Hybrid Solar-Mains Traffic Signal Systems for Critical Intersections
Introduction
A hybrid solar-mains system uses both grid power and solar+battery for redundancy. The signal runs on solar during the day, grid at night, and switches seamlessly if either source fails. Critical intersections benefit from the resilience. This guide covers the design.
Why Hybrid?
Three reasons to choose hybrid over pure solar or pure mains:
1. Grid outage resilience: if the grid fails, the battery carries the load for 3-5 days. 2. Lower operating cost: solar carries the day load (60-70% of total energy); grid only at night. 3. Lower carbon footprint: same reliability as grid, with 60-70% renewable energy.
The premium over pure mains is 15-25%; the premium over pure solar is 5-10%. Most critical intersections (urban arterials, hospitals, fire stations) benefit from hybrid.
System Components
A hybrid system has:
- Mains input (110V or 220V AC) with surge protection
- Solar panel and MPPT charge controller
- Battery bank sized for night autonomy (3 days typical)
- Inverter/charger that combines mains and battery
- Controller and signal heads (same as pure solar or pure mains)
The charger/transfer switch is the key component: it manages the source selection without dropping the load. GAOQIAO supplies hybrid chargers with < 5 ms transfer time.
Sizing the Battery
For hybrid, the battery only needs to cover night and grid-outage loads. The daily load is split:
- Day (12 hours, solar): 0 W from battery
- Night (12 hours, battery): full signal load (e.g., 80 W average for a 4-leg intersection)
- Grid outage (up to 3 days): night load only
Battery capacity = night load × autonomy ÷ DoD = 80 W × 12 h × 3 days ÷ 0.5 = 5760 Wh = 480 Ah at 12 V
Half the size of a pure-solar battery, since the day load is carried by solar directly.
Featured Products
GAOQIAO supplies hybrid solar-mains controllers and hybrid signal heads. See the solar vs mains comparison.
Conclusion
Hybrid is the right choice for critical intersections that need grid-outage resilience. GAOQIAO supplies hybrid chargers and matched battery banks. Send us your load profile and grid reliability stats for a hybrid sizing.
Get a Quote
Email: sky-sale@njgq.net WhatsApp/Phone: +86-18805173545 Tel: +86-25-84471080
Frequently Asked Questions
What happens if both grid and battery fail?
The signal goes dark. For critical intersections, post temporary stop signs and dispatch a technician.
How fast does the transfer switch operate?
GAOQIAO hybrid chargers transfer in <5 ms, which is invisible to drivers and compatible with all controller types.
Can I retrofit a hybrid system to an existing mains-powered signal?
Yes. Add a solar panel, MPPT charger, battery bank and transfer switch. GAOQIAO supply retrofit kits.
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 with MUTCD, EN12368, GB14886 compliance.
- Signal polesVertical, signal arm and double-arm poles for any intersection geometry.
- Spare parts and accessoriesSpare LED modules, lenses, visors, surge arrestors and anchor bolts.