ENERGY EFFICIENT TECHNIQUES AND SIMULATION OF ENERGY CONSUMPTION FOR THE SHANGHAI ECOLOGICAL BUILDING

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1 The 2005 World Sustainable Building Conference, ENERGY EFFICIENT TECHNIQUES AND SIMULATION OF ENERGY CONSUMPTION FOR THE SHANGHAI ECOLOGICAL BUILDING BU Zhen M.Sc 1 LU Shanhou Ph.D 2 ZHU Weifeng Ph.D 1 Shanghai Research Institute of Building Science, Room 3-517, No.75 Wanping Road(S), Shanghai , P.R.China, 2 Shanghai Research Institute of Building Science, Room 3-313, No.75 Wanping Road(S), Shanghai , P.R.China, Keywords: ecological building, energy efficiency, energy simulation, natural ventilation Summary This paper introduces the energy efficiency technologies applied to Shanghai first ecological building, including high energy performance envelopes, natural ventilation, humid dependent air-conditioning system and renewable energy. To evaluate the energy performance of the eco-building and analyze the energy efficiency effects of different energy efficiency technologies, a simulation tool, DeST, is used to calculate the annual energy consumption for heating and cooling in this building. The simulation results show that the annual energy consumption for heating and cooling in this building is super low and movable shading for outer windows is the most important factor affecting its energy loss, especially in summer. The construction of this eco-building will be helpful to spread the energy efficient technique in China. 1. Background With the rapid development of economy and continuously improvement of living standard in Shanghai, the energy consumption of buildings is increasing year by year. Consequently, there is an urgent demand for advent of high quality building to bring people a healthy, comfort, stimulating environment and at the same time, to save energy. In Sep.2004, the construction of the first eco-building was completed in Shanghai. Enjoying the status of a national key project, this building not only makes people see the direction and target of future construction development, but also is an exhibition stage for domestic and international advanced technique, adapting the Shanghai development program of eco-city. At the same time, it will become a propagandizing and education base of sustainable development building, by setting up a series of energy efficient green building technique and provide science foundation for established the 10~15 years development program of Shanghai energy efficient building. It will also become an environmental research laboratory of National Construction Department. 2. Introduction Figure 1 Front View of Shanghai Eco-Building

2 The Shanghai eco-building was built in Shanghai XinZhuang Industrial District with an area about 1,900 m 2 (as shown in Figure 1). The building has three floors in the north part and two floors in the south part, acting as laboratories and office rooms separately. The middle of the building adopts an atrium as lobbies and demonstrating space. On the top of the atrium are five skylights, letting the sunlight into the inner part of building so as to ensure lighting in day time. The design of this atrium with skylights on the slope roof is also a remarkable characteristic of the building. In order to minimize the energy consumption, lower its impacts on the environment and provide the people a healthy, comfortable, efficient working environment, the designer applied many advanced energy efficiency technique from many aspects, including compound building envelopes, natural ventilation, advanced HVAC system with high COP, solar energy and related automatic control. The representative energy efficiency measures applied in this building will be introduced in detail in the following part of this paper and a dynamic energy simulation tool was used to verify and compare the energy saving effects of the above measures. 3. Energy Efficiency Technique From four aspects, building envelope thermal design, natural ventilation utilization, application of new air conditioning system and renewable energy using, energy saving technique of this building are discussed. 3.1 Thermal Design of the Building Elements The climate of Shanghai is characterized by a marked seasonal variation of temperatures with warm summers, cold winters and a predominantly high relative humidity throughout the year. The maximum temperature could hit 38 in summer whereas the minimum temperature can decline to -6 in winter. To moderate the influences of outdoor climate and balance the heat gain or loss required to maintain a comfortable interior, the building envelope design should take both the summer and the winter outdoor conditions into accounts. In this eco-building, different facades use different insulation systems for demonstration from reference to Europe design criteria of energy efficiency for buildings. Seven kinds of insulation systems were applied in all, four kinds for exterior compound walls and other three for roofs. Envelope construction and the thermal parameters are shown in Table1 and Table2 for exterior walls and roofs respectively. Highly glazed for windows and skylights are also used, as shown in Table3. Table1 Construction and thermal parameters for exterior walls Elements Eastern Exterior Main Construction (from outside surface to inside surface sequentially) SureBlock Complex : Concrete Block (90mm)+Foam insulation (60mm)+Aerated autoclaved concrete block (240mm) U-Value W/(m 2 K) 0.32 Southern Exterior EPS insulation (140mm)+Concrete block (190mm) 0.38 Western Exterior SureBlock Complex : Concrete Block (90mm)+Foam insulation (60mm)+Concrete Block(240mm) 0.26 Northern Exterior XPS insulation (75mm)+Concrete block (190) 0.33 Overheating caused by solar radiation through outdoor windows has great influence on indoor climate and energy consumption for common office building in Shanghai in summer. Since this eco-building has skylights with area over 100m 2 and the ratio between windows and walls at south facade reaches 0.59, effective shading systems, with shading devices adjustable in accordance to the sun s angle and not adjustable in fixed position, are applied to keep solar radiation from entering interior space and saving energy due to running of air conditioning at summer.

3 Table2 Construction and thermal parameters for roofs Elements Inaccessible flat roofs Accessible flat roofs Main Construction (from outside surface to inside surface sequentially) Roof greening (600mm)+Foamed glass (150mm)+Haydite Concrete (100mm) Roof greening (600mm)+XPS insulation (95mm)+Haydite Concrete (100mm) U-Value W/(m 2 K) Pitched roofs Foam insulation (180mm) 0.16 Table3 Glazing applied in eco-building Elements Glazing descriptions U-Value W/(m 2 K) Shading Coefficient Skylight in pitched roofs Pet Low-E double glazing Southern outdoor windows Low-E double glazing Northern outdoor windows Low-E double glazing Western and Eastern outdoor windows Solar-E double glazing Utilization of Natural Ventilation From the aspects of indoor thermal comfort and energy efficiency, the passive measures should be taken with priority. It is absolutely reasonable to use natural ventilation to cool the building during the summer night and other seasons based on the analysis of climate characteristic. Through careful design and analysis, natural ventilation can be applied to take the surplus heat gain out of the building, keep the indoor thermal environment comfort, shorten the running time of AC system and reduce energy use. As for the Shanghai eco-building, CFD technique was use to simulate the air flow of the surrounding and optimized its location to use natural ventilation effectively under the effect of dominant wind (shown in Figure 2). Moreover, apertures size and location on different facades and on the top of the building Figure 2 CFD simulation results were carefully analyzed to control the natural ventilation and investigate the combined effects of wind-driven natural ventilation and stack effect. With an aperture of 30m in length and 0.8m in width, a wind tunnel located on the top of the building was designed to act as an air exhaust for natural ventilation and reinforce its effects at the same time (shown in Figure 3). 3.3 The Application of Solar Energy It is a trend of eco-building to use renewable energy source, such as sun, wind etc., instead of fossil resources to meet energy demand. A hybrid system of heating and air conditioning based on solar energy was used in the Shanghai eco-building. On the pitched roofs were installed evacuated tube heat collectors

4 with area about 170m 2 along the sloped angle. The solar heat collectors can supply hot water to floor heating system in first and second layer to controlled indoor thermal environment in winter. Moreover, the solar collectors can also provide heat source to two solar-powered air conditioning units which act as subsidiary cooling measure to take on the sensible cooling load of the exhibition hall in summer. Additionally, there are seven groups of heat collectors hidden in the wind tunnel under the pitched roof as heat exchangers to heat the air in the tunnel so as to strengthen the chimney effect of natural ventilation. Besides the application of solar thermal technique, building integrated photovoltaic technique (BIPV) is also used with the average capacity of 5kW electricity output. 3.4 New Air Conditioning Systems High performance, healthy and environment friendly are all important requirements for ecological air conditioning system in eco-building. One independent humidity control air Figure 3 Natural ventilation of eco-building conditioning system is developed and used in Shanghai eco-building for the first time. This system has advantages over traditional ones in three aspects. Firstly, the new AC system is a healthy and energy efficient system. In order to keep indoor humidity within a comfortable range from 40% to 60%, it is necessary to dehumidify supplied air due to the outdoor air relative humidity of Shanghai is relatively high both in summer and in winter. For traditional air conditioning systems, most of them use cooling methods to remove water vapor from air, which means that the air in air handling units(ahu) must be cooled down to its dew point firstly and then be heated to designed condition of supplied air. It is inevitable to cause the energy counteraction between heating and cooling during the air handling procedure. Moreover, if the traditional coils are placed within rooms, the dampness environment in cooling units caused by the condensed water provide spaces for germs to grow so as to badly affect human health. In addition, the refrigerating efficiency of traditional system is not high as a quite low evaporating temperature is needed. To avoid these, air latent cooling load is separated from sensible cooling load in the air handling procedure of the new system and is taken on directly by absorption effects of mixed liquid of LiBr and LiCl in the fresh air handling unit. The sensible cooling load is mostly taken on by a heat pump plant with a high evaporation temperature so to avoid the condensation of indoor coil. Secondly, the new system is a environmental friendly system as it does not use HCFC and CFC as refrigerant. As known to all, HCFC and CFC refrigerants can do obvious harm to O 3 layer of atmosphere which is bound to be forbidden in the future. Thirdly, the new system has high performance with COP value over 5 at least. On the one hand, the new system does not need to reheat the supplied air to meet requirements. On the other hand, the system can utilize the heat created by the heat pump condenser as a heat source to provide energy for regeneration of the absorption liquid. 4. Analysis of Energy Efficiency Effects on Eco-Building In order to verify and analyze the energy efficiency effects of the above techniques applied in the eco-building, a building energy simulation tool, DeST, was used to calculate the annual energy consumption of heating and cooling for this eco-building. Based on primary energy use of the building, the simulation was carried out, not taking performance of air conditioning system into account. 4.1 Simulation Tool & Cases Studied DeST, the abbreviation of Designer s Simulation Toolkit, is a program for building energy simulation and indoor thermal analysis, developed by Department of Building Science of Tsinghua University since early 1980s. DeST can be used to simulate and analyze both building dynamic energy consumption and HVAC system design so as to improve the reliability of system design, to ensure the quality of the system performance and to reduce energy consumption of buildings. It integrates AutoCAD as modeling tool. The geometric representation of the eco-building was created based on the Figure 4 Eco-building model of DeST

5 architectural drawings (shown in Figure 4). Input data required by simulation, such as internal loads, infiltration rate, operational profiles and environmental control strategies were defined with reference to the Standards of Energy Efficient Design for Public Buildings of Shanghai. Based on the settings, the effects of some key energy efficiency techniques, including advanced glazing, insulated envelopes, adjustable shading devices, natural ventilation and the combinations, were studied and compared. Five cases were simulated in all: Case1 1 : building with no energy techniques (taken as comparing basis) Case2: building with only application of windows shading devices Case3: building with application of windows shading devices plus advanced glazing Case4: building with application of windows shading devices, advanced glazing plus highly insulated envelopes Case5: building with application of windows shading devices, advanced glazing, highly insulated envelopes plus natural ventilation 4.2 Simulation Results Figure 5 shows the simulation results of annual heating and cooling energy consumption of eco-building for 5 cases listed above. Energy Consumption Index(kWh/m 2 ) Heating Cooling Total Case1 Case2 Case3 Case4 Case5 Figure 5 Simulation Results of Energy Consumption for Shanghai Eco-Building From the above simulation results, further results can be achieved. Compared with Case1, the energy saving effects for different combinations of energy efficiency techniques are shown in Table 4 and the contribution of each energy efficiency technique can be separated, as shown in Figure 6. Table 4 Energy Efficiency Effects for Different Simulation Cases Case Total energy efficiency effect(%) / Analysis & Discussion The results in Table 4 show that different combinations of energy efficiency techniques result in different energy consumption due to the different contributions of different energy saving measures. As shown in figure 6, accounting for 41.2% in the whole contributions, windows shading is the most effective way to save energy consumption for the eco-building. Since this building has large area fenestration both in the four orientation walls and on the top pitched roofs, it is vulnerable to solar radiation especially during summer, which causes overheating and increasing of cooling load. From the simulation results for common office building (Figure 5), the annual cooling load largely exceeds annual heating load. However, the cooling load decreases to a great extent after the application of windows shading. Furthermore, the application of insulated envelopes and 1 The building with no energy techniques is a representative office building of Shanghai. The U-value of walls, roofs and glazing are 2.0, 1.5 and 6.4 W/(m 2 K) respectively and outdoor windows have no shading devices.

6 advanced glazing mainly help to decrease heating load but has a little effects on cooling load. The effect of insulation is beneficial in winter and may play a counter effect in summer as it prevents solar radiation and internal gains from leaving the interior space. Natural Ventilation has also a remarkable influence on energy saving which also plays an important role to improve the indoor thermal comfort. It should be noted that the simulation results and the analysis presented here do have an instructive effect on eco-buildings design but cannot be fully applied to any other office buildings in other places. Natural Ventilation 16.1% windows shading 41.2% insulated envelope 24.5% advanced glazing 18.3% Figure 6 Contributions of Different Energy Efficiency Techniques for Shanghai Eco-Building 5. Concluding Remarks The paper describes the energy efficiency techniques applied in the Shanghai first eco-building and analyze their effects through the simulation of annual heating and cooling load by using building energy simulation program DeST. This eco-building had adopted many new advanced building techniques to improve the energy performance while attached great importance to create a healthy, comfortable and efficient environment indoors. Through the integrated application of highly insulated envelopes, advanced glazing and shading devices, natural ventilation and solar energy etc., the eco-building provides the first base for spreading and promoting advanced energy efficiency technique for Shanghai and its neighboring region. The simulation results show that compared with the common office building, the total effect of all the integrated energy efficiency techniques is quite significant among which windows shading are most helpful to decrease energy consumption. The on-site testing of thermal performances of shading devices needs to be carried out to verify the real effects in the future. Windows shading techniques probably play a more important role than just increasing the thickness of insulation layers on walls and roofs for buildings with large area fenestration in climate in Shanghai. References Elisabeth Gratia, Andre De Herde 2003, Design of low energy office building. Energy and Buildings, 35, pp ASHRAE, 2000 ASHRAE Handbook, HVAC systems and Equipment, SI ed, Chapter 22,pp SRIBS eco building environmental design advice report. 2004, WSP Environmental Ltd., The standard of energy efficient design for public buildings. 2003, Code of Shanghai engineering & construction, pp Wang Ruzhu, Zhai Xiaoqiang 2004, Energy Technology of green buildings based on solar energy thermal utilization. Building Energy & Environment, 23, pp Zhu Weifeng, Deng Lianghe. 2004, Independent humidity control air conditioning systems in green building. Proceedings of SB04 China Conference, pp Sam C.M. Hui 2001, Low energy building design in high density urban cities. Renewable Energy, 24, pp Yan Da, Xie Xiaona. 2004, Building environment design simulation software DeST(1): an overview of developments and information of building simulation and DeST China Journal of Heating Ventilation and Air Conditioning, 34(7), pp Jiang Yi, Xue Zhifeng. 2004, Demonstrating building with ultra-low energy consumption in Tsinghua University. China Journal of Heating Ventilation and Air Conditioning, 34(6), pp