Design And Research Of Smart Luminescent Solar Concentrator

In recent years,energy conservation has been much discussed in the development ofthe construction industry.Building integrated Concentrated Photovoltaic provides a potential solution,which integrates concentrated photovoltaic into parts of buildings and converts solar energy into electric energy,thus meeting the power demand of quite a few buildings and reducing the consumption of fossil energy.As a common method of BICPV,it’s common to integrate photovoltaic into windows in modern architectural design.Low-cost transparent materials are integrated into the window as a concentrating system,thus reduce total manufacturing costs.Generally speaking,it is necessary to balance the light transmittance and power generation efficiency in the design of BICPV window.A common method to improve the power generation efficiency is to expand the area of solar cells,however,that leads to the decrease of the light transmittance of windows.In this thesis,a new type named smart luminescent solar concentrator composed of fluorescent materials and thermochromic materials is proposed.Compared with the existing BICPV system,the system gives consideration to not only the improvement of power generation efficiency,but also the intelligent adjustment of light transmittance.Fluorescent materials have the function of absorbing shorter wavelength light and isotropically emitting longer wavelength light;Thermochromic materials can change their optical properties according to changing temperature.In the system,the light is focused by total internal reflection(TIR).Specifically,when the temperature exceeds the critical temperature,the optical properties of the thermochromic layer are high reflectivity and low transmittance,which is used to block strong sunlight.In addition,the sunlight reaching the surface of the thermochromic layer would be reflected back into the fluorescent layer to be reabsorbed and utilized again.However,when the temperature is lower than the critical temperature,the optical properties of the thermochromic layer show high transmittance,allowing sunlight to enter the room.Meanwhile,the system can still generate electricity through the focusing ability of fluorescent materials.In this thesis,the optical and electrical properties of the“smart window”system are studied by combining simulation with experiment.Trace Pro software is used to establish the optical model,and ray tracing technology is used to study the influence of various factors.The module with photovoltaic cells coupled at the bottom of the waveguide has better optical efficiency than those coupled at the edge of the waveguide.The influence of the dimension and the geometric concentration ratio on optical efficiency are unidirectional,and optical efficiency decreases with the increasing size and geometric concentration ratio.However,the influence of the thickness and concentration of fluorescent layer on the optical efficiency is non-unidirectional,and there exists optimal thickness and concentration.When the system is used as a facade structure,its optical efficiency decreases with the increasing solar altitude angle.To study daylighting conditions,a room model with an external dimension of 1.5 m×2 m×2 m is established,integrated with a“smart window”system with an area of 1 m~2 composed of 100 single modules of 10 cm×10 cm×0.3 cm.The minimum indoor average illuminance is above300 lux,which meets the lighting requirements,and the thermochromic layer can alleviate the excessive lighting situation when the solar irradiation intensity is the highest.On the basis of simulation analysis,a smart luminescent solar concentrator with a sizeof 10 cm×10 cm×0.3 cm and the geometric concentration ratio of 10,integrated with an amorphous silicon cell with an efficiency of 7.6%is fabricated.By analyzing the experimental data measured outdoors,it is found that the energy conversion efficiency of the system is up to 1.24%and the power gain is up to 1.26.The thermochromic layer effectively improves the output electric power by up to 9.9%,and its semitransparent state covers the period with the strongest solar radiation in a day,effectively alleviating the situaiton of indoor overheating.The error between simulation and experiment is within 4%.