Solar energy is the most direct, common and clean energy on the earth. As a huge amount of renewable energy, the radiant energy reaching the earth’s surface every day is about 250 million barrels of oil, which can be said to be inexhaustible and inexhaustible. exhaust. The spectrum of LED is almost all concentrated in the visible light frequency band, so the luminous efficiency is high. Most people think that it is a great pioneering work that energy-saving lamps can save energy by 4/5, but LEDs can save energy by 1/4 than energy-saving lamps. reform.
Solar LED lighting integrates the advantages of solar energy and LED.
#1 Introduction and working principle of solar LED lighting system
The system is composed of solar cell components (including brackets), LED lamp holders, control boxes (with controllers and batteries inside) and light poles; the solar panel luminous efficiency reaches 127Wp/m2, which is high in efficiency and has a high impact on the wind resistance of the system. The design is very favorable; the lamp head part is integrated with 1W white light LED and 1W yellow light LED on the printed circuit board and arranged as a dot matrix with a certain interval as a High Power Ultra Waterproof Long Range LED Searchlight source.
The control box is made of stainless steel, which is beautiful and durable; the maintenance-free lead-acid battery and the charge and discharge controller are placed in the control box. This system uses valve-controlled sealed lead-acid battery, which is also called “maintenance-free battery” because of its little maintenance, which is conducive to the reduction of system maintenance costs; the charge and discharge controller is designed with complete functions (with light control) , time control, overcharge protection, over-discharge protection and reverse connection protection, etc.) and cost control to achieve a high cost performance.
The working principle of the system is simple. The solar cell made of the principle of photovoltaic effect receives solar radiation during the day and converts it into electric energy output, which is stored in the battery through the charge and discharge controller. At night, when the illumination gradually decreases to about 101ux, the solar cell The board open circuit voltage is about 4.5V, the charge and discharge controller will act after detecting this voltage value, and the battery will discharge the lamp head. After the battery has been discharged for 8.5 hours, the charge and discharge controller operates, and the battery discharge ends. The main function of the charge and discharge controller is to protect the battery.
#2 Design idea of solar LED lighting system
2.1 Selection of solar cell modules
Design requirements: Guangzhou area, load input voltage 24V power consumption 34.5W, working hours 8.5H per day, guaranteed 7 consecutive rainy days.
- The average annual radiation in Guangzhou area in the past 20 years is 107.7Kcal/cm2, and the peak sunshine hours in Guangzhou area is about 3.424H through simple calculation;
- Load daily power consumption = 12.2AH
- The total charging current of the required solar modules=1.05×12.2×÷(3.424×0.85)=5.9A；Here, the design minimum number of days between two consecutive rainy days is 20 days, 1.05 is the comprehensive loss coefficient of the solar cell module system, and 0.85 is the battery charging efficiency.
- The minimum total power of solar modules=17.2×5.c=102W；The selection of standard battery components with a peak output power of 110Wp and a single 55Wp should be able to ensure the normal operation of the street lighting system in most cases for a year.
2.2 Battery selection
The calculation of battery design capacity is simpler than the peak wattage of solar modules.
According to the above calculation, the daily power consumption of the load is 12.2AH. When the battery is fully charged, it can work continuously for 7 rainy days, plus the work of the first night, the battery capacity:
12.2×(7+1)=97.6(AH), two 12V100AH batteries can meet the requirement.
2.3 Solar cell module support design
In order to allow the solar cell module to receive as much solar radiation as possible throughout the year, we need to choose an optimal inclination angle for the solar cell module.
Regarding the discussion on the optimal inclination angle of solar cell modules, the area where the street lamps are used this time is Guangzhou, and the inclination angle of the solar cell module brackets is selected as 16 degrees.
Wind resistance design of solar LED lighting system
In the solar street light system, a structural issue that requires great attention is the wind resistance design. The wind resistance design is mainly divided into two parts, one is the wind resistance design of the battery module bracket, and the other is the wind resistance design of the light pole. Let’s analyze the above two parts separately.
Wind-resistant design of solar cell module support
According to the technical parameter data of the battery module manufacturer, the wind pressure that the solar battery module can withstand is 2700pA. If the wind resistance coefficient is selected as 27M/s (equivalent to a ten-level typhoon), according to non-viscous fluid mechanics, the wind pressure that the battery module can withstand Only 365pA. Therefore, the components themselves can fully withstand the wind speed of 27M/s without damage. Therefore, the key thing to consider in the design is the connection between the battery module bracket and the Aluminum Die Casting 50W To 150W IP66 LED Street Light pole.
In the design of this set of street light system, the connection between the battery component bracket and the light pole is designed to be fixedly connected by bolts.
Wind-resistant design of street light poles
The parameters of the street lights are as follows:
Panel inclination angle A=16° Light pole height=5M
The design selects the width of the weld at the bottom of the light pole δ=4MM, the outer diameter of the bottom of the light pole=168MM
The surface where the weld is located is the damaged surface of the light pole. The distance from the calculation point p of the failure surface resistance moment W of the light pole to the action line of the panel load F on the light pole is pQ=[5000+(168+6)/tAn16°]×Sin16°=1545MM=1.545M. So , the moment of wind load on the failure surface of the light pole M=F×1.545.
According to the design maximum allowable wind speed of 27M/s, the basic load of 2×30W double-lamp solar street light panels is 730N. Considering the safety factor of 1.3, F=1.3×730=949N.
According to mathematical derivation, the resistance moment W=π×(3r2δ+3rδ2+δ3) of the circular failure surface.
In the above formula, r is the inner diameter of the ring, and δ is the width of the ring.
Failure 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 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 seam selected in the design meets the requirements. As long as the welding quality can be guaranteed, there is no problem with the wind resistance of the light pole.
2.4 Solar LED Lighting System Controller
The main function of the solar charge and discharge controller is to protect the battery. The basic functions must have overcharge protection, overdischarge protection, light control, time control and anti-reverse connection, etc.
The general parameters of battery anti-overcharge and over-discharge protection voltage are shown in Table 1. When the battery voltage reaches the set value, the state of the circuit will be changed.
In the selection of devices, there are currently single-chip microcomputers and comparators. There are many schemes, each with its own characteristics and advantages. The corresponding scheme should be selected according to the needs of the customer group, and will not be detailed here.
2.5 Surface treatment of solar LED lighting system
This series of products adopts the new technology of electrostatic coating, mainly based on Fp professional building material coatings, which can meet the customer’s requirements for product surface color and environment coordination. climate environment. The processing technology is designed to be coated on the basis of hot-dip galvanizing, which greatly improves the product performance and meets the most stringent requirements of AAMA2605.2005, and other indicators have reached or exceeded the relevant requirements of GB.
The overall design basically takes into account all aspects; the peak wattage selection design of photovoltaic modules and battery capacity selection design adopt the most common design method at present, and the design idea is relatively scientific; the wind resistance design consists of two parts: battery module bracket and light pole The analysis has been done, and the analysis is relatively comprehensive; the surface treatment adopts the most advanced technology at present; the overall structure of the street lamp is simple and beautiful; the actual operation proves that the matching between various links is good.
At present, the initial investment of solar LED lighting is still a major problem that plagues us. However, the luminous efficiency of solar cells is gradually increasing, while the price will gradually decrease. Similarly, the luminous efficiency of LEDs in the market is rapidly increasing, but the price is decreasing. Compared with the renewable, clean and non-polluting solar energy and the environmental protection and energy saving of LED, conventional fossil energy is becoming increasingly tense, and will cause increasingly serious pollution to the environment after use. Therefore, as a kind of outdoor lighting in the ascendant, solar LED lighting will show us infinite vitality and broad prospects.