Foreword: As the world's energy crisis intensifies, all countries are seeking ways to solve the energy crisis. One path is to seek the use of new energy and renewable energy; the other is to seek new energy-saving technologies, reduce energy consumption and improve energy. usage efficiency.
Solar energy is the most direct, common, and cleanest energy source on the planet. Solar energy, as a huge renewable energy source, reaches the surface of the Earth every day and radiates about 250 million barrels of oil. It can be said to be inexhaustible and useless. exhaust. The spectrum of low-pressure sodium lamps is almost all concentrated in the visible light band, so the luminous efficiency is high. Most people think that energy-saving lamps can save energy 4/5 is a great innovation, but low-pressure sodium lamps also need energy-saving 1/4 than the energy-saving lamps, which is more solid light source Great reform.
Low-pressure sodium lamp is recommended as a light source
1, system introduction
1.1 Introduction to the basic components of the system
The system consists of solar cell modules (including brackets), solar charge and discharge controllers (including light control and time control), control boxes, low pressure sodium lamp rectifiers, low pressure sodium lamps, battery packs, and light poles; solar panel light effects Achieve 127Wp/m2, high efficiency, very good for the system's wind resistance design.
The box of the control box is made of stainless steel or galvanized iron plate as a material, 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. The discharge time of the battery can be set by itself or can be controlled by light. The main function of the charge and discharge controller is to protect the battery and control the switch of the street lamp.
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. The following will take the solar energy special low-pressure sodium lamp of Shenzhen Leixin Solar Technology Co., Ltd. as an example and analyze it in several aspects.
2.1 Solar Module Selection
Design requirements: Shenzhen region, load input voltage 24V power 34.5W, working hours of 8 hours a day, to ensure continuous rainy days 6 days. The streetlight is designed for 26W, 3600LM.
The annual average radiation dose in Shenzhen in the past two decades is 107.7 Kcal/cm2. After a simple calculation, the peak sunshine hours in Shenzhen is about 3.424h.
Selecting two standard battery packs with a peak output power of 110Wp and a single 55Wp should ensure normal operation of the streetlight system during most of the year.
2.2 Battery Selection
Choose 2 12V100AH ​​batteries to meet the requirements.
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 of ​​use of the street lamp is in Shenzhen. According to the data in the relevant reference of this design [1], 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.
(1) Wind resistance 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=6m
The design selects the bottom of the lamp post and the width of the weld δ=4mm The outer diameter of the bottom of the lamp pole=168mm
The surface of the weld is the damage surface of the pole. 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
Stress caused by the moment of action of 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.
2.4 Controller
The main role of the solar charge and discharge controller is to protect the battery. Basic functions must have overcharge protection, overdischarge protection, light control, time control and reverse connection.
In the selection of devices, currently there are microcontrollers, comparators, and more. Each has its own characteristics and advantages. It should be based on the characteristics of the customer group to select the appropriate program, not described in detail here.
Take the LX12-10A/ST2 solar lamp special charge and discharge controller of Shenzhen Leixin Solar Technology Co., Ltd. as an example. Its performance is as follows:
1.Manage storage battery: prevent overcharge and over discharge of battery and prolong battery life;
2. Manage the automatic turn-on and turn-off of solar lights; light control and self-adjusting lighting time
3. Coordinate the work of solar panels and batteries: prevent the batteries from discharging to the solar panels at night and save energy;
4. With temperature compensation.
3ã€Conclusion
The overall design basically considers all links; the peak-wattage selection design of the PV modules and the battery capacity selection design adopt the most common design method at present, and the design concept is more scientific; the wind-resistant design consists of two parts: the battery assembly bracket and the light pole. Analyzed and analyzed comprehensively; Surface treatment adopts the most advanced technology; The overall structure of the street lamp is simple and beautiful; After actual operation, it is proved that the matching between each link is better.
At present, the initial investment in solar low-pressure sodium lighting is still a major issue that plagues us. However, the efficiency of solar cells is gradually increasing, and the price will be gradually reduced. Compared with the renewable energy of solar energy, clean pollution-free, and environmental protection and energy saving of low-pressure sodium lamps, the conventional fossil energy becomes increasingly tense, and it will cause serious environmental problems after use. Pollution. Therefore, solar low-pressure sodium lighting as an emerging outdoor lighting, show to us will be endless vitality and broad.
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