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Battery autonomy: for roadway lighting most specs ask for 3 nights of autonomy, but in cloudy regions 4–5 nights is safer. Size the usable capacity from the nightly load (LED wattage x dimmed hours), then divide by the allowed depth of discharge. LiFePO4 at 80% DoD is a sensible default; lead-acid needs roughly double the nominal capacity for the same usable energy. Also derate for cold, since capacity drops noticeably below 0°C.
Panel sizing vs. winter sun hours: design around the worst month, not the annual average. Take peak sun hours for December (or June in the southern hemisphere) at your tilt angle, apply about 70–75% system efficiency for the controller, wiring, dirt and temperature, and make sure the panel can fully recharge the battery within that worst-case day. A fixed tilt close to latitude + 10° works well for winter-critical sites; keep at least 10–15° so rain washes the dust off.
LED efficacy and optics: aim for 150+ lm/W at the module level. Efficacy matters more in solar than on the grid because every saved watt shrinks the panel and battery. Pay as much attention to the lens (Type II / III road distribution) as to lumens, because good optics put light on the road instead of the verge and let you cut wattage.
Pole height and spacing: as a rule of thumb the spacing is about 3–4x the mounting height for roads, so a 6 m pole is typically spaced at 20–25 m, and an 8–9 m pole at 30–35 m. Check the target illuminance for the road class (for example 10–15 lux average on collector roads, 5–7 lux on residential streets) and uniformity (min/avg of at least 0.3–0.4). Keep poles out of tree shade and away from tall buildings that cut winter sun.
Smart dimming and motion sensing: this is where autonomy is won. A typical profile runs 100% for the first 3–4 hours after dusk, 30–50% in the quiet hours, with radar or PIR boosting to 100% when a vehicle or pedestrian is detected. It can cut the nightly energy use by 40–60%, which means a smaller battery or more days of autonomy. MPPT charging, a programmable controller and remote monitoring (4G/LoRa) also help catch failing batteries early.
Happy to compare notes on any of these. I work with SOLARTODO on solar street lights and smart poles (website in my profile and signature).
Panel sizing vs. winter sun hours: design around the worst month, not the annual average. Take peak sun hours for December (or June in the southern hemisphere) at your tilt angle, apply about 70–75% system efficiency for the controller, wiring, dirt and temperature, and make sure the panel can fully recharge the battery within that worst-case day. A fixed tilt close to latitude + 10° works well for winter-critical sites; keep at least 10–15° so rain washes the dust off.
LED efficacy and optics: aim for 150+ lm/W at the module level. Efficacy matters more in solar than on the grid because every saved watt shrinks the panel and battery. Pay as much attention to the lens (Type II / III road distribution) as to lumens, because good optics put light on the road instead of the verge and let you cut wattage.
Pole height and spacing: as a rule of thumb the spacing is about 3–4x the mounting height for roads, so a 6 m pole is typically spaced at 20–25 m, and an 8–9 m pole at 30–35 m. Check the target illuminance for the road class (for example 10–15 lux average on collector roads, 5–7 lux on residential streets) and uniformity (min/avg of at least 0.3–0.4). Keep poles out of tree shade and away from tall buildings that cut winter sun.
Smart dimming and motion sensing: this is where autonomy is won. A typical profile runs 100% for the first 3–4 hours after dusk, 30–50% in the quiet hours, with radar or PIR boosting to 100% when a vehicle or pedestrian is detected. It can cut the nightly energy use by 40–60%, which means a smaller battery or more days of autonomy. MPPT charging, a programmable controller and remote monitoring (4G/LoRa) also help catch failing batteries early.
Happy to compare notes on any of these. I work with SOLARTODO on solar street lights and smart poles (website in my profile and signature).
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