•The energy performance of radiative cooling and low-E coatings is investigated.•Radiative cooling coatings yield energy saving in most climates.•Low-E coatings provide better energy savings for ...poorly insulated buildings.•Heating penalties are countered in most climate zones.•A strong linear correlation between outdoor temperature and energy saving is noted.
Radiative cooling and low-emissivity coatings are promising strategies for building energy savings. Despite their potential, comprehensive assessments across diverse climate zones remain limited. This study addresses this gap by investigating the potential energy performance associated with these coatings in buildings at 250 locations worldwide, spanning all ASHRAE climate zones. To quantitatively assess the energy efficiency benefits, this study employs EnergyPlus simulations to analyse annual thermal energy needs in two-floor, single-family detached apartments with varying levels of thermal transmittance. Results indicate that radiative cooling coatings provide considerable energy-saving effects for most locations, including those with higher heating demands than cooling demands. For buildings with poor insulation, low-emissivity coatings provide substantial annual energy savings in over 74% of the case locations. Moreover, the study also assesses heating penalties due to overcooling effects, revealing that these are generally less critical than the cooling energy savings in most climate zones. Furthermore, a strong linear correlation was found between yearly energy savings and the annual average outdoor temperature for each coating type in zones 0 to 6. The insights from this study have broad implications for the applicability of radiative cooling and low-emissivity coatings in new constructions and existing building retrofits across various climate zones.
(Double) Daylight Saving Time (DST/DDST) synchronizes human daily activities with sunlight hours, aiming to save energy. China implemented DST/DDST in 1986 and annulled it in 1991, which has not ...since been observed. This study aims to revisit the household lighting energy-saving potentials of DST/DDST implementation in six representative highly urbanized Chinese cities across different latitudes and within different climate zones, based on the electricity consumption behaviour of Chinese people in the 2020s. We constructed country-specific Multiple Linear Regression (MLR) analysis models interrelated with the local characteristic features of the DST/DDST in China, including latitude, age structure, industrial structure, get-up and bedtime schedules. The results showed the following: (1) Both DST and DDST can effectively reduce household lighting consumption in all the studied case cities, while DDST has a superior energy-saving potential; (2) Considering China-specific lifetime schedules, April to October is the most recommended duration for DST/DDST implementation; (3) Northern cities in China exhibit greater potential for energy savings in lighting than southern regions. (4) Cities with larger portions of primary industry have more household lighting-saving potential in China. Based on the obtained results, monthly data and separate statistical data on household lighting could help promote the precision of regression models.
Concentrated Photovoltaics (CPV) technology, as an energy saving method which can directly generate electricity from the Sun, has attracted an ever-increasing attention with the deepening worldwide ...energy crisis. However, operating temperature is one of the main concerns that affect the CPV system. Excess cell temperature causes electrical conversion efficiency loss and cell lifespan decrease. Thus, reasonable cooling methods should decrease the operating temperature and balance the flare inhomogeneity. They also need to display high reliability, low power consumption, and convenient installation. This paper presented the architectural, commercial, and industrial usage of CPV system, reviewed the recent research developments of different cooling techniques of CPV systems during last few years, including the spectral beam splitting technology, cogeneration power technology, commonly used and promising cooling techniques, active and passive cooling methods. It also analysed the design considerations of the cooling methods in CPV systems, introduced the classification and basic working principles and provided a thorough compilation of different cooling techniques with their advantages, current research limitations, challenges, and possible further research directions. The aim of this work is to find the research gap and recommend feasible research direction of cooling technologies for CPV systems.
The current status and remaining issues of coupling CWE models with mesoscale meteorological models (MMM) are reviewed from the viewpoint of computational wind engineers. By way of three examples to ...demonstrate the typical application areas where the coupling approaches are needed, the governing equations considered, and the difficulties to couple the models despite the different spatial and temporal scales are described. Next, recent attempts of single-model up-scaling of CWE models to meteorological scale wind flow and thermal environment are shown. The need to upgrade existing CWE models for appropriate up-scaling and the issues that require to be solved by the collaboration with meteorologists are pointed out. Finally, the recent achievements attained by other researchers are reviewed and the future directions of CWE studies are discussed. Emphasis is placed on coupling LES with MMM.
In recent years, residents in high-rise residential complexes (HRCs) in China have been placing an increasing demand on the living quality in HRCs. Particularly, the outdoor wind conditions are ...garnering more attention; however, few studies on the wind conditions within HRCs with densely arranged buildings and high plot ratios have been reported. Therefore, this study investigated the relation between the buildings’ layouts in HRCs and their wind conditions and it proposes optimization strategies to enhance body comfort in their outdoor environments. The research methods in this work involved field surveys, computational fluid dynamics (CFD) simulations, and field monitoring. The field surveys were used to determine the types of activities undertaken by the residents in the selected HRCs and their perceptions of the wind conditions within the HRCs. Field monitoring was primarily conducted to measure the present wind conditions in the HRCs. The CFD simulations were performed to analyze the interactions between individual buildings and the wind as well as the performance of the wind conditions in the HRCs before and after a building layout optimization. The simulation results and monitoring data showed that the present wind conditions in the HRCs were uncomfortable due to high wind speeds (exceeding 5 m/s) and large windless areas. To achieve a comfortable outdoor wind environment, future HRCs should adopt a point-to-point building layout and the buildings should be oriented south. Moreover, the ratios of the height to width (Hb/Wb) for individual buildings should be kept at approximately 1.33. For existing HRCs, landscape walls, trees, and moveable windbreak panels can be used to reduce the wind speeds, especially in open exit/entrance areas and windward areas.
Researchers have conducted extensive research on the thermal environments of rural houses worldwide. The greatest number of studies on thermal comfort in rural areas have been conducted in China. ...However, no studies have reviewed or summarised the literature. This paper summarises the literature from three perspectives: climate zones, thermal comfort approach, and other factors (wind speed, humidity, and building construction) that influence thermal comfort. The research commenced by categorising and examining all relevant papers based on climatic comfort and thermal comfort approaches to find commonalities and differences. The limits of existing thermal comfort standards were then inspected. Finally, suggestions for further research on rural thermal comfort were provided. Our conclusion was that thermal comfort temperature is influenced by various factors. Further research on the thermal comfort of older adults is required, especially in rural areas. The Adaptive Thermal Comfort model was more suitable for rural housing than the Rational Thermal Comfort model. Large-scale studies on thermal comfort in rural houses are required to establish specific thermal comfort standards. Wind speed and humidity are two aspects that require further research in rural thermal comfort.
Display omitted
•This is the first paper that examines past research on thermal comfort field investigation in rural houses.•Summarising the thermally neutral temperature and thermal comfortable temperatures of rural residents across different in China.•Comparing the results of applying different thermal comfort approaches to rural dwellings.
PDF
