I. Project background
"Strategic Design of Ecological Benefits" was written by American ecological architect William? WilliamMcDonough and his partner * * * completed the planning and design project of the new campus of the University of California, Davis, aiming at creating an ecological and comfortable living environment for nearly 7,000 freshmen and faculty, and won the ASLA Professional Award in 2004. Under the background of 200 1 California energy crisis, how to save energy has become the planning focus of this project. According to the statistical comparison of annual average solar radiation in some cities in the United States (such as Seattle, Washington, 3.67kWh/m2? Fairbanks, Alaska d 3.99 kWh/m2? D), the designer thinks that Davis City (5. 10kWh/m2? D) It has superior solar energy resources, so the utilization of solar photovoltaic system is included in the planning and design of the project.
Second, the project planning
1. Architectural planning
(1) The planned building direction is deflected to the east 10 degrees (shown by grid in figure 1), which can not only ensure the lighting in the south and meet the needs of residents in winter, but also reduce the absorption of afternoon solar heat by buildings in summer and slow down the fluctuation of room temperature. In addition, in summer, afternoon winds pass through this area from the south and southwest, which can provide opportunities for its natural cooling. When the winter wind blows in from the south, it is dispersed and weakened due to the barrier of the northwest building wall (as shown by the wavy line in figure 1). The water flowing through this area is led to the shady north and northeast, which can make up for the lack of wind power by evaporation and cooling, while avoiding excessive evaporation of water. (2) Planning of Building Height The building height in the planning area is determined by the sunshine in winter, so as to ensure that the shadows of buildings in winter cannot completely cover the streets. In summer, the solar radiation in the south and west of the building is strong. In this area, special building materials can be used to reduce the fluctuation of indoor temperature, and some deciduous trees can be planted appropriately to provide shade for the building. Large-scale courtyards surrounded by buildings can capture wind vortices (as shown in the circle in Figure 2), and carefully planted plants in the courtyards are used to divert the breeze. (3) The expansion of building space can maintain and improve the comfort of outdoor space microclimate through careful design, stimulate the use of the environment, increase people's outdoor stay time, and thus reduce the energy consumption of the building. As shown in Figure 3, the roof space and vertical space of the building can be optimized to form available private or public outdoor space, and the area of outdoor space can be further expanded by setting up underground parking lots; Forming an open space inside the building can not only improve the lighting and ventilation conditions of the building, but also provide more comfortable rest space for residents.
2. Single building design
The designer's ideal building monomer is shown in Figure 4. Materials: install large windows in the south of the building to increase lighting; Use building materials that can absorb and slowly release solar heat inside the building to collect solar energy; Plant turf on the roof to form a green roof. Equipment: solar photovoltaic panels are used in the open-air garage, which not only collect and utilize solar energy, but also play a certain role in shielding; Use solar water heaters to reduce energy consumption; The interior of the building is heated by floor radiation to create an indoor space with suitable temperature. On the device: a movable sun visor is installed on the upper part of the south-facing window to meet the different requirements of solar illumination in different seasons and different time periods; Push-pull ventilator is installed at the top of the building to increase air flow. In addition, some deciduous trees should be planted reasonably on the south side of the building to meet the needs of residents for shading in summer and lighting in winter.
3. Ecological measures
Figure 5 shows the ecological measures involved in building planning. In addition to using solar photovoltaic panels and planting turf on the top of the building mentioned above, the designer also suggested using permeable pavement in the building group, and setting grass ponds with waste treatment system and vegetation depressions with advanced water-saving technology to strengthen the control of rainwater on the site. On the other hand, it is required to choose native tree species with strong adaptability and easy management, which is also a key issue in the current ecological park.
Three. Energy-saving measures adopted by the project
1. Heating measures
(1) Geothermal system is different from air, the temperature fluctuates obviously with seasons, and the underground temperature is relatively constant. In summer, the heat released by buildings is absorbed by circulating pipes and then transferred to the earth; In winter, the circulating pipe absorbs heat from the earth and then transmits it to the floor and buildings for heating. The design of geothermal system can usually meet all the cooling needs and 80% ~ 100% heating needs of a building, which greatly reduces the energy consumption of HVAC (systems or related equipment responsible for heating, ventilation and air conditioning indoors or in cars) and is efficient and energy-saving; Moreover, it is not easy to cause convection of dirty air, and it can keep indoor air clean, which is the most comfortable and healthy heating method. However, due to the long cold season in Davis, the "heating" of geothermal system is likely to extend to the surrounding environment, thus reducing the effectiveness of the system until the end of winter, so attention should be paid to alleviating this problem in the application process. (2) Heat Pump By using renewable heat sources (such as geothermal energy), heat pumps can provide the most energy-saving heating and cooling strategies for many applications. It has good conversion rate, and can reduce energy consumption and emissions of carbon dioxide and other polluting gases. However, because the performance of heat pump is highly dependent on the nature of heat source, other auxiliary equipment is needed when the heat source is unstable, and the cost is relatively expensive. Therefore, in practical application, it is necessary to select the heat source according to the capacity of the distribution network, and it is best to make the heat source close to the heat load (such as student dormitory) to reduce the transmission and distribution cost and achieve the best use efficiency.
2. Cooling measures
(1) Plant cooling and green planting can not only form a cool and comfortable visual landscape in summer, but also provide shading, improve air quality and relieve the highest temperature in summer. In this project, the designer mainly expounds and analyzes the ground greening and roof greening. As far as ground greening is concerned, the tree coverage rate of Sacramento, California is simulated to increase by 30% (3 trees per household), and the results show that the energy used for cooling is saved by about 30% throughout the year. As far as roof greening is concerned, summer temperature can increase the surface temperature of sandstone roof to 140℃ ~ 175℃, while the temperature of green roof will not exceed 77℃ under the same conditions, which will greatly reduce the consumption of refrigeration energy. In addition, the traditional roof structure will begin to deteriorate after 20 years, while the green roof can slow down the deterioration to 35 years by reducing the fluctuation of daily temperature and annual temperature, thus prolonging the service life of the house and reducing the maintenance and replacement costs. Of course, plant cooling also has certain limitations, such as tree maintenance has certain technical and cost requirements; In addition, the growth of trees needs sunlight, which also limits the use of solar photovoltaic panels. (2) Ventilation and cooling ventilation can be divided into natural ventilation and mechanical device (such as fan) ventilation. Natural ventilation is driven by the temperature difference inside and outside the space or the pressure difference between the two sides of the building. In order to promote cross ventilation, ventilation holes or movable windows should be set on the opposite sides of the building, and large obstacles (such as walls) should be avoided; In a multi-unit building complex, only one surface of a residential unit can communicate with the outside. In this case, setting an "air ventilation duct" at the top of the building can also promote the air circulation in the internal space (Figure 6). According to the survey, in a family's energy consumption in a year, the energy consumption generated by ventilation of indoor space with electrical equipment such as fans accounts for a considerable proportion. In this project, it is suggested that electrical equipment should not be used or used only in the hottest summer and coldest winter, and the push-pull ventilator (driven by wind) should be used for natural ventilation at other times to minimize the use time of electrical equipment. It should be noted that in Davis, the temperature at night in summer is usually much lower than that during the day. It is necessary to control the cooling time at night to avoid using heating equipment caused by excessive cooling, which will lead to additional energy consumption.
3. Wastewater and rainwater treatment measures
In this project, constructed wetlands are mainly used for the treatment and utilization of wastewater and rainwater, and four basic applications are put forward: first, shallow swamp system, based on a considerable watershed area (usually greater than 1.67ha), needs considerable space, stable basic flow or groundwater supply to support newly planted wetland plants; The second is the pond wetland system, which includes a pond area and a shallow swamp area, in which the pond can slow down the inflow and runoff, collect sediments and remove pollutants (this system needs less space and is considered to be the most stable system); The third is to prolong the stranded wetland, which has the function of temporarily storing and discharging runoff and can reduce the space occupied by the wetland; The fourth type is pocket wetland, which is suitable for small sites with no stable basic flow source and frequent water level fluctuation, and is most suitable for dry conditions (difficult to monitor and unstable compared with other systems). Considering the low annual rainfall and the problems of sanitation and odor in Davis, it is suggested that the wetland should be located where there is a wastewater treatment system.
Fourth, the application status and enlightenment of China.
The climate deterioration caused by environmental pollution makes people rely too much on electrical equipment to obtain a suitable indoor climate environment, which leads to a large amount of energy consumption and even the emission of polluting gases, which in turn aggravates the climate deterioration and forms a serious vicious circle. As one of the pillar industries of China's national economy, the energy saving and emission reduction of the construction industry has attracted the attention and research of many domestic scholars. The ecological ideas and measures put forward in the project of "Strategic Design of Ecological Benefits" have been applied and developed in China to varying degrees.
1. Solar photovoltaic
Building energy consumption is mainly generated by building energy consumption and use energy consumption. In modern cities, building energy consumption accounts for a considerable proportion of all energy consumption of human activities, among which the building consumes the most electric energy during use. Taineng photovoltaic power generation system can directly convert clean and renewable solar energy into electric energy, and reduce the electricity consumption of buildings to some extent. At present, there are some cases applied to architecture in China. The intelligent ecological office building of China Putian Information Industry Shanghai Industrial Park, jointly designed by the School of Architecture of Southeast University, the Architectural Design and Research Institute of Southeast University and the Department of Industrial Ecology of the Royal Swedish Institute of Technology, has installed 10kW experimental solar photovoltaic cells on the roof, which can generate 4% of the total electricity consumption of the building, and is mainly used for building facade lighting and EPS system charging. However, due to the cost and other issues, the application of solar photovoltaic buildings in China is still in the exploratory stage, and the future development still depends on the improvement of technology and the support of the government.
2. Green roof
Compared with solar photovoltaic power generation system, the application of green roof is more popular in China. With the development of society and the progress of science and technology, today's green roof is not only as simple as spreading turf on the roof, but also can plant all kinds of flowers and trees, arrange facilities to create a comfortable and pleasant "hanging garden", and can also plant all kinds of vegetables to form a "hanging farm" with farmhouse fun, or as an educational base, which can be said to be the ultimate use of the roof. Nanjing Zidong International Creative Park, awarded the title of "World Roof Greening Research and Teaching Demonstration Base" by the World Roof Greening Association, plans to build a roof garden or an aerial farm on top of all buildings in the park to achieve 100% roof greening. The vegetables grown in the air farm do not use pesticides and fertilizers, and the organic vegetables produced are supplied to the canteen in the park. Driven by relevant policies and norms, roof garden construction in big cities such as Beijing, Guangzhou and Shanghai has begun to take shape, and small and medium-sized cities still need active publicity and guidance from the government.
3. Constructed wetland
Constructed wetland, as a new sewage treatment measure, started late in China, but developed rapidly, and achieved certain results in theory and practice. Constructed wetland sewage treatment technology has been applied to the environmental protection park of Shenyang World Horticultural Exposition in 2006, the Beijing Olympic Forest Park built to welcome the Beijing Olympic Games in 2008 and the Houtan Park of the 20 10 Shanghai World Expo. Among them, Beijing Olympic Forest Park is the first large-scale urban park in China that uses reclaimed water to supply water for water system and main landscape. The total area of constructed wetland park in Nanyuan is 4 1500m2, and the area of wetland oxidation pond is 30500m2. With the patented technology of "Composite Vertical Flow Constructed Wetland" independently developed by Institute of Hydrobiology, Chinese Academy of Sciences, it can treat 2600m3 of reclaimed water from Qinghe Sewage Treatment Plant and 20000m3 of circulating water from the main lake of the park every day, and 60 tons of cattail, onion, reed and Pennisetum have been planted. It should be pointed out that although constructed wetlands have many benefits, they cannot completely replace natural wetlands. While vigorously researching and developing, we should conform to the laws of nature and actively protect the "natural kidney" of the earth.
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