The Skoog Buoy Capillary Sweating Liana (SCSL) is the world’s first zero-electricity, industrial-scale freshwater production system that extracts water directly from atmospheric humidity offshore. It operates on purely passive thermodynamic and mechanical principles: deep-sea cold (≈4°C), solar heat, wave motion, and the continuous recovery of latent heat from condensation. No grid electricity, no desalination membranes, no chemical treatment, and no brine discharge are involved in any part of the process.

The system is developed by Göran Skoog within Skoog Architecture and released entirely as open source under Skoog Open Marine Technology (SOMT), licensed under Creative Commons CC BY 4.0 — with no patents and no licensing fees — so that any community or government can implement it immediately using local resources and local labour.

Production scales directly with the condensation matrix area and local climate conditions:

Under real-world conditions in a high-humidity environment such as Peru (25°C, 70–90% relative humidity), a single large industrial unit can realistically achieve 500,000 L/day, and a cluster of 11 units can generate approximately 5 million litres per day. The chimney is dimensioned to support up to 10,000 m² of condensation area if needed, enabling further scaling.

The latent heat released during condensation is the primary continuous energy source — it drives airflow and thermal expansion 24 hours a day, including at night. Solar gain adds an additional boost during daylight.

Note on performance: The 500,000 L/day figure represents peak output under optimal conditions, not a guaranteed yield. Actual performance depends on humidity, temperature gradients, airflow dynamics, and system geometry.

The process follows six integrated passive steps:

1. Cooling supply: Wave motion circulates 4°C deep-sea water from 1,000 m depth upward through the thermal liana (closed HDPE loop) to the buoy.
2. Air intake: Humid ambient air enters through a labyrinth inlet filter (removes particulates and sea spray) and is directed downward into the SAFA module.
3. Flow conditioning: The Skoog Aerofoil Filter Accelerator (SAFA) splits and accelerates the airflow, using a Venturi effect to pull it efficiently through the condensation matrix.
4. Condensation: Air passes over the 4°C-cooled capillary matrix, dropping below its dew point. Water vapour condenses as a continuous liquid film; capillary action drains condensate by gravity into the sealed expansion tank above the waterline.
5. Heat recovery and thermal piston: A dedicated freshwater thermosiphon recovers 3–4% of the latent heat from the braided chimney and transfers it to the expansion tank. The heating water undergoes 0.43% volumetric expansion at ~30°C, acting as a hydraulic piston that pushes water through the land pipeline.
6. Delivery to shore: A fully water-filled pipeline (no air pockets, sealed by a compensation valve) carries freshwater passively to shore over distances of 20–30 km without pumps.

The thermal liana is a 1,000-metre closed-loop flexible polymer hose (marine-grade HDPE or equivalent corrosion-resistant thermoplastic) that reaches below the ocean thermocline, where seawater stabilises at approximately 4°C regardless of season or surface temperature. It is not a segmented steel pipe — it is manufactured in continuous lengths for structural integrity and flexibility.

The upper 0–150 m of the cold upward riser uses a pipe-in-pipe design with syntactic foam (glass microspheres) insulation, which both preserves the 4°C temperature against warm surface layers and generates positive buoyancy to keep the liana vertically tensioned. Below 150 m, the surrounding water is already cold, so insulation is unnecessary. The return leg is deliberately uninsulated along its entire length so that absorbed heat dissipates back into the ocean, ensuring the water returns to baseline temperature before the next cycle.

Operation at shallower depths (200–400 m) is also feasible where conditions allow, though thermal stability is lower.

At 1,000 m depth, both the upward and downward pipes are joined by a 180° U-bend mounted on a hinged swivel unit with ceramic sliding bearings, rated for 100 bar hydrostatic pressure. This construction manages torque and prevents material fatigue at depth. The liana connects to the structure at the lowest point of the spar, beneath the ballast, transitioning via a rigid riser pipe to the internal condensation matrix. This isolates the assembly from surface turbulence and cyclic mechanical stress while positioning the cooling circuit in water characterised by high thermal stability and low biological activity.

The upward and downward water columns remain nearly density-balanced because the cooling water returns only slightly warmer after passing through the buoy. As a result, the system does not lift a full 1,000 m water column and primarily overcomes hydraulic friction and flow inertia.

Continuous circulation is generated by a wave pump, a flexible folded HDPE structure beneath the buoy, which uses the buoy’s mass as an inertial reference rather than relying on large vertical displacement. Hydrodynamic control surfaces and flexible joints amplify low-amplitude ocean motion into stable pressure variations while limiting structural loads during storms. In Skoog S-Vessel configurations, hydrofoils or drag-flaps integrated with the lianas perform the same function through passive oscillation and check valves.

The objective is not high peak pumping force, but continuous high-volume circulation with low mechanical stress. A small LiFePO₄ backup pump activates only during rare periods of complete calm to prevent stagnation.