The Design Of Photovoltaic Energy In City Street Lighting

In the 21st century,with the intensification of the world energy crisis, solar energy is considered as the most common and clean energy. It is focused on by human with its inexhaustible and unpollution advantages. In the human life, the solar PV has very extensive use, the basic form of which can be divided into two categories: independent power generation and combined to the grid. With the development of photovoltaic technology and the need of world sustainable development, the developed countries have also started to promote photovoltaic combined to the grid in the city, mainly to build the PV system of household rooftop and the MW-level large-scale combined to the grid system. At the same time, the application of solar PV in the construction of urban lighting has also been greatly promoted. At present, the domestic solar photovoltaic technology in the city lighting has shown rapid development momentum,such as street lights, signs, lawn lamp of roads, schools, parks, residential quarters and other places, making the city more environmentally, energy saving, convenient and safe in the public lighting.In order to respond positively to the call of national energy saving and emission reduction and developing low-carbon economy,for the purpose of its practical application, from the starting of the photovoltaic properties of solar cells, arounding the solar photovoltaic technology and LED lighting technology, the solar LED lights systems is designed to meet the use of road lighting in Taiyuan city. The system consists of solar cells, batteries, controller, LED light source and constant current drive circuit and other components. The solar silicon photovoltaic panels convert solar energy into electrical energy stored in batteries, which provides power for the entire system.The task analyzes the selected principles of solar cell power and the matching method of battery capacity,and calculates solar power and battery capacity, which solves the problem of the short battery life and low reliability of system,because the controller protects the battery inadequatly to make it often being over discharge or overcharge. At the same time,the drive of LED street light is analyzed. Therefore, the main works are as follows:First of all, the hardware about the controller of solar street lamp is designed. ATmega128 MCU is selected as the master controller chip and the charge and discharge of battery is controlled by the master chip. Based on the ATmega128 MCU,the solar street lamp controller with adaptive function is designed. So the phenomenon of overcharge and overdischarge of the battery will not occur, which extends the battery life and increases the reliability of solar LED street light system. In the battery charging part, the design of the fast charge and slow charge at two different stages, can better protect the battery circuit. Meanwhile, software programming and debugging of solar controller are done.Secondly, it is studied about the LED's electrical characteristics, power selection,combination method and so on, focusing on the optimizing design of LED hardware driver circuit. Finally, on the basis of PAM2842 drive chip,LED drive circuit is designed to achieve their applications. Input voltage is selected as 24V by PAM2842, to drive street light which is composed of ten white LEDs with 3W by a series. Input constant current is 700mA to ensure the stability of the lights work,and there is overvoltage protection circuit, making voltage limited to 37.2V. If a single LED is short circuit, it can pretect all the other LED against burning because of the high voltage,to ensure the safe usage of street lamps. Therefore,based on the above research, the system of solar LED street lighting has been designed.Finally,the comparisons of laying of street lamps and cost in Wanbailin District of Taiyuan City are analyzed as an example.