We present a comprehensive review of modelling approaches and associated software tools that address district-level energy systems. Buildings play an important role in urban energy systems regarding ...both the demand and supply of energy. It is no longer sufficient to simulate building energy use assuming isolation from the microclimate and energy system in which they operate, or to model an urban energy system without consideration of the buildings that it serves. This review complements previous studies by focussing on models that address district-level interactions in energy systems, and by assessing the capabilities of the software tools available alongside the theory of the modelling approaches used.
New models and tools that address these district-level interactions are reviewed and their competences assessed. These are divided into the following sections: district energy systems (including heat networks, multi-energy systems and low-temperature networks), renewable energy generation (including solar, bioenergy, wind and the related topic of seasonal storage), and the urban microclimate as it relates to energy demands. The scope and detail covered by twenty cross-disciplinary tools is summarised in a matrix; many other tools that focus on specific areas are also discussed. We end by summarising the current state of district-scale urban energy modelling as it relates to the built environment, along with our perspective on future challenges and research directions.
Urban microclimate studies are gaining popularity due to rapid urbanization. Many studies documented that urban microclimate can affect building energy performance, human morbidity and mortality and ...thermal comfort. Historically, urban microclimate studies were conducted with observational methods such as field measurements. In the last decades, with the advances in computational resources, numerical simulation approaches have become increasingly popular. Nowadays, especially simulations with Computational Fluid Dynamics (CFD) is frequently used to assess urban microclimate. CFD can resolve the transfer of heat and mass and their interaction with individual obstacles such as buildings. Considering the rapid increase in CFD studies of urban microclimate, this paper provides a review of research reported in journal publications on this topic till the end of 2015. The studies are categorized based on the following characteristics: morphology of the urban area (generic versus real) and methodology (with or without validation study). In addition, the studies are categorized by specifying the considered urban settings/locations, simulation equations and models, target parameters and keywords. This review documents the increasing popularity of the research area over the years. Based on the data obtained concerning the urban location, target parameters and keywords, the historical development of the studies is discussed and future perspectives are provided. According to the results, early CFD microclimate studies were conducted for model development and later studies considered CFD approach as a predictive methodology. Later, with the established simulation setups, research efforts shifted to case studies. Recently, an increasing amount of studies focus on urban scale adaptation measures. The review hints a possible change in this trend as the results from CFD simulations can be linked up with different aspects (e.g. economy) and with different scales (e.g. buildings), and thus, CFD can play an important role in transferring urban climate knowledge into engineering and design practice.
•A total of 183 CFD studies on urban microclimate are investigated.•Yearly number of studies on the topic increased rapidly from 1998 till 2015.•Investigated cities, target parameters and keywords are summarized for every study.•Past achievements on the field are documented and future perspectives are provided.•The keywords used in the reviewed studies are evaluated based on their popularity.
Solar energy has the potential to offset a significant fraction of non-renewable electricity demands globally, yet it may occupy extensive areas when deployed at this level. There is growing concern ...that large renewable energy installations will displace other land uses. Where should future solar power installations be placed to achieve the highest energy production and best use the limited land resource? The premise of this work is that the solar panel efficiency is a function of the location's microclimate within which it is immersed. Current studies largely ignore many of the environmental factors that influence Photovoltaic (PV) panel function. A model for solar panel efficiency that incorporates the influence of the panel's microclimate was derived from first principles and validated with field observations. Results confirm that the PV panel efficiency is influenced by the insolation, air temperature, wind speed and relative humidity. The model was applied globally using bias-corrected reanalysis datasets to map solar panel efficiency and the potential for solar power production given local conditions. Solar power production potential was classified based on local land cover classification, with croplands having the greatest median solar potential of approximately 28 W/m
. The potential for dual-use, agrivoltaic systems may alleviate land competition or other spatial constraints for solar power development, creating a significant opportunity for future energy sustainability. Global energy demand would be offset by solar production if even less than 1% of cropland were converted to an agrivoltaic system.
Efficient sweat release and heat dissipation are required for functional textiles that improve comfort and productivity while being worn in daily life. However, the porous structure of textiles ...exhibits an opposite effect on water transport and heat transfer capacities, leading to a longstanding bottleneck for the design of multifunctional drying and cooling textiles. Here, a biomimetic transpiration textile based on the hierarchical and interconnected network of vascular plants is demonstrated for highly efficient personal drying and cooling. The transpiration‐inspired design offers a textile with distinct advantages, including a desired one‐way water transport index (1072%), rapid water evaporation rate (0.36 g h−1), and outstanding through‐plane (0.182 W m−1 K−1) and in‐plane (1.137 W m−1 K−1) thermal conductivities. Moreover, based on the optimized performance, plausible mechanisms are proposed and calculated to provide insight into the water transport and heat transfer within the hierarchical and interconnected network, which provide promising benefits to the development of multifunctional drying and cooling textiles. Overall, the successful synthesis of this biomimetic transpiration textile provides a comfortable microclimate to the human body, thus satisfying the growing demand for better health, productivity, and sustainability.
A biomimetic transpiration textile with a hierarchically fibrous structure and an interconnected boron nitride nanosheet network is fabricated for personal drying and cooling. Benefitting from its optimized structure, this textile exhibits a desired directional water transport capacity and unimpeded heat dissipation, which synergistically contribute to the highly efficient drying and cooling, thus creating a comfortable microclimate for the human body.
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•Combining solar panels and crops on the same land increases the total productivity.•Use of solar trackers permits to balance or promote food/energy production.•Controlling mode of ...trackers strongly affect the total production per unit area.•Dynamic agrivoltaic systems increases productivity without competing with food.
Agrivoltaic systems, consisting of the combination of photovoltaic panels (PVPs) with crops on the same land, recently emerged as an opportunity to resolve the competition for land use between food and energy production. Such systems have proved efficient when using stationary PVPs at half their usual density. Dynamic agrivoltaic systems improved the concept by using orientable PVPs derived from solar trackers. They offer the possibility to intercept the variable part of solar radiation, as well as new means to increase land productivity.
The matter was analysed in this work by comparing fixed and dynamic systems with two different orientation policies. Performances of the resulting agrivoltaic systems were studied for two varieties of lettuce over three different seasons.
Solar tracking systems placed all plants in a new microclimate where light and shade bands alternated several times a day at any plant position, while stationary systems split the land surface into more stable shaded and sunlit areas. In spite of these differences, transient shading conditions increased plant leaf area in all agrivoltaic systems compared to full-sun conditions, resulting in a higher conversion of the transmitted radiation by the crop. This benefit was lower during seasons with high radiation and under controlled tracking with more light transmitted to the crop. As expected, regular tracking largely increased electric production compared to stationary PVPs but also slightly increased the transmitted radiation, hence crop biomass. A large increase in transmitted radiation was achieved by restricting solar tracking around midday, which resulted in higher biomass in the spring but was counterbalanced by a lower conversion efficiency of transmitted radiation in summer. As a result, high productivity per land area unit was reached using trackers instead of stationary photovoltaic panels in agrivoltaic systems, while maintaining biomass production of lettuce close or even similar to that obtained under full-sun conditions.
•A meta-analysis of the Envi-met evaluation results of 52 studies is performed.•The median of the reported MAE and RMSE of Tair is 1.34 °C and 1.51 °C respectively.•The cooling potential of trees and ...cool materials, reported in 97 studies is analyzed.•The median peak temperature drop due to urban trees is 1.0 °C.•The median peak Tair drop due to cool pavements and extra trees is 2.0 °C.
Increased urban air temperatures due to urbanization affect the buildings’ energy performance and the outdoor thermal comfort. Aiming on the establishment of adaption strategies, urban microclimate studies using numerical simulation tools are gaining great scientific attention. The ENVI-met model is one of the most widely employed dynamic simulation tools. Considering its increasing use, this review aims to perform a meta-analysis of the reported evaluation results, reflecting the capability of the model to accurately calculate the diurnal profile of microclimatic variables. The analysis relies on the definition of the range of the reported metrics and on the investigation of the relationship between the various indices, applied for the model evaluation. Secondly, the study assesses the existing ENVI-met simulation results, indicating the cooling potential of urban greenery and cool materials regarding air, surface and mean radiant temperature modifications. The analysis revealed that the model can be considered as a helpful tool for urban climate analysis, provided that its limitations and features are accounted for by the user during the interpretation of the simulation outcome. Concerning the performance of the examined mitigation strategies, the most popular technology is the urban greenery while the mitigation potential is increased when different strategies are combined.
This paper provides an updated literature review about greenhouse systems and helps to identify the most preferable characteristics of a greenhouse for diverse climates and operating conditions. Data ...on appropriate properties of the covering materials and comparisons of several cladding materials were extensively discussed. The selection process of the greenhouse shape and orientation for different climates is presented, and comparisons between several shapes and orientations are made. This paper also examines the existing thermal models and simulation tools used to optimize the thermal operating conditions of the greenhouse. Furthermore, many recent studies are presented where greenhouses are combined with several systems to provide a favorable microclimate for crops, under extreme, tropical and subtropical climates. Finally, other applications such as greenhouse dryers and seawater greenhouse desalination are also discussed.
•Long term data in different seasons in residential communities was collected.•Outdoor thermal sensation and comfort varied with seasons.•The resident adapted to outdoor space by adjusting behaviors ...in different seasons.•The attendance related to the values of PET variesly in different seasons.•Sunny and shady subspaces should be setted in residential community planning.
A comfortable thermal environment is extremely important for the enjoyment of outdoor spaces. The relationship among microclimate, thermal sensation, and human behavior is expected to provide guidelines and implications for outdoor space design and planning practice. Given that, this study aimed at a better understanding of outdoor thermal comfort and activities in the residential community in a humid subtropical area of China. This study counted the number of people staying at the outdoor space, recorded physical measurements, and collected questionnaire surveys to determine the thermal comfort and activities of the outdoor space. Analysis results confirmed that the thermal experience and expectation existed and changed people’s perceptions about the outdoor thermal environment in different seasons. The 90% acceptable physiologically equivalent temperature (PET) range affected by the local climate and thermal adaptation was 18.1–31.1°C. The residents adapted to the outdoor spaces through adjustment of clothing, activity spaces and activity times in different seasons. These findings shed light on the optimal design of outdoor spaces for increasing the utilization rate. Sunny and shady subspaces should be considered to provide residents with more opportunities to interact with the environment for different seasons, thus improving their thermal comfort and the usage rate.
Residential district is the important space for people living and outdoor activities. Vegetation is proved to be effectively regulate microclimate. Living in Wuhan, residents have to suffer heat ...stress in summer and strong cold wind in winter simultaneously. It is necessary to dictate vegetation types and layout in residential area to get comfortable environment both in hot summer and cold winter. This study examined the vegetation influences of residential wind environment in hot and cold seasons by using the ENVI-met model V4. Field measurement validated the performance of ENVI-met model. The simulation was based on multi-story buildings representing the current primary form of residential area in Wuhan. 3 scenarios with three tree arrangements and 8 vegetation species were simulated. Height-to-distance ratio of trees (as “Aspect ratio of trees”, ART) was used to describe the tree distribution. Results showed that the impact of vegetation on both heat environment and ventilation depended on tree arrangement, LAI, crown width and tree height. The comparison of 3 tree distributions revealed that trees with an ART < 2 should be a priority to mitigate hot environments due to the large effects on PET reduction in summer. Evergreen species with an ART < 2 also effectively decreased wind speed in winter as well as blocked direct sunlight, resulting in negative effects on PET. Tall trees with a large LAI and canopy diameter should be a priority to improve the comfort of outdoor environments.
•Trees with an ART <2 should be a priority to mitigate hot environments due to the large effects on PET reduction in summer.•Evergreen species with an ART <2 also effectively decreased wind speed in winter as well as blocked direct sunlight.•Tall trees with a large LAI and canopy diameter should be a priority to improve the comfort of outdoor environments.
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