Study Of Surface Shape Measurement Of The Solar Concentrator Mirrors In Solar Thermal Power Applications

The solar concentrator is a key component of the solar thermal power plants. It is an energy concentrating device which delivers the energy from the sun to the receiver. The solar concentrator generally consists of several pieces of reflective mirror. Therefore, the optical quality in particular the geometric precision of the mirrors has a significant impact on the solar concentration efficiency of the solar concentrator and thus on the performance of the power plant. Thence study on surface shape measurement techniques for the qualification of solar reflectors has important significance.Based on the above background, this dissertation is mainly looking for a fast, accurate and economical method for surface shape measurement of reflective mirrors of the solar concentrator. Meanwhile this dissertation aims to develop the corresponding measurement equipment which can offer a detection support for the design, manufacture, assembly and maintenance of the solar concentrator. Overall, the main work of this dissertation is as follows:1. The existing surface shape measurement methods for solar concentrators were analyzed and the general development trend was summarized. The fringe reflection technique which was considered as a suitable measurement method was proposed. The measurement principle of fringe reflection method was studied in depth. And the phase shift algorithm and phase unwrapping which involved by this method were analyzed in detail. A self-iterative algorithm for surface shape reconstruction was introduced. Thus the measured mirror shape which is closer to the real situation can be fitted. And the evaluation methods for the solar curved reflector were discussed at the same time.2. Based on fringe reflection method, a surface shape measurement instrument named Fringe Reflection Measurement System(FRMS) was developed. The design and hardware implementation of this measurement system were elaborated in detail. The impact of measurement distance on image processing was analyzed and the calibration method of the measurement system was studied.3. The control and evaluation software of the Fringe Reflection Measurement System was developed. It features a graphical user interface that allows easy operation of the system. And it can evaluate the data and display the results automatically.4. By using the Fringe Reflection Measurement System, the shape accuracy of a standard RP3 parabolic trough inner mirror and a heliostat which produced by a certain manufacturer were tested. And the representative measurement results which verified the correctness and feasibility of the instrument were showed in this dissertation.5. A detailed analysis of the measurement uncertainty of the system was conducted and some relevant experiments were carried out. The experimental results indicate that the measurement uncertainty of this system obtained by a water surface test is about 0.6 mrad and the repeatability precision of this system is better than 0.01 mrad.