Short answer: a solar panel mounted at the top of a street light pole is a sail. In our worked examples it raises the wind moment at the pole base 3.5 to 4.6 times compared with an LED head alone. A pole chosen for a grid-powered light is usually not strong enough for a split solar street light: specify panel size, wind speed and height, and ask for the calculation.
Buyers often order “8 m pole, 200 W panel” as two separate items. The pole, bracket, base plate and anchor bolts have to be checked together for the panel actually fitted and the wind at the site. This article shows the size of the effect with a simple calculation.
Key numbers
- Wind pressure rises with the square of wind speed: about 670 Pa at 33 m/s (120 km/h) and 1,080 Pa at 42 m/s (150 km/h).
- A 1 m² panel at the top of an 8 m pole adds about 0.9–1.4 kN of horizontal force at those speeds, acting more than 8 m above the base.
- Base moment for an 8 m pole: 2.9 kNm with an LED head only, 10.1 kNm with a 1 m² panel at 33 m/s.
1. The calculation
For each element, horizontal force F = q × Cf × A, where q = ½ ρ v² is the wind pressure (ρ = 1.225 kg/m³), Cf the force coefficient and A the exposed area. We used Cf = 1.3 for a tilted panel, 1.0 for the LED head and 0.8 for a tapered round shaft. The base moment is the sum of each force times its height above the base. The required elastic section modulus is the moment times a combined safety factor of 1.5, divided by the yield strength of Q355 steel (355 MPa).
This is a simplified check to show orders of magnitude. A design calculation follows the local code (for example EN 1991-1-4 or ASCE 7), with terrain category, gust factor, dynamic effects and fatigue, and checks the bracket, door opening, base plate, welds and anchor bolts as well as the shaft.
2. Worked table
| Pole height | Panel area | Wind speed | Base moment, LED head only | Base moment with panel | Panel share | Required section modulus | Example round section at base |
|---|---|---|---|---|---|---|---|
| 6 m | 0.7 m² (about 100 W) | 33 m/s | 1.5 kNm | 5.3 kNm | 72 % | 22 cm³ | 130 mm × 2.5 mm |
| 6 m | 0.7 m² | 42 m/s | 2.4 kNm | 8.6 kNm | 72 % | 36 cm³ | 130 mm × 3 mm |
| 8 m | 1.0 m² (about 200 W) | 33 m/s | 2.9 kNm | 10.1 kNm | 71 % | 43 cm³ | 160 mm × 2.5 mm |
| 8 m | 1.0 m² | 42 m/s | 4.7 kNm | 16.4 kNm | 71 % | 69 cm³ | 160 mm × 4 mm |
| 10 m | 2.0 m² (two panels) | 33 m/s | 5.0 kNm | 22.9 kNm | 78 % | 97 cm³ | 190 mm × 4 mm |
| 10 m | 2.0 m² | 42 m/s | 8.1 kNm | 37.1 kNm | 78 % | 157 cm³ | 220 mm × 5 mm |
Our own calculation. Shaft modelled as a tapered round tube (base 130/160/190 mm, top 70/80/90 mm); panel centre 0.3 m above the pole top; LED head 0.15–0.25 m². The example section is the thinnest standard wall that meets the required modulus; it is not a design.
3. What the table tells a buyer
- The panel, not the pole, drives the design. Doubling the panel area roughly doubles the base moment; going from 33 to 42 m/s raises it by about 60 %.
- Wall thickness alone runs out. At 10 m with two panels in a 42 m/s zone, a 190 mm base would need more than 6 mm of wall; a 220 mm base does it with 5 mm. Diameter is the more efficient lever.
- Anchor bolts and base plates scale with the moment too. A pole re-used from a grid design with the original anchor cage can fail at the foundation, not at the shaft.
- Coastal and cyclone zones need the local wind map. Mombasa, Dar es Salaam, Lagos and Abidjan are coastal; northern Mozambique and Madagascar face cyclones. Do not use a generic 120 km/h.
4. What to put in the specification
| Item | Specify |
|---|---|
| Panel | Wattage, dimensions, number of panels, tilt and height above the pole top |
| Wind | Basic wind speed and terrain category from the local code, or the speed in the tender |
| Pole | Mounting height, section (round or octagonal), steel grade, base and top diameter, wall thickness |
| Connections | Bracket, base plate thickness, number and size of anchor bolts, door opening reinforcement |
| Finish | Hot-dip galvanizing standard and minimum zinc thickness; powder coat if required |
| Proof | Wind-load calculation for the exact panel and luminaire fitted, signed by the supplier’s engineer |
FAQ
Can I put a solar panel on an existing street light pole?
Only after checking. In our examples the panel multiplies the base moment by 3.5 to 4.6 times, so an existing pole, its anchor bolts and its foundation usually need a calculation and often reinforcement or replacement.
What wind speed should a solar street light pole be designed for?
The basic wind speed in the national code for the site, adjusted for terrain and height. Many tenders state 120 to 150 km/h; coastal and cyclone areas can be higher.
Is an all-in-one solar light easier on the pole?
Usually yes, because the panel is smaller and close to the luminaire. But large all-in-one units still have 0.5–0.8 m² of panel at the top and need the same check.
Octagonal or round pole?
Both work. For the same steel weight, a round section resists wind bending well; octagonal sections are common in tenders and easy to form. Compare by section modulus at the base, not by shape.
How we help
We supply solar street light poles with panel brackets and steel lighting poles up to 15 m, matched to our solar street lights, with a wind-load calculation for the panel and luminaire actually fitted. Send us the height, panel and wind speed.
Sources: wind pressure q = ½ρv² with standard air density; force coefficients are typical values used in EN 1991-1-4 for flat plates and circular cylinders; yield strength of Q355 steel per GB/T 1591. The worked table is our own calculation for illustration. Related: pole height and spacing, all-in-one vs split solar street lights.