This article summarizes essential formulas commonly used in solar street light design, integrating national standards and practical case studies from various papers:

1. Average Road Illuminance Calculation

Formula:

Eavg = (N × Φ × U × K) / A

● Parameter Description:

　● N: Number of fixtures

　● Φ: Total luminous flux per lamp (lm)

　● U: Utilization factor (0.4-0.6)

　● K: Maintenance factor (0.7-0.8)

　● A: Road area (m2) = Road width × Lamp spacing

Example:

6m wide road, lamp spacing 30m, using 10,000 lm LED, one-sided lighting:

Eavg ≈ (1 × 10,000 × 0.5 × 0.75) / (6 × 30) ≈ 20.8 lx

2. Solar Panel Power Calculation

Formula:

Ppv = Qday / (Hpeak × ηsys)

● Parameter Description:

　● Qday = PLED × Twork (Daily energy consumption, Wh)

　● Hpeak: Local annual average peak sunlight hours (check meteorological data, e.g., Beijing 4.5h)

　● ηsys: System efficiency (0.6-0.75, including line losses, controller losses)

Example:

Load power 80W, daily operation 10h, Shanghai Hpeak=3.8h:

Ppv ≈ (80 × 10) / (3.8 × 0.65) ≈ 324 W

3. Battery Capacity Calculation

Formula:

C = (Qday × D) / (DOD × ηbat × Vsys)

● Parameter Description:

　● D: Number of consecutive cloudy days (usually 3-5 days)

　● DOD: Depth of discharge (0.5 for lead-acid batteries, 0.8 for lithium batteries)

　● ηbat: Charge/discharge efficiency (0.85-0.95)

　● Vsys: System voltage (12V/24V)

Example:

Daily consumption 800Wh, 24V system, 3 days backup, lithium battery:

C ≈ (800 × 3) / (0.8 × 0.9 × 24) ≈ 138.9 Ah → Choose 150Ah battery

4. Solar Panel Installation Angle

Formula:

θ = φ + (5° to 15°)

● Parameter Description:

　● φ: Local geographical latitude

　● Winter optimization: latitude +10°~15°, summer optimization: latitude -5°

Example:

Nanjing latitude 32°, fixed bracket tilt angle set at 37° (32°+5°) to improve winter power generation.

5. Wind Pressure on Solar Panels

Formula:

F = 0.61 × v2 × A

● Parameter Description:

　● v: Maximum wind speed (m/s)

　● A: Wind-facing area of the photovoltaic panel (m2)

   Example:

Panel area 2m2, design wind speed 30m/s:

F = 0.61 × (30)2 × 2 = 1098 N

Need to verify the wind resistance of the lamp pole and foundation.

6. Component Operating Voltage Correction (Temperature Effect)

Formula:

Vmp = Vmp(STC) × [1 + α × (T – 25)]

● Parameter Description:

　● α: Temperature coefficient (approximately -0.35%/°C for monocrystalline silicon)

　● T: Actual operating temperature (°C)

Example:

Nominal component voltage 18V, operating temperature 60°:

Vmp ≈ 18 × [1 – 0.0035 × (60-25)] ≈ 15.3 V

7. Voltage Drop Compensation Due to Temperature

Formula:

ΔV = Nseries × α × ΔT × Vmp(STC)

● Example:

　● 3 series-connected components, each Vmp=30V, temperature difference 35°:

　● ΔV ≈ 3 × (-0.0035) × 35 × 30 ≈ -11V

　● Need to adjust the MPPT voltage range.

8. Solar Panel Capacity Optimization Design

Empirical Formula:

Ppv(opt) = 1.2 × Ppv

● Consider shadowing, dust loss (efficiency reduction of 10-20%)

● When paralleling multiple components, increase bypass diodes to reduce hotspot effects.

9. Typical Design Parameter Comparison Table

Note: Actual design should be combined with PVsyst simulations and DIALux lighting simulations, and validated through field tests.