How solar street lights work
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1, system introduction
1.1 Introduction to the basic components of the system
The system consists of solar cell module parts (including brackets), LED lamp heads, control box (with controller, battery) and lamp post parts; solar panel light efficiency reaches 127Wp/m2, high efficiency, and wind resistance to the system The design is very advantageous; the lamp head part is a planar light source with 1 W white LED and 1 W yellow LED integrated on a printed circuit board arranged at a certain pitch. The control box body is made of stainless steel and is beautiful and durable. The maintenance-free lead-acid battery and charge and discharge controller are placed in the control box. This system chooses valve-regulated sealed lead-acid batteries. Because of its low maintenance, it is also called “maintenance-free batteryâ€, which is beneficial to the reduction of system maintenance costs; the charge-discharge controller is designed with both functions (with light Control, time control, overcharge protection, over-discharge protection and reverse connection protection, etc.) and cost control, achieving a very high cost performance.
1.2 Working Principles
The working principle of the system is simple. The solar cell made by using the photovoltaic effect principle absorbs solar radiation energy and converts it into electricity output. After the charge and discharge controller is stored in the battery, the illuminance gradually decreases to about 10 lux at night. The open circuit voltage of the board is about 4.5V. After the charge and discharge controller detects this voltage, the battery discharges to the lamp. After the battery was discharged for 8.5 hours, the charge-discharge controller was actuated and the battery was discharged. The main function of the charge and discharge controller is to protect the battery.
2, system design ideas
The design of solar street lamps is the same as the general solar lighting. The basic principles are the same, but there are more links to be considered. In the following, this solar LED high-power street lamp of Hong Kong Neo-Neon Group Co., Ltd. will be taken as an example and analyzed in several aspects.
2.1 Solar Module Selection
Design requirements: Guangzhou region, load input voltage 24V power 34.5W, working hours per day 8.5h, to ensure continuous rainy days 7 days. (1) The annual average radiation dose in Guangzhou in the past two decades is 107.7 Kcal/cm2. The simple calculation of the peak sunshine hours in Guangzhou is about 3.424h; (2) The daily electricity consumption of the load = 12.2AH (3) The total charging current of the required solar modules = 1.05 × 12.2 × ÷ (3.424 × 0.85) = 5.9 A Here, the minimum number of days between two consecutive rainy days is 20 days, 1.05 is the comprehensive loss factor of the solar cell module system, and 0.85 is the battery charging efficiency. (4) The minimum total power of the solar module = 17.2 × 5.9 = 102 W The standard battery pack with peak output power of 110 Wp and single 55 Wp should ensure normal operation of the street light system in most cases in one year.
2.2 Battery Selection
The battery design capacity calculation is simple compared to the peak wattage of the solar module.
According to the calculation above, the daily power consumption of the load is 12.2AH. When the battery is full, 7 rainy days can be worked continuously. With the first night's work, the battery capacity is 12.2×(7+1)=97.6(AH). The use of two 12V100AH ​​batteries can meet the requirements. Now.
2.3 Solar Module Bracket
2.3.1 inclination design
In order to allow solar modules to receive as much solar radiation energy as possible during the year, we must choose the best angle of inclination for the solar module.
The discussion of the best dip angle of solar cell modules has appeared in many academic journals in recent years. The area where the streetlights are used is in the Guangzhou area. According to the data in this design reference related literature, the tilt angle of the solar cell module bracket is selected to be 16o.
2.3.2 wind resistance design
In the solar street light system, one of the most important issues in the structure is wind resistance design. The wind resistance design is mainly divided into two major blocks, one is the wind-resistant design of the battery module bracket, and the other is the wind-resistant design of the light pole. According to the above two separate analysis. Wind-resistant design of solar cell module bracket
According to the technical parameters of the battery module manufacturers, the solar battery module can withstand wind pressure of 2700Pa. If the wind resistance coefficient is chosen to be 27m/s (equivalent to a tenth-class typhoon), the wind pressure on the battery module is only 365Pa based on the non-viscous fluid mechanics. Therefore, the assembly itself can withstand wind speeds of 27m/s without damage. Therefore, the key consideration in the design is the connection of the battery module bracket and the lamp post.
In the design of the street lamp system, the connection design of the battery assembly bracket and the lamp post is fixedly connected using a bolt rod. (2) Wind resistance design of street light poles
The parameters of the street lamp are as follows:
Panel angle A=16o pole height=5m
The design selects the width of the bottom of the lamp post as δ = 4mm and the outer diameter of the bottom of the lamp pole = 168mm. As shown in Fig. 3, the surface of the weld is the damage surface of the lamppost. The distance between the calculation point P of the pole damage surface resisting moment W and the panel load applied to the pole is F. The distance from the action line is PQ=[5000+(168+6)/tan16o]*Sin16o=1545mm=1.545m. Therefore, the moment of action of the wind load on the damage surface of the pole is M=F×1.545. According to the design maximum allowable wind speed of 27m/s, the basic load of the 2×30W dual-lamp solar street lamp panel is 730N. Consider the safety factor of 1.3, F=1.3×730=949N. Therefore, M=F×1.545=949×1.545=1466 N.m.
According to the mathematical derivation, the resistance moment of the circular ring failure surface is W=π×(3r2δ+3rδ2+δ3). In the above equation, r is the inner diameter of the ring and δ is the width of the ring.
Destruction surface resistance moment W=π×(3r2δ+3rδ2+δ3) =π×(3×842×4+3×84×42+43)=88768mm3=88.768×10-6m3
The stress caused by the moment of action of the wind load on the failure surface = M/W =1466/(88.768×10-6)=16.5×106pa=16.5Mpa<<215Mpa
Among them, 215Mpa is the bending strength of Q235 steel.
Therefore, the width of the weld to be selected satisfies the requirements. As long as the welding quality is guaranteed, the wind resistance of the lamp stem is no problem.
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