Energy and Built Environment最新文献

Electric vehicles (EV) played an important role fighting greenhouse gas emissions that contributed to global warming. The construction of the charging pile, which was called as the "gas station" of EV, developed rapidly. The charging speed of the charging piles was shorted rapidly, which was a challenge for the heat dissipation system of the charging pile. In order to reduce the operation temperature of the charging pile, this paper proposed a fin and ultra-thin heat pipes (UTHPs) hybrid heat dissipation system for the direct-current (DC) charging pile. The L-shaped ultra-thin flattened heat pipe with ultra-high thermal conductivity was adopted to reduce the spreading thermal resistance. ICEPAK software was used to simulate the temperature and flow profiles of the new design. And various factors that affected the heat dissipation performance of the system were explored. Simulation results showed that the system had excellent heat dissipation capacity and achieved good temperature uniformity. Rather than solely relied on the fans, this new design efficiently dissipated heat with a lower fan load and less energy consumption.

This study aims to evaluate airborne transmission risk in university towns during the COVID-19 pandemic based on surveys of indoor environmental quality (IEQ). Both on-site measurements and questionnaire surveys were carried out in public buildings in university towns in Changsha, China. Air temperature, relative humidity, and CO₂ concentration in one library, ten classrooms, eight canteens, seven restaurants, and sixteen malls were measured. 2220 valid questionnaires concerning occupants’ sensation on thermal environment, air movement, and indoor air quality were collected. A 3-level evaluation method of airborne transmission risk that is dependent on building type and indoor CO₂ concentration was developed. Excessive CO₂ concentration is found in library (1045 ppm), classrooms (1151 ppm), restaurants (1242 ppm), and malls (1057 ppm). The percentage time of “high risk” accounts for 18–100% in these buildings. The results reveal a serious problem: numerous public buildings in China and probably other resource limited countries are not basically prepared and equipped to cope with airborne transmission. This fact should be taken into account when developing guidelines and formulating mitigation measures. Real-time monitoring and displaying IEQ and thus the transmission risk level should be an important way to be widely implemented in public buildings.

The cogeneration system of heat, power, and biogas (CHPB) driven by renewable energy provides an effective solution for carbon emission reduction in rural China. Starting from fully meeting the energy demand of 17 new rural residential households in Lanzhou, considering the annual dynamic local climate change, energy consumption characteristics, and environment parameters, a model of environmental benefit index for the CHPB system is constructed. The concept of emission factor is used to quantitatively analyze the environmental benefits of the system. The equivalent CO₂ emission factor is defined to connect emissions with energy output, evaluating the environment-friendly potential of energy supply system. Compared with the conventional systems of independent power and thermal generation, the year-round characteristics of CO₂ emission and emission structure chart of the proposed system are analyzed. The results show that the total CO₂ emission and the average equivalent CO₂ emission factors of the conventional and CHPB system are 85.45t, 1.53 kg/kWh, and 308.46t, 0.22 kg/kWh, respectively. The maximum CO₂ emission reduction ratio of the CHPB system is 113.47%. Anaerobic digestion technology is employed to consume biomass feedstock, which reduced CH₄ emission (equivalent to 86.36t of CO₂ emission reduction). Five typical cities were selected to study the regional adaptability of the system and analyze environmental benefits. The results indicate that the CHPB system has the best environmental performance in Guangzhou, where the average CO₂ emission reduction rate is 103.52%.

Natural ventilation (NV) has been considered a simple and effective method of ventilation. However, the introduction of NV does not achieve better indoor air quality (IAQ) when the outdoor atmospheric environment is polluted. Therefore, portable air cleaners (PACs) are increasing in use in recent years, but their effectiveness is highly dependent on the residents' habits. A typical residence in Xi'an, China was selected to examine the effects of the use of NV alone and the use of NV and PACs together on IAQ in the three occupant states, i.e., unoccupied, sleeping and leisure. Parameters, such as temperature, relative humidity, CO₂, and PM_2.5 concentration were measured when changing the window opening and the position of the PAC. The results showed that in the unoccupied state, opening the inner door can promote a more uniform thermal and humid environment. In the sleeping state, the I/O ratio of the PM_2.5 concentration was the lowest when the window opening of the bedroom was 1/2 or 3/4, with a mean value of 0.3. In the leisure state, only using NV, when the purification rate reaches 90%, the mean purification time of each window opening in the living room is 87.5 min. The mean purification time was reduced to 25 min when both NV and PAC were used. The on-site purification efficiencies were 91.0% and 94.5%, when the window opening was 1/2 (i.e., the PAC was placed in the center of the room) and 3/4 (i.e., the PAC was placed away from the outer window), respectively.

The noise reduction effect of noise barriers has been extensively studied, but the effect on pollutant dispersion remains unclear. A computational fluid dynamics (CFD) simulation is conducted to investigate the effects of different heights, lengths, and types of noise barriers and different wind speeds on pollutant dispersion in street canyons with viaducts. The field synergy theory of the convective mass transfer process is used for quantitative analysis of pollutant dispersion in street canyons. The results show that as the height and length of the noise barrier increase, the pollutant dispersion capacity decreases. As the wind speed increases, the rate of decrease in the average CO concentration declines. The effect of the wind speed on the synergistic improvement of the speed and concentration gradient vectors differs for different types of noise barriers. The performance follows the order: fully-closed noise barrier > left noise barrier > right noise barrier > semi-closed noise barrier. The different noise barrier types significantly impact the flow field and pollutant dispersion and reduce the CO concentration to varying degrees, except for the fully-closed type. The average CO concentration in the pedestrian breathing zone is reduced by a maximum of 55.85% on the leeward side and by 53% on the windward side, indicating that an appropriate noise barrier on the viaduct reduces noise pollution and improves the air quality in street canyons, especially in the pedestrian breathing zone.

In this paper, a numerical study is carried out to investigate the performance of a coupled BIPV/T-AHU system in Sudan. A mathematical model was utilized, Matlab Simulink was used to do simulation. Results showed good agreement with experimental data from the literature. The problem studied in this paper is reducing the energy required for heating in winter (preheating BIPV/T) and avoiding the high photovoltaic cell temperature in summer. We compare the energy consumption with and without BIPV/T-AHU in different cities in Sudan. The results showed that utilizing the exhaust air to cool the photovoltaic cell could reduce the PV/T cell temperature in the range ${(9-12)}^{\circ }C$, which can increase the electrical power output in a range of $(12-21.44)W/m^2$. In winter, utilization of the preheating BIPV/T system can decrease the heating load in Wadi Halfa in the range of $(6-107.1\%)$. Damazein does not need a high heating power in the daytime for the air conditioning system depending on the local climate, so the heat energy produced by the system can be used for drying, desiccant cooling, or heating water, with increasing the electric power produced by cooling PV/T cells. The results indicated a great possibility to use the BIPV / T system under the studied conditions, in addition, this study provides important information for the application of the BIPV / T system in these areas.

Construction and operation of buildings are responsible for about 20% of the global energy consumption. The embodied energy of conventional buildings is high due to the utilization of energy-intensive construction materials and traditional construction methodology. Higher operational energy is attributed to the usage of power-consuming conventional air-conditioning systems. Therefore, moving to an energy-efficient cooling technology and eco-friendly building material can lead to significant energy savings and CO₂ emission reduction. In the present study, an energy-efficient thermally activated building system (TABS) is integrated with glass fiber reinforced gypsum (GFRG), an eco-friendly building material. The proposed hybrid system is termed the thermally activated glass fiber reinforced gypsum (TAGFRG) system. This system is not only energy-efficient and eco-friendly but also provides better thermal comfort. An experimental room with a TAGFRG roof is constructed on the premises of the Indian Institute of Technology Madras (IITM), Chennai, located in a tropical wet and dry climate zone. The influence of indoor sensible heat load and the impact of natural ventilation on the thermal comfort of the TAGFRG system are investigated. An increase in internal heat load from 400 to 700 W deteriorates the thermal comfort of the indoor space. This is evident from the increases in operative temperatures from 29.8 to 31.5 °C and the predicted percentage of dissatisfaction from 44.5% to 80.9%. Natural ventilation increases the diurnal fluctuation of indoor air temperature by 1.6 and 1.9 °C for with and without cooling cases, respectively. It reduces the maximum indoor CO₂ concentration from 912 to 393 ppm.

Thermal comfort is an important factor in hostel buildings when the aim is to maximize the productivity of the students. Due to the extreme weather conditions, achieving thermal comfort in a hostel building in a hot and humid climate is even more difficult. Studies conducted in naturally ventilated hostel buildings in warm-humid climates involved the influence of outdoor air temperature only up to 34.4 °C and have been conducted in a specific season. In contrast, the Tiruchirappalli climate is characterized by a higher range of environmental variables. Therefore, to understand the thermal comfort conditions and usage of the environmental controls in naturally ventilated hostel buildings at the higher range of the environmental variables, a thermal comfort field study spread over one year was carried out at the National Institute of Technology, Tiruchirappalli, India, in twenty-seven hostel buildings. This study relies on field observation and thermal comfort responses from 2028 questionnaires collected from the students between September 2019 to August 2020. The analysis revealed a neutral temperature of 29.5 °C and a comfort range from 26.1 °C to 32.8 °C, indicating a wide range of thermal adaptation than suggested by the National Building Code of India and ASHRAE standard 55. The preferred temperature was 27.8 °C, indicating that students preferred a cooler environment. Acceptability with sweating conditions extended the upper limit of thermal acceptability from 31.8 °C to 32.4 °C. The use of a mosquito net can increase the probability of opening a window. Results indicated that overall behavioral adjustment could extend the comfort limits. The study results would be helpful to develop guidelines and designs for naturally ventilated hostel buildings in warm and humid climates that will contribute to reducing energy demand.

The growing global demand for clean and sustainable energy sources has sparked interest in hybrid energy systems that combine multiple renewable energy technologies. This review paper explores the integration of cow dung biogas, solar thermal, and kinetic energy for power production. The synergistic utilization of these energy sources holds significant potential for addressing the energy challenges faced by various communities. This paper provides an overview of each technology, discusses the benefits and challenges of integration, and highlights successful case studies. Furthermore, it discusses this hybrid energy generation system's potential future developments and implications.

Energy savings in air-conditioning systems are important for achieving energy efficient buildings. A central air-conditioning system in the large building is installed with air ductwork. Alternative materials are replacing conventional (Galvanized Iron Steel) air ducts for supplying air to the air-conditioned area. This research studies the objective function relationship between exergy and economic variables in the alternative air ductwork compared with conventional air ductwork. The optimization method to identify the optimal type and thickness of air ducts in Thailand's buildings. The result shows that the alternative ductwork has achieved maximum worthiness with more useful exergy than conventional air ductwork. The Pre-insulated duct (PID) with 30.00 mm wall thickness is 82.14 %. It is the maximum of all exergies generated by the Air Handling Unit.