Comment on A $5 Lamp Powered Solely by GravityparentComments−icoder13yExactly, and since they state that they think they can make it twice as efficient, that would mean they run at max 50% now.−duskwuff13yI suspect it's even less than that. A fancy (= expensive!) bicycle hub dynamo has an efficiency of about 70%, and that's assuming that it's operating at peak efficiency, and that there are no additional mechanical losses in the lamp.
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Exactly, and since they state that they think they can make it twice as efficient, that would mean they run at max 50% now.
I suspect it's even less than that. A fancy (= expensive!) bicycle hub dynamo has an efficiency of about 70%, and that's assuming that it's operating at peak efficiency, and that there are no additional mechanical losses in the lamp.