•Properties of chitosan films were evaluated at a wide range of aw.•Most changes in the properties of chitosan films started at aw=0.3.•RH affects the mechanical and thermal properties of chitosan ...films.•WVP in chitosan films depends on the moisture content.
Water molecules modify the properties of biodegradable films obtained from hydrophilic materials. Most studies dealing with thermal, mechanical and barrier properties of hydrophilic films are carried out under one relative humidity (RH) condition. The objective of this work was to evaluate the effect of the moisture content on the thermal, mechanical and barrier properties of chitosan films under several RH conditions. Microclimates, obtained with saturated salt solutions were used for conditioning samples and the properties of the films were evaluated under each RH condition. Chitosan films absorbed up to 40% of moisture at the higher RH studied. The percentage of elongation and the water vapour permeability increased while tensile strength, Young’s modulus and glass transition temperature decreased, when the moisture content increased. The results suggest that the water molecules plasticized the polymer matrix, changing the properties when the films were in contact with high RH environments.
The aim of this study was to investigate the effect of semi-transparent building integrated photovoltaics (BIPV) mounted on top of a greenhouse, on the growth of tomatoes and microclimate conditions ...as well as to estimate the generated energy and the payback period of this system. Three modules were settled at 20% of the greenhouse roof area at a tilt angle of 30° facing south at a distance of 0.08 m between the plastic cover and the BIPV. Each module has a peak power of 170 Wp and efficiency of 8.25%. Results revealed that the annual generated electric energy of the BIPV was 637 kWh. Furthermore, there were no significant differences (P < .05) in the growth of tomatoes between shaded greenhouse by the BIPV and the un-shaded greenhouse. The reduction of solar radiation under the BIPV was 35%–40% more than the Polyethylene covers on clear days. The BIPV shading decreases the air temperature by (1 °C–3 °C) on clear days and has no effect on relative humidity. The payback period was found to be 9 years. Moreover, this system can provide most of the annual energy demands for the greenhouse environmental control systems.
•A specific integration of a semi-transparent photovoltaic (BIPV) with greenhouse was studied.•The generated electric energy of BIPV and the payback period were estimated.•The ideal tilt angle to generate electric energy at the south roof was at 25° and at the north roof was 20°.•The BIPV shading decreased the light intensity and air temperatures without harming the tomato growth.
Research on outdoor comfort generally focuses on the thermal sensation as a substitute for actual comfort. The assessment of outdoor comfort, however, is complex in nature because it involves various ...contextual settings in open spaces, individuals' social demographics, and psychological factors. In contributing to the existing literature, this study attempts to extend the modelling framework of outdoor comfort assessment by incorporating physical microclimate, spatial contexts, social demographics and individuals' subjective perceptions, expectations and preferences. A path analysis is conducted to capture the direct and indirect effects of various factors on comfort using the data collected in a field experiment. Results show that the causal dependency, which is normally simplified in existing studies, can be better illustrated with the indirect effects through mediators. The use of objective indicators and individuals’ subjective factors are fundamental to adequately capture the actual comfort in urban public spaces.
•Extended the modelling framework for outdoor comfort assessment.•Incorporated individuals' perception, expectation and preference.•Investigated the endogenous and exogenous relationship with actual comfort.•Captured indirect effects through mediators.
Currently, sustainability is one of the most important subjects in architecture and urban design. Sustainable design strategies reduce energy consumption of buildings and environmental pollution. ...Moreover, these strategies improve the microclimatic conditions of urban spaces. In this regard, courtyard design is an efficient sustainable strategy to improve thermal and microclimatic conditions of urban spaces. For 5000 years, courtyards have been developed to adapt to severe climatic conditions, particularly in hot and arid climates. Inaccurate courtyard thermal estimations may occur due to the complexity of optimal thermal design and insufficient tools for simulating the thermal conditions of indoor and outdoor spaces simultaneously. In the last four decades, researchers have recommended several methods to study the thermal function of courtyards. Although the variety of the modelling particularities makes it difficult to obtain appropriate results that encompass all influential factors of courtyard climatic performance, this paper provides a comprehensive review of the papers of this type of building form. The main goal is to clarify if and how the construction of courtyards can decrease energy consumption and improve the microclimate of buildings. The present study focuses on the impact of courtyard design factors (such as proportion, orientation, geometry, opening characteristics, and material) and its components (such as shading devices, vegetation, and water pool) on energy consumption, indoor and outdoor temperatures, solar radiation, and natural ventilation in different climates. Regarding the researchers’ frameworks in the reviewed papers, three main categories are identified: 1- those examining the microclimatic function of courtyards, 2- those based on the thermal function of courtyards, and 3- those that incorporate an integrative approach (considering the thermal and microclimatic functions of courtyards simultaneously). Afterward, the paper reviews the role of three main climatic factors — solar gain, humidity, and natural ventilation — in each category.
•Thermal and microclimatic function of courtyards were studied.•The role of three main climatic factors — solar gain, humidity, and natural ventilation — were observed in courtyard climatic function.•The courtyard length-to-height ratio is one of the most influential factors on courtyard climatic function.
Hot summers in the subtropics cause thermal discomfort, which is intensified by the urban heat island effect in heavily built-up areas. Use of urban greenery has been proposed as a mechanism for ...microclimate regulation. In this study, the microclimatic effect of urban trees was investigated in the context of high-density cities in subtropical hot and humid climates. Measurements were conducted in urban areas with sky view factors (SVF) ranging from 0.2 to 0.8, and mean radiant temperatures were calculated. The measurements show that the effects of urban trees are related to SVF and that the impact of building morphology is more evident under cloudy conditions than under sunny conditions. In heavily built-up areas, the mean radiant temperature (Tmrt) was reduced to a comfortable level (33 °C) by roadside trees in the early afternoon. Simulation results indicate that roadside trees reduce the physiological equivalent temperature (PET) to 29 °C in urban areas with SVFs of 0.2 under cloudy conditions. The SVF-oriented planning method was tested using the existing building geometry of two high-density districts of Hong Kong, Mong Kok and Sham Shui Po, and site-specific design strategies for tree planting were developed. The study results show that a comfortable microclimate can be provided by roadside trees in heavily built-up urban environments in subtropical cities for nearly 70% of the summer. Design suggestions for refining the Green Master Plans of Hong Kong in future planning are provided.
•The thermal effects of urban trees are related to the sky view factor.•Impact of urban morphology on tree effects is more evident in cloudy conditions.•Trees in areas with low sky view factors provide comfortable microclimates.•Site-level planning should consider subtropical sun angle and areal wind direction.
When modelling outdoor microclimates, researchers and designers need to be aware of the modelling capabilities and limitations of tools. This comparative study attempts to understand how tools such ...as CitySim Pro, ENVI-met, RayMan, Grasshopper plug-ins Honeybee / Ladybug and Autodesk CFD, evaluate the Mean Radiant Temperature (MRT), one of the main parameters governing human energy balance. To this purpose, the space underneath and surrounding the Rolex Learning Center, located on the EPFL campus in Lausanne, were modelled. Significant variations of MRT predictions were recorded. This led to the review of the physical modelling assumptions that each of the calculation engines operates. Based on the tools’ available documentation, answers to forums, interviews with the developers, and tool codes, the paper lists how all the variables that affect MRT are considered. Although not exhaustively, the paper lists the main differences among tools, leading to the understanding of the types of physical context that they could simulate.
Urban heat island is an anthropogenic phenomenon affecting urban outdoor thermal comfort conditions and energy utilization. This is even truer in urban canyon configurations, characterized by low sky ...view factor and where the effect of short-wave and long-wave solar radiation on construction surfaces is able to produce massive outdoor local overheating. Traditional solutions cannot always be applied in urban historical canyons, where the exteriors of buildings cannot be modified due to preservation. Here, the capability of innovative cool materials to mitigate local microclimate of historical urban canyons is investigated. A preliminary experimental characterization of the materials is performed. A numerical simulation of the microclimate effect generated by the application of such materials is performed. Results show that the proposed materials improve the microclimate without neglecting preservation constrains. Such materials set the best scenarios in terms of thermal comfort, by enhancing albedo on canyon surfaces. Their application on the vertical surfaces of narrow canyons can lead to deleterious effects on outdoor thermal comfort. Such findings are confirmed by PMV and MOCI analyses. Energy efficiency solutions may be effectively implemented in historical districts, opening the doors to other tailored solutions, such as integrated renewables, to make these environments more sustainable and comfortable.
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•Urban canyon microclimate in historical districts is investigated and mitigated.•Novel cool materials for energy saving and outdoor comfort are implemented.•Radiative heat is reduced and more comfortable environment is achieved.•Energy efficient historic districts may deliver “green” message to the society.
Monitoring microclimate variables within cities with high accuracy is an ongoing challenge for a better urban resilience to climate change. Assessing the intra-urban characteristics of a city is of ...vital importance for ensuring fine living standards for citizens. Here, a novel mobile microclimate station is applied for monitoring the main microclimatic variables regulating urban and intra-urban environment, as well as directionally monitoring shortwave radiation and illuminance and hence systematically map for the first time the effect of urban surfaces and anthropogenic heat. We performed day-time and night-time monitoring campaigns within a historical city in Italy, characterized by substantial urban structure differentiations. We found significant intra-urban variations concerning variables such as air temperature and shortwave radiation. Moreover, the proposed experimental framework may capture, for the very first time, significant directional variations with respect to shortwave radiation and illuminance across the city at microclimate scale. The presented mobile station represents therefore the key missing piece for exhaustively identifying urban environmental quality, anthropogenic actions, and data driven modelling toward risk and resilience planning. It can be therefore used in combination with satellite data, stable weather station or other mobile stations, e.g. wearable sensing techniques, through a citizens' science approach in smart, livable, and sustainable cities in the near future.
During European states' development, various past societies utilized natural resources, but their impact was not uniformly spatially and temporally distributed. Considerable changes resulted in ...landscape fragmentation, especially during the Middle Ages. Changes in state advances that affected the local economy significantly drove trajectories of ecosystems' development. The legacy of major changes from pristine forest to farming is visible in natural archives as novel ecosystems. Here, we present a high-resolution densely dated multi-proxy study covering the last 1500 years from a peatland located in CE Europe. The economic activity of medieval societies was highly modified by new rulers-the Joannites (the Order of St. John of Jerusalem, Knights Hospitaller). We studied the record of these directorial changes noted in the peat profile. Our research revealed a rapid critical land-use transition in the late Middle Ages and its consequences on the peatland ecosystem. The shift from the virgin forest with regular local fires to agriculture correlates well with the raising of local economy and deforestations. Along with the emerging openness, the wetland switched from alkaline wet fen state to acidic, drier Sphagnum-dominated peatland. Our data show how closely the ecological state of wetlands relates to forest microclimate. We identified a significant impact of the Joannites who used the novel farming organization. Our results revealed the surprisingly fast rate of how feudal economy eliminated pristine nature from the studied area and created novel anthroecosystems.
The application of the photovoltaic (PV) energy to the European greenhouse industry has led to installations designed to maximise the energy production but detrimental for the greenhouse crops, due ...to the effect of shading of the PV panels on the roof. To assess these issues, the first step is to characterize the PV greenhouse microclimate, especially in terms of solar radiation at canopy level. After a comprehensive review of the current state-of-art of the PV greenhouse sector, four representative commercial PV greenhouse types are compared, with a percentage of the area covered with PV panels (PV cover ratio) ranging from 25% to 100%. The aim is to define the general relations between the main design parameters (PV cover ratio, greenhouse height and orientation, checkerboard pattern) and the available solar radiation, to provide original information on the design of next-generation PV greenhouses with improved agronomic sustainability. The yearly global radiation decreased averagely by 0.8% for each additional 1.0% PV cover ratio and increased by 3.8% for each further meter of gutter height. The N-S orientation increased the average cumulated global radiation on the greenhouse area by 24%, compared to the E-W orientation. Both the checkerboard pattern and the N-S orientation improved the uniformity of light distribution. All PV greenhouse types are provided with light distribution maps to evaluate the light variability on the greenhouse area. The light distribution is crucial to support adequate agronomic plans for both preexisting and new PV greenhouses, aiming to sustainable mixed systems for both energy and crop production.
•The solar light distribution was calculated on the main PV greenhouse types.•The effect of design criteria on the sustainability of PV greenhouses is estimated.•The available global radiation decreases by 0.8% for each additional 1.0% PV area.•Each additional meter of gutter height increases the global radiation of 3.8%.•The N-S orientation allows averagely 24% more global radiation than E-W orientation.
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