Solar Traffic Light Panel Wattage and Tilt Angle Selection

Introduction

Size a solar traffic-signal system using site-specific solar-resource data, shading, seasonal conditions, actual electrical load and the required autonomy. Latitude alone is not sufficient. Evaluate panel and battery capacity together with losses, reserve margins and maintenance; both inadequate capacity and unnecessary oversizing can increase lifecycle cost. The following calculations should be checked against the project design assumptions.

Peak Sun Hours

Peak sun hours (PSH) expresses daily solar irradiation as equivalent hours at 1000 W/m². For a fixed-tilt panel, use site-specific data for the intended panel orientation and the design month. Determine the worst-case design period from local seasonal conditions rather than assuming December is the lowest-sun month everywhere.

• Tropical sites: obtain location-specific solar-resource data for the design month, including cloud and shading effects.
• Use site-specific winter peak sun hours from a suitable solar resource dataset; latitude alone does not establish the design value.
• Winter solar resource: use site-specific monthly data, including shading and variability

Use a suitable solar-resource dataset, such as NASA POWER or PVGIS, and verify its location, time period and limitations for the project’s PSH calculation.

Panel Wattage Calculation

For an initial daily-energy estimate, panel rated power (W) = daily energy demand (Wh/d) / [peak-sun-hours (h/d) × applicable system derating factor]. Separately include the required battery-recharge recovery energy and recovery period in the approved design; multiplying daily load by autonomy days alone does not define panel size.

Daily-energy example: assume 200 Wh/day, 3.0 peak sun hours and a 0.7 derating factor. Battery autonomy and recharge recovery require separate calculations.

Illustrative daily-energy estimate: with an assumed 200 Wh/d demand, 3.0 h/d peak sun and a 0.7 derating factor, panel power = 200 / (3.0 × 0.7) ≈ 95.2 W before any additional recharge-recovery allowance. Battery autonomy and the required recovery period must be assessed separately; this is not a product panel specification.

Select the panel rating from the approved energy calculation, seasonal solar resource and charging-recovery requirement. Check the selected panel’s compatibility with the controller and battery. Ask GAOQIAO to confirm the quoted panel configuration rather than assuming a standard 200-400 W range or selecting 300 W or 350 W without verifying the calculation.

Tilt Angle by Latitude

Select panel tilt using the site’s seasonal solar resource, shading, mounting limits and required energy balance. Latitude-based rules can provide an initial estimate, but the chosen tilt should be checked for the actual operating season and system requirements. Review winter generation separately where it determines autonomy:

• At latitudes of 0-10°, assess panel tilt for energy yield, drainage, cleaning and the approved mounting design.
• At latitudes of 10-30°, assess panel tilt against seasonal energy needs, shading and the mounting design.
• Panel tilt: assess site solar data, shading and seasonal energy requirements
• For high-latitude sites, evaluate panel tilt with the local seasonal solar resource, shading, snow and required operating period. A latitude + 10° estimate for locations above 50° is not a universal winter design rule and must be checked against the approved energy calculation.

GAOQIAO supplies adjustable mounting brackets for sites where the optimal tilt differs from the pole or cabinet mounting angle.

Panel Type and Degradation

Select the solar-panel technology and configuration from the approved energy design and site constraints. Monocrystalline panels are one option; verify the selected module’s performance and compatibility rather than treating one technology as mandatory for every solar traffic signal.

• Compare the selected panels’ documented efficiency and rated power under the stated test conditions. Higher efficiency can reduce the area needed for the same rated wattage, but do not assume every panel exceeds 20% efficiency.
• Compare documented low-irradiance performance for the selected panel models under the relevant seasonal conditions.
• Confirm the panel’s documented annual degradation rate and warranty conditions; 0.5% per year is not guaranteed for every product.

Compare solar-panel technologies using the selected modules’ documented power, efficiency, dimensions and operating characteristics. Confirm the panel model supplied by GAOQIAO and its product and power-warranty terms. Do not assume one technology is always cheaper or that every panel carries the same warranty.

Featured Products

GAOQIAO supplies solar traffic signals with matched panel sizing. See the solar site survey guide.

Conclusion

Size the solar array using site-specific solar-resource data, the load profile, system losses and the required battery-recovery performance in the design month. Provide GAOQIAO with the location, shading and installation constraints to discuss panel, bracket and tilt options. Confirm the sizing assumptions and available documentation for the selected configuration.

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Frequently Asked Questions

What tilt angle should I use for my latitude?

Select panel tilt from a site-specific seasonal energy assessment. Latitude-based values can serve as initial estimates, but shading, mounting constraints and the required operating season must be considered. Ask GAOQIAO to confirm the proposed tilt and design assumptions; do not assume a fixed latitude + 10° rule or an undocumented factory default.

Should the panel face true south?

Panel orientation should be selected from the site’s location, seasonal solar resource, shading and installation constraints. An equator-facing orientation is a common starting point, but east- or west-facing arrangements are not universally prohibited. Have the designer verify the selected azimuth, tilt and energy yield for the required operating season.

Can I use a bifacial panel?

Bifacial panels can collect reflected light on their rear side, but the energy benefit depends on ground reflectance, shading, mounting geometry and site conditions. Compare a site-specific yield assessment with the load and battery requirements. Confirm the available panel configuration with GAOQIAO rather than assuming a fixed percentage gain.

Relevant GAOQIAO products

These public GAOQIAO catalogue pages are related to the guide. Open them for the representative description, then confirm the latest drawing and configuration before ordering.

• Traffic signal controllersWired and solar controllers with 6, 22, 44 and 56 output options.
• LED traffic signal heads200mm, 300mm and 400mm signal heads; confirm the selected model and applicable project requirements.
• Signal polesVertical, signal arm and double-arm poles; confirm suitability for the approved site design.
• Spare parts and accessoriesSpare LED modules, lenses, visors, surge arrestors and anchor bolts.

Related buyer resources

• Traffic Signal Controller Cabinet Guide
• Traffic Light Wiring Diagram Guide
• Traffic Light IP Ratings Guide
• Traffic Signal Head Specification Guide
• Solar Traffic Signal Site Survey
• Contact GAOQIAO

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