling load of up to 80% can be obtained by PCMs in the low to medium-low temperature range. PCM storage for heating applications can improve operation efficiency from 26% to 66%, depending on specific applications. Solar thermal direct steam generation (DSG) is the most common electricity generation application coupled with PCM storage systems in the high temperature range, due to the capability of PCMs to store and deliver energy at a given constant temperature. The recommendations for future research are also presented which provide insights about where the current research is heading and highlights the challenges that remain to be resolved.

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11Results from both experimental measurements and 3D numerical simulations of Ground the performance of the GSHP system showed that the COP decreased with the running time. 19The average COP of the horizontal coupled GSHP was 2.5. The numerical prediction showed 20 that there was no significant difference in the specific heat extraction of the slinky heat 21 exchanger at different coil diameters. However, the larger the diameter of coil, the higher the

8 This paper will explore the potential of employing thermotropic (TT) windows as a means of 9 improving overall building energy performance. Capitalising on their ability to dynamically 10 alter solar and visible light transmittance and reflectance based on window temperature,

With the developments in virtual reality technologies, significant researches have been conducted for human response on indoor luminous environment using head-mounted display to replace those in real environment. However, the limited resolution and luminance values offered by the devices might affect the perceived appearance and high-order impressions in the simulated virtual environment. In this study, a simulated 3-dimensional virtual office was compared against a real one. Both settings presented similar physical and luminous conditions to twenty participants (N=20). The study investigated subjective and objective visual responses and participants' interaction with the virtual environment based on measurements of perceived presence. Subjective assessments included questions on luminous environment appearance (brightness, colour-temperature, distribution) and high-order perceptions (pleasantness, interest, spaciousness, excitement and complexity). Objective assessments measured contrastsensitivity and colour-discrimination tasks to assess visual performance across the two representation environments. Results showed no significant differences between the two environments based on the studied parameters, indicating a high level of perceptual accuracy of appearance and high-order perceptions. Minor physical symptoms related to the headset 2 use and high level of perceived presence were found, indicating the proposed methodology's capability to provide realistic immersive environments. Although attributes regarding scene quality: colours, details, and contrast were perceived significantly different to the real environment, objective tasks showed that similar contrast and colour appearance can be produced in the virtual environment with minor impact on fine-details due to limited resolution.Virtual reality maybe a promising alternative representation medium to investigate visual perceptions as the overall appearance of the scene can still be correctly acquired.

Hydroxypropyl cellulose (HPC) hydrogels exhibit thermal-responsive transparency change due to their temperature-sensitive miscible–immiscible transitions, making them promising thermochromic materials for fabricating energy-saving smart windows. However, their transition temperatures, named lower critical solution temperature (LCST), are too high for building window applications, and it is also challenging to reduce LCST to comfortable room temperature range (e.g., 26–28 °C) in hot seasons. In this work, we report smart windows prepared using poly­(acrylic acid) (PAA)-modified HPC hydrogels and demonstrate that the LCST of the resulting HPC/PAA hybrid hydrogels can be effectively tuned by solution pH, from 44 to 10 °C with decreasing pH from 6.0 to 1.0. At pH 2.5, an optimized LCST at 26.5 °C has been achieved. The sandwich-structured smart window, composed of two glass panes and an optimized HPC/PAA hydrogel in between, shows a high visible-light transmittance (T lum = 90.1%), excellent solar energy modulation (ΔT sol = 47.5%), outstanding heat-shielding performance, and excellent stability after 100 heating and cooling cycles. These optical properties outperform the reported thermosensitive cellulose-based materials, vanadium oxide based smart windows, and other thermosensitive hydrogel-based smart windows. Furthermore, HPC/PAA hydrogels are easy to prepare, nontoxic, biocompatible, low-cost, and environmentally friendly, making them very promising materials for energy-saving and climate-adaptable smart windows.

Two types of transparent wood composites with anisotropic structure for energy-saving windows were successfully fabricated by infiltration of epoxy resin dispersion containing tungsten-doped vanadium dioxide nanoparticles (W-doped VO 2 NPs) into the delignified wood template and subsequent polymerization. The well integration of the epoxy resin, W-doped VO 2 NPs, and the pore-structured wood endowed the anisotropic composites with high visible transmittance (68.2% for the composite prepared from longitudinally cut trees (L-composite), 73.3% for the composite prepared from radically cut trees (R-composite)), obviously different mechanical performance (fracture stress of 74.57 MPa (L-composite) and 56.14 MPa (R-composite) and modulus of 1.47 GPa (Lcomposite) and 1.23 GPa (R-composite)), and low thermal conductivity (0.20 W•m −1 K −1 (L-composite) and 0.32 W•m −1 K −1 (R-composite)). Moreover, these two kinds of W/VO 2 transparent wood composites both show an outstanding thermoregulation ability when they are used as windows. A significant amount of heat (from a simulated light source) was reflected by VO 2 NPs, and as a result, the indoor temperature of a demo system had a significant slower temperature increase rate when compared with that for a similar system with a common glass panel applied. Novel transparent wood composites combining a low thermal conductivity wood template and thermochromic VO 2 NPs provide a potential solution for replacement of heavy, high thermal conductivity, and infrared transparent glass but still meet indoor occupancy view perception.