Research On Comprehensive Utilization Of Concentrating Solar Photovoltaic-Daylighting Based On Building Integration

With the rapid development of the society,the requirement for the comfortable living environment is becoming more ugent,and the share of the building energy consumption in the total energy consumption increases as well,in the area of which the electricity and lighting are two main contributors.Thus,to promote the use of renewable energy technologies on the building,such as combining solar energy utilization systems to building external structures,is one of the key research directions to offset the building-related energy consumption.Concentrating solar energy utilization systems is an effective way to achieve this golal,which also makes new requirements for the design of the concentrator device.On the one hand,for a concentrator,its geometric concentration ratio and acceptance angle are usually inversely proportional.To male it suitable on the buiding,with the same geomentricical concentration ratio,the angular acceptance range should be larger to confirm more annual solar energy collection time.Especially for the building south wall,the range of incidence angles varies greatly throughout the year,which presents higher requirements on the structural design of the concentrator.On the other hand,because the traditional photovoltaic cells are usually opaque,the rays transmission intrinsically conflicts with the concept of photonic absorption for power generation.This thesis focuses on the concept of the low-cocnentration-ratio concentrator and aims to design novel building integrated concentrating solar systems.For the building south wall,we designed a novel asymmetric compound parabolic concentrator(ACPC)with large acceptance range and high optical efficiency.At the same time,this thesis developed the new idea of combining the active electricity generation(PV)and Daylighting into one device,which means that through the optimization design of the concentrator structure,the function of the natural daylighting was introduced into the concentrating PV technology:with the proper coating strategy on the outer surfaces,the majority of penetrating solar radiation can be focused onto the PV cell for the electricity generation while a small portion that can't be collected to the PV cell(i.e.escape sun rays)will be redirected into the interior space through the "daylighting window" for daylighting.Thus to increase the efficiency of the system and better suit the building energy consumption,and to promote the application of the concentrating solar energy technologies on the building.This thesis conducted series theoretical and experimental research on the building integrated concentrating systems,which can be concluded as follows:1.A novel asymmetric compound parabolic concentrator(ACPC)was designed for the application on the building south wall.The optical model for a 2.4×ACPC was built based on the Monte-Carlo principle to study its optical performance at various incidence angles.Based on the ray-tracing simulation algorithm,the structure optimization analysis was conducted and the percentages of different energy collection ways were also predicted.The optimization structure was further proposed to enhance its annual performance and the shading effect was also analyzed;2.Using the low cost,high optical transmittance and strong resistance to oxidation and aging material i.e.acrylic to process the ACPC-PV module.The electrical performance of the ACPC-PV module was tested under the solar simulator as compared with the bare cell,and the actual optical efficiency of the ACPC was thereby obtained.The mathematical model of the equivalent solar incidence angle for the ACPC was established,and the annual performance of the ACPC was evaluated and analyzed;3.The novel idea of introducing the function of natural daylighting into the concentrating PV device was proposed,which was accomplished through the structure optimization from the traditional symmetric compound parabolic concentrator(SLWCPC).Through the newly proposed coating strategy,the concentrator with the "daylighting window" i.e.TSLWCPC was designed,which can redirect escape sun rays into the building for daylighting without decreasing its optical efficiency.The SLWCPC-PV and TSLWCPC-PV modules were manufactured and experimentally tested.The electrical and optical performance of the SLWCPC-PV and TSLWCPC-PV were compared,and results indicated that setting the "daylighting window" on the SLWCPC to get TSLWCPC won't bring any negative effects on its optical performance but obtain a daylighting efficiency of around 8%,thus increasing the system efficiency significantly;4.Based on the TSLWCPC,a concentrating photovoltaic/daylighting system(TSLWCPC-PV/D)was designed and built for outdoor experimental study.The electrical and daylighting performance were tested under different weather conditions and seasons.The daylighting performance of the TSLWCPC-PV/D system under the sunny and over-cast weather conditions was further compared and analyzed while its actual daylighting propoerty was also analyzed;5.In order to analyze the annual daylighting performance of the TSLWCPC-PV/D module,the annual daylighting simulation model for the TSLWCPC-PV/D module as well as the building was built in Daysim(a Radiance algorithm based annual dynamic daylighting simulation software)and experimentally validated.With this model,the effects of installation angle and window-to-ceiling ratio on the annual daylighting performance were analyzed.Finally,five cities with various latitudes were selected to conduct the annual daylighting performance simulation to analyze the performance potential of the TSLWCPC-PV/D system under different weather conditions and geographical location.