The green lighting projects implemented in China since 1996 have promoted the development of solar lighting product technology, accelerated the implementation of relevant policy measures such as product and engineering construction standards, and made solar lighting the main force of green lighting projects.
1. Introduction to Solar LED Street Lights
1.1 Working principle
The solar light-emitting diode (LED) street light system consists of a solar panel, battery, intelligent controller, LED light source, battery box, main lamp head, lamp post, and cable. During the day, under the control of an intelligent controller, the solar panel absorbs solar energy and converts it into electrical energy to charge the battery pack; At night, the battery pack discharges to supply power to the LED light source and achieve lighting functions.
1.2 Light source
LED uses solid semiconductor chips as luminescent materials, and releases excess energy through carrier recombination in the semiconductor, causing photon emission, emitting red, yellow, blue, green, cyan, orange, purple, and white light.
1.3 Lighting fixtures
The shell of the lamp is made of die cast aluminum material, with advanced nano coating technology applied on the surface. It has no oxidation problem, and the surface does not collect dust or corrode. It meets the requirements of effective waterproof, dustproof, and sealing, and reaches IP65 protection level, meeting the requirements of urban main road environment.
1.4 Controller
The controller can achieve precise discharge control, intelligent infrared remote control, stepless power control, etc; Equipped with comprehensive automatic protection and control functions such as anti overcharging and over discharging, electronic short circuit, overload protection, and anti reverse connection; Using digital LED display and settings is extremely convenient and intuitive.
1.5 Light poles
The lamp post is made of high-quality steel parts molded and formed by continuous automatic arc welding in one go. The lines are smooth, the shape is beautiful, the taper ratio is reasonable, and the wind resistance and waterproof measures are reliable.
2. Application examples
The cross-sectional view of the street lamp layout on Xinhua Avenue in Mianchi County is shown in Figure. The starting point of the road is located south of the intersection of Yangshao Road and Xinhua Road in Mianchi County, and the ending point is connected to the Harmony Avenue built by the Guoyuan Township Government.
Based on the current average technical level of solar street lights in China and the local solar energy resources, all the lighting street lights in this project use solar LED street lights. The power supply of the lighting fixtures can be completely provided by the built-in battery pack, without the need for additional municipal power supply. All lighting fixtures are of cut-off type, and all light sources are of Class I energy efficiency products.
By predicting the traffic volume of the route plan, it is determined that the road level of the project is urban main road, and the designed driving speed is 60 km/h. Road lighting follows national standards, and the road is designed as a Class I main road in the city. The average illuminance (Ea) of the motor vehicle lane is ≥ 20 lx, and the illuminance uniformity is u ≥ 0.4; The average illuminance (Ea) of non motorized vehicle lanes is ≥ 10 lx, and the illuminance uniformity is u ≥ 0.4; The average illuminance (Ea) in the intersection area is ≥ 30 lx, and the illuminance uniformity is u ≥ 0.4. The road lighting engineering design adopts 10 m+8 m double cantilever street lights, with 180 W split type IoT smart lighting fixtures installed on the roadway side and 72 W integrated IoT smart lighting fixtures installed on the sidewalk side. Symmetrically arranged along both sides of the road, with a spacing of 30 meters. The lamp post protrudes a cantilever of 1.5 meters and has a tilt angle of 5 °. When there is a side divider on the road, install the street lights within the side divider, with a distance of 1-1.5 meters from the edge of the motor vehicle lane; When there is no side divider, install it on the inner side of the sidewalk, 0.75-1 meters away from the inner edge.
According to the formula in the lighting design manual, calculate the road surface illuminance value, and the results are shown in Table 1.
| Road section | Location | Standard value/lx | Calculated value/lx |
| K0+000 to K6+650 | Motorway | 20-30 | 22.00 |
| K0+000 to K6+650 | Intersection (K0+000) | 30-50 | 40.70 |
| K0+000 to K6+650 | Pedestrian and non motor vehicle lanes | 10 | 23.76 |
| K6+650 to Harmony Avenue | Motor vehicle lanes | 20-30 | 23.65 |
| K6+650 to Harmony Avenue | Intersection (K7+850) | 30-50 | 35.00 |
| K6+650 to Harmony Avenue | Pedestrian and non motor vehicle lanes | 10 | 14.90 |
The calculation results indicate that the design scheme meets the regulatory requirements. According to the layout plan, the required number of street lights is 480 sets of double arm lights (H10/8180 W/72 W).
3. Comparison between solar LED street lights and traditional high-pressure sodium lights
3.1 Performance and Safety Performance
(1) The solar LED street light source is LED, which is a green and pollution-free light source.
(2) The luminous color of LED street lights is closer to natural light, with a color rendering index of over 80, while the color rendering index of traditional high-pressure sodium lamps is only about 20.
(3) LED street lights do not have startup delay issues and can achieve intelligent energy-saving control. However, traditional high-pressure sodium lights have a longer startup time, taking 5-10 minutes to reach normal brightness after startup, and the interval between two starts needs to be greater than 5 minutes.
(4) LED light sources belong to cold light sources, and the temperature difference between the light on and off is not significant. However, the temperature difference between the light on and off of traditional high-pressure sodium lamps is relatively large, and a breathing system needs to be added to reduce the temperature difference.
(5) LED street lights have no glare and uniform road illumination, which helps reduce traffic accidents and improve driving safety.
(6) The power supply voltage of solar street lights does not exceed 36 V, which is a safe voltage level and safer.
Through comparison, it can be seen that compared to traditional high-pressure sodium lamps, solar LED street lamps have better performance and safety performance.
3.2 Economy and Environmental Protection
If dual arm high-pressure sodium lamps (H10/8300 W/100 W) are selected for the Xinhua Avenue lighting project in Mianchi County, 524 sets of YJV-0.6/1-4 need to be installed, while meeting the requirements for road lighting × 25+1 × 16 cables 33.8 km, laying YJV-8.7/10-3 × 50 power cables with a length of 10 km, 9 sets of 20 kVA street light box transformers, and 9 sets of street light controllers. If using dual arm solar LED lights, only 482 sets (H10/8180 W/72 W) are required. The investment comparison between solar LED street lights and high-pressure sodium lights is shown in Table 2.
| Lighting scheme | Rated power/W | Total power consumption over 10 years/(kW · h) | Electricity price/(yuan · kW-1 · h-1) | Total electricity cost for 10 years/yuan | Purchase cost per street lamp/yuan | Street lights and installation costs/yuan | Cable cost/yuan | Box transformer and control/yuan | Maintenance cost for 10 year/yuan | Total operating cost for 10 years/yuan | CO2 emissions from coal-fired power generation/(kg · kW-1 · h-1) | 10-year CO2 reduction/t |
| High pressure sodium lamp scheme | 400 | 1071.7×10^4 | 0.72 | 771.61×10^4 | 4500 | 282.96×10^4 | 663.75×10^4 | 85×10^4 | 419.2×10^4 | 3294.24×10^4 | 0.997 | 1068.48×10^4 |
| Solar LED Street Light Scheme | 252 | — | — | — | 15000 | 723.00×10^4 | — | — | 96.4×10^4 | 819.40×10^4 | — | — |
| Difference | — | — | — | 771.61×10^4 | -10500 | -440.04×10^4 | 663.75×10^4 | 85×10^4 | 322.8×10^4 | 2474.84×10^4 | — | — |
4. Conclusion
In summary, if all the streetlights on Xinhua Avenue in Mianchi County use solar LED streetlights, it can save a large amount of electricity expenses for the local government’s finance, and enable Mianchi County to achieve better green development in the application of new energy. Therefore, it is recommended to promote its use. At the same time, it should be noted that when selecting solar street light products, products produced by manufacturers with complete production qualifications should be selected.