Application of night cooling concept to social housing design in dry hot climate

A passive night cooling system was developed and implemented for a new project of social housing. The passive cooling system incorporates a solar chimney in combination with high thermal mass in the building construction. The natural ventilation is enhanced with the help of the solar chimney and night fresh air cools the building structure. The design of this concept was calculated by balancing energy using basic thermal equations for a summer reference day and evaluated using two simulation tools, TRNSYS and TAS. The building has been constructed and actually in process of monitoring.     

Enhancement of natural ventilation in buildings using a thermal chimney

A new module was developed for and implemented in the EnergyPlus program for the simulation and determination of the energy impact of thermal chimneys. This paper describes the basic concepts, assumptions, and algorithms implemented into the EnergyPlus program to predict the performance of a thermal chimney. Using the new module, the effects of the chimney height, solar absorptance of the absorber wall, solar transmittance of the glass cover and the air gap width are investigated under various conditions. Chimney height, solar absorptance and solar transmittance turned out to have more influence on the ventilation enhancement than the air gap width. The potential energy impacts of a thermal chimney under three different climate conditions are also investigated. It turned out that significant building cooling energy saving can be achieved by properly employing thermal chimneys and that they have more potential for cooling than for heating. In addition, the performance of a thermal chimney was heavily dependent on the climate of the location.     

A numerical study of daytime passive radiative coolers for space cooling in buildings

A passive daytime radiative cooler is made of a sky facing surface which can preserve the indoor air temperature below ambient without energy consumption by simultaneously reflecting solar radiation and emitting thermal radiation to the universe through the atmospheric window located between 8–13 μm of the electromagnetic spectrum. After the first demonstration of radiative cooling under direct sunlight, a solar mirror coated with a mid-infrared (MIR) emissive thin film has become the standard device architecture. This study firstly reviews recent developments in daytime passive radiative cooling, followed by describing the development of an energy balance mathematical model to study the potential application of passive radiative coolers in HVAC systems of buildings. Some micro-channels are fabricated on the back side of the passive radiative cooler, allowing fluid to flow in an isolated loop such that the coolant can be chilled and transported to the demand side for spacing cooling. This leads to the partial replacement of conventional vapor compression refrigeration by the radiative cooling panel. Considering the steady state energy balance within the radiative cooling panel integrated HVAC systems, the cooling performance and indoor air temperature are evaluated by numerical analysis. A 100 m2 passive radiative cooling panel could chill water for the cooling of air, reducing indoor air temperature by 10 °C, equivalent to a net cooling power of 1600 W. This study suggests that the proposed passive radiative cooling system should be used to pre-cool the ambient hot air such that the overall energy consumption of a traditional air-conditioning system can be reduced. The findings promise the application of passive daytime radiative cooling in building HVAC systems.     

Application of passive cooling systems in the hot and humid climate: The case study of solar chimney and wetted roof in Thailand

The thermal performance of two passive cooling systems under hot and humid climate condition is experimentally investigated. The experimental results were obtained from a test cell and a controlled cell with identical walls but different roof configurations. The passive cooling systems applied to the test cell are solar chimney and water spraying on roof. The experimental results obtained from the test cell are compared with the closed and no passive cooling controlled cell. In addition, the significant of solar-induced ventilation by using a solar chimney is realized by utilizing a wind shield to reduce the effect of wind-induced ventilation resulting in low measured air velocities to the solar chimney and low computed value of coefficient of discharge. The derived coefficient of discharge of 0.4 is used to compute Air Changes rates per Hour (ACH). The ACHs with application of solar chimney solely are found to be in the range of 0.16–1.98. The studies of air temperature differences between the room and the solar chimney suggest amount of air flow rates for different periods in a year. The derived relationships show that the air flow rate during February–March is higher than during June–October by 16.7–53.7%. The experimental results show that application of the solar chimney in the test cell could maintain the room temperature at 31.0–36.5 °C, accounting for 1.0–3.5 °C lower than the ambient air and 1.0–1.3 °C lower than the controlled cell. However, to make the test cell's room temperature much lower than the ambient temperature and increase the flow rate of air due to the buoyancy, the application of water spraying on roof is recommended together with solar chimney. The application of the two systems in the hot and humid climate are discovered to sustain the room temperature of the test cell to be lower than the ambient air by 2.0–6.2 °C and lower than the controlled cell by 1.4–3.0 °C.     

拉萨市直接受益式太阳房居住建筑被动式设计优化研究

随着社会经济的进步和人民生活水平的不断提高,拉萨市的建筑规模和建筑能耗都有了大规模的提高。通过两次冬季现场调研,拉萨市现有集合式居住建筑的室内温度分布,室内热环境评价等现有建筑的室内热环境特点被测试分析。结果表明:拉萨市现有居住建筑大多自发采用直接受益式太阳能利用系统,但其冬季室内热环境仍然普遍不理想。考虑到拉萨市已经被列为采暖区,当地的冬季采暖能耗面临巨大增幅的可能。以拉萨市最常见的直接受益式居住建筑为基础,建立热环境模拟模型,通过模拟软件分析了影响室内热环境的各项被动式设计基本要素。最终结果给当地的居住建筑设计工作提供了合理建议。     

Physical and numerical modelling of a solar chimney-based ventilation system for buildings

This paper describes an experimental and numerical study to analyse the thermal performance of a bio-climatic building prototype in Nigeria. The roof performs as a solar chimney, generating an air flow through the living space of the building to provide cooling. Experimental tests on a 1:12 small-scale model of the prototype are outlined, and the results, bith qualitative and quatitative, are used to validate a two-dimensional flow simulation model, in which the steady state conservation equations of mass, momentum and thermal energy are solved using a finite volume formulation.

The experimental and numerical results, expressed in terms of temperature and velocity fields, for two different window geometries are critically evaluated and compared with good agreement.     

Organismes members du CIB La Nouvelle‐Zélande

Introducing a feature on the controlled storage and release of energy; especially captured solar energy; this article describes a design for a curtain wall which will provide seasonal heating and cooling in a passive solar building. It is being tested at the EEC Commission's Joint Research Centre at Ispra, Northern Italy: The principles and techniques employed in this phase-change concept produce a module which can collect, store and release solar heat at around 20 °C with forced air circulation. It is dimensioned to meet the daily energy demand for air conditioning during the summer and most of the heating demand in the winter.     

山地住宅被动式致凉策略初探

“凉”是一种人体对环境的感觉描述。被动式致凉即指通过自然通风、遮阳体系等不依赖能源和设备的低技方式使人获得凉爽体感的致凉策略。山地作为人类的居住场所有着悠久的历史,山地居住建筑在于环境的不断互动中形成了自身独特的形式。本文希望通过结合山地住宅的自身特点,针对山地的地形特征和气候特征提出与之适应的被动式致凉策略。主要包括通风致凉、遮阳致凉、绿化致凉和水体致凉四个方面。     

浅论建筑学专业的风景园林教育

文章从建筑学专业特点人手,分析了建筑学和风景园林学的关系,强调了在建筑学专业开展风景园林教育的意义,明确了风景园林教育在建筑学专业中的角色定位,提出了针对建筑学专业学生开展风景园林教育的课程内容设置和教学策略。     

Solar chimney—A passive strategy for natural ventilation

Passive ventilation systems are being increasingly proposed as an alternate to mechanical ventilation systems because of their potential benefits in terms of operational cost, energy requirement and carbon dioxide emission. Solar chimney is an excellent passive ventilation system which relies on natural driving force, that is, the energy from the sun. A significant amount of research work has been done on solar chimney since the 1990s. This article presents an overview of solar chimney research that has taken place in the last two decades. The review focuses on two main areas of research - the effects of geometry and inclination angle on the ventilation performance of a solar chimney. The experimental investigations of solar chimney have dominated the existing literature. However, numerical modelling of solar chimney using computational fluid dynamics (CFD) technique has attracted increasing attention. Moreover, this review found that solar chimney as a passive ventilation strategy has not been fully understood.     

Solar thermal modelling of a building with a roof pond and ventilation control systems

The paper proposes and presents thermal modelling of a ventilation-controlled, non-air-conditioned building with evaporative cooling (e.g. open water pond) over the roof for passive solar air conditioning. The ventilation rate, expressed in terms of number of air changes per hour, is assumed to be time-dependent, as should be the case in normal practice. A self-consistent periodic heat transfer analysis for a non-air-conditioned building with roof cooling and ventilation control systems, furnishing (assumed isothermal mass), windows, door and basement ground heat storage effects has been developed to assess the feasibility of the proposed passive space air-conditioning. It is shown that for no-ventilation summer nights the inside air temperature remains higher than the ambient air temperature even with an effective roof cooling system, and hence the windows should be opened to lose the internal heat and to introduce cool and fresh outside air. It is found that for a ventilation-controlled building with a roof pond the passive solar air conditioning can be achieved more effectively.     

各气候区被动建筑节能技术适用性分析

被动式建筑节能,是通过利用自然气候资源的生态建筑设计原理,赋予建筑本身节能自然特性而实现的建筑节能,因而更为绿色环保,更有利于人类生存环境的可持续发展,成为建筑节能积极倡导的方向。针对中国各气候区典型城市的气候特点进行被动式太阳采暖、自然通风、蓄热墙体、诱导+夜间通风、直接蒸发冷却和间接蒸发冷度这六种被动式建筑节能技术适用性进行分析,并对各气候区的各种被动式建筑节能技术的适用性进行对比。     

Investigation on energy performance and energy payback period of application of balcony for residential apartment in Hong Kong

The provision of balcony to the living room of a residential flat offers a number of merits including improved view enjoyment, enhanced ventilation and increased planting space. In addition, a balcony can act as an overhang and provide solar shading as well as electricity saving of the air-conditioning system. This paper reports the findings on the energy and environmental impact due to the provision of a balcony. In this study, a typical residential flat with balcony constructed at the living room was modeled and the energy performance was investigated with the use of the typical weather data set of a subtropical city, Hong Kong. The effects of balcony's orientation and glazing material of window were also evaluated. It was found that the residential flats facing various orientations (N, E, S, W, NE, SE, SW and NW) can offer substantial energy saving in air-conditioning system due to the shading effect of balcony. The building case with southwest facing balcony and clear glass glazed window gave the highest saving percentage of 12.3% in annual air-conditioning consumption. In terms of cost payback period, the values were estimated as 25.9 years (based on extra construction cost of a balcony) and over 100 years (based on extra purchasing cost), respectively. On the other hand, the energy payback period was 22.4 years for this building case. The provision of balcony to the living room of residential flat was found environmentally feasible in Hong Kong.     

Using passive cooling strategies to improve thermal performance and reduce energy consumption of residential buildings in U.A.E. buildings

Passive design responds to local climate and site conditions in order to maximise the comfort and health of building users while minimising energy use. The key to designing a passive building is to take best advantage of the local climate. Passive cooling refers to any technologies or design features adopted to reduce the temperature of buildings without the need for power consumption. Consequently, the aim of this study is to test the usefulness of applying selected passive cooling strategies to improve thermal performance and to reduce energy consumption of residential buildings in hot arid climate settings, namely Dubai, United Arab Emirates. One case building was selected and eight passive cooling strategies were applied. Energy simulation software – namely IES – was used to assess the performance of the building. Solar shading performance was also assessed using Sun Cast Analysis, as a part of the IES software. Energy reduction was achieved due to both the harnessing of natural ventilation and the minimising of heat gain in line with applying good shading devices alongside the use of double glazing. Additionally, green roofing proved its potential by acting as an effective roof insulation. The study revealed several significant findings including that the total annual energy consumption of a residential building in Dubai may be reduced by up to 23.6% when a building uses passive cooling strategies.     

On the efficiency of night ventilation techniques applied to residential buildings

Climatic change and heat island effect in combination with the non-proper design of buildings have increased substantially the cooling load of buildings. Night ventilation appears to be one of the more promising passive cooling techniques. Many important theoretical and experimental studies have been performed however the existing information is presented in a segmented way. The present paper analyses energy data from two hundred fourteen air conditioned residential buildings using night ventilation techniques. The specific absolute energy contribution of night ventilation has been calculated. The relation of the cooling demand of the buildings with the specific contribution of night ventilation has been investigated. It is found that the higher the cooling demand of the building, the higher the potential contribution of night ventilation under specific boundary conditions. The role of air flow rate is investigated as well. It is found that the global utilisability of the energy stored during the night increases as a function of the air flow rate and the tilt of the regression line between the energy contribution and the air flow rate increases significantly with the air flow rate applied, although the energy contribution per unit of air flow is decreasing. The whole analysis contributes towards a better understanding and evaluation of the expected energy contribution of night cooling techniques.     

A passive evaporative cooling system by natural ventilation

Evaporative cooling is used extensively for cooling in climates with medium to low humidity. In residential buildings the conventional mechanical systems tend to be both noisy and unsightly protuberances on buildings, whilst traditional cooling systems incorporated into the building structure which employ chimneys and the like tend to be designed for the specific building and so may not have wide application. Here a proposal is presented for a passive evaporative cooling system which makes use of natural ventilation at the building facade. The system makes use of the evaporative effect from water falling vertically along guides to produce a reduction in the temperature of the air entering the building. It can also be used as a design element in the building facade. Such a system provides an inexpensive, energy efficient, environmentally benign (not requiring ozone-damaging gas as in active systems) and potentially attractive cooling system.

A numerical study is presented to demonstrate the system efficiency and airflow rate through a building, making use of measured outside wind speed and direction, building geometry and surroundings. The likely effect of the system on the indoor air temperature is discussed; further work is being undertaken to explore the integration of such a system into the building fabric.     

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.     

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。     

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。     

A simple procedure to size active solar heating schemes for low-energy building design

The energy consumption of a building depends on the thermal demand and on the mean performance of the system. Apart from passive solar indoor climate control techniques, it is also possible to reduce conventional energy consumption of a building, even bringing it close to zero by installing solar heating. Hence, better knowledge of these techniques and of how they can be implemented in a simple but effective way will further progress towards more energy efficient buildings.