| The tight situation of energy supplying is a major challenge for China in the process of economic and social development.Low energy efficiency has become one of the bottleneck issues to overcome in the process of modernization.The ratio of building energy consumption to total energy consumption of a society is usually among 30?40%in developed countries.Since the conflict between environment-energy issues and economy growth has been deteriorating day by day,the ideas of energy conservation,environment protection,and sustainable development are gaining more and more attention.Consequently,it has grown into an extensively concerned issue as how to reduce the building energy consumption.Further,from the viewpoint of whole lifecycle of building,most of building energy consumption occurs in the running and employed process of building.According to the statistic data from Chinese Ministry of Construction in 2009,the energy consumption for heating and air-conditioning has occupied 55%of the total building energy consumption in China;among which,the air-conditioning energy consumption is around 20%of the total.Hence,reducing the air-conditioning loads and energy consumption is very important and urgent.In this work,the author elaborated to investigate the influence of the radiation characteristics of the transparent and non-transparent building envelopes,on the building cold/heat load and energy consumption.The main contents of this work are organized into three parts:Firstly,the author has developed a simulation software named as BuildingEnergy to evaluate the building dynamic load and energy consumption.According to the standard calculating cases supplied in ASHRAE Standard 140,BuildingEnergy was examined,and several experiments were tested.The results proved that BuildingEnergy can correctly predict the dynamic cooling and heating load in active temperature control mode,and the indoor temperature in passive mode.The maximum error is less than 10%.Secondly,BuildingEnergy was applied to optimize the radiation characteristics of the non-transparent building envelopes.Three cities,representing the three types of distinct climate regions in China,were selected to compare the variation of the annual heating and air-conditioning energy consumption of the top-floor room,whose roofs and external walls are covered with the low solar absorption coating(LSAC)or not.The following conclusions are obtained:1.If using the LSAC in Beijing,a typical city of the cold regions,the increment of heating consumption is close to the reduction of the air conditioning consumption,which means there is no obvious energy conservation in a whole year.And the external insulation layer should be the first choice to reduce the energy consumption in such regions.2.In the regions of "hot summer and cold winter",taken Shanghai as an example,the influence of the LSAC on the energy consumption depends on the way of heating:if EERh/EERc<1.18,for instance using heat pump,the whole year energy conservation gain will be negative;if the way of heating is central heating,the whole year energy conservation gain when using the LSAC with or without the external insulation layers is 2.1 or 5.6 kWhe/m2 respectively.3.In the regions of "hot summer and warm winter" such as Guangzhou,the energy conservation gain per unit area of using the LSAC is 1.85 times higher than that of using the external insulation layer.Besides,a six-story residential building located in the three major building thermal-climatic regions,respectively,was taken as the simulation objects.The annual energy consumption of the top-floor room and the whole building were discussed in detail.It was found that the lowest values of energy consumption can be obtained by adjusting the radiation characteristics of the building opaque envelope surface.The averaged lowest values based on the usable indoor floor area of the whole building are:29.3 kWhe/m2 in Beijing,36.3 kWhe/m2 in Shanghai(heat pump adopted in winter),and 5.6 kWhe/m2 in Guangzhou.The significance of these specific results lies in that the lowest energy consumption limits the scope of energy-saving potential achieved by adjusting the radiation characteristics of the non-transparent surface in theory.At the same time,the lowest values can also be used as the normalized basis of building energy consumption,and to obtain the index of building energy consumption easily.Thirdly,BuildingEnergy was applied to study the radiation characteristics of the transparent building envelopes.The effects of the important parameters of the transparent envelopes,include the solar spectral transmittance,the solar absorptivity,and the long-wave thermal emittance,on the annual building energy consumption were analyzed.Moreover,the energy-saving mechanism of the reversible window consisted of the low-e and tinted glazing were studied,and three types of reversible window were designed.With the detailed simulation,the minimum value of building energy consumption by regulating the thermal radiation characteristics of transparent envelope can be obtained with an optimal structure of the reversible window,i.e.a bleach glazing and a tinted glazing with the enclosed cavity-side surface coated with low-e film.When a minimum value of 0.38 for solar spectrum transmittance of the tinted glazing,a maximum value of 0.55 for solar absorptivity,and a minimum value of 0 for thermal emittance of the low-e film are satisfied synchronously,the lowest value of the building energy consumption could be obtained with the reversible window,and the numerical value of which is 21.5kWhe/m2?... |
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