Energy simulation of vertical greenery systems

The objective of this research is to simulate the effects of vertical greenery systems on the temperature and energy consumption of buildings. Firstly, it involves performing TAS simulations to determine their effects on thermal comfort and energy consumption. It is found that 100% greenery coverage from vertical greenery systems is effective in lowering the mean radiant temperature of a glass facade building. Furthermore, to lower the energy cooling load significantly, the shading coefficient of plant species has to be low. Secondly, a thermal calculation of the envelope thermal transfer value (ETTV) to obtain their effects on the thermal performance of building envelope is performed. Results show a linear correlation between shading coefficient and leaf area index where a lower shading coefficient leads to a greater thermal insulation. 50% greenery coverage from vertical greenery systems and a shading coefficient of 0.041 reduce the ETTV of a glass facade building by 40.68%. Lastly, vertical greenery systems in mitigating the UHI effect within an estate is simulated using STEVE model. The increase of greenery coverage from vertical greenery systems is most significantly felt with a drop in the minimum estate air temperature throughout a large region of the estate.     

一种自然通风办公建筑主动式立面的环境评价

主动式立面经常在建筑中应用以促进建筑通风,为了保证这个过程的有效性,主动式立面必须朝南,然而这样,太阳辐射就会穿过玻璃直射室内,夏热季节则需要借助遮阳设施来遮挡,这可能会导致室内采光达不到标准。另一方面,采用主动式立面的建筑倾向于提高蓄热性能来强化夜间蓄冷效果,结果可能导致声回响时间延长,干扰人的工作。本文对采用主动式立面的办公建筑室内光、声和热环境性能进行测试评价,初步分析结果表明,主动式立面的优点是能够通过被动方式利用太阳能,提供高质量的工作环境,而如何确保空气流动路径通畅,以及如何采取相应措施减少声回响时间值得关注。     

Simulation of ventilated facades in hot and humid climates

The Hong Kong climate is sub-tropical with hot and humid weather from May to September and temperate climate for the remaining 7 months period. A mechanical ventilation and air-conditioning (MVAC) system is usually operated to avoid the high temperatures resulting in high peak cooling loads. The facade design has a significant influence on the energy performance of office buildings. This work evaluates different ventilated facade designs in respect to energy savings.Thermal building simulations (TRNSYS) were linked to nodal airflow network simulations (COMIS) for detailed ventilated double-skin facade performance. In order to validate the model, simulations were carried out for an office building in Lisboa; the results were compared with measured data from the same building. The simulation results of surface and air temperatures show good agreement with the measurements. The results of the study can be used to reduce surface temperatures by using different materials for the roller blind that is positioned in the cavity of the double-skin facade. The results can further be used to reduce the high peak cooling loads during the summer period. This may result in significant energy savings and a reduction in the system's cooling capacity. It proved that a careful facade design can play an important role in highly glazed buildings and provides potential for energy efficiency.     

蒸发冷却式空调在我国南方地区的应用分析

以广州某3层建筑为例,采用动态模拟方法,详细计算分析了其采用蒸发冷却式空调的可行性和使用蒸发冷却式空调后的节能效果.结果显示,在类似于广州的我国南方地区,可以采用间接利用蒸发冷却式技术的蒸发冷却空调集成系统.     

深圳大梅沙万科集团总部

对于生态节能的重视使得客户要求对所建项目有最合理的安排，因此在万利总部的项目上，建筑师们希望通过设计，尽可能的表现出他们的创意，可信任度与持久性太阳能板，蒸发冷却，自然通风等技术处理都融入建筑设计之中，双层立面以及竹质与玻璃材质的运用，都体现了生态建筑的设计理念，整个建筑物被提高到5m以上的层面，并设置了不同的入口，这种设计方式不仅为建筑本身带来轻盈的感觉，     

蒸发冷却空调新风系统的全年应用研究

结合干热、严寒或寒冷地区全年气候特点及冬夏季建筑能耗特性,通过逐时新风能耗模拟计算,得到设置热回收装置的全年用蒸发冷却空调系统冬季新风节能量远大于夏季节能量,选用热回收装置时应重点关注冬季热回收效率,各类热回收装置中转轮热回收装置全年节能量最大,节能效果最好。基于此,深入分析了蒸发冷却空调系统冬夏季新风加湿需求、新风量变化范围和水系统管径选择,给出了全年用蒸发冷却空调机组冬季运行的防冻措施。     

On-site experimental testing of a novel dew point evaporative cooler

Technologies which utilise the advantages of evaporative cooling to reduce the temperature of air without the addition of moisture have existed for some time. These systems use a heat exchange media between the evaporation of water process and cooling of air. Research has been conducted on a number of systems utilising these technologies in various configurations and it has been demonstrated that temperatures of the incoming air can approach its dew point temperature. This is considerably lower than the wet bulb temperature which is the limit achieved with conventional direct evaporative cooling systems. Prototypes have been built to demonstrate the principles and temperatures achievable, but the technology has never been developed due to its high cost and complexity. These disadvantages have been addressed in a newly developed indirect evaporative cooler. The paper presents results obtained from testing a prototype cooler installed in both a commercial and residential application in a wide range of ambient conditions. The performance characteristic of the indirect evaporative cooler in regards to its outlet temperatures and electrical energy efficiency is presented.     

上海地区双层垂直绿化办公建筑实测研究

本文通过实测,研究了夏季工况下双层垂直绿化对上海地区办公建筑热工环境的影响。实验结果表明,带有双层垂直绿化的办公室室内空气温度较普通房间平均降低了1.5℃,外墙外表面温度平均降低了1.3℃,双层垂直绿化可以有效改善上海地区办公建筑夏季热环境。本文通过实测探索了双层垂直绿化应用于办公建筑的节能潜力,并对双层垂直绿化植被选择、种植方式给出建议。     

Energy savings in a building using regenerative evaporative cooling

This paper explores the potential of reducing the annual energy consumption of a central air-conditioned building through advanced evaporative cooling systems. The building considered is a typical three floor library building of a University. The regenerative evaporative cooling technology is coupled with the liquid cooled water chiller system to accomplish the energy conservation objective. Comparisons of the regenerative evaporative cooling are made with simple evaporative cooling to bring out the importance such a system. The well-known building simulation software, TRNSYS is used to carry out the heat load calculations and the dynamic simulations of the building. Annual energy consumptions of different components of the air-conditioning system are estimated for the existing water chiller system as well as for both coupled evaporative cooling systems (simple and regenerative). The annual energy consumptions, the indoor temperature, the relative humidity and the thermal comfort index ‘PMV’ are compared for all the three different air-conditioning systems. The coupling of direct and regenerative evaporative cooling technologies with water chiller system has shown, respectively, 12.09% and 15.69% savings in annual energy consumption of the building, while maintaining PMV between ?1 and +1 for most of the hours in the year.     

Estimation of heat rejection based on the air conditioner use time and its mitigation from buildings in Taipei City

The main work in the research focuses on the analysis and mitigation of the anthropogenic heat discharged from buildings, which is one of the main reasons leading to the heat island effect. The residential and commercial buildings, divided into 10 categories, with HVAC systems were analyzed by the building energy program, EnergyPlus. With the help of GIS, the heat rejection of all the residential and commercial buildings in DaAn Ward of Taipei City were evaluated, in which the spatial data and diurnal variation of the heat rejection were described by 3-h time periods. Furthermore, the effect of mitigation strategies was discussed. The first strategy was to change the wall/roof material of building envelope. The second and third strategies, from the viewpoint of energy saving, were to change the temperature setting of air conditioners and to turn off the lighting and equipment when not in use. The fourth strategy was to use a better efficiency of the cooling systems. Finally, the evaluation of installing the water-cooled cooling system, which discharges heat in the form of sensible and latent heat, was also included.     

Influence of building parameters and HVAC systems coupling on building energy performance

The performance of different HVAC systems varies when coupled with different buildings. This paper examines the relationship between building heating and cooling load and subsequent energy consumption with different HVAC systems. Two common HVAC systems in use throughout the UK office building stock, variable air volume (VAV) system and fan coil (FC) with dedicated outside air system, have been coupled with a typical narrow plan office building with and without daylight control and for both cellular and open plan.The results presented in this paper clearly indicate that it is not possible to form a reliable judgment about building energy performance based only on building heating and cooling loads. For the two investigated systems, variable air volume system and fan coil with dedicated outside air system, the difference between system demand and building demand varied from over −40% to almost +30% for cooling and between −20% and +15% for heating. If a heat recovery unit is used, the difference in heating performance is even greater, rising to −70%.     

Thermal performance of a non-air-conditioned building for passive solar air-conditioning: Evaluation of roof cooling systems

A periodic heat transfer analysis has been presented to predict the dynamic thermal behaviour of a non-air-conditioned building with evaporative cooling systems over the roof. Three different cases of evaporative cooling systems, namely, open roof pond, moving water layer over the roof, and water spray over the roof, have been studied in detail to assess their effectiveness for passive space air-conditioning. The effects of air ventilation, furnishings and ground heat conduction have been incorporated in the present analysis. Numerical computations using typical data of a harsh summer day in the Delhi climate, have been made to assess the analytical results quantitatively.It was found that the maximum cooling is achieved by water spray over the roof. However, the roof pond system with stationary water is more effective in stabilizing the fluctuations of indoor temperature as well as heat flux entering through the roof. Furthermore, with the increase in the number of air changes per hour, the time variation of indoor air approaches to that of outdoor air in phase as well as in magnitude.     

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.     

再循环蒸发冷却技术及其应用

基于直接蒸发冷却和间接蒸发冷却方法,提出了一种再循环蒸发冷却方法。设计了一套再循环蒸发冷却装置,并通过试验测试了它的冷却效果。对再循环蒸发冷却技术在空调行业的应用进行了具体分析,提出了相应的系统应用设计方法。最后指出这种技术为开发节能环保空调设备和空调系统提供了一个新的途径。     

外呼吸双层通风玻璃幕墙热工性能模拟分析

对某建筑外呼吸双层通风玻璃幕墙内的速度场和温度场进行了模拟分析。讨论了遮阳设施、空气层宽度等因素对综合传热系数的影响。分析比较了外呼吸双层玻璃幕墙建筑和四种单层玻璃幕墙建筑的供暖空调能耗。结果表明,外呼吸双层通风玻璃幕墙是一种节能的生态建筑围护结构形式。     

Water-use efficiency for alternative cooling technologies in arid climates

In arid climates, evaporative cooling technologies are generally valued for their reduced energy consumption in comparison to compressor-based air conditioning systems. However, two concerns that are often raised with respect to evaporative cooling equipment are their on-site water use and the impact of poor water quality on their performance. While compressor-based systems do not use water on-site, they do consume water through their use of electricity, which consumes water through evaporation at hydroelectric power plants and cooling at thermal power plants. This paper defines a water-use efficiency metric and a methodology for assessing the water use of various cooling technologies. The water-use efficiencies of several example cooling technologies are compared, including direct evaporative, indirect evaporative in two different configurations, compressor-based systems, compressor-based systems with evaporative pre-cooling of condenser inlet air, and hybrid systems that consist of an indirect evaporative module combined with a compressor-based module. Designing cooling systems for arid climates is entwined in the close relationship between water and energy and the scarcity of both resources. The analyses presented in this paper suggest that evaporative systems that significantly reduce peak electricity demand and annual energy consumption need not consume any more water than conventional systems.     

An internal assessment of the thermal comfort and daylighting conditions of a naturally ventilated building with an active glazed facade in a temperate climate

An active facade is often used to promote the flow of air through a building, however in order to ensure that this process is effective the facade should face a southerly orientation. This means that not only solar energy is transferred across the glazing but in sunny periods shading is needed to prevent excess brightness levels occurring on the working areas where it may result in the luminance distributions not complying with current lighting requirements. The building investigated is located in Sheffield, England and is one of the University of Sheffield's recently built green buildings. It has a high thermal mass which is used to promote the use of night cooling. This paper reports the initial findings of an internal assessment of the thermal comfort and daylighting conditions in such a building. The results have indicated that such designs are to be commended for their passive use of solar energy and can provide a high quality working environment.     

Indirect evaporative cooling potential in air–water systems in temperate climates

Recent developments have prompted a review of evaporative cooling technology as an effective means of cooling modern deep plan buildings. Prominent among these developments is the success of high temperature sensible cooling systems, particularly, chilled ceilings, which require a supply of cooling water at 14–18 °C. Crucial to the success of evaporative cooling technology, as a significant means of cooling in modern applications, is the ability to generate cooling water, in an indirect circuit, at a temperature which closely approaches the ambient adiabatic saturation temperature (AST) or wet bulb temperature (WBT). Recent experimental research has demonstrated that it is technically viable to generate such cooling water at a temperature of 3 K above the ambient AST.While the frequency of ambient AST occurrence can be obtained from meteorological sources, there is little in-depth analysis of the potential for this form of cooling water generation, based on the approach temperatures which have now been shown to be viable. The decision to use an evaporative cooling system depends largely on an assessment, in-depth, of net energy saved against capital expended. Such an assessment requires detailed data on the availability of cooling water, generated by evaporation, for each location. This paper quantifies evaporative cooling availability in-depth for a northern and southern European city, Dublin and Milan and suggests a method of analysing such data for any world wide location, for which suitable meteorological records are available. The paper, incorporates recent experimental research findings and bases the availability analysis on meteorological test reference weather year data.The results of this research confirm a major potential for the generation of cooling water by evaporative means, which can be used to provide effective cooling of deep plan buildings by means of contemporary water based sensible cooling systems, such as fan coil systems, radiant chilled ceiling panels and ceiling cooling convectors (chilled beams). While the technique offers most potential in locations with a northern European temperate climate, it has significant potential to contribute to cooling in some southern European cities, during the non-summer months and also at other times, particularly where load shaving techniques are incorporated.     

国内外蒸发冷却空调技术研究进展(3)

介绍了多级蒸发冷却空调系统、除湿与蒸发冷却相结合的空调系统、半集中式蒸发冷却空调系统、建筑物被动蒸发冷却技术、蒸发冷却自动控制系统及蒸发冷却水的水质处理。     

Thermal performance of a cool-pool system for passive cooling of a non-conditioned building

The thermal performance of a cool-pool system for passive cooling of a non-conditioned building is presented. The system consists of a water pond over the roof which is shaded in such a way that incident solar radiation does not reach the roof surface and the pond loses heat by convection and evaporation to its surroundings. Using periodic analysis, explicit expressions have been obtained for various performance parameters, namely room air temperature and water temperature and the amount of water evaporated from the system. Numerical calculations carried out for a typical day at New Delhi (28.6°N) show that the cool-pool system is more effective than the conventional evaporative cooling techniques such as water film and roof pond; the system also consumes less water in comparison with other evaporative cooling techniques.