Study On Concentrating Photovoltaic System Based On Mirror Reflection

Due to the solar energy’s properties of randomness and low energy density, the potential of PVcells in most of installed PV systems is not fully utilized, resulting drawbacks such as expensiveinstallation, high cost of generated electricity, long term to repay the investment, etc. Thosedrawbacks are criticized in connection to the high energy consuming and environment polution inthe PV cell manufacturing procedure and indeed affect the wide acceptance of PV power generatingsystems. The dissertation is an attempt to multiply the power generating capacity of same PV cellsby mirror-based solar concentration, aiming at the reduction the installation budget and thewidening road to the application of PV power generating system.The main tasks of the dissertation work and associated contributions are as following:A synthetical study and analysis is done on the physics and technology basics of PV powergeneration, the sun-earth geometry, and various approaches for concentrated PV. Important andfundamental formulae are deduced for sun-earth geometry with the help of spherical geometry andvector algebra. A number of problems such as the validity of solar-time based solar tracing andconcentration, the sunrise and sunset time, the sunlight duration of each calendar day, as well as thecalculation of air mass are solved. A sum-up and analysis of the techniques based on imaging andnon-imaging optics for solar concentration is made. The above mentioned studies form thepreliminary of succeeding study on mirror-reflection-based PV concentration system.A mimic paraboloid solar concentration system composed of a moving PV panel and multiplemoving flat mirrors is proposed. Study is carried out on the positioning, posing and motioning ofeach system components, as well as the system’s optimal operation and coordinated control.An approach of PV concentration system in which the PV panel and multiple flat mirrors arefixed along the longitude is proposed, and the uniformity of the irradiation on the PV panel’s surfaceis an important issue of such a system. The size optimization of rectangular mirrors, the PVpanel-mirrors overall arrangement are studied by synthetical analysis based on projective geomeitry.The motion control of the2-axes servo-mechanism and the network hierachical control system arealso studied and designed in detail in the development of the system. Some optimization problemssuch as the obliquity of the PV panel, the locations and allowed minimal sizes of multiple flatmirrors, as well as thelow power operation of servos are discussed and have reached respectiveconclusion.A secondary reflection based concentration structure is proposed. The parametric design isperformed with the help of the deduction of the laws of secondary reflection in vectorized form.Based on such structure, two new structures (propeller type and double-cone type) are put forwardby respectively using symmetry and rotation and new types of solar concentration devices might bedeveloped.The work done is summarized and discussed at end of the dissertation as conclusion.