Project Sea Silent — Engineering Appendix A.1
Solar Array Sizing Study
David Murray · Media 20-20 LLC · Published July 2026 · Planning estimates, to be validated against measured data during refit and sea trials
Project Sea Silent is the retrofit of a 50–60 ft displacement vessel into a series-hybrid diesel-electric liveaboard. The design includes an aft boat-deck solar array supplementing the hybrid electrical system. This study sizes that array from first principles: how many watts does a square foot of deck realistically produce on a flat-mounted marine installation, and what does that power actually cover?
Assumptions
- Premium rigid monocrystalline panels (22%-efficiency class) at 21 W rated per square foot — deck area is the binding constraint, so top-tier cell efficiency pays for itself
- Flat (horizontal) mounting; Florida-typical horizontal irradiance of 3.5 / 5.0 / 6.0 peak-sun-hours (winter / annual average / summer)
- 0.75 overall system derate covering cell heating, wiring, salt film, and controller losses
- Per-panel MPPT or optimizers assumed, so partial shading from the radar arch and mast degrades gracefully instead of collapsing whole strings
Array scenarios
| Array scenario | Panel area | Rated power | Est. daily yield
(winter / annual avg / summer) |
|---|
| Boat deck only — conservative packing | 120 sq ft | 2.5 kW | 6.6 / 9.5 / 11.3 kWh |
| Boat deck — well-packed | 150 sq ft | 3.2 kW | 8.3 / 11.8 / 14.2 kWh |
| Boat deck + pilothouse roof / hardtop | 200 sq ft | 4.2 kW | 11.0 / 15.8 / 18.9 kWh |
Reference house-load budget
Daily house loads at anchor, no air conditioning
| House load | Est. kWh / day |
|---|
| Refrigeration | 2.5 |
| Freezer | 1.5 |
| Inverter overhead (24 h idle draw) | 1.2 |
| Navigation, communications, satellite internet | 2.0 |
| Lighting and fans | 1.0 |
| Galley — light induction use | 1.5 |
| Fresh/gray water pumps, miscellaneous | 0.8 |
| Total daily house budget | ~10.5 |
Findings
- The well-packed 150 sq ft array roughly breaks even with daily house loads on an annual-average day. In summer at anchor the vessel runs house loads entirely on sunshine; the winter shortfall of 2–3 kWh equates to roughly 20–30 minutes of generator time per day.
- Air conditioning is deliberately excluded: two to three marine AC units running 8 hours add 20–30 kWh/day, which is generator or shore-power territory regardless of array size. This study makes no solar-AC claim.
- Solar is a house-load and recharge asset, not a propulsion source: a 55 ft displacement hull draws roughly 10 kW at a 5-knot slow cruise, so a full average day of solar harvest buys about one hour — roughly 5 nautical miles — of silent cruising. The array's propulsion role is topping the battery bank at anchor so each day starts with full silent-running range.
- Because deck area is the constraint, panel efficiency is the lever: at 150 sq ft, the premium panel class yields ~11.8 kWh/day versus ~10.5 for standard 20% panels.
These figures are planning estimates built from published component specifications and standard marine derating practice. They will be validated against measured data during the refit and sea trials, and this page will be updated with the measured results.