外遮阳系数对住宅能耗的影响

通过e QUEST能耗模拟分析表明,当天津地区住宅建筑南向或者北向采用遮阳时,建筑的制冷电耗是减少的,而制热电耗和总电耗是增加的,并且南向遮阳系数影响远大于北向的影响;南向遮阳系数从0.5增加到0.8时,制冷能耗增加16.75%,制热能耗减少9.52%,总能耗减少4.52%;北向遮阳系数值由0.4增加到0.8时,建筑的制冷能耗增加1.75%,制热能耗下降0.52%,总能耗下降0.16%,该研究对于建筑节能具有指导意义。     

Daylighting and energy implications due to shading effects from nearby buildings

Daylighting has long been recognized as a potential energy-efficient design strategy for buildings. Natural light can help reduce the electrical demand and the associated sensible cooling load due to artificial lighting. In Hong Kong, however, many buildings are constructed close to each other and hence the external environment plays a significant role in daylighting designs. This paper investigates the shading effects due to nearby obstructions when daylighting schemes are being employed. We used the computer simulation tool, EnergyPlus, to illustrate the energy performance of a generic commercial building with daylighting controls obstructed by neighbouring buildings of various heights. Analysis of electricity savings was carried out for the perimeter zones of the whole building and individual floors. Regression techniques were conducted to correlate the building energy savings and the angles of obstructions. It was found that the shading effects due to nearby obstructions strongly affect the building energy budget when daylighting designs are used. Building designers should critically consider the external environment in order to achieve energy-efficient building designs.     

建筑南窗遮阳及设计分析研究

一前言被动式采暖太阳房是我国最成熟、应用范围最广、产业化发展最快的太阳能建筑技术之一。被动式太阳能供暖系统根据各地区气象条件,基本上不添置附加设备,只依靠建筑物本身的构造和材料的热工性能,使房屋尽可能多的吸收和贮存热量,以     

The geometry of the shading of buildings by various tree shapes

This paper describes a design tool to be used in assessing the shading effects of trees in relation to buildings. More specifically, an interactive computer program has been written which determines the area and position of the shadows cast by a tree or a group of trees on a surface of any orientation and inclination. The program outputs numerical and graphical hourly results at any time of the day between the sunrise and the sunset, for any day of the year, at any location on the earth for any relative positioning between the tree and the building. The program allows four different shapes of tree (spherical, cylindrical, upright cone or reversed cone) or any combination of these fundamental shapes to be used.     

An analysis of solar gain through externally shaded window of buildings

The development of computer software for analyzing the solar gain through windows of buildings is presented. The program which is capable of stating the hourly values of solar altitude angles, azimuth angles and extra-terrestrial intensity is written in the BASIC Language. The main feature of the program is that it can be used to determine the hourly values of normal solar intensity and solar energy incident on windows treated with reveals, over-hangs and side-fins. Application of the software in analyzing the solar gain through windows in some experiments yield results which are as consistent as those done manually. The experiments show that in every case, reveals have the effect of reducing the incident solar intensities, and hence incident solar energy on windows. Further analysis shows that over-hangs are much more effective in shading than vertical side-fins.     

Computer simulation of shading effects in photovoltaic arrays

A simulation of shading effects in arrays with different string configurations has been done. Simulation has been performed using as the basic unit the solar cell, modelled in direct bias by the conventional one exponential model, and in reverse bias by an equation previously validated in different types of photovoltaic cells reverse characteristics. The influence of the amount of shading, the type of reverse characteristic of the cell, the string length and the number of shaded cells has been analysed, and some recommendations are extracted.     

Evaluation of the effect of nanocoated window glazing films on the thermal behavior of buildings

In this study, different coating samples of antimony tin oxide (ATO) films on clear glass were prepared and their optical and thermal properties were evaluated. Performance parameters such as glass U-factor, solar heat gain coefficient, temperature distribution, and net heat transfer gain using the glazed walls inside the test room were determined through numerical simulations. The results obtained indicate that the nanocoating thickness and doping level concentration of ATO films have a pronounced effect on the thermal insulation of the window glass. When compared with normal window clear glass, the transmittance of solar radiation for ATO thin-film coating of thickness 1140 nm reduced from 0.881 to 0.114 in the visible (VIS) region and 0.817 to 0.012 in the infrared (IR) region, whereas radiation in the ultraviolet (UV) region was almost completely blocked. Similarly, for the ATO films with doping level 15%, the transmittance value reduced from 0.742 to 0.432 in the VIS region and from 0.718 to 0.114 in the IR region, and radiation in the UV region was almost totally blocked. Finally from the analysis of results, it was observed that the ATO thin films show exceptional optical and thermal properties and exhibit improved solar blocking behavior when compared with commercially available glazing (eg, from Saudi Arabian glass companies).     

A distant-learning training module on the environmental design of urban buildings

The present paper aims to present a distant-learning training module that concerns the environmental design of urban buildings. The whole approach attempts to integrate topics that concern the design of urban buildings from various points of views, e.g. active and passive systems, automation systems, indoor air quality, economic aspects, energy and resources management. The package offers both printed and electronic material that gives the possibility to the students to study the various topics by using different educational methods. Additionally, the present package contains software tools that permit the students to examine real or hypothetical situations and to study further the influence of various parameters that concern the environmental building design.     

Energy, economic and environmental analysis on RET-hydrogen systems in residential buildings

The aim of this study was to analyze energy, economic and environmental performances of a set of scenarios dealing with the production and the use of hydrogen as energy carriers in residential applications in combination with renewable energy (RE).The authors also made an investigation into the required economic conditions necessary for making H₂–RE residential systems competitive with conventional ones, which are based on the use of grid electricity and natural gas.A case study was enacted in a small residential district in Palermo (Italy) made by five multi-storey buildings.Many energy systems have been considered according to several fuel-device combinations (electric grid, fuel cell, PV panels, wind turbines, boiler etc.).The software HOMER (hybrid optimization model for electric renewables), developed by NREL and Midwest Research Institute (USA), was used, in order to study the energy balance of the system and its components. Moreover, it was possible to simulate the hourly operation of each system and to calculate technical, economic and environmental performance parameters.The net present cost and the cost of energy are the two main parameters used to compare economic performances of the systems with both actual and expected costs in the medium term.A sensitivity analysis was carried out in order to appreciate the most important parameters influencing the economic performances of the systems and to define possible future scenarios of competitiveness between technologies.Emissions of CO₂ (the most important greenhouse gas) and other pollutants have been considered for an environmental benefits analysis.     

Quantifying the potential of automated dynamic solar shading in office buildings through integrated simulations of energy and daylight

The façade design is and should be considered a central issue in the design of energy-efficient buildings. That is why dynamic façade components are increasingly used to adapt to both internal and external impacts, and to cope with a reduction in energy consumption and an increase in occupant comfort. To gain a complete picture of any façade’s performance and subsequently carry out a reasonable benchmarking of various façade alternatives, the total energy consumption and indoor environment need to be considered simultaneously. We quantified the potential of dynamic solar shading façade components by using integrated simulations that took energy demand, the indoor air quality, the amount of daylight available, and visual comfort into consideration. Three types of façades were investigated (without solar shading, with fixed solar shading, and with dynamic solar shading), and we simulated them with various window heights and orientations. Their performance was evaluated on the basis of the building’s total energy demand, its energy demand for heating, cooling and lighting, and also its daylight factors. Simulation results comparing the three façade alternatives show potential for significant energy reduction, but greater differences and conflicting tendencies were revealed when the energy needed for heating, cooling and artificial lighting were considered separately. Moreover, the use of dynamic solar shading dramatically improved the amount of daylight available compared to fixed solar shading, which emphasises the need for dynamic and integrated simulations early in the design process to facilitate informed design decisions about the façade.     

High temperature solar heated seasonal storage system for low temperature heating of buildings

A preliminary study of a solar-heated low-temperature space-heating system with seasonal storage in the ground has been performed. The system performance has been evaluated using the simulation models TRNSYS and MINSUN together with the ground storage module DST. The study implies an economically feasible design for a total annual heat demand of about 2500 MWh. The main objective was to perform a study on Anneberg, a planned residential area of 90 single-family houses with 1080 MWh total heat demand. The suggested heating system with a solar fraction of 60% includes 3000 m² of solar collectors but electrical heaters to produce peak heating. The floor heating system was designed for 30°C supply temperature. The temperature of the seasonal storage unit, a borehole array in crystalline rock of 60,000 m³, varies between 30 and 45°C over the year. The total annual heating costs, which include all costs (including capital, energy, maintenance etc.) associated with the heating system, were investigated for three different systems: solar heating (1000 SEK MWh⁻¹), small-scale district heating (1100 SEK MWh⁻¹) and individual ground-coupled heat pumps (920 SEK MWh⁻¹). The heat loss from the Anneberg storage system was 42% of the collected solar energy. This heat loss would be reduced in a larger storage system, so a case where the size of the proposed solar heating system was enlarged by a factor of three was also investigated. The total annual cost of the solar heating system was reduced by about 20% to about 800 SEK MWh⁻¹, which is lower than the best conventional alternative.     

遮蔽问题对光伏系统的影响

<正>一引言通过太阳电池板将太阳能转换为电能,是目前市场上最有前景的可再生能源技术之一。光伏技术已发展成熟,具有稳固、可靠的特点。由于传统电能成本不断攀升,加上政府推出退税和收购电价补助等高效激励计划,光伏系统已成为极具吸引力的     

Application of holographic optical elements in buildings for various purposes like daylighting, solar shading and photovoltaic power generation

Since four years the ILB is developing lightdirecting building components, using holographic optical elements (HOE). The holograms are produced on films, which are laminated between two panes of floatglass. By the physical effect of diffraction different forms of light manipulation are possible, comparable to those of mirrors, prisms, lenses and other optical elements. Laminated glass with lightdirecting holograms allows a great variety of applications in architecture for utilization of solar energy, improvement of room comfort as well as design of solar light- and colour effects.     

An empirical validation of modeling solar gain through a glazing unit with external and internal shading screens

Empirical validations are integral components in assessing the overall accuracies of building energy simulation programs. Two test cell experiments were performed at the Swiss Federal Laboratories for Material Testing and Research’s (EMPA) campus in Duebendorf, Switzerland to evaluate the solar gain models with external and internal shading screens in four building energy simulation programs including: (1) EnergyPlus, (2) DOE-2.1E, (3) TRNSYS-TUD, and (4) ESP-r. Detailed information about the shading screen properties, modeling procedures, and thorough statistical and sensitivity analyses of simulation results are provided. For the external shading screen experiment, the mean percentage of the absolute difference between measured and simulated cooling power to maintain a near-constant cell air temperature for EnergyPlus, DOE-2.1E, TRNSYS-TUD and ESP-r were 3.7%, 5.5%, 10.6%, and 7.5%, respectively. EnergyPlus and DOE-2.1E were considered validated within 95% credible limits. For the internal shading screen experiment, the mean percentage of the absolute mean differences for EnergyPlus, DOE-2.1E, TRNSYS-TUD, and ESP-r were 6.7%. 13.8%, 5.7%, and 4.3%, respectively; only ESP-r was considered validated within 95% credible limits.     

Two-dimensional modeling of a salt-gradient solar pond with wall shading effect and thermo-physical properties dependent on temperature and concentration

In this paper,the behavior of a salt-gradient solar pond with the square cross-section has been studied experimentally and numerically.A small-scale solar pond were designed and built to provide quantitative data.A two-dimensional,transient heat and mass transfer model has been solved numerically by using finite-control-volume method.In this study,all the thermo-physical properties are variable as the function of temperature and salt concentration.Numerical results as obtained for the experimental pond have been satisfactorily compared and validated against measured data.Furthermore,the wall shading effect has been elaborated to improve the agreement between two sets of results.The temperature of the storage zone is predicted well by the model.It also can be observed that the initial concentration profile is preserved with time.The stability of the pond in time has been investigated in order to distinguish the critical zones.Finally,the application of an energy analysis gives an efficiency of about 12%for the pond.     

The effects of internal gains on residential space-heating analyses

Analyses of the energy used for winter space heating in residences (and other buildings) often involve only the energy source used in the space-heating system. We demonstrate that serious errors can result from this approach, since the internal heat gains from other energy sources may play an important or dominant role in meeting the heating requirements. It is even possible for energy-conservation measures to lead to apparent increases in energy consumption if the analysis does not include all energy sources. Internal gains should also be considered in analyses of annual energy consumption.     

Evaluation of the environmental quality of buildings towards a more environmentally conscious design

Appropriate design and construction can reduce the environmental impact of buildings over their entire life cycle. Such a prevention strategy can be supported by an evaluation tool. Our approach consists of applying life cycle analysis to the building sector. The use of computers is preferred for an easier comparison of alternative designs and to test possible improvements of a project. We adopted an object oriented approach in order to link models with professional practice. A data structure has been defined, in which a building is decomposed into objects. The corresponding classes include both data (inventories of basic materials and processes) and methods (accounting for fabrication, recycling, etc.). The result of such an evaluation is an environmental profile, constituted from various indicators on natural resources used, environmental effects and waste produced. First sensitivity analysis were performed showing the importance of the utilisation phase with its associated energy, water and waste fluxes. The environmental performance of a building is a result of a sequence of decisions like the choice of the building site, design choices, occupant's behaviour, etc. The potential applications of this research are to inform the various actors about the consequences of their choices, to assess the environmental interest of innovative technologies (e.g. solar components) and to develop new tools for practitioners.     

A method to predict cooling load of large commercial buildings based on weather forecast and internal occupancy

Considering the fact that customers of large commercial buildings have the characteristics of the higher density and randomness, this paper presented an airconditioning cooling load prediction method based on weather forecast and internal occupancy density. The multiple linear feedback regression model was applied to predict, with precision, the air conditioning cooling load. Case analysis showed that the largest mean relative error of hourly and the daily predicting cooling load maximum were 18.1% and 5.14%, respectively.     

The economic and environmental optimisation of integrating ground source energy systems into buildings

There are currently two main drivers for the consideration of ground source energy systems in the built environment in the UK. Firstly, building occupiers and owners are becoming increasingly concerned at rising energy prices whilst building designers are also required to reduce, due to European and national and local legislation, the operational CO₂ emissions from new and existing buildings. This paper considers the application of Bivalent (dual fuel) ground source heat pump heating and cooling systems as a way to reduce the installation costs whilst also providing considerable economic and environmental savings. A case study building is used to demonstrate the importance of optimising ground loop heat exchanger length, considering differing future energy prices and the chosen appraisal period. An incremental approach is used to consider the relative benefits of increasing the size of the GSHP. Designers can also be misled by the assumption that by sizing a GSHP system to just meet the legislative targets the most economically sized system will be installed. The optimum system shows a >60% reduction in the capital cost vs. a peak sized GSHP system whilst still providing >70% of the respective economic savings and CO₂ reduction.