Passive solar still (basin distillation) — the simplest, most durable, most area-hungry option
#00059
A black-lined basin of saltwater under a sloped glass cover: sun evaporates the water, it condenses on the glass and runs off as distillate. No moving parts, no consumables, repairable with local materials — but output is ~4–6 L/m²/day, so area demand is the binding constraint.
Parent issue
#00052 Off-grid coastal and island communities cannot sustain conventional desalination for safe drinking water
Sustainable Development Goals
Description
Mechanism
A shallow basin with a blackened bottom holds saltwater; a sloped transparent glass (or film) cover lets sunlight in and traps heat; water evaporates, condenses on the underside of the cover, and trickles into a collection channel as pure distillate, leaving salts behind. No pumps, no membranes, no electricity; buildable and repairable from local materials (wood, glass, black liner).
Where it fits
This is the robustness benchmark against which the high-tech laser-textured panel should be judged — what "passive solar desalination" has meant for 150 years. Its virtue is durability and repairability; its cost is area. The key question it poses to the SWBM panel: does a femtosecond-laser-fabricated surface actually beat a sheet of glass over a black tray, and by enough to justify that fabrication cost?
Operating profile
- Output: ~4–6 L/m²/day for a simple single-basin still — directly illustrating the throughput-ceiling sub-issue, with a 150-year evidence base.
- The 1872 Las Salinas plant (Atacama Desert) ran ~40 years with minimal maintenance.
Honest limits
- Area-hungry: same evaporation ceiling as the SWBM panel, with lower per-m² yield in basic designs.
- Distillate lacks minerals and can taste flat; remineralisation or blending is usually needed.
- Recontamination risk in storage and handling — an argument for a service/handling model regardless of technology.
Sub-issues
0Case studies
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