Study On The Control Strategy And Overall Performance Of Electrochromic Windows In Different Climate Zones

Electrochromic window can adjust the visible light and solar radiation by changing the transmittance according to the requirements,thus affecting the indoor light environment and building energy consumption.Study on control strategy of electrochromic windows is one of the important ways to achieve the optimal indoor photo-thermal environment.Most previous studies optimize the control strategy aiming at the lowest energy consumption,and the control parameter threshold usually does not consider the seasonal difference of sun position,so it is often difficult to keep the lowest annual total energy consumption and create a comfortable light environment.In addition,The electrochromic windows currently used in the market are four-gears,and there is little information on how the gears are determined and how applicable they are in various climate zones.Therefore,in order to achieve a comfortable indoor photo-thermal environment,this paper adopts experimental and simulation methods to explore the layered control strategy and the best gear combination of the electrochromic windows in five climate zones.The experiment mainly includes measuring the spectral parameters of the electrochromic glass,verifying the accuracy of the model of electrochromic window,comparing the advantages of layered control over the overall control,and verifying the accuracy of the layered control law.The Energy Plus and Honeybee simulation software were used to study the optimal gears of electrochromic windows and the relationship between the hourly state of window based on layered control and the solar radiation intensity of vertical facade to get the layered control strategy of electrochromic windows in each climate zone.By comparing different control strategies and ordinary windows to evaluate performance of electrochromic windows from the energy consumption,daylighting and visual comfort.The main conclusions of this paper are as follows:(1)The accuracy of the electrochromic window model was verified through the electrochromic window lighting experiment.At the same time,in the experiment comparing the layered control and the overall control,it was obviously found that the layered control mode had better effects on daylighting and eliminating the glare than overall control mode.In addition,the accuracy of the layered control strategy is verified by experiments.At the same time,through the experiment,reasonable doubt is put forward on the window gears,which increases the persuasion and credibility of the simulation.(2)Through the study of the optimal gears of the electrochromic window in each climate region,it is found that for the cold and mild regions,the gear of Case2 is recommended for the electrochromic window,namely 60%,20%,6% and 1%;For areas with hot summer and cold winter,it is recommended to use Case6,namely 60%,30%,10% and 1%;For hot summer and warm winter areas,it is recommended to use Case5 adjustable gears,namely 60%,20%,10% and 1%.Therefore,when mainly for heating or cooling,the transmittance of the electrochromic window is relatively low,due to the high demand for cooling or heating in these two types of climate areas,and the electrochromic window with low transmittance is more favorable to save energy consumption.For cooling and heating areas,the relatively high transmittance can give good consideration to energy consumption,daylighting and visual comfort.(3)By comparing the comprehensive performance of electrochromic windows and ordinary windows under layered control and overall control in each climate zone,it is found that ordinary windows have the best daylighting,but produce glare in more than half of the year,which is extremely unfavorable to visual comfort.Due to the large demand for heating,the energy saving effect of electrochromic windows is not obvious in the climate zone mainly focused on heating,but compared with the overall control,the total energy consumption of electrochromic windows controlled by layers is still reduced by 6.96% ～ 11.93%.At the same time,the electrochromic windows with layered control can significantly improve the annual glare-free time,and are superior to the overall control and ordinary windows in terms of visual comfort.For areas with similar refrigeration requirements,the total energy consumption of electrochromic windows can be reduced by 10.45% and 9.85% respectively under layered control and overall control,with little difference in daylighting.However,layered control can shorten glare time by about 13% and greatly improve visual comfort.However,when cold demand is most important,the energy saving potential of the overall control up to 33.69%,but the layered control can improve the non-glare time by 10%,which has a significant effect on visual comfort.It can be seen that the electrochromic windows with layered control have no absolute advantage in energy saving,but have obvious effects on daylightig and visual comfort.