Enhancement of ventilation performance of a residential split-system air-conditioning unit

The design of ventilation performance of air-conditioning systems in large commercial and office buildings is quite established. However, it is not the same with the designs of air-conditioning systems in most residential buildings. Split system air-conditioning units are commonly employed in residential buildings in the tropics due to their convenience in terms of energy conservation, aesthetics, flexibility, acoustic performance and ease of operation. Such units are also popular among small offices, shopping complex and even as supplementary air-conditioning units beyond normal office-hours in large commercial and office buildings. This paper presents findings from a recent study of the ventilation performance and indoor air quality (IAQ) in a master bed room of a condominium unit in Singapore, employed with a split system air-conditioning unit. The attached bathroom is equipped with an exhaust fan, whose operation and its impact on the resulting ventilation characteristics was also studied. Four adults occupied the room throughout the course of the experiments. It was observed that the carbon dioxide level in the bed room can exceed 2000 ppm without the exhaust fan in about 2 h. The operation of the exhaust fan quickly lowered the level of carbon dioxide to about 1000 ppm. The findings suggest the need to design for ventilation provision in split system air-conditioning units.     

A study of the effectiveness of passive climate control in naturally ventilated residential buildings in Singapore

Singapore has the hot and humid climate throughout the year. Many passive climate control methods are adopted in the naturally ventilated residential buildings to help achieve thermal comfort and reduce the energy consumption of air-conditioning. A field measurement and computational energy simulations were conducted to examine the effectiveness of commonly used passive climate control methods for these buildings. The effect of building orientation, façade construction, special roof system and window shading device on indoor thermal environment and cooling load was studied. The surface temperature of external wall and indoor thermal environment was measured to analyze the façade thermal performance. The cooling load was simulated to evaluate the effectiveness of various passive climate methods. Using the special roof system as thermal buffer is the most efficient method to reduce the room cooling load.     

Benchmarking Hong Kong and China energy codes for residential buildings

Mandatory energy codes to curb energy use of residential buildings have been formally launched in China for more than two decades but little has been publicized in literature. Similar codes are not available for residential buildings in Hong Kong, but most residential buildings in Hong Kong, especially public housing estates, are HK-BEAM certified to demonstrate their compliance with regulatory and basic design requirements. Given HK-BEAM is internationally recognized and there are doubts about the effectiveness of the China codes, how the energy efficiency of the HK-BEAM certified buildings compare with buildings in compliance with the China codes is of interest to most building designers and policy makers. This paper describes how the energy efficiency of a case study building in compliance with the China codes compare with the one in compliance with HK-BEAM. The energy simulation by HTB2 and BECRES reveal that the case study building in compliance with the China codes is 51.1% better in energy use. In the study, the relative impact of each compliance criterion on energy use and cooling load has been quantified by sensitivity analysis. The sensitivity values indicate that energy use is most sensitive to air-conditioning operation hours, indoor design temperature, coefficient of performance (COP) of the room air-conditioners (RAC) units, and the envelop characteristics. The results of this study indicate that a HK-BEAM certified building cannot satisfy the China codes requirements. This provides good reference to the policy makers, the building owners, and to the China and Hong Kong Governments when considering reciprocal recognition of building energy codes.     

The impact of air filter pressure drop on the performance of typical air-conditioning systems

Filters are used in heating, ventilation, and air-conditioning (HVAC) systems for both commercial and residential buildings to protect the equipment and improve indoor air quality in conditioned spaces. Although there are many benefits of using the air filter in an air-conditioning system, the resistance associated with it can increase fan energy use and may adversely affect air-conditioning system performance and efficiency. The paper explores the impact of air filtration on energy consumption for a typical air-conditioning (AC) system with constant- or variable-speed fan. A whole building simulation model is used to simulate the annual energy consumption for various air-conditioning system capacities, different levels of filter cleanliness, and various filter minimum efficiency reporting values (MERV). The results indicate that with a constant-speed fan, the cooling energy use increases as the filter gets dirty over time and the energy use in the fan may increase but this depends heavily on the investigated fan performance curve. With a variable-speed fan, the fan energy use increases with a dirty filter but the cooling and heating energy uses are slightly affected. The fan energy use rise due to the dirty filter depends mainly on air system capacities, filter MERV ratings, and the degree of the filter cleanliness.     

辐射供冷空调系统间歇运行启动阶段特性分析

针对南京某住宅房间的毛细管辐射供冷空调系统,研究房间空调系统在间歇运行情况下启动段的特性,探究室内空气预理模式、毛细管辐射面积、送风量对室内温湿度的动态影响规律。研究结果表明,基于连续运行模式下的设备设计容量不能满足间歇运行的要求,需要增大辐射毛细管和新风机的处理能力。采用新风机内循环和新风2种运行模式,可有效缩短间歇运行启动阶段时长。增加新风机送风量可减少预处理时间,通过改变毛细管的辐射面积和新风机的送风量可以满足夏热冬冷地区居住建筑间歇运行的需求,为后期设计同类型的建筑提供新的思路。     

长沙市居住建筑能耗调查及偏相关分析

对长沙市70户具有代表性住户的居住建筑概况、生活方式、对热环境的评价及能耗情况进行了调查统计,采用SPSS统计分析软件对长沙市居住建筑能耗的影响因素进行了分析。长沙市居住建筑能耗具有明显的季节性,上一年12月至2月和6月至8月是能耗的高峰期。偏相关分析表明居住建筑总能耗、单位建筑面积能耗与家庭年收入、家庭常住人口密切相关,与建筑面积、建筑总层数、住户所在楼层、建筑朝向、供暖方式、空调方式不显著相关。     

上海世博园部分建筑室内空调环境状况测试分析

为了了解上海世博园建筑室内空调环境状况和行为节能情况,采用实测方法对上海世博园13栋建筑的夏季室内空调环境进行了测试分析。结果表明:一些被测建筑的夏季室内空气温度偏低,最低室温为21.7℃;对于南方湿热地区的剧场建筑,采用开敞式建筑方案不利于室内热舒适环境的营造和节能,且仅利用自然通风和蒸发冷却降温手段难以营造出满足人体基本热舒适性要求的室内环境;展厅观众人数快速增加时室温变化较大,但相对湿度变化较小;一些展馆外门常开,冷风渗漏现象比较严重,加强行为节能是展馆建筑节能设计和运行管理需要考虑的一个重要问题。     

Field experiments on natural energy utilization in a residential house with a double skin façade system

Energy consumption in the residential and commercial sector accounts for over 25% of the total in Japan. With the information technology revolution and the improving requirement for indoor air environment, energy consumption for household air conditioning is increasing. In this research, a double skin facade is proposed for a two-story house in Kitakyushu of Japan. The stack effect in the double skin space during the summer, the green house effect during the winter and the availability for free air-conditioning during the autumn have been studied. The temperature distribution, thermal performance in the double skin space and its impact on air-conditioning load in rooms have been measured. Results show that the double skin façade leads to about 10–15% energy saving for cooling in the peak of summer because of heat exhausted by natural ventilation, 20–30% energy for heating in winter because of the green house effect, and the temperature adjustment is quite large with the different operation mode of the double skin system during the intermediate seasons. Therefore the double skin system is proved to be effective in energy conservation in residential buildings.     

Estimating the effect of using cool coatings on energy loads and thermal comfort in residential buildings in various climatic conditions

The impact from using cool roof coatings on the cooling and heating loads and the indoor thermal comfort conditions of residential buildings for various climatic conditions is estimated. The energy cooling loads and peak cooling demands are estimated for different values of roof solar reflectance and roof U-value. The results show that increasing the roof solar reflectance reduces cooling loads by 18–93% and peak cooling demand in air-conditioned buildings by 11–27%. The indoor thermal comfort conditions were improved by decreasing the hours of discomfort by 9–100% and the maximum temperatures in non air-conditioned residential buildings by 1.2–3.3 °C. These reductions were found to be more important for poorly or non-insulated buildings. For the locations studied, the heating penalty (0.2–17 kWh/m² year) was less important than the cooling load reduction (9–48 kWh/m² year). The application of cool roof coatings is an effective, minimal cost and easy to use technique that contributes to the energy efficiency and the thermal comfort of buildings.     

空调系统和组合通风系统的联合应用

近年来,各种新型的室内装饰材料使室内空气中有害气体的种类和含量都有所增加,为使用者创造一个健康的、良好的室内空气环境是设计人员的首要任务。但目前室内所采用的空调系统大都不能满足要求,本文介绍一种能够改善住宅室内空气品质的系统——空调系统和组合通风系统联合运行的系统,并采用实验和仿真相结合的方法对其进行了初步分析,对该系统在我国民用建筑中推广应用具有一定的参考价值。     

既有建筑空调系统节能措施探讨

指出空调系统节能在建筑节能中的重要性,介绍了既有建筑空调系统常用节能技术措施、原理、特点及实施方法,并简单分析其各自特点及适用场所,对不同的建筑应根据其空调系统特点采取不同的节能措施.     

Influence of household air-conditioning use modes on the energy performance of residential district cooling systems

During technical evaluations of cooling systems in residential buildings, it is necessary to consider the influence of the household air-conditioning (AC) use modes. In other words, how the occupants control the AC, for instance, when it is turned on, what the temperature setting is, and how long it is used. Field measurements and spot interviews indicate that AC usage by residents should be environmental, event and random related. A reduced-order AC conditional probability (CP) model was developed in this study to describe AC usage. The AC CP model was integrated with a building energy modeling program (BEMP) to reflect the interaction of the AC operation and the indoor environment. With consideration of stochastic AC use modes, the uncertainty of user compositions was studied. Additionally, simulation results revealed that AC use modes and user compositions can cause up to a 4.5-fold difference in the system efficiency of district cooling systems. The Lorenz curve and Gini coefficient were applied in this study to describe the load distribution in a quantitative manner. Through a comparison with the constant schedule definition model, the study also identified inclusion of the stochastic feature of AC use modes and their compositions in simulations as being important to the technical evaluation of district cooling systems.     

住宅建筑能耗评估与能效标识制度及其运行机制的研究

住宅建筑节能对我国社会可持续发展具有重要意义,本文在分析我国住宅建筑节能管理现状的基础上,设计了符合我国国情的住宅建筑能耗评估、能效标识制度及其运行机制,同时提出政府应利用财政、税收等经济杠杆对不同利益主体实施激励,并积极培育节能住宅中介评价机构。     

上海高层住宅夏季室内热环境研究

为了研究上海高层住宅夏季室内热环境,达到优化上海高层住宅节能设计的目的,对上海高层住宅进行了夏季问卷调查和现场测试,通过对测试结果和问卷结果的分析,显示了上海高层住宅室内热环境在不同楼层之间存在一定差异,整体来说夏季室内热环境相对恶劣,但上海居民对夏季室内炎热环境具有一定的适应性。     

上海某住宅建筑围护结构能耗模拟与节能性分析

本文在对长江流域气候和住宅建筑能耗特点及嗣护结构保温隔热措施适应性的分析基础上,以上海某节能住宅小区内建筑为例,采用DeST软件对其典型住宅楼进行了能耗模拟,比较了不同围护结构保温隔热方式对采暖、空调及全年总能耗的节能率的影响,最终得到最适用于上海地区的围护结构节能措施,为夏热冬冷地区住宅建筑的节能设计方案提供依据。     

Presence and variability of culturable bioaerosols in three multi-family apartment buildings with different ventilation systems in the Northeastern US

Bioaerosol concentrations in residential buildings located in the Northeastern US have not been widely studied. Here, in 2011-2015, we studied the presence and seasonal variability of culturable fungi and bacteria in three multi-family apartment buildings and correlated the bioaerosol concentrations with building ventilation system types and environmental parameters. A total of 409 indoor and 86 outdoor samples were taken. Eighty-five percent of investigated apartments had indoor-outdoor (I/O) ratios of culturable fungi below 1, suggesting minimal indoor sources of fungi. In contrast, 56% of the apartments had I/O ratios for culturable bacteria above 1, indicating the prominence of indoor sources of bacteria. Culturable fungi I/O ratios in apartments serviced by central heating, ventilation, and air-conditioning (HVAC) system were lower than those in apartments with window AC. The type of ventilation system did not have a significant effect on the presence of indoor culturable bacteria. A significant positive association was determined between indoor dew point (DP) levels and indoor culturable fungi (P < .001) and bacteria (P < .001), regardless of ventilation type. Also, residents in apartments with central HVAC did not experience extreme DP values. We conclude that building ventilation systems, seasonality, and indoor sources are major factors affecting indoor bioaerosol levels in residential buildings.     

室内设计温度对夏热冬冷地区新风冷热耗量的影响

针对夏热冬冷地区住宅热环境特点，提出了节能住宅空调期、除湿期和供暖期的确定方法，分别建立了其新风冷热耗量的计算程序。计算了该地区主要城市的新风冷热耗量，重点分析了不同设定温度对新风耗冷量的影响，揭示了降低新风耗冷量的途径。     

Predicting air-conditioning energy consumption of a group of buildings using different heat rejection methods

Water-cooled air-conditioning systems (WACS) are, in general, more energy efficient than air-cooled air-conditioning systems (AACS). The Laws of Hong Kong prohibit the use of fresh water from town mains for comfort air-conditioning, which rules out the use of cooling towers to most air-conditioned buildings. In the absence of lakes or major rivers in Hong Kong, only those buildings that are situated near the harbor can adopt WACS. As a measure to cut down greenhouse gases emissions, the Hong Kong Government is currently exploring the feasibility and viability of widening the use of WACS by the provision of centralized, district-wide water supply systems, which include seawater supply systems for once-through condenser cooling or for making up of water losses at cooling towers, and district cooling systems. Evaluation of the likely energy, economic and environmental benefits of such capital-intensive infrastructure developments requires estimation of the simultaneous cooling demand of a large group of buildings on a district scale, and the energy use for air-conditioning such buildings. This paper describes the method used in these estimations. Comparisons of the results estimated by this method with results obtained by detailed simulation, and with building energy use data obtained from surveys and audits are presented.     

污水热泵在城市生活小区的应用

从就近利用小区污水冷热能的角度出发,对重庆市主城区某居住小区生活污水的温度和流量进行了测试分析,提出了小区污水热泵系统应用于建筑空调、供暖和卫生热水供应的综合节能系统模式;调研了小区生化池内污水温度分布,分析了小区污水逐时流量及逐月流量的变化,讨论了小区污水所能提供的冷量与建筑实际需要冷负荷的匹配关系,提出了生活小区污水热泵系统与常规冷热供应系统的复合式冷热供应方案。     

北京市某住宅楼夏季空调能耗调查分析

对北京市1栋普通住宅楼夏季空调能耗进行逐周调查分析,结果表明,目前北京市住宅空调器装得多、用得少,平均能耗水平较低,并且各住户空调能耗的差异很大、集中度很高,20%的空调能耗大户消耗了全楼约70%的空调能量。该楼空调能耗分布的基尼系数为0.64,因此空调运行模式是影响住宅空调能耗的最重要因素,住宅空调行为节能的潜力和“耗能”潜力均很大。