A submerged sphere sits in the best heat sink on the planet: cool, endless, moving seawater. The design move is to make most of the hull a good insulator, and one small patch at the keel a good conductor - so heat leaves where you want it to and stays put everywhere else. In Bermuda that turns cooling from a power bill into free physics.
The interior runs warm; the deep water runs cool. A conductive concrete patch at the keel lets that difference bleed heat out by conduction alone - no pump, no compressor. Slide the depth and the patch conductivity and watch the passive cooling power.
Model: 6 m² keel patch, 200 mm thick, 24 °C inside. Bermuda water is taken as ~26 °C at the surface cooling with depth. Plain concrete is ~1.4 W/m·K; carbon-fibre tows in the patch raise that toward ~5.
| Element | Role | Why it works here |
|---|---|---|
| Insulating aircrete liner | Keeps the living space thermally isolated from the shell | Low conductivity foamed concrete; the bulk of the hull resists heat flow |
| Conductive keel patch | Directs waste heat into the cool deep water | Carbon-enhanced concrete conducts several times better than plain; sits in the coldest water |
| Fresh-water ballast tanks | Thermal flywheel | Large water mass damps day/night swings; also low-CG ballast and storage |
| Deck solar collector | Water heating + power when surfaced | ~1.4 kW thermal from a modest 4 m² collector; free rooftop when floating |
| Depth as a thermostat | Choose your ambient temperature | Deeper water is cooler and steadier; the habitat picks a comfortable layer to sit in |
A sealed one-atmosphere interior needs managed ventilation and dehumidification - the same kit a boat or an efficient house uses. Cool hull surfaces want vapour control so they do not sweat; the insulating liner keeps interior surfaces above the dew point.
Active seawater cooling works but adds through-hull penetrations, pumps and biofouling - each a maintenance and leak risk. Conducting heat through a solid patch keeps the pressure boundary intact: no holes below the waterline is a strong safety principle to hold.