Ideal thermophysical properties for free-cooling (or heating) buildings with constant thermal physical property material

Free-cooling is understood as a means to store outdoors coolness during the night, to supply indoors cooling during the day in summer, while free-heating is understood as a means to store the solar radiation during daytime, to supply indoors heating during the night in winter. In principle, free-cooling or free-heating can make the indoor air temperature in the comfortable region all the year if the thermophysical properties of building envelope material are in the desired range (defined as ideal thermophysical properties in this paper). Those properties are obviously related to the outdoor climate condition, internal heat source intensity, building configuration, ventilation mode etc. For a given region and a given building, the critical values of those ideal thermal physical properties can be determined through modeling and simulation. Two parameters, I_win and I_sum, are defined to describe the overcool degree in winter and the overheat degree in summer, respectively. To illustrate, the critical values of thermophysical properties of building envelope of a building located in Beijing are obtained through modeling and simulation. The simulated results are validated with experiments. The model, the methodology and the results are helpful for selection of suitable building envelope materials and for design of energy efficient buildings.     

Effects of double skin envelopes on natural ventilation and heating loads in office buildings

The influence of natural ventilation on heating load and energy savings in a building with a double skinned envelope (DSE) was examined in this study. Field measurements and computer simulations were performed under various weather conditions. The DSE was effective for saving energy and creating natural ventilation rates under clear and partly cloudy skies. Due to insufficient irradiance, the DSE was not effective for reducing the heating load under overcast sky conditions. When natural airflow rates from the cavity space between internal and external skin to the indoor space were controlled, the southwest-facing DSE effectively reduced heating loads due to the accumulation of solar irradiance.Regression models showed that outdoor air temperature was the most significant factor governing variations in cavity temperature under all sky conditions. Computer simulations indicated that natural ventilation was practical at an appropriate supply temperature only when the sky ratio was less than 0.7. The airspace in cavity of the DSE provided additional natural ventilation rates to the indoor space and effectively reduced heating loads. Natural ventilation was available for 135 h during three winter months without consuming additional energy to heat the outdoor air. The heating load was reduced by the DSE ranged from 17.98% to 18.7% depending on the airflow control options for the cavity space.     

Application of latent heat thermal energy storage in buildings: State-of-the-art and outlook

Latent heat thermal energy storage (LHTES) is becoming more and more attractive for space heating and cooling of buildings. The application of LHTES in buildings has the following advantages: (1) the ability to narrow the gap between the peak and off-peak loads of electricity demand; (2) the ability to save operative fees by shifting the electrical consumption from peak periods to off-peak periods since the cost of electricity at night is 1/3–1/5 of that during the day; (3) the ability to utilize solar energy continuously, storing solar energy during the day, and releasing it at night, particularly for space heating in winter by reducing diurnal temperature fluctuation thus improving the degree of thermal comfort; (4) the ability to store the natural cooling by ventilation at night in summer and to release it to decrease the room temperature during the day, thus reducing the cooling load of air conditioning. This paper investigates previous work on thermal energy storage by incorporating phase change materials (PCMs) in the building envelope. The basic principle, candidate PCMs and their thermophysical properties, incorporation methods, thermal analyses of the use of PCMs in walls, floor, ceiling and window etc. and heat transfer enhancement are discussed. We show that with suitable PCMs and a suitable incorporation method with building material, LHTES can be economically efficient for heating and cooling buildings. However, several problems need to be tackled before LHTES can reliably and practically be applied. We conclude with some suggestions for future work.     

重庆农村住宅热环境调查与能耗模拟分析

通过对重庆地区农村住宅的实地调研和对农村典型住宅室内外温度的连续监测,获得农村住宅的主要围护结构类型及典型农村住宅供暖季与空调季的室内、外热环境状况,利用重庆地区自然通风适应性热舒适性评价模型进行分析。在现有农村住宅围护结构热工性能条件下,供暖季室内温度达到舒适范围的有0 d,空调季有73 d;室内热环境状况差,冬季保温要求比夏季隔热要求更高。在供暖空调设备典型运行模式下,以调研数据为基础,借助DeST-h软件对农村典型住宅供暖空调能耗进行模拟,获得了农村住宅单位建筑面积供暖空调设备耗电量。     

居住建筑围护结构的节能问题

从适宜居住的角度讲,我国绝大部分地区的居住建筑都要采取一定的技术措施来保证冬夏两季的室内热舒适环境。冬夏两季室内维持的温度与室外的温度有很大的差别,这个温差导致能量以热的形式流出或流入室内,采暖,空调设备消耗的能量主要就是用来补充这个能量损失的。在相同的室内外温差条件下,建筑围护结构保温隔热性能的好坏,直接影响到流出或流入室内的热量的多少。建筑围护结构保温隔热性能好,流出或流入室内的热量就少,采暖,空调设备消耗的能量也就少;反之,建筑围护结构保温隔热性能差,流现或流入室内的热量就多,采暖,空调设备消耗的能量也就多。我国现行的居住建筑节能设计标准对建筑围护结构保温隔热性能提出了明确的要求,按照节能设计标准的要求去设计,新建的居住建筑就能比具有传统围护结构的同类建筑节约25％－35％的采暖,空调能耗,而且节能的潜力还十分巨大。     

降低建筑空调能耗研究

在分析贵阳市气候特点及实例建筑空调负荷特性的基础上,采用建筑环境模拟软件DeST对实例建筑室内基础室温以及全年建筑冷热负荷进行模拟,在分析模拟结果的基础上,结合贵阳市气候特点,提出如下三条贵阳市降低建筑空调能耗建议：1)舒适性空调设计应首先满足冬季采暖,然后考虑夏季制冷;2)自然通风是夏季降温的优先考虑方式,过渡季节调节是降低建筑制冷能耗的重要手段;3)增加围护结构保温和控制窗墙比是降低建筑采暖能耗的首要手段。研究结果不但能对贵阳市的建筑节能提供参考,而且还对广大温和地区建筑节能有参考意义。     

中小型游泳馆无送热风暖通系统节能设计

以天津市某小型室内游泳馆为研究对象,计算了冬季带送热风的供暖通风系统的通风热负荷及其占总热负荷的比例。提出无送热风供暖通风系统方案,对室内空气设计参数的确定,围护结构、供暖通风系统的节能设计进行了探讨。为保证距地面2m以下空间内人员活动区的舒适度和防止围护结构结露,应采用散热器＋地板辐射供暖系统。围护结构结露可通过对金属构件施镀防腐层,设置墙体的保温、隔气层及涂抹防结露、防霉变的特种涂料等方法解决,设置通风系统仅是为了保证馆内空气品质。     

新建居住建筑供暖效果影响因素的计算分析

以北京市两栋装有分户热计量装置的新建住宅楼为研究对象,对楼内的113个住户进行冬季供暖耗热量、热水流量以及供回水温度等相关数据的定期采集,并在供暖季对其中9个住户的房间进行室温的连续测试。统计结果表明,住户的供暖耗热量高于北京现行节能标准的要求,但围护结构并不是影响住户供暖能耗大小的主要原因。通过对典型住户室内热环境的模拟计算及分析对比发现,房间通风状况、邻室室温状况、房间遮阳状况以及客厅与阳台门的开关状况等人的行为因素对住户的供暖效果产生不可忽视的重要影响。     

Categories of indoor environmental quality and building energy demand for heating and cooling

Maintaining suitable indoor climate conditions is a need for the occupants’ well being, while requiring very strictly thermal comfort conditions and very high levels of indoor air quality in buildings represents also a high expense of energy, with its consequence in terms of environmental impact and cost. In fact, it is well known that the indoor environmental quality (IEQ), considering both thermal and indoor air quality aspects, has a primary impact not only on the perceived human comfort, but also on the building energy consumption. This issue is clearly expressed by the European Energy Performance of Buildings Directive 2002/92/EC, together with the most recent 2010/31/EU, which underlines that the expression of a judgment about the energy consumption of a building should be always joint with the corresponding indoor environmental quality level required by occupants. To this aim, the concept of indoor environment categories has been introduced in the EN 15251 standard. These categories range from I to III, where category I refers to the highest level of indoor climate requirement. In the challenge of reducing the environmental impact for air conditioning in buildings, it is essential that IEQ requirements are relaxed in order to widen the variations of the temperature ranges and ventilation air flow rates. In this paper, by means of building energy simulation, the heating and cooling energy demand are calculated for a mechanically controlled office building where different indoor environmental quality levels are required, ranging from category I to category III of EN 15251. The building is located in different European cities (Moscow, Torino and Athens), characterized by significantly different wheatear conditions. The mutual relation between heating and cooling energy demand and the required levels of IEQ is highlighted. The simulations are performed on a typical office room which is adopted as a reference in validation tests of the European Standard EN 15265 to validate calculation procedures of energy use for space heating and cooling.     

深圳某国际性酒店中央空调系统改造情况综述

目前深圳酒店业竞争激烈,国际性酒店功能分区复杂,旅客对室内温度、湿度、新风量等室内空气品质（IAQ）要求更高。国家《采暖通风与空气调节设计规范》（GBJ19-87）及《旅游旅馆建筑热工与空气调节节能设计标准》（GB501899-93）等为此做了一定的规定,酒店改造中遇到的问题仍具有一定的普遍性。     

The influence of the zone's indoor temperature settings on the cooling/heating loads for fixed and controlled ventilation

In this study, the thermal performance and the energy requirements of a building single-zone are investigated for both the cooling and heating seasons by employing a thermal-network model. The model has six primary heat-flow paths, in order to take into account the position of insulation in the building envelope, and two secondary paths for the ventilation and the cooling/heating unit. The desired indoor temperature of the zone is defined by a pair of preset points of a thermostat. The energy demands and the resulting indoor temperature variations are determined for fixed ventilation as well as for temperature-controlled ventilation. Computer results for both seasons show how the combined influence of slab structure formations, the desired indoor temperature and ventilation control affect the cooling and heating loads.     

Building energy efficiency and thermal comfort in tropical climates: Presentation of a numerical approach for predicting the percentage of well-ventilated living spaces in buildings using natural ventilation

The paper deals with the optimization of building energy efficiency in tropical climates by reducing the period of air-conditioning thanks to natural ventilation and a better bioclimatic design. A bioclimatic approach to designing comfortable buildings in hot and humid tropical regions requires, firstly, some preliminary, important work on the building envelope to limit the energy contributions, and secondly, an airflow optimization based on the analysis of natural ventilation airflow networks. For the first step, tools such as nodal or zonal models have been largely implemented in building energy codes to evaluate energy transport between indoor and outdoor. For the second step, the assessment of air velocities, in three dimensions and in a large space, can only be performed through the use of detailed models such as with CFD. A new modelling approach based on the derivation of a new quantity—i.e. the well-ventilated percentage of a living space is proposed. The well-ventilated percentage of a space allows a time analysis of the air motion behaviour of the building in its environment. These percentages can be over a period such as 1 day, a season or a year. Twelve living spaces with different configuration of openings have been studied to compare the performance of ventilation function of the opening distribution. Results and discussion are presented in the paper. This method is helpful for an architect to design the rooms according to their use, and their environment. Finally, the developed models can be used in building projects to estimate the period of the natural ventilation and to reduce the energy consumption due to air-conditioning.     

Preparation,thermal performance and application of shape-stabilized PCM in energy efficient buildings

Shape-stabilized phase change material (PCM) is a kind of novel PCM. It has the following salient features: large apparent specific heat for phase change temperature region, suitable thermal conductivity, keeping shape stabilized in the phase change process and no need for containers. The preparation for such kind material was investigated and its thermophysical properties were measured. Some applications of such material in energy efficient buildings (e.g., in electric under floor space heating system, in wallboard or floor to absorb solar energy to narrow the temperature swing of a day in winter) were studied. Some models of analyzing the thermal performance of the systems were developed, which were validated with the experiments. The following conclusions are obtained: (1) the applications of the novel PCM we put forward are of promising perspectives in some climate regions; (2) by using different paraffin, the melting temperature of shape-stabilized PCM can be adjusted; (3) the heat of fusion of it is in the range of 62–138 kJ kg⁻¹; (4) for PCM floor or wallboard to absorb solar energy to narrow the temperature swing in a day in winter, the suitable melting temperature of PCM should be a little higher than average indoor air temperature of the room without PCM for the period of sunshine; (5) for the electric under-floor space heating system, the optimal melting temperature can be determined by simulation; (6) PCM layer used in the aforementioned application should not be thicker than 2 cm; (7) the models developed by us are helpful for applications of shape-stabilized PCM in buildings.     

空气源热泵直接地板辐射供暖运行模式实验研究

对采用数码涡旋空气源热泵的直接地板辐射供暖系统的供暖性能进行了实验研究。分别测量了在连续和间歇运行模式下的室内温度、围护结构表面温度、地板表面温度和电能消耗量。引入操作温度的概念对两种运行模式下的热舒适性和能耗情况进行了分析比较。实验结果表明,连续供暖运行模式是一种理想的供暖运行模式,但其电能消耗量较大;对于一些特定住宅采用间歇供暖运行模式不仅能够较好地满足热舒适性要求,而且具有显著的节能效果。     

广州市自然通风类建筑围护结构内表面温度的计算与分析

在完全靠自然通风调节而没有空调的建筑中,围护结构内表面温度对人体的热舒适性影响很大.分析了自然通风类建筑各种围护结构的内表面温度,并针对广州地区的气候特征,提出了围护结构的合理隔热保温措施.研究表明在该地区完全靠自然通风的建筑中使用重质材料加外保温层的围护结构对于改善室内热环境是非常有利的.     

Estimates of the energy impact of ventilation and associated financial expenditures

Ventilation is essential for the maintenance of good indoor air quality, although there is evidence to suggest that energy loss through uncontrolled or unnecessary air infiltration is excessive. In this study, estimates are presented for air change (ventilation and infiltration) energy use in non-industrial buildings for 13 countries. Various methods are used for the estimates, but they are mainly based on calculating the total annual enthalpy change needed for the conditioning of air. The potential for reduced energy use by improved ventilation control is also briefly reviewed. Considering the non-industrial building stock of the 13 countries collectively, the total annual loss of heating energy due to air change is estimated to amount to 48% of delivered space conditioning energy (including heating equipment losses). The results emphasise that air change related energy losses are as important as conduction and equipment losses (including ‘flue’ losses) in dissipating delivered space conditioning energy from buildings.In addition, estimated financial expenditures, as well as carbon dioxide emissions associated with this energy use are indicated. The financial expenditures are derived from the air change energy estimates using published International Energy Agency (IEA) energy pricing information. The magnitudes of the carbon dioxide emissions have been based on published IEA estimates of total emissions from energy-related sources for each country.     

相变材料在建筑节能应用领域的实验研究方法初探

相变材料可在较窄的温度范围内,蓄存或释放大量的潜热,可应用于建筑外围护结构,提高建筑的热惰性,缓解室内温度波动,削减空调负荷的峰值；又可与传统空调采暖系统相结合,蓄存廉价或免费的冷热量,从而起到建筑节能的作用.应用形式的多样化,导致了研究方法及测试方法的多样化.根据测试场景和测试建筑的不同,对研究手法及测试方法进行了分类汇总,结合一些实测案例重点分析了各类实验方法的测试对象、测试工况、测试手段等,分类整理了各类实验方法的优缺点及测试的要点,为今后的研究提供了重要参考.     

Energy, comfort and indoor air quality in nursery and elementary school buildings in the cold climatic zone of Greece

Schools are the most suitable type of building for the application of energy efficiency and good indoor air quality measures. This is justified by the fact that such measures can promote sustainability to the future citizens, and even more, ensure a comfortable and healthy environment for educational purposes. Unfortunately, in practice school buildings face the same, or even more intense, energy performance and indoor air quality problems as any other building. The purpose of this study is to investigate the energy efficiency, thermal environment and indoor air quality in public nursery and elementary school buildings in the city of Kozani, located at the cold climatic zone of Greece. The survey, conducted both by in-field measurements and by questionnaires, reveals the main parameters affecting the overall performance of the investigated buildings. The problematic building envelope, the improper control of heating and lighting systems, the absence of proper legislative measures and, above all, the lack of interest concerning the efficiency of such buildings are the main factors in the reported efficiency.     

Defects and moisture problems in buildings from historical city centres: a case study in Portugal

Conservation of ancient buildings is a major issue for modern societies, both from economical and cultural viewpoints. Information about the ancient built heritage is vital to plan adequate remedial measures. Taking a historic centre in Portugal as a case study, this paper presents an extensive survey of building typology and materials, damage in the building envelope, indoor survey of damage, and measurements in indoor air temperature and relative humidity. Water-related problems can be confirmed as the single most important defect combined with inadequate sun exposure, ventilation and heating, and excessive moisture indoor production. Extremely low temperatures, high humidity and presence of mould therefore, compromise the indoor quality of life of the inhabitants; and make urgent repair at many levels necessary.     

建筑气密性对被动房室内温度的影响

简要介绍了气密性评价方式与被动房标准。从被动房的角度出发,建立了建筑模型,利用TRNSYS软件分析了在不采取供暖和制冷措施的情况下,3种不同围护结构工况下气密性的改变对室内温度影响。结果表明,在冬季,室内温度的升高趋势随气密性改善而递增;在夏季,不开窗时,气密性性能提高会提升室内温度,降低舒适度;采取夜间通风策略后,气密性对室内温度基本无影响。