Solar street light uses the photovoltaic effect principle of solar cells. During the daytime, the solar cell absorbs solar photon energy to generate electricity, which is stored in the battery through the photovoltaic controller; when night falls or the light level around the lamp is low, the electricity stored in the battery is used to power the light source through the control of the photovoltaic controller, and the controller cuts off the power of the light source after the set time. Solar street light is composed of the following parts: solar battery, solar street light controller, battery, solar street light source, light pole and lamp housing.
Solar battery is the core part of solar street light, and is also the highest value part of solar street light, which is about the conversion of solar radiation energy into electricity. In many solar cells more common and more practical monocrystalline silicon solar cells, polycrystalline silicon solar cells and amorphous silicon solar cells 3 kinds. In the sunny, sunny areas in the east and west, to use polycrystalline silicon solar cells is good, because polycrystalline silicon solar cells production process is relatively simple, the price is lower than monocrystalline silicon solar cells. In the southern region where there are more rainy days and relatively less sunshine, it is better to use monocrystalline silicon solar cells because the sexual parameters of monocrystalline silicon solar cells are more stable.
For silicon solar cells, under standard conditions [irradiance of 100w/ ㎡, the spectrum is aml.5 temperature of 25 ℃], its open-circuit voltage is 0.48 ~ 0.6v. will be connected to multiple single solar cells, and encapsulation, can constitute a different area, different power of solar modules, can also be collectively referred to as solar cells are generally not available, the actual application of solar Battery modules.
At present, the encapsulation form of solar cells are mainly lamination process and drip adhesive process. The solar cell using the lamination process can guarantee a working life of more than 25 years, and its process characteristics and service life is better than the drip process packaging form. Regardless of which type of solar cell, all have the following five major electrical parameters.
Solar cell peak power is the power output of the solar cell under the conditions, the unit is peak watt, or expressed by the symbol wp. The output power of a solar cell depends on the solar irradiance, the solar spectrum distribution and the operating temperature of the solar cell. At different times and locations, the output power of the same solar cell is different.
By area, the output power of a solar cell is about 120w per square meter; as the conversion efficiency increases, the output power increases accordingly. The choice of solar cell output power should be determined according to the light source power of the solar street light, the time of use and the local climate and geographic conditions.
Solar cells in the process of use, if there is a solar cell monomer alone is blocked by leaves and other shade for a long time, the solar cell monomer blocked in the strong sunlight will heat damage, or even cause damage to the entire solar cell, which is the so-called heat island effect, the general solar cells will be placed at an angle so that the solar cell surface can not be attached to the shade.
As China's north and south latitudes span large, solar cell installation tilt angle to change with the installation area latitude differences. In general, in the area south of the Yangtze River, the installation tilt angle is about 30 degrees; in the area north of the Yangtze River, the installation tilt angle is about 45 degrees; in the northeast, the installation tilt angle should be about 50 degrees. The installation direction is 5 degrees due south or west. The output power of solar cells placed horizontally is reduced by 15% to 20%.
Regardless of the size of solar lamps and lanterns, a good performance charge and discharge controller is essential. In order to prolong the service life of the battery, it must be limited to its charging and discharging conditions to prevent the battery from overcharging and deep charging. In places with large temperature differences, qualified controllers should also have a temperature compensation function. At the same time, the solar street light controller should have both street light control function, with light control, time control function, and automatic cut control load function at night, in order to extend the working time of solar street light on cloudy days.
For any solar lighting system, the merits of the charge/discharge control circuit will directly affect the success or failure of the system application. Due to the highly unstable energy input to the solar photovoltaic power generation system, the control of battery charging in the photovoltaic power generation system is more complicated than the control of the battery using the mains charging system. A good performance of the photovoltaic controller should have control battery charging and discharging, temperature regulation, maximum power tracking and overcharge protection, over discharge protection, reverse connection protection and other protection functions and automatic switching and time adjustment function, so as to ensure the reliable operation of the system. At the same time, the photovoltaic controller should also have the solar cells can be in different temperatures and different solar irradiation situation intelligent maximum power output function, in order to make the solar photovoltaic system has a high efficiency.
As the solar photovoltaic system battery charging direct solar cell to provide, the strip of energy is extremely unstable, so to configure a reasonable capacity, reliable performance of the battery. To ensure the normal operation of the solar photovoltaic system. In the solar photovoltaic system, usually selected maintenance-free lead-acid battery. Maintenance-free lead-acid batteries are fully sealed, with high discharge rate, stable characteristics, no need to add water, simple installation and small footprint. It can be installed horizontally and vertically; the expected life span is generally 5-7 years. The general principle of choosing the amount of battery is: first of all, it should be able to meet the requirements of night lighting, and can store the energy of the long body of solar cells during the day as much as possible, but also should be able to meet the electrical energy needed for lighting at night on consecutive rainy days. If the battery capacity is too small. Can not meet the night lighting requirements; such as battery capacity is too large, the battery is in a long-term buckle point state. Shorten the life of the battery. At the same time will also Liang Fei unnecessary investment.
A simple method can be used to determine the relationship between them, that is, the solar cell power must be higher than four times the load power, the system can work properly; solar cell voltage to exceed the battery working voltage of %20-%30, in order to ensure normal charging of the battery: battery capacity must be higher than six times the daily consumption of the load.
The basic requirements for the battery used in solar street lights are: ① low self-discharge rate; ② long service life; ③ strong deep discharge capacity; ④ high charging efficiency; ⑤ less maintenance or maintenance-free; ⑥ wide operating temperature; ⑦ low price.
According to the needs of the actual situation, you can choose among low-voltage energy-saving lamps, low-voltage sodium lamps, induction lamps, LED lamps, a variety of solar street light sources. No matter which light source is selected, its brightness and the power of the light source has a direct relationship, but also directly affect the system configuration and investment costs. In the same lighting time conditions, the greater the power of the light source. The higher the brightness, the higher the system configuration, the higher the cost; the smaller the power of the light source. The smaller the brightness, the lower the brightness, the lower the system configuration, the lower the cost. What kind of light source is used in solar street light is an important indicator of whether the solar street light can be used properly, generally using low-voltage energy-saving lamps, low-voltage sodium lamps, induction lamps, LED lights.
① Solar street light special low-voltage energy-saving lamps. Solar street light special low-voltage energy-saving lamps are characterized by low current, which can extend the discharge time of the battery. The luminous efficiency is 40lm/W, color temperature can be 2700K, 4000K, 6400K, color white, red, green. The rated voltage can be DC12V/DC24V, and the voltage range can be DC10.8~14.4V, DC22~28V.
②Solar street light special low pressure sodium lamp. Compared with common light sources, low-pressure sodium lamp can save up to 50% electricity under the same luminous flux and illuminance. As the luminous tube of low-pressure sodium lamp is sealed in a high vacuum and coated with infrared reflective film in the glass shell, its luminous rate is basically unaffected by the external environment, its radiation spectrum is pure, stable and free of stray light, and the wavelength of light is strong through fog. Low pressure sodium lamp emits monochromatic yellow light with wavelengths of 589.0nm and 589.6nm, and its luminous efficiency can reach up to 200lm/w. For 35W low pressure sodium lamp, the total luminous flux is 4600lm, and the luminous efficiency is 137lm/w, which is the highest luminous efficiency among low power electric light source products, and the life span is 1800h.
DC24V (12V) input to electronic ballast, output low-frequency (or high-frequency) electrical energy to supply double arc tube high-pressure sodium lamp, double electric solitary tube high-pressure sodium lamp high-pressure pulse start, due to the use of electronic ballast lamp, the lamp life is greatly beneficial, can extend the life of more than 30% (the premise of electronic ballast must have a reliable design and quality). The advantages of the double arc high pressure sodium lamp are.
-Extraordinarily long service life, twice that of a single tube.
-Two tubes are used alternately, and the other lamp is automatically replaced after restarting.
-In the event of an emergency, it can be restarted immediately.
-There is an arc tube bad still can be normal lighting.
-Applicable to high requirements for the service life of the light source and not easy to replace the maintenance of the place.
④induction lamp. Induction lamp has small power, high luminous efficiency (series luminous efficiency ≥ 631lm / w), high color rendering (≥ 80), long life (≥ 50000h), no strobe (working frequency of 2.65MHz), environmental protection (no liquid mercury), can immediately start and restart, not afraid of vibration, can be installed in any direction and other advantages. It can supply constant voltage under wide range of power supply voltage change and output stable luminous flux. The purification circuit and anti-radiation at the input make the electromagnetic interference (EMG) fully comply with the national testing standards. Since its starting voltage and current are basically the same as normal working voltage and current, it is especially suitable for solar street light system and is a new light source specially developed for solar energy system. Since there is no filament inside the bulb, it has a long service life of up to 80,000h. In addition, since the light-emitting coating of the bulb is trichromatic powder, the light emission is soft and the glare is greatly reduced. High-frequency induction discharge lamps do not require maintenance and less maintenance, with reliability.
⑤ Metal halide lamp for solar street light. The biggest advantage of metal halide lamp is the luminous efficiency is particularly high, the luminous efficiency is as high as 80-90lm/w, less heat generation when normal luminous. Due to the spectrum of metal halide lamp metal halide lamp spectrum is based on the continuous spectrum superimposed on the dense line spectrum, so the color rendering index is particularly high, and color reproduction is particularly good, up to 90%. In addition, the metal halide lamp color temperature is high, up to 5000-6000k, life expectancy of 2000-18000h. The disadvantage of the metal halide lamp is difficult to start, low power metal halide lamp start difficulty is more prominent. Metal halide lamps will gradually increase brightness after starting, if the start energy is too large, start too fast will affect the life of the bulb, so in the circuit design should be fully considered.
LED lights have a long life (up to 100000h), low operating voltage does not require an inverter, high luminous efficiency (domestic for 50lm / w, imported for 80lm / w) and other advantages. With technological progress, the performance of LED lights will be further improved. LED lights are a new type of lighting through DC low-voltage lighting LED modules to achieve lighting needs, with high brightness, good color rendering, etc. In addition, because the input of LED lights for low-voltage DC can be combined with solar cells LED lights as a solar street light source, will be the trend of future development.
