碟式太阳能自动跟踪系统传动机构的误差分析

    Errors analysis of transmission mechanism of dish solar auto-tracking system

    • 摘要: 虽然碟式太阳能集热发电的效率高、开发潜力巨大,但是需要实时对太阳的位置进行精确跟踪。为了提高碟式太阳能自动跟踪系统的精度,该文设计了一种碟式太阳能自动跟踪系统的工作原理图和传动机构,并使用ADAMS软件对其进行了物理仿真,仿真主要基于传动机构运动学特性,包括跟踪角度及主驱动件的角速度、角加速度等方面。分析结果显示传动机构运动学误差约为0.02°,与目前整机系统最小误差±0.20o的标准相比,仅为其误差量的10%。同时,对碟式太阳能自动跟踪系统的误差进行了分析,该研究为提高碟式太阳能自动跟踪系统精度提供了一定的理论依据。

       

      Abstract: Abstract: The energy crisis and environmental pollution have become increasingly prominent, therefore human beings have been exploring and making use of new energy resources. Solar energy, a new energy resource that is clean, renewable, economical, universal, etc., has grown fast worldwide. Taking advantage of solar energy can solve the energy shortage, and solar energy has an important effect on our country’s future development. Solar power is considered to be one of the most ideal utilizations of solar energy. The solar thermal power generation is widely concerned. Among dish, groove, and tower solar thermal power generation, dish solar thermal power generation has the highest photoelectric conversion efficiency, and it belongs to point collector generation technology, which makes it worth to develop. The ever-changing solar radiation direction and the instability of the solar radiation energy lead to the inaccuracy of tracking systems and lower utilization. When the incident sunlight parallels the solar collector, the conversion efficiency is higher. Tracking mode can greatly improve the solar utilization rate. Research shows that energy receiving rate improves 37.7% when solar thermal power generation uses tracking mode. Accurate sun tracking can greatly improve the receiver’s thermal efficiency. Compared to fixed systems, power output of single-axis and dual axis tracking systems can increase 25% and 41% under the same condition. It is clear that an accurate auto-tracking control system can make solar collectors receive more solar radiation energy to improve the solar energy utilization. Although the tracking system is more complex and costs higher than the fixed system, increasing the annual output power can reduce cost effectively. Program tracking mode, which is not affected by the weather, has high adaptability. When the control software calculates the sun’s position, inevitably it would have round-off error. Photoelectric tracking mode has higher tracking accuracy because it can automatically track the sun and is seriously influenced by the weather. Auto-tracking mode of the dish solar tracking system commonly uses hybrid tracking that is a combination of program tracking mode and photoelectric tracking mode. Each tracking mode makes up for the other, so as a result, the precision and stability of the tracking system is further improved and guaranteed. The tracking system works outside, therefore it is easily influenced by environmental factors so tracking accuracy and stabilization is lower. In order to improve tracking accuracy of the dish solar auto-tracking system, this paper chose the more precise transmission mechanism to match the system and mainly focuses on the transmission mechanism error of the dish solar tracking system. Based on a working platform of the existing 1 kW dish solar auto-tracking system, this paper designs a kind of transmission mechanism. The azimuth angle uses double worm single worm wheel; two worms work together to drive the worm wheel. The running speed and direction of the worms are the same, and the screw nut transmission mechanism with self-locking function tracks the altitude angle. Second, deduce the driving equation of the altitude angle and azimuth angle. Thenusesa software named ADAMS is used to do the system’s simulation. The simulation focuses on spring equinox, summer solstice, autumn equinox, and winter solstice in 2013 in Lanzhou based on kinematics of the tracking transmission mechanism. The analytical result shows that kinematics errors of the tracking transmission mechanism are nearly +0.021°. Compared to the minimum systematic error, which is ±0.20º, the kinematics errors are just 10%. At the same time, the errors of the dish solar auto-tracking system are analyzed. It lays a theoretical foundation of the study to improve the precision of the dish solar auto-tracking system. Transmission mechanism error is only part of the dish solar auto-tracking system’s errors; relevant follow-up studies on other errors of the system are ongoing.

       

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