Research and Application Analysis of Solar LED Street Light System
With the improvement of human life quality, the consumption of energy also increases rapidly. The depletion of petroleum resources and the deterioration of the earth's ecological environment have also led to the lack of energy and environmental pollution, which have become important issues for sustained economic development and have aroused people's widespread concern .
According to relevant statistics, lighting accounts for about 20% of the global energy consumption. In China, the electricity used for lighting is more than 300 billion kWh each year, of which road lighting accounts for about 30% of the total lighting. The effective use of natural energy is the focus of technological research. By effectively collecting solar energy and recycling it, it can save nearly 1/3 of lighting electricity consumption per year, equivalent to the annual generating capacity of the Three Gorges Project with a total investment of more than 200 billion yuan.
Some barren areas are still using non-renewable candles, wood and kerosene lamps and other biofuels to illuminate the effective use of solar energy pollution-free and never-depleted features, combined with LED lighting energy efficient, environmentally friendly, long life and easy to control the light color and other advantages , Through the application of solar LED street lamp to improve energy efficiency and ease the energy crisis and promote the development of energy recycling technology in our country, to improve the lighting quality and adjust the social and economic structure is of great significance.
1. Solar LED street lighting system
1.1 Solar LED street lamp program
Solar LED street lights consist of solar cells (physically referred to as PV photovoltaic, PV), wind turbines, storage batteries, controllers, inverters, LED street lights, mounting brackets and lamps Rod and other components, according to the structure combination is divided into wind and solar, complementary and independent electricity and other types.
Affected by the distribution density of solar radiation, light time, continuous cloudy and snowy weather and other factors, the PV or battery capacity is usually calculated accurately, using wind and solar power or complementary to ensure the project lighting needs.
Shenzhen Spike Optoelectronics Technology Co., Ltd. through years of project experience, research and development of independent solar LED lights shown in Figure 1, the product is not subject to geographical constraints and the impact of electrical installation conditions, do not need to excavation pavement buried pipe construction, PV Can be adjusted according to the geographical location of the installation, battery and controller into the box fixed to the pole, the controller can also be installed in the bottom of the pole inspection port and battery buried.
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Figure 1 stand-alone solar LED lights
1.2 product standards
Check the current standards in our country, the safety of solar LED street lamp shall comply with GB 24460-2009 "General Specifications of Solar Photovoltaic Lighting Device" standard, the overall structure has sufficient strength to withstand 10 wind load test, the protection level of not less than IP54,4m The height of the pole should have good lightning protection and grounding protection measures, the grounding resistance should be less than 30 Ω, live body and metal parts between the insulation resistance should be greater than 2 MΩ, the box should be designed to use special tools to open the structure.
In the product design or determine the program, the components should meet the requirements of the appropriate national standards, no corresponding national standards should be IEC standards, industry standards, coalition standards or corporate standards required to ensure product safety and performance standards.
PV should be consistent with GB / T 9535-2006 "ground with crystalline silicon photovoltaic module design identification and stereotypes" standard requirements, fixed-type valve-regulated lead-acid batteries should be consistent with the corresponding requirements of GB / T 19638 series of standards, general valve-regulated lead-acid batteries Should meet the corresponding requirements of GB / T 19639 series of standards, the controller and inverter should meet the GB / T 26849-2011 "performance requirements for solar photovoltaic lighting control" standard requirements, LED lights should meet the GB 7000.1 and GB 7000.5 standards , Poles and mounting brackets and other components should be consistent with GB 24460-2009 standard 6.5 requirements.
1.3 solar cells
PV is a kind of optoelectronic semiconductor component that can convert the light energy into electrical energy through photoelectric effect or photochemical effect, and output voltage when it is certain to light and generate current in the case of loop. And it has certain anti-corrosion, rain-proof and anti-hail And wind resistance.
PV crystalline state can be divided into two categories: crystalline film and amorphous film, the former is divided into monocrystalline silicon and polycrystalline silicon, the current industrialization of N-type monocrystalline PV conversion efficiency of about 21% -24%, P The conversion efficiency of single crystal PV is about 18.7% -19.2%, and the conversion efficiency of polycrystalline PV is about 17% -17.5%. Ultra-high efficiency silicon PV newly developed by the University of Delaware uses a new type of lateral optical Focusing system will improve the conversion efficiency to 42.8%, about 1 times higher than the P-type monocrystalline PV.
PV open circuit voltage, short circuit current, maximum output power, fill factor and conversion efficiency indicators to determine the merits of the performance benchmark, in order to prevent PV in series PV hot spot effect, in parallel between the positive and negative bypass Diode, to avoid the energy generated by the light-emitting components are shaded by the PV consumption.
1.4 battery
As the energy storage unit of the solar LED street lamp, the PV converts the received effective light energy into the electric energy and inputs it into the battery for storage, and provides the electric energy for the LED street lamp when the lighting needs.
Usually single battery with over-voltage, under-voltage and over-temperature protection, as well as overcharge, over discharge and over-current protection, recharge the battery when the active material regeneration (the electrical energy stored as chemical energy), the need to discharge Convert chemical energy to electricity.
In terms of usage and maintenance costs, the need for continuous heating of the sodium-sulfur battery and the fluid control of the vanadium redox flow battery undoubtedly add cost, and the two types of batteries are not yet industrialized. The lithium-ion battery has Strong competitive but expensive, almost no need to maintain the advantages of high-end projects have been widely used, according to the current situation and cost of solar LED street lighting applications at home and abroad, the program will usually adopt a moderate cost and maintenance-free lead-acid batteries, well-known Brand lead-acid batteries in the case of frequent charge and discharge of about 3 years of life.
1.5 controller
The controller is the core component of the solar LED street lamp. On the one hand, it controls the battery's charge and discharge to protect the battery from overcharging, on the other hand, it switches and adjusts the operating mode of the battery according to the PV sunshine intensity and the load change, After the constant current is allocated to the load LED lights.
The controller plays a key role in the continuity and stability of system operation and should comply with the low power consumption requirement of the current national standard GB / T 26849 that the maximum no-load current should not exceed 1% of its rated current. The controllers and coordinators with intelligent control functions form a system network using wireless communication (WC) or power line carrier (PLC) technology to grasp LED street lamps and environmental conditions and analyze and process data in real time. According to the LED street lamp and power status control instructions sent to achieve the LED street lamp network illumination and power distribution of intelligent monitoring and control, solar LED street lamp to change the status of decentralized independent control, the use of wireless networking and intelligent control system shown in Figure 2.
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Figure 2 solar LED street lamp system
(1) Operation Processing: The controller uses the advanced RISC machine (ARM) to analyze the data transmitted by the acquisition module and issue the appropriate decision instruction. ARM battery and PV between the charge and discharge control, the PV can not be normal to the load power supply, through the controller on the charge and discharge and power switching, voltage regulation, short circuit protection and soft-start control to maintain the stability of the load power supply, The control center will grasp the running status of all the terminals in the system and use the remote control to set various operation modes and data.
(2) Control data acquisition: The data acquisition of the controller includes the working status of the PV, the storage data of the battery and the collection of the working status data of the LED street lamp. The controller's acquisition module collects the voltage, current, temperature and ambient light in real time respectively, and provides it to the microprocessor for operation analysis and processing. The circuit of voltage and current collection is under the control of ARM processor and can control the equalization circuit into the working state. The important data such as system operation mode and parameters can be saved in the data storage and will not be lost after power failure.
(3) load control: The controller of the LED street lamp sub-time brightness control to achieve the second energy-saving purposes. System design multi-load output, the circuit output has an independent control and detection functions, when P0.6 = 1 when the transistor is turned on when the relay is closed, the MOS tube is turned on after the battery power LED lights, when the night after 12:00 control The device reduces the power of the LED street light by half and cuts off the power supply to the LED street light when the PV output voltage is higher than 8 V (set according to project requirements).
(4) Charge and discharge control: The controller controls the charging current according to the voltage of the battery and whether to supply power to the LED street lamp to ensure that the battery is in a full state and prevent the battery from being overcharged, overdischarged and reverse charged to the PV at night. The controller uses maximum power point tracking (MPPT) to quickly charge the battery. A fixed duty cycle D = 1/2 is used to control the output at start-up using MPPT, and interference is used when the output frequency is 200 K Detection method to change the duty cycle with a fixed step size to detect increased input power to continue to increase the duty cycle, reduce the duty cycle when the power is reduced to find a near point, according to the rate of change of power to adjust the step, the The DC power from the PV is effectively stored in the battery. Control circuit is also equipped with anti-anti-charge Schottky diodes, the PV voltage is lower than the battery voltage, to avoid the battery to the PV anti-charge, the battery reverse connection will automatically disconnect the circuit to play a protective effect.
1.6 LED lights
LED street lamp energy consumption is one of the important factors affecting the system efficiency. As technology advances, LED has exceeded 160 lm / W luminous efficiency, according to the typical road lighting needs of the lens designed for wide angle, wide viewing angle and bat wing Secondary optical distribution system to fully meet the CJJ 45-2006 "Urban Road Lighting Design Standards" on the quality of lighting requirements, LED lamps using natural convection cooling fin structure, the air flow through the heat sink flue gas to improve LED module cooling Efficiency, waterproof and dustproof grade IP67 independent module LED street lamp shown in Figure 3, product modular design to improve the reuse rate of key pieces and suitable for mass production.
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Figure 3 LED street light
1.7 poles and structural parts
Based on the solar LED street lamp may be long-term application in high humidity and salt content of the coastal area, light poles and mounting brackets and other structures should be Q235 steel, hot dip galvanized surface and then dusted to ensure that at least 72 h salt Fog test to meet the outdoor use of more than 5 years of warranty. Hot-dip galvanized should meet the national standard GB / T 13912-2002 "metal-coated steel parts hot-dip galvanized layer technical requirements and test methods" requirement, if the poles and brackets selected wind resistance coefficient of 27 m / s ( Equivalent to a typhoon of magnitude 10). Its structural design should be able to withstand a windward pressure of 2700 Pa, taking into account the requirements of snow load and mild earthquakes. In addition, the PV mounting bracket should be designed with the best dip angle and any direction adjustable structure to ensure the maximum utilization efficiency of the solar LED street lamp installation and use.
2 technical difficulties
2.1 energy complement each other
In practical applications by the impact of natural conditions, a long-term solar LED street light in the shade or clouds shelter,
The battery will be in undervoltage condition and cause the LED lights not to affect the lighting. Figure 4 Energy Complementary Solutions In each LED street light configuration intelligent control module, the use of WC or PLC technology for LED street light network management, coordinator through a variety of communication methods will all LED lights running information to the remote monitoring platform, After obtaining the energy balance control information of one of two LED street lamps, the system sends the energy balance control signal to the relevant measurement and control module through the ZigBee wireless network intelligent management function and the application of optimized energy complementary operation algorithm, and the corresponding measurement and control module turns on after receiving the command Connect the two power MOS tube, so that high-capacity battery to the low battery charge, to fully rationalize the allocation of energy intelligent management mode to achieve real-time monitoring of each LED street light and data collection and analysis, to resolve the system LED lights Disparity between the deployment of electricity.
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Figure 4 regional complementary schematic
2.2 specific sunshine
Because solar energy resources are affected by geographical environment and climatic conditions, solar energy resources in different regions are not the same, and precise system configuration calculation is the key point of solar LED street lamp control system design. Therefore, System matching calculation method to give a more practical application of the calculated power generation formula.
The system uses the solar radiation meteorological data in the area to calculate the power generation of the PV group in 12 months and calculates the system matching based on the energy power balance of 12 months in a year to avoid errors introduced by artificial interpolation or discrete data, Solar panels and batteries composed of solar LED lighting system.
Wirelessly connect the controller to the network and set up a wireless data collection platform. The system uses the system platform to complete the optical data collection on a periodic basis. According to the data analysis, draw the power distribution curve under different lighting conditions and configure the corresponding software to accurately evaluate the project. [6]
2.3 battery optimization
Battery for a long time in a low battery state will cause irreversible capacity decline, usually by detecting the battery controller to adjust the charge and discharge time to ensure that the life of the battery, but with the battery internal resistance varies with the curve presented by the curve The difference is large, often affecting the accuracy of measurement results.
Test proved that the controller built-in current and voltage two variable storage unit, keep track of the current and voltage values ​​of charge and discharge, through the integral way to detect the battery capacity, deep cycle charge and discharge three times a month, the controller of the battery The actual capacity of the correction and adjustment, and according to the working status of the battery using different control modes, when the voltage is below the lower limit directly into the protection mode or adjust the output power to protect the battery.
2.4 Reliable operation
Solar LED lights of the various components of industrial quality components selected by strict manufacturing process, suitable for reliable operation under harsh conditions. The controller is equipped with a dedicated remote monitoring software and remote control, the system can be set according to the status of the geographical environment and modify the operating mode, the controller has a perfect protection to prevent PV reverse and battery overcharge, discharge and anti-reverse , Load short circuit overload, lightning protection and so on. At the same time control the PV battery safe and efficient charging, for different characteristics of LED lights to provide adaptive constant current output.
3. Marketing and application
The distribution of solar energy resources is closely related to the altitude, geographical conditions and climatic conditions of various regions. China belongs to one of the countries with very rich solar energy resources. The total radiation amount is about 930-2330 MJ / m2. The total area of ​​the country is 2/3 The annual sunshine time in these areas is more than 2000 hours. In most places, more than two-thirds of all the fine weather can use solar energy.
The sustainable use of green solar energy resources, coupled with the LED energy saving and environmental protection, as well as independent solar LED street lights without cable overhead and other characteristics, with significant energy saving effect, a large number of applications at home and abroad.
Solar LED street lights are more and more applications and concerns, energy-efficient and green features will be more suitable for municipal road reconstruction projects, in the square, campus, parks, streets and remote areas with poor energy poor The promotion and application of space.
In December 2015, Spark Park assumed the commitment of the Chinese government to 2,000 sets of solar
LED street light projects in Antigua and Barbuda. Figure 5 shows the positions of our country's ambassador to Antigua and Barbuda, Prime Minister Antigua and Barbuda Gaston Brown and Spike President Wu Feng and other representatives attended the handover ceremony of the project, Antigua and Barbuda Prime Minister Gerson Brown said it will introduce more energy-efficient solar LED lighting products and strengthen cooperation with China Green energy utilization and other aspects of cooperation.
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Figure 5 China Antigua and Barbuda solar LED street lamp handover ceremony
Conclusion
Reuse of renewable energy is the benchmark for energy saving and emission reduction, and also an important measure for China's new energy industry to implement its national policy. While actively promoting the application of solar LED street lights, the system design should be done according to the local solar energy resources and PV's operating characteristics and operating rules. Avoid system does not work as expected. China is a densely populated energy-consuming country. We should combine the structural hardware and control software of the project program with the appropriate optimization design in the light of the seriousness of the current energy problems, and use the intelligent control technology to optimize the control management to achieve the secondary energy saving and promote the new energy and Renewable energy applications.
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