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At present, thermal conductivity is usually taken as a constant value in the calculation of building energy consumption and load. However, in the actual use of building materials, they are exposed to the environment with continuously changing temperature and relative humidity. The thermal conductivity of materials will inevitably change with temperature and humidity, leading to deviations in the estimation of energy consumption in the building. Therefore, in this study, variations in the thermal conductivity of eight common building insulation materials (glass wool, rock wool, silica aerogel blanket, expanded polystyrene, extruded polystyrene, phenolic foam, foam ceramic and foam glass) with temperature (in the range of 20–60 °C) and relative humidity (in the range of 0–100%) were studied by experimental methods. The results show that the thermal conductivity of these common building insulation materials increased approximately linearly with increasing temperature with maximum growth rates from 3.9 to 22.7% in the examined temperature range. Due to the structural characteristics of materials, the increasing thermal conductivity of different materials varies depending on the relative humidity. The maximum growth rates of thermal conductivity with humidity ranged from 8.2 to 186.7%. In addition, the principles of selection of building insulation materials in different humidity regions were given. The research results of this paper aim to provide basic data for the accurate value of thermal conductivity of building insulation materials and for the calculation of energy consumption.

A transparent radiative cooling (T-RC) film with low transmittance in solar spectra and selectively high emissivity in the atmospheric window (8–13 μm) is applied on roof glazing for building energy saving. To evaluate the performance of the T-RC film, two identical model boxes (1.0 m × 0.6 m × 1.2 m, L × W × H) were constructed and the inside air temperatures were measured in August in Ningbo, China. Results show that the maximum temperature difference between the two model boxes with and without the T-RC film was 21.6 °C during the experiment. A whole building model was built in EnergyPlus for the model box. With a good agreement achieved between the calculation results and the measured temperature data, the experimentally validated EnergyPlus model was then extended to an 815.1 m2 exhibition building with roof glazing to analyze the annual air conditioning (AC) energy consumption. The results show that by incorporating both the T-RC film's cooling benefit in summer and heating penalty in winter, the annual AC energy consumption of the exhibition building can be reduced by 40.9–63.4%, varying with different climate conditions.

In order to solve the problems of low thermal conductivity and easy liquid leakage of a stearic acid (SA), the composite phase change material(PCM) was prepared by adding boron nitride (BN) and expanded graphite (EG) to melted SA, and its thermal conductivity, crystal structure, chemical stability, thermal stability, cycle stability, leakage characteristics, heat storage/release characteristics, and temperature response characteristics were characterized. The results showed that the addition of BN and EG significantly improved the thermal conductivity of the material, and they efficiently adsorbed melted SA. The maximum load of SA was 76 wt. % and there was almost no liquid leakage. Moreover, the melting enthalpy and temperature were 154.20 J • g − 1 and 67.85°C, respectively. Compared with pure SA, the SA/BN/EG composite showed a lower melting temperature and a higher freezing temperature. In addition, when the mass fraction of BN and EG was 12 wt. %, the thermal conductivity of the composite was 6.349 W • m−1 • K−1, which was 18.619 times that of SA. More importantly, the composite showed good stability for 50 cycles of heating and cooling, and the SA / BN / EG-12 hardly decomposes below 200°C, which implies that the working performance of the composite PCM is relatively stable within the temperature range of 100°C. Therefore, the composite can exhibit excellent thermal stability in the field of building heating.

With the continuous deepening of China's rural construction and development, people's living conditions are improved day by day, while accompanied by energy and environment crisis issues. This paper mainly analyzes the energy consumption pattern and the indoor environment of rural households in China and discusses the energy-saving optimization strategies for improving the thermal environment of buildings. Questionnaire surveys and field surveys were conducted in three villages in Guanghan, China. The measurement results show that the annual indoor temperature range of the region in the summer is 15–31 °C and the relative humidity range is 34%-96%. The average indoor temperatures in summer and winter are 28 °C and 16 °C respectively. The indoor thermal environment of rural buildings is usually poor and cannot meet the requirements of Chinese standards. At the same time, the architectural design and energy consumption pattern of rural households are different from those in urban areas as countryside has unique characteristics. Finally, we put forward certain energy-saving improvement measures at the end of the article.

The building sector is one of the largest energy user and carbon emitters globally. To increase the utilization rate of renewable energy and reduce carbon dioxide emissions, the optimal technical scheme of active public institutions and coupled utilization of renewable energy is studied. In this study, the energy consumption of three types of public institutions in various regions of China was simulated by using DeST building energy consumption software, combined with energy conversion efficiency and data released by the National Bureau of Statistics, and the total energy demand and total energy supply of public institutions were predicted using the load density method. Based on the coupling mechanism of the MARKAL model, the optimal proportion of renewable energy in the energy supply of public buildings in different regions is determined. Through the study of the number of public institutions in various regions of China, energy consumption characteristics, construction area, and other related data, the reverse energy flow method is creatively proposed, and the active and renewable energy coupling algorithm from the energy demand side of public institutions to the energy supply side is established. The results show that the central region has the highest utilization rate of renewable energy in the public sector, reaching 36.18%. The use of renewable energy in public buildings in hot summer and warm winter zones decreased to 35.08%, and it was 12.82% in cold zones. By 2025, the proportion of renewable energy resources in China is expected to reach 29.2%. The energy coupling model and algorithm constructed in this paper can provide a basis for the coupling macro configuration of renewable energy in public institutions in China.

Enhancing the energy efficiency of structures has been a staple of energy policies. The key goal is to slash electricity usage in order to minimize the footprint of houses. This goal is sought by putting restrictions on the design specifications with respect to the properties of the raw materials and components as well as the exploitation of sustainable sources of energy. These facts for the basis for zero-energy building (ZEB) being established. This novel technology has faced several obstacles impeding its commercialization and future advancement. This investigation therefore holistically explored and evaluated the state of zero energy building and factors impeding their commercialization. The review further proposed some suggestion in terms of technology that can be considered by the sector to augment existing technologies. Similarly, the investigation touched on the effect of occupant's character in zero energy structures. Policies in terms of government subsidies and tax rebates were recommended to encourage more investors into the sector. Finally, the perception of zero energy building being more expensive compared to the traditional structures can equally be curbed via efficient and effective public sensitization.

Radiative cooling (RC) shows good potential for building energy saving by throwing waste heat to the cosmos in a passive and sustainable manner. However, most available radiative coolers suffer from low cooling flux. The situation becomes even deteriorated in the daytime when radiative coolers are exposed to direct sunlight. To tackle this challenge, an idea of employing both a spectrally selective cover and a spectrally selective emitter is proposed in this study as an alternative approach. A comparative study is conducted among four RC modules with different spectral characteristics for the demonstration of how the spectral profiles of the cover and the emitter affects the RC performance. The results under given conditions show that the RC module with a spectrally selective cover and a spectrally selective emitter (SC/SE) reaches a net RC power of 62.4 W/m2 when the solar radiation is 800 W/m2, which is about 1.8 times that of the typical RC module with a spectrally non-selective cover and a spectrally selective emitter (n-SC/SE). When the ambient temperature is 30°C, the SC/SE based RC module realizes a daytime sub-ambient temperature reduction of 20.0°C, standing for a further temperature decrement of 9.2°C compared to the n-SC/SE based RC module.

Renewable paper reusing plays a significant role in the sustainable environment under the background of the shortage in forest resources and the pollution from the paper industry. The conventional reusing stream of waste office paper appears to have low reusing rates while consuming massive amounts of energy in intermediate steps. In this study, we developed a novel portable renewable desktop paper reusing system based on font area detection and greyscale sensor. The proposed system consists of two main parts, namely, a greyscale sensor and font area detection model and a polishing mechanism. Acting as an ink mark detector for waste desktop paper, the greyscale sensor and font area detection model can detect the font in the waste desktop paper using an adaptive dynamic compensation schematic. The polishing mechanism will grind the font area of the wasted desktop paper, and this paper reusing processing is non-chemical, energy saving and environmentally friendly. The proposed system is demonstrated through simulations and experimental results, which show that the proposed renewable desktop paper reusing system is portable and is effective for reusing waste office paper in the office. An accuracy of 99.78% is demonstrated in the greyscale sensor and font area detection model, and the average reuse rate of one piece of paper is 2.52 times, verifying that the proposed portable system is effective and practical in renewable desktop paper reusing applications.