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LiFePO4 stores light at $0.0252 per 1,000 lumen-hours over ten years; a flywheel retains only 26.21% after a 6-hour hold and thermal-TEG round-trip efficiency is 4.17% — both killed for diurnal lighting. Households off the grid need light after dark, not stored energy in the abstract: which store delivers an evening of light most cheaply over its life?
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William Alexander Aldred (2026) studied this question.
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