Solar Street light System Design and Implementation

Solar street lights, with their advantages of zero electricity charges, low pollution and flexible installation, have been widely applied in municipal roads, rural revitalization construction, industrial parks, scenic area walkways and other scenarios. However, in actual projects, problems often arise due to unscientific design and non-standard implementation: In a certain rural road, the solar street lights installed could only be lit for three hours because they did not take into account the shortened daylight in winter. Due to the fact that the foundations of the street lights in a certain park did not meet the wind resistance standards, many of the light poles tilted after the typhoon. These problems not only affect the user experience but also increase the cost of later maintenance.

This article will break down the technical key points of the solar street light system from the two core links of "design planning" and "implementation", and explain the methods of parameter calculation, component selection and standardized installation through practical cases, helping the engineering party and the purchasing party avoid common misunderstandings and achieve efficient and stable operation of the system.

The Design Stage of the Solar Street Light System

The core objective of the design phase is "on-demand configuration" - meeting the lighting requirements while avoiding component waste. The process should be gradually advanced in accordance with the logic of "lighting requirements → energy consumption calculation → component selection", and each step needs to be verified in combination with the actual scenario.

Determine the Lighting Requirements and the Height of the Light Pole

Lighting requirements are not necessarily "the brighter, the better". They should be determined in combination with the national standards of the usage scenario to avoid excessive energy consumption or insufficient lighting.

First, clarify the light intensity standards (lux value) : According to the "Urban Road Lighting Design Standard" (CJJ45-2015), the average illuminance of main roads should be ≥20lux, that of secondary roads ≥10lux, and that of rural roads ≥5lux (lux is the unit of light intensity, and 1lux is approximately equal to the light intensity of a candle at a distance of 1 meter).

Secondly, match the height of the light pole with the width of the road: The height of the light pole directly determines the coverage area of the lighting. If it is too low, it will cause overlapping and waste of light; if it is too high, it will reduce the ground illuminance. Common matching relationships are as follows:
 

Road/Walkway Type	Road Width	Recommended Light Pole Height	Lighting Coverage / Installation Method
Rural roads	3–5 meters	4–5 meters	Each single light covers an area of 6–8 meters
Municipal secondary roads	6–8 meters	6–8 meters	Install one light every 30–40 meters, with coverage intervals of 6–8 meters
Park/scenic area footpaths	2–3 meters	2.5–3 meters	Focus on ambient lighting

Screen Suitable LED Lights

LED lights are the "light-emitting core" of solar street lights. When selecting them, both "lighting effect" and "energy consumption control" should be taken into account, with a focus on three parameters:

lumen output

The lumen value directly determines the luminous intensity of the light and should be estimated according to "illuminance standard × coverage area". The formula is: Required lumen value = Target illuminance (lux) × Illumination coverage area (㎡).

Taking a 6-meter light pole (covering an area of approximately 50 square meters) and a secondary road with a 10lux standard as an example, the required lumen value = 10×50=500lm. Therefore, LED lights with 600-800lm can be selected (reserving 10%-20% redundancy to deal with LED aging).

Power selection

The power of LED lights is positively correlated with the lumen value. Common specifications include 15W, 20W, 30W, and 50W. Energy consumption should be calculated in combination with the "average daily lighting duration" to avoid excessive burden on solar modules.

For instance, in rural areas, street lights are lit for 6 hours a day (from 18:00 to 24:00). A 20W LED light can meet the 5lux demand. If a 50W light is chosen, the daily energy consumption will double, and a solar panel and battery with greater power will be required.

Protection grade

Outdoor solar street lights need to withstand wind, rain and dust erosion. The protection grade of the lights should reach IP65 or above (the first digit after IP represents the dust-proof grade, with 6 indicating complete dust-proof; the second digit represents the water-proof grade, with 5 indicating resistance to spray water).

In coastal areas, anti-corrosion shells (such as those made of aluminum alloy) should also be selected to prevent the shells from rusting due to the salt in the sea breeze. In snowy areas in the north, it is recommended to choose lights with "anti-snow design" to prevent snow coverage from affecting heat dissipation.

Calculate the Average Daily Energy Consumption of the Solar Street Light System

The average daily energy consumption is the core basis for the subsequent component selection. It needs to be precisely calculated based on the power and lighting duration of the LED lights to avoid making hasty estimates.

Basic calculation formula

The average daily energy consumption (Wh, watt-hours) = LED light power (W) × daily lighting duration (h).

Additional energy consumption loss that needs to be considered

In actual operation, line transmission and controller conversion will result in energy loss of 10% to 20%. Therefore, redundancy should be reserved during calculation. It is recommended to calculate the actual demand based on "basic energy consumption ×1.2".

Select and Match the Power of Solar Panels Reasonably

Solar panels (PV modules) are the "energy source" of the system and need to meet the "average daily energy consumption demand + loss", while determining the power in combination with the local duration of sunlight.

Key parameter: Duration of sunshine

Sunshine duration refers to the time in a day when solar panels can effectively generate electricity in a local area (not the total duration of the day), and it is necessary to refer to the "annual average daily sunshine duration" released by the local meteorological bureau.

Solar panel power calculation formula

The power of solar panels (W) = the actual average daily energy consumption demand (Wh) ÷ the local average daily sunshine duration (h).

Component type selection

At present, there are mainly two types of solar panels on the market: monocrystalline silicon and polycrystalline silicon

• Monocrystalline silicon plates: High conversion efficiency (18%-23%), low-temperature resistance, suitable for regions with short sunlight and large temperature differences (such as Northeast China), but slightly more expensive;
• Polycrystalline silicon board: Conversion efficiency 15%-18%, high cost performance, suitable for southern regions with abundant sunlight.

For general municipal projects, it is recommended to choose monocrystalline silicon plates, which are more energy-efficient for long-term use. When the budget for rural projects is limited, polycrystalline silicon boards are also a reliable choice.

Determine the Capacity of the Battery

The battery is the "energy warehouse" of solar street lights and needs to meet the "backup days" requirement - that is, the system can still light up normally under continuous rainy and cloudy weather.

Backup days setting

The number of backup days should be combined with the local rainfall conditions

• Rainy areas: It is recommended to back up every 5 to 7 days.
• Dry areas: It is recommended to back up every 3 to 5 days.
• In extremely arid areas: It can be shortened to 2 days.

Formula for calculating battery capacity

Battery capacity (Ah) = (Actual daily energy consumption demand × backup days) ÷ Battery voltage (commonly 12V or 24V).

Comparison of battery types

Different types of batteries are suitable for different scenarios. Please choose according to your needs

• Colloid battery: Resistant to low temperatures (-20℃ to 50℃), long lifespan (3-5 years), suitable for outdoor use in the north, but heavy and requiring regular maintenance;
• Lithium batteries (lithium iron phosphate) : Lightweight (weighing only 1/3 of gel batteries), maintenance-free, and long-lasting (5-8 years), suitable for scenarios in the south or where the load-bearing capacity of light poles is limited. However, they have poor low-temperature performance (insulation layers need to be added when the temperature is below -10 ℃).

Select and Match the Charging Controller

The charging controller is the "energy distribution center", responsible for storing the electrical energy from the solar panels into the battery, while preventing overcharging and overdischarging from damaging the components. When selecting the model, two core parameters should be focused on:

Current compatibility

The "maximum photovoltaic input current" of the controller should be greater than the output current of the solar panel to prevent overload and burnout. For instance, for 80W and 12V solar panels, the output current is approximately 6.7A (80÷12≈6.7). Therefore, A controller with a maximum input current of ≥10A should be selected (with redundancy reserved).

Functional adaptability

Give priority to choosing controllers with the following functions:

• Overcharge/overdischarge protection: Stop charging when the battery voltage is too high and cut off the power supply to the light when it is too low.
• Dual-mode light control + time control: Automatic charging during the day, light control turns on in the evening, and supports timed off (such as setting the light to automatically turn off after 8 hours).
• Data monitoring: Some high-end controllers are equipped with an APP connection function, allowing remote viewing of charging capacity and battery power, which is convenient for later operation and maintenance.

The Implementation Stage of the Solar Street Light System

After the design plan is determined, the implementation stage must strictly follow the procedures, with a focus on controlling the three major links of "site selection, component installation, and wiring testing" to avoid system failures caused by improper operation.

Choose Suitable Installation Sites

The power generation efficiency of solar panels directly depends on the lighting conditions. The site selection needs to meet two core requirements:

Unobstructed light

The installation site must ensure that there are no trees, buildings or utility poles blocking the view from 10 a.m. to 3 p.m. (the period with the strongest sunlight). If there is any obstruction, the obstruction ratio needs to be calculated: if the obstruction area exceeds 10% of the solar panel, the installation position needs to be changed.

The ground firmness meets the standard

The light pole needs to withstand strong winds (most areas in China are designed for wind loads of level 10), and the ground should meet the following requirements:

• Hardened ground (such as asphalt or cement roads) : The light pole foundation can be directly fixed with expansion screws.
• Soft ground (such as soil or grassland) : A concrete foundation needs to be poured. The depth of the foundation is determined by the height of the light pole (for a 3-5 meter light pole, the depth should be ≥0.6 meters; for a 6-8 meter light pole, the depth should be ≥0.8 meters).

Light Pole Foundation and Pretreatment

The foundation of the light pole is the "root" of the system's safety and should be constructed in accordance with the standard procedures:

Foundation pouring steps

Excavate the foundation pit according to the design dimensions (such as a 6-meter light pole foundation pit with a diameter of 80cm and a depth of 80cm).

Lay a 10cm thick layer of crushed stone at the bottom to enhance drainage (prevent rainwater from soaking the foundation).

Place the prefabricated basic steel cage and ensure that the top of the steel cage is level with the ground.

Pour C30 concrete, vibrate it tightly to avoid air bubbles;

Cover with plastic film for 7 days of curing. Install the light pole only after the concrete strength meets the standard.

Pre-treatment of light poles

Inspect the surface of the light pole: The hot-dip galvanized coating should be uniform, without any missed plating or rust (a thickness gauge can be used for detection, with the galvanized coating thickness ≥85μm).

Reserved wiring holes: When the light pole leaves the factory, it needs to be pre-set with wiring holes from top to bottom (diameter ≥20mm) to facilitate the later passage of cables.

Installation bracket: Fix the solar panel bracket at the top of the light pole and weld the battery box bracket at the bottom. Ensure that the bracket is firmly welded (weld height ≥5mm).

Installation of solar panels

The installation Angle and orientation of solar panels directly affect the power generation efficiency and need to be adjusted in accordance with local geographical conditions.

Orientation adjustment

Solar panels in the Northern Hemisphere should face south (with an error of no more than 5°), and a compass can be used for positioning. The Southern Hemisphere faces true north to ensure that the sun shines directly on the panel at noon.

Angle calculation

The installation Angle is recommended to be set at "local latitude ±5°"

• Regions below 30° latitude: Angle = latitude -5 °;
• Regions with latitudes ranging from 30° to 40° : Angle = latitude;
• For regions above 40° latitude: Angle = latitude + 5°.

In winter, the Angle can be appropriately increased (such as by 5 to 10 degrees) to take advantage of low-angle sunlight to enhance power generation. In summer, the Angle can be adjusted to a smaller size to avoid high temperatures affecting the conversion efficiency.

Fixed requirements

The solar panels are fixed to the brackets with stainless steel screws. Spring washers need to be added to the screws to prevent them from loosening due to wind. The gap between the edge of the panel and the bracket should be ≥2cm to facilitate heat dissipation.

Battery and Controller Installation

The battery and controller need to be well protected against water, sun and theft. When installing, please note:

Battery installation

Place the battery in a waterproof box (with a protection level of ≥IP65), and lay sponge pads inside the box to reduce vibration damage.

The box should be fixed at the bottom of the light pole or buried underground (if buried underground, gravel should be laid around the box for drainage), and direct sunlight should be avoided (high temperature will shorten the battery life).

When multiple batteries are connected in series, ensure that the positive and negative terminals are correctly connected (positive terminals to positive terminals and negative terminals to negative terminals). Press the terminals firmly with copper noses and then wrap them with waterproof tape and heat shrink tubing.

Controller installation

The controller should be mounted at a height of 1.5 to 2 meters on the light pole (for easy maintenance in the future), ensuring that there are no obstructions around and good ventilation (the controller will generate heat during operation, so it is necessary to avoid a closed environment).

The terminal blocks of the controller should be marked with "Photovoltaic Input", "Battery" and "load" to avoid wiring confusion.

Before wiring, disconnect all power sources. First connect the battery, then the solar panel, and finally the light (to prevent short circuits).

Installation and Wiring of LED Lights

The installation of LED lights should take into account both "lighting effect" and "cable protection" :

Fixed lights

Mount the lights on the preset light brackets of the light pole, with the height as per the design requirements (for example, the height of the light on a 6-meter light pole is 5 meters).

The Angle of the light can be slightly adjusted (generally up and down by 15°) to ensure that the light covers the target area and avoid direct exposure to pedestrians' eyes.

Cable connection

The cable of the light passes through the wiring hole of the light pole and is connected to the "load" terminal of the controller. A 10cm redundancy is reserved for the cable (to avoid pulling and breaking).

The joint should be sealed with a waterproof junction box or wrapped with three layers of waterproof tape (starting from the root of the cable, with each layer overlapping by 1/2), and then covered with heat shrink tubing for heating and fixation.

Full system wiring connection

Wiring is the most error-prone part. It is necessary to strictly follow the sequence of "DC first, then AC; positive pole first, then negative pole". The specific steps are:

Solar panel → Controller: Pass the positive and negative pole cables of the solar panel (red positive pole and black negative pole) through the light pole and connect them to the "photovoltaic input" terminal of the controller, then tighten the screws.

Battery → Controller: Connect the positive and negative cables of the battery to the "Battery" terminal of the controller. At this time, the controller should display "Charging" (if it does not display, check whether the positive and negative terminals are connected in reverse).

light → Controller: Connect the light cable to the "Load" terminal of the controller. After connection, the controller should detect the load.

Organize the cables: Secure the cables inside the light pole with cable ties to prevent them from shaking and wearing out the insulation layer. Seal the wiring holes with fireproof putty (to prevent insects and rodents from entering).

Testing and Debugging of Solar Street Light Systems

After installation is completed, it is necessary to test step by step to avoid missing any problems.

Charging test

During the day, observe the controller display under the sunlight: The voltage of the solar panel should be between 18-24V (12V system) and 36-48V (24V system). The current varies with the intensity of light, indicating that the charging is normal.

Lighting test

Manually trigger the "Test mode" of the controller. The light should light up immediately and observe whether the brightness meets the design requirements.

After natural darkness in the evening, the lights should automatically turn on (light control function), and automatically turn off at the set time in the early morning (time control function).

Use an illuminance meter to test the illuminated area to ensure that the average illuminance meets the target standard (for example, secondary roads ≥10lux), and there are no obvious dark areas.

Troubleshooting

If the light does not light up, follow these steps to troubleshoot:

Check if the controller shows "Battery low Voltage" (if it is, supplementary charging is required).

Check if the cables of the lights are connected in reverse (LED lights do not light up if the positive and negative poles are connected in reverse).

Use a multimeter to measure the voltage across the light. If there is voltage but the light does not light up, it indicates that the light is damaged and needs to be replaced.

Component Reinforcement and Protection

Finally, all components need to be reinforced to ensure long-term stability

Tighten all the screws: Use a wrench to retighten the screws of the solar panel bracket, light bracket and battery box.

Increase protective measures: In coastal areas, apply anti-corrosion paint to the bottom of the light poles; in northern areas, add insulation layers to the battery boxes.

Clear the site: Remove construction waste and set up warning signs beside the light poles (to prevent pedestrians from bumping into them).