In road solar safety projects, continuous rainy weather is the most common cause of insufficient lighting duration for solar road studs. Many engineering contractors and purchasers often encounter various practical problems when selecting models.
During the procurement consultation process, three core issues are repeatedly mentioned:
Is the charging speed of single-crystal solar panels really faster than that of polycrystalline ones on rainy days?
Polycrystalline solar panels are cheaper, but is their cost-performance ratio higher and more cost-effective?
Can solar road studs maintain stable night-time lighting after three consecutive rainy days?
This article, based on professional solar industry principles, real road project experience, and public authoritative research data, focuses on weak light and rainy conditions and conducts a deep comparative analysis of single-crystal and polycrystalline solar panels specifically for solar road studs.
Solar road studs are completely off-grid road safety devices without municipal grid access conditions, working entirely by absorbing solar energy during the day and storing it in built-in batteries.
The night-time lighting duration and brightness of the road studs depend entirely on the amount of solar energy charged during the day. Insufficient daytime energy storage directly leads to inability to light normally at night.
Many people mistakenly believe that low temperature is the main factor affecting solar power generation on rainy days. In fact, solar irradiance is the core key.
Rainy, cloudy weather significantly blocks direct sunlight compared to sunny days. Solar irradiance decreases by 60% to 90% in such conditions, with specific drops varying by region, cloud thickness, and rainfall intensity.
In this low irradiance environment, the daytime energy storage of the road studs’ batteries significantly decreases, directly causing insufficient power supply at night.
The charging efficiency of the solar panel forms a closed-loop impact on road safety. The logical relationship is clear and definite:
Solar panel charging efficiency → Battery SOC (battery state of charge) → LED continuous lighting duration → Road night-time traffic safety
In rainy and weak light conditions, the solar panel with better charging performance can maintain higher battery energy, ensuring longer LED working time and stable brightness, effectively alerting drivers to road boundaries and potential road conditions risks.
The performance and cost differences between single-crystal and polycrystalline solar panels mainly lie in the crystal structure, power generation efficiency, weak light adaptability, cost, etc. The following table visually summarizes the key parameters of both:
| Comparison Item | Monocrystalline Solar Panel | Polycrystalline Solar Panel |
| Cell Structure | Made from a single continuous silicon crystal, providing a uniform crystal structure | Made from multiple silicon crystal fragments with visible crystal boundaries |
| Photovoltaic Conversion Efficiency | Higher, with mainstream products achieving 20%–23% efficiency | Lower, with mainstream products achieving around 18% efficiency |
| Low-Light Performance | Excellent, highly responsive to diffuse and scattered sunlight | Moderate, with lower power generation efficiency under weak-light conditions |
| Temperature Coefficient | Better temperature performance, maintaining stable output in high-temperature environments | Slightly less efficient at high temperatures, with a greater reduction in power output |
| Cost | Higher manufacturing cost | Lower manufacturing cost and more cost-effective |
| Installation Space Required | Requires less installation space for the same power output | Requires more installation space to achieve the same power output |
Rainy-day solar power generation does not rely on high-intensity direct sunlight but mainly on atmospheric scattering light. Therefore, weak light performance is the core criterion for evaluating the suitability of solar panel panels for road studs in rainy seasons.
According to Boston solar weak light performance test data, single-crystal solar panels have unique structural advantages. The complete single-crystal silicon structure has no internal crystal boundary resistance, and electron conduction is more smooth.
This characteristic enables single-crystal panels to efficiently capture and convert scattered light on rainy days. In contrast, polycrystalline panels have numerous crystal gaps inside, which hinder the conversion of light energy and significantly reduce the output efficiency of weak light.
Although the actual performance of the panels is affected by production processes, packaging technologies, and the overall design of the components, the comprehensive advantages of monocrystalline panels in weak light scenarios are stable and prominent.
We simulated the attenuation process of solar irradiance during continuous rainy days and compared the charging performance of two panels with the same power and the same type of lithium iron phosphate battery (the following is the schematic test data).
The trend of solar irradiance: 700 watts/square meter (cloudy weather) → 450 watts/square meter (light rain) → 220 watts/square meter (moderate rain) → 120 watts/square meter (continuous heavy rain)
Under high irradiance conditions (700 watts/square meter), the battery charge growth rates of the two panels are basically the same. As the light intensity continues to decrease, the performance gap between the two gradually widens.
When the irradiance drops to 120 watts/square meter (continuous heavy rain), the battery charge increment of the monocrystalline panel is about 35% higher than that of the polycrystalline panel, fully demonstrating the stable charging capacity of the monocrystalline panel in rainy and weak light environments.
In tropical and subtropical regions during rainy seasons, the effective sunshine duration is significantly shortened, and the daily available solar energy resources for solar panels to generate electricity are very limited.
According to the Oxford University photovoltaic module testing method, high-efficiency monocrystalline panels can collect more watt-hours (Wh) of electricity within the limited short sunshine time.
The battery capacity of solar panels is generally small, and the small daily power generation difference will accumulate continuously, becoming the key to determining whether the panels can operate stably for several consecutive rainy days.
To intuitively verify the performance differences of the two panels in rainy conditions, we used the Malaysian highway solar panel project as a simulated test scenario. Malaysia has a tropical and rainy climate, with continuous rainfall throughout the year, making it a typical scenario for testing the weak light power generation capacity of the panels.
Application scenario: Malaysian coastal highway | Duration of continuous rainy days: 3 days | Test product: Embedded solar panels
Matching battery: 3.2V lithium iron phosphate battery | Test control group: Panels with the same power of monocrystalline and polycrystalline solar panels
| Test Dimension | Monocrystalline Solar Panel | Polycrystalline Solar Panel |
| Day 1 (Light Rain): Remaining Battery Capacity / Nighttime Operating Duration | 78% / 10 hours of full-brightness lighting | 72% / 10 hours of full-brightness lighting |
| Day 2 (Moderate Rain): Remaining Battery Capacity / Nighttime Operating Duration | 55% / 9.5 hours of stable-brightness lighting | 42% / 8 hours of slightly dimmed lighting |
| Day 3 (Continuous Heavy Rain): Remaining Battery Capacity / Nighttime Operating Duration | 32% / 8 hours of normal lighting | 15% / 4 hours of slightly dimmed lighting |
After 3 consecutive rainy days, the solar panels with monocrystalline panels can still maintain stable nighttime lighting. While the solar panels with polycrystalline panels have insufficient battery charge storage, the lighting duration and brightness decrease significantly, unable to meet the safety standards for highway traffic.
Monocrystalline panels can maintain over 80% peak conversion efficiency in weak light and variable temperature complex environments; while under the same conditions, polycrystalline panels can only retain about 60% of the peak efficiency. Solar panels exposed to outdoor wind and rain, variable light conditions, stable and efficient charging ability is the core guarantee for the reliable operation of the product.
Solar panels have limited volume, and cannot carry large-sized solar panels. For the same power solar panels, the monocrystalline panel occupies 20%-25% less space than the polycrystalline panel. The compact size is more suitable for the miniaturization and integration of road studs, avoiding the panel bulging that may affect the road’s smoothness and driving safety.
The long-term tracking research by Oxford Academic Institute on photovoltaic components shows that the annual degradation rate of monocrystalline panels is lower. After 3-5 years of outdoor use, its weak-light power generation performance is far superior to that of the aged polycrystalline panels.
The lifespan of road infrastructure projects is generally over 5 years. Monocrystalline panels can ensure long-term stable power generation and effectively reduce the later operation and maintenance costs.
The performance advantage of monocrystalline panels is significant, but polycrystalline panels are not inferior products. They have an irreplaceable application value in specific scenarios. Polycrystalline solar panels are particularly suitable for the following project scenarios:
Polycrystalline panels have lower production costs and can effectively reduce the overall project procurement budget.
Regions with sufficient annual sunlight duration and few rainy days, with sufficient light intensity, the power generation efficiency gap between monocrystalline and polycrystalline panels is extremely small.
Nighttime safety level requirements are low in urban auxiliary roads, community roads, etc. Polycrystalline panels can fully meet the usage needs.
The selection of solar road stud panels should be combined with regional climate and project actual needs. Do not simply pursue high configuration or low price. The following table can help the purchaser quickly match the appropriate panel type.
| Project Scenario & Core Requirements | Recommended Solar Panel Type |
| Tropical rainy areas (frequent prolonged rainfall) | Monocrystalline solar panel |
| Mountain roads (changing light conditions, frequent fog and rain) | Monocrystalline solar panel |
| Coastal expressways (high humidity and extended rainy seasons) | Monocrystalline solar panel |
| Urban roads (stable sunlight with no extreme weather conditions) | Either monocrystalline or polycrystalline solar panels |
| Low-budget, short-term road renovation projects | Polycrystalline solar panel |
In strong sunny and clear weather conditions, the difference in charging speed between the two is extremely small. However, in cloudy, rainy, and weak light environments, monocrystalline panels have an excellent ability to capture scattered light, and their charging speed and photoelectric conversion efficiency are much higher than those of polycrystalline panels.
It depends on the type of solar panel and battery configuration. Road studs equipped with monocrystalline panels + large-capacity lithium iron phosphate batteries can work stably for 3-5 consecutive rainy days; polycrystalline panel road studs can only maintain normal lighting for 1-2 days and then will experience severe power supply shortage.
Monocrystalline solar panels have a longer lifespan. They have a lower attenuation rate in outdoor complex environments, stronger anti-aging performance, and a stable service life of over 5 years; polycrystalline panels will show significant power generation efficiency degradation after 3 years of use.
Yes, but only for specific scenarios. In areas with sufficient sunlight, few rainy days, and low requirements for road safety, polycrystalline panels can provide stable power supply; they are not suitable for high-standard expressways or core roads in rainy areas.
For high-standard road infrastructure projects, the premium of monocrystalline panels is completely worth it. Its stable rainy-day performance, longer service life, and lower operation and maintenance costs can significantly reduce the total life cycle cost of the project. For ordinary low-budget short-term projects, polycrystalline panels are a more cost-effective choice.
Through principle analysis, parameter comparison and actual case verification, the applicable scenarios and performance positioning of monocrystalline and polycrystalline solar panels in the application of solar road studs have become very clear.
In scenarios of continuous rainy weather, weak light illumination, and limited installation space, monocrystalline modules have higher charging efficiency and more stable power generation performance, making them the preferred power supply solution for high-performance and high-standard solar road stud projects.
Polycrystalline modules have unique cost advantages and are more suitable for budget-sensitive projects, areas with abundant sunlight resources, and applications with lower requirements for continuous rainy weather endurance.
In actual procurement and project design, do not simply select based on performance or price. Comprehensive consideration should be given to the average annual rainfall days in the project location, solar irradiance, battery capacity of the road studs, LED power consumption, and the full life cycle cost of the project, to make the most suitable selection decision that meets the project requirements.
