Study And Optimization On Daylighting Performance And Energy-saving Potential Of Semi-transparent Window

With the advent of the energy crisis,vigorously developing renewable energy has become the main theme of present society.Building Integrated Photovoltaic(BIPV),as an application form of solar energy utilization combined with architecture envelope to produce clean electricity for building use or grid,can not only avoid the electricity loss during the transmission,but also relieve the power peak load.Among them,Semi-transparent photovoltaic(STPV)window is a typical form of BIPV technology.It can effectively improve the building comprehensive energy efficiency under the premise of meeting the indoor lighting requirements,and is considered as an effective way to realize green and lowcarbon building.However,most of studies pay more attention to thermal performance and power generation of STPV window,the studies of indoor daylighting quality and comprehensive energy efficiency of STPV window is still rare,and there are still some deficiencies in current studies which need to be further explored.The paper uses Daysim and EnergyPlus software to simulate the indoor daylighting quality and comprehensive energy efficiency of STPV window respectively.Firstly,The reliability of Daysim is validated by the experimental data under typical meteorological conditions.Then,a new daylighting evaluation index — N-Daylit area is used to investigate the dynamic changes of indoor indoor daylighting quality.Finaly,the EnergyPlus software is used to simulate the cooling/heating electricity consumption,lighting electricity consumption and PV electricity generation,and analyzes the energy-saving potential of STPV window.The main content of the study includes the following two parts:1)The first section investigates the indoor daylighting quality and the comprehensive energy-saving potential of STPV window for different PV cell coverage ratio,orientation,and window to wall ratio(WWR)according to climatic characteristics of Harbin,Taiyuan,Shanghai and Guangzhou,and the design parameters of different architectural factor are optimized from the perspective of improving the indoor daylighting environment and comprehensive energy efficiency.2)Based on above-mentioned result,the second section of the paper compares and analyzes the performance difference between STPV window and traditional single-glazed clear window,double-glazed clear window and doubleglazed Low-E window,and furtherly explores the application prospects and energy-saving potential of STPV window.The study found out that the energy-saving potential of double-glazed STPV window is better than single-glazed STPV window because of the excellent insulation performance.For severe cold area Harbin,when the double-glazed STPV window with PV cell coverage ratio of 20% and WWR of 50% is installed in south,the N-Daylit area accounts for 63% of the total indoor area and the overall electricity consumption reduces15.2% compared to single-glazed STPV window.For cold area Taiyuan,the combination of south installed double-glazed STPV window,with PV cell coverage ratio of 30% and WWR of 30% make the ratio of N-Daylit area reach 63%,meanwhile,the overall electricity consumption reduce 10.9% compared to single-glazed STPV window.However,for hot summer and cold winter area Shanghai and hot summer and warm winter area Guangzhou,the energy-saving effect of double-glazed STPV window is not as significant as that in Harbin and Taiyuan.When the double-glazed STPV window is applied in Shanghai(south,PV cell coverage ratio of 30% and WWR of 40%)and Guangzhou(north,PV cell coverage ratio of 20% and WWR of 30%),the ratio of N-Daylit area both exceed 60%,and the overall electricity consumption is only 3.46% and 3.32% lower than single-glazed STPV window.The STPV window system achieve the best energy-saving effect in Harbin and Taiyuan where the heating energy consumption is dominant.Compared with single-glazed clear window,double-glazed clear window,double-glazed Low-E window,the overall energy consumption of double-glazed STPV window respectively reduce 27.8%,11% and 15.8% in Harbin,and 28.9%,17.1% and 7.2% in Taiyuan.For Shanghai and Guangzhou where the cooling energy consumption is dominant,the Low-E window achieve the best energy-saving effect due to its higher surface reflectance and excellent thermal insulation properties.The results of the study can provide some theoretical support and design reference for the BIPV design in different climate regions,and put forward a set of practical model and method for further research of STPV window.