A slowly descending weight drives a small generator through a gear train, powering an LED for roughly 20-30 minutes per lift (a few seconds of lifting effort) at a modest 5-15 lumens, no battery, no grid, no sunlight needed, so it works identically at 3pm or 3am, indoors or out. Roughly five times brighter than an open-wick kerosene lamp, with none of the indoor air pollution. Genuinely closes the passive-lighting gap flagged 2026-08-08 (`02-Decisions-and-Tradeoffs-Log.md`), but honestly scoped: 5-15 lumens is task/emergency lighting, not a room's primary light source. Positioned as a backup alongside LED, not a replacement for it.
Note: Cost, carbon and footprint are rated against the other options for this same need, not in absolute terms.
No sizing or quantities: how much a technique yields, and how much a household needs, both depend on the build and the people, so the catalogue compares options rather than dimensioning them. It carries no bill of materials and no build sequence, and it is written for an oceanic, clay-soil climate (Normandy, France). Regulatory notes are indicative and need confirming locally.