Detail design of solar street lights

The design principle of solar street lights

I. Introduction

With the increasing scarcity of the earth's resources, the investment cost of basic energy is rising, and various safety and pollution risks are everywhere. Solar energy is becoming an inexhaustible and safe new energy source. The more attention is paid. At the same time, with the development and progress of solar photovoltaic technology, solar lighting products have double advantages in environmental protection and energy conservation, and the application of solar street lamps, garden lamps and lawn lamps has gradually formed scale. The development of solar power in the field of street lighting has been gradually improved. . The author's experience on the design of solar street lights is for peer reference.

Second, the composition of solar street lights

The solar street light consists of the following components: solar panels, solar controllers, battery packs, light sources, poles and fixture housings. If the output power is AC 220V or 110V, configure the inverter.

1. Solar panels:

Solar panels are the core of solar streetlights and the most valuable part of solar streetlights. Its role is to convert the solar radiation capacity into electrical energy, or send it to the battery for storage. Among the many solar cells, there are three types of monocrystalline silicon solar cells, polycrystalline silicon solar cells and amorphous silicon solar cells. In the eastern and western regions where sunlight is abundant, it is better to use polycrystalline silicon solar cells because the production process of polycrystalline silicon solar cells is relatively simple and the price is lower than that of single crystal. In the southern regions where there are more rainy days and less sunshine, it is better to use monocrystalline silicon solar cells because the performance parameters of monocrystalline silicon solar cells are relatively stable. Amorphous silicon solar cells are better in the case of insufficient outdoor sunlight, because amorphous silicon solar cells have lower requirements for solar lighting conditions.

2, solar controller

Regardless of the size of the solar luminaire, a good performance charge and discharge controller is essential. In order to extend the life of the battery, its charging and discharging conditions must be limited to prevent overcharging and deep charging of the battery. In places with large temperature differences, qualified controllers should also have temperature compensation. At the same time, the solar controller should have the function of street light control, with light control and time control functions, and should have the function of automatic cutting and controlling load at night, which is convenient for extending the working time of street lamps in rainy days.

3, battery

Since the input energy of the solar photovoltaic system is extremely unstable, it is generally necessary to configure the battery system to work. Generally, there are lead-acid batteries, Ni-Cd batteries, and Ni-H batteries. The choice of battery capacity generally follows the following principles: First, the energy of the daytime solar cell module is stored as much as possible while meeting the nighttime illumination, and at the same time, it is also necessary to store the electric energy required for the nighttime illumination of the continuous rainy day. If the battery capacity is too small, it can not meet the needs of night lighting. The battery is too large. On the one hand, the battery is always in a deficient state, which affects the battery life and causes waste. The battery should match the solar battery and the electrical load (street light). A simple way to determine the relationship between them. The solar cell power must be more than 4 times higher than the load power for the system to work properly. The voltage of the solar cell should exceed 20~30% of the working voltage of the battery to ensure normal negative charge to the battery. The battery capacity must be more than 6 times higher than the daily load of the load.

4, the light source

What kind of light source is used for solar street lamps is an important indicator for whether solar lamps can be used normally. Generally, solar lamps use low-voltage energy-saving lamps, low-pressure sodium lamps, electrodeless lamps, and DLED sources.

(1) Low-voltage energy-saving lamps: low power, high light efficiency, but the service life is 2000 hours, the low voltage tube is black, generally suitable for solar lawn lights, garden lights.

(2) Low-pressure sodium lamp: low-pressure sodium has high light efficiency (up to 200Lm/w), but requires inverter, low-pressure sodium lamp is expensive, and the whole system is made high, and it is used less.

(3) Induction lamp: low power and high luminous efficiency. The lamp is used under normal commercial conditions of 220V (pure sine wave, frequency 50 Hz), and its life can reach 50,000 hours. The service life on solar lamps is greatly reduced compared with ordinary energy-saving lamps (because solar lamps are square wave inverters) The solar power 220V output frequency, position and voltage are not comparable to ordinary utility power).

(4) LED: LED light source, long life, up to 1000000 hours, low working voltage, no inverter, high light efficiency, domestic 50Lm/w, imported 80Lm/w. As technology advances, the performance of LEDs will increase further. The author believes that LED as a source of solar street lights will be a trend.

5, light pole and lamp housing

The height of the pole should be determined according to the width of the road, the spacing of the luminaires, and the illuminance standard of the road. According to the collection of many foreign solar light materials, most of the lighting and heat saving are selected. Most of them choose energy saving. The appearance requirements of the lamps are not high, so it is relatively practical.

Third, the design of solar street lights

1. Road illumination and scope of application

According to the "Urban Road Lighting Design Standards": the average illuminance of the expressway is 20lx, the uniformity is 0.4, the average illuminance of the main road is 15lx, the uniformity is 0.35, the average illuminance of the secondary trunk is 8lx, the uniformity is 0.35, the average illumination of the branch is 5lx, uniformity 0.3. LED street lights are now in use, due to technical conditions, LED power is 30~100w, light efficiency is 50~80lx/w, road illumination is low, the author has done tests, the pole height is 8.5 meters, the spacing is 30 meters, the light source 2×50wLED The lamp has a illuminance of 19lx under the lamp, 11lx between the two lamps, and 3.5lx at the darkest point.

The above number is the initial illuminance value of the newly installed luminaire, so the illuminance cannot satisfy the expressway and the trunk road. Solar street lights should be used on secondary roads and branch roads, and the main roads should be used with caution.

2, lighting time

The working hours of LED street lamps should be the same as the working requirements of general street lamps. The design should consider the short-term sunshine hours in winter, and the working time should be above 12 hours. Since the LED lights are greatly affected by the weather, in the event of continuous rainy days, the LED lights lack power and cannot be used. There is no standard in the country for LED street lights in low irradiance (continuous rainy days), allowing for minimum working hours without provisions, now generally according to the lighting manufacturers and local meteorological conditions, should work in low illuminance (continuous rainy days) Work in the situation for 15 to 20 days. The capacity of solar panels and batteries should be fully considered in the design.

3, lightning protection grounding

The working voltage of the LED street lamp is generally 12V or 24V, which is a safe voltage and does not make electrical protection grounding. However, the LED street light metal pole should be grounded and the grounding resistance is not more than 10 ohms.

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