This analysis examines whether to add solar panels to the three vertical triangular walls of the living area in addition to the roof solar already planned.
Each wall is a rectangle 41.3 ft long × 7 ft tall. There are 3 walls.
| Item | Value |
|---|---|
| Wall length | 41.3 ft |
| Wall height | 7 ft |
| Area per wall | 289.1 ft² (26.86 m²) |
| Total wall area (3 walls) | 867.3 ft² (80.6 m²) |
| Roof area (equilateral triangle, side 41.3 ft) | 738.6 ft² (68.6 m²) |
Usable area assumes ~90% coverage after deducting doors, windows, hardware, and the kite track: ~72.5 m² usable side area.
The triangle has 3 sides oriented 120° apart. At any moment, the sun illuminates the walls whose outward normal has a positive dot product with the sun vector — at most 2 walls.
For a wall with outward normal at angle φ from the sun's azimuth, and sun elevation θ:
Integrating over a typical day at mid-latitudes (~30°), assuming the seastead's orientation is random (or rotates slowly with currents — a reasonable average), and using a clear-sky model with daily horizontal insolation of ~6 kWh/m²/day:
| Surface | Daily insolation (kWh/m²/day) | Relative to horizontal |
|---|---|---|
| Horizontal (roof) | ~6.0 | 100% |
| South-facing vertical (fixed) | ~3.5 | 58% |
| East or West vertical | ~2.5 | 42% |
| North vertical (N. hemisphere) | ~1.2 | 20% |
| Average vertical wall (random orientation) | ~2.4 | 40% |
So averaging over all 3 walls with random/changing orientation, expect ~2.4 kWh/m²/day of direct + diffuse sky insolation per wall.
The ocean reflects ~6% of incoming light on average (specular albedo varies strongly with sun angle — much higher at low sun angles, low when sun is high). Because the walls are vertical and face the water, they receive reflected light from a large solid angle of ocean surface.
View factor from a vertical wall just above water to the infinite ocean ≈ 0.5 (the wall "sees" half its hemisphere as water).
Ocean reflection adds a modest ~0.2–0.3 kWh/m²/day, or about 10% on top of the direct/diffuse total. Higher in tropical sunrise/sunset and in glittery seas.
Total effective insolation per wall: ~2.6 kWh/m²/day.
Assume modern panels: 200 W/m² peak, ~20% efficiency, system losses 15%. Effective conversion: insolation × 0.20 × 0.85 = insolation × 0.17.
| Surface | Area (m²) | Insolation (kWh/m²/day) | Energy (kWh/day) | Avg power (W) |
|---|---|---|---|---|
| Roof solar (existing) | ~62 (90% of 68.6) | 6.0 | 63.2 | 2,633 |
| Side solar (3 walls) | ~72.5 | 2.6 | 32.0 | 1,335 |
| Total with sides | 134.5 | — | 95.2 | 3,968 |
Adding sides increases daily energy by about +50% over roof-only.
Using flexible / semi-flexible marine-grade PV panels (suited to vertical mounting on a composite/aluminum wall, with low weight and good shock tolerance):
| Item | Value |
|---|---|
| Panel cost (flexible marine PV) | ~$1.50–$2.50 / W |
| Side panel installed cost (200 W/m² × 72.5 m² = 14.5 kWp) | ~$22,000 – $36,000 |
| Extra MPPT / charge controllers / wiring | ~$2,000 – $4,000 |
| Total extra cost | ~$25,000 – $40,000 |
| Panel weight (flexible PV, ~2.5 kg/m²) | ~180 kg (400 lb) |
| Mounting / wiring weight | ~80 kg (175 lb) |
| Total extra weight | ~260 kg (~575 lb) |
Extra production: ~32 kWh/day × 365 = ~11,700 kWh/year.
Off-grid electricity value (avoided diesel/genset, or extra battery capacity): ~$0.30–$0.50/kWh.
Annual value: ~$3,500 – $5,800.
Payback: roughly 5–10 years, well within panel life (20–25 years).
Yes, putting solar on the sides is worthwhile.
The main caveat is to design the walls with this in mind: keep windows clustered (not scattered) so you can lay down large contiguous PV laminates, and route wiring to avoid through-hulls in the walls.