Economic and social benefits of popularizing energ

Economic and social benefits of promoting "energy-saving windows"

the key to building energy conservation is energy conservation of doors and windows, which has been discussed for many years but not implemented effectively. In China, the energy consumption of windows accounts for about half of the energy consumption of the entire building envelope. This assertion is scientifically based, and many experts have done a lot of research work on it

in hot summer and warm winter areas, the ratio of "heat gain" of solar radiation through window glass and "heat gain" of temperature difference through window heat transfer is about 2:1, and the sum accounts for% of the total heat gain of enclosure structure

it should be noted that there are a large number of glass curtain wall buildings in China's existing 4.5 billion M2 public buildings. According to statistics in 2006, the total installation of curtain walls in China has exceeded 100million m2, accounting for nearly 1/2 of the world's total, becoming the kingdom of curtain walls in the world. The latest statistics show that the annual construction volume of curtain walls reached 65million m2 in 2006. In Shanghai alone, about 2300 glass curtain wall buildings with an area of 10million M2 have been built since the middle age of marine engineering such as 1984fpso. The window wall ratio of glass curtain wall buildings is generally greater than 0.5

from the above analysis, it can be seen that the energy consumption caused by poor window insulation, heat insulation and sealing in China is converted into standard coal, which is a shocking number of hundreds of millions of tons. In the 1980s, the Research Report of American scientists pointed out that in the Pacific Northwest Coast of the United States, replacing single-layer glass windows with vacuum glass windows can save 700 megajoules (MJ) of energy per square meter of windows every year. In a popular analogy, this is equivalent to the energy consumption of lighting a 22W long-term lamp all year round. The situation in the severe cold regions of our country may be even worse. It can be vividly said that every non energy-saving window is equivalent to lighting a long-term lamp with dozens of watts, devouring tons of oil and coal. Therefore, using energy-saving windows in new buildings and refitting or installing energy-saving windows in old buildings is the fastest, easiest and most effective measure to reduce building energy consumption

two kinds of energy-saving glass Low-E insulating glass and vacuum glass

insulating glass is the mainstream product of energy-saving glass at present. The space between the two pieces of glass is mm, and the periphery is sealed with structural glue. There is air or other gases in the space. Molecular sieve hygroscopic agent is placed in the frame or in the sealant strip (called warm edge strip) to absorb water vapor in the gas to prevent internal condensation. The membrane surface of Low-E glass is placed on the hollow inner surface. Considering the cost performance, it is generally a single Low-E structure

vacuum glass is a new emerging product in energy-saving glass. In principle, vacuum glass can be compared to a flat thermos bottle. The same point between the two layers of glass is that the interlayer of the two layers of glass is a vacuum with a pressure lower than PA, so that the heat transfer of gas can be ignored; The inner walls of both are coated with low radiation film, so that the radiation heat transfer is as small as possible. The differences between the two: first, vacuum glass used for doors and windows must be transparent or transparent. It cannot be plated with opaque silver film like a thermos, but with different kinds of transparent low radiation films; Second, from a cylinder or ball thermos bottle that can withstand pressure to a flat plate, a square array of "supports" must be set between the two layers of glass to bear about 10 tons of atmospheric pressure per square meter, so that the space between the glasses can be maintained to form a vacuum layer. The spacing of the "support" square array is designed to be between 20mm and 40mm according to the thickness and mechanical parameters of the glass plate. In order to reduce the heat transfer formed by the "thermal bridge" of the support and make it difficult for human eyes to distinguish, the diameter of the support is very small. At present, the diameter of the support in the product is between 0.3mm-0.5mm and the height is 0 2mm. In order to keep the vacuum stable for a long time, the vacuum layer is built with getter

due to different structures, the heat transfer mechanism of vacuum glass and insulating glass is also different. The heat transfer in the center of vacuum glass is composed of radiation heat transfer, support heat transfer and residual gas heat transfer. The residual gas heat transfer in qualified products can be ignored, while the hollow glass is composed of gas heat transfer (including conduction and convection) and radiation heat transfer

to reduce the heat transfer caused by temperature difference, both vacuum glass and insulating glass should reduce the radiation heat transfer. The effective method is to use the above low radiation film glass (Low-E glass). Under the condition of taking into account other optical performance requirements, the lower the emissivity (also known as emissivity) of the film, the better. The difference between the two is that vacuum glass should not only ensure the necessary vacuum degree, so that the heat transfer of residual gas is negligible, but also reduce the heat transfer of support as much as possible, while hollow glass should reduce the heat transfer of gas as much as possible. In order to reduce gas heat transfer and take into account factors such as sound insulation and thickness, the air layer thickness of insulating glass is generally mm, mostly 12mm. To reduce gas heat transfer, high molecular weight gases (such as inert gases: argon, krypton) can also be used to replace air. But even so, gas heat transfer is still dominant

K value of various glasses

professor m.r1 of Berkeley Lorentz laboratory in the United States and Professor Ubin who selected the wrong sample have made simulation calculation of K value of glass. The simulated outdoor temperature is -18 ℃, and the wind speed is 24kmh-1. Through the simulation experiment, we can draw the following conclusions:

(1) Low-E film plays an important role in reducing the K value, and the surface emissivity of ordinary building glass ε About 0.84, with ε From 0.84, the corresponding curve of each glass shows a significant downward trend

(2) the K value of the single glass film on the second surface (i.e. the inner surface) is much lower than that on the first surface of the emerging industry with the fastest growth rate in the city. Therefore, when using Low-E glass, the film surface should be placed inside the room

for hollow glass or vacuum glass composed of two pieces of glass, the K value of Low-E membrane placed on the inner surface (2or3) is much lower than that of membrane placed on the outer surface (1or4). For double hollow or vacuum glass composed of three pieces of glass, Low-E membrane must also be placed on the inner surface (2or3or4or5) to get a low k value. In short, the film must be placed at the position with the least influence on gas convection and conduction in order to highlight the effect of reducing radiation heat transfer, which is easy to understand physically

(3) in terms of the efficiency of reducing K value, Low-E membrane is far better than single-chip use for insulating glass, and it is far better than insulating glass for vacuum glass, with ε The K value curve of vacuum glass decreases more steeply, and the K value is much lower than that of double insulating glass. Not to mention double vacuum glass. This is also one of the reasons why vacuum glass has development prospects

at present, the emissivity of Low-E (dura mater) that can make vacuum glass in China can reach 0.17, and the emissivity of offline Low-E dura mater that can make vacuum glass can reach 0.10