When designing solar street lights, several important factors must be considered, primarily related to the structural type of the light—split-type, two-in-one, or all-in-one—as each has distinct advantages and limitations.
Split-Type Lights
Split-type solar street lights, where the panel, battery, and lamp are separate components, offer the most design flexibility.
- System Sizing: Their main advantage is flexibility, making them ideal for large systems that require high power or long operating times [2][5]. Components can be sized independently to meet specific demands without the physical constraints of integrated models [2].
- Battery Choice: A key design decision is the battery type. Gel batteries are bulky and typically buried, which protects them from temperature extremes but requires more complex wiring and digging a pit [2][3]. Lithium batteries are lighter, more compact, have a longer lifespan, and are easier to wire, but may be less suitable for burial due to moisture sensitivity and maintenance access [2][4].
- Installation Complexity: While flexible, their design requires assembling and wiring separate parts on-site, which increases labor and the probability of installation errors [2].
Two-in-One Lights
In this design, the battery and controller are integrated into the lamp housing, with a separate solar panel. This popular design presents a trade-off between convenience and performance.
- System Balancing: The battery compartment size is fixed by the lamp's mold. This creates a design limitation where you must balance three factors: high power, long working hours, and backup for rainy days. It is often necessary to make a compromise on one or two of these requirements [1].
- Cold Climate Limitation: Because the lithium battery is housed within the lamp, it cannot be buried for thermal protection in cold regions [1]. This necessitates the use of special, more expensive low-temperature batteries to ensure normal operation in freezing climates [1].
- Versatility: Despite limitations, this design is cost-effective and available in a wide range of power options (from 20-60W being most common), making it suitable for everything from rural roads to town main roads [4].
All-in-One Lights
This design integrates the solar panel, battery, controller, and light source into a single unit. While convenient, it has significant design limitations.
- Charging and Lighting Efficiency: The solar panel's size and power are restricted by the lamp's frame, limiting energy generation [1][6]. The panel is also fixed at a non-optimal angle (around 15 degrees) and its orientation is determined by the direction of the road, not the sun. This severely reduces charging efficiency, especially in mid-latitude regions [1]. The lamp's angle is also restricted, which can compromise lighting coverage [6].
- Application Suitability: Due to these efficiency issues, their design and application should be carefully considered. They are best suited for low-latitude regions with excellent sunlight (e.g., Africa, Southeast Asia) and for pedestrian-centric areas like courtyards, parks, and small paths where lighting demands are lower [6].
- Maintenance: If any single component fails, the entire unit must be removed for repair, which can lead to high maintenance costs [6].
