> I think the reason this contraption is valuable is that LEDs don't need much power to produce enough light
Actually, that contraption cannot produce enough light, unless you have a crazy weight, a lot of elevation, and a magical efficient system that converts energy to electricity, and then transforms it to whatever voltage/amperage appropriate for you LED lights.
As posts upthread have shown, the light output will be comparable to a kerosene lamp, which is what these lights are supposed to replace. It doesn't take a "crazy weight" or "a lot of elevation". And the difference between 50% efficiency and 100% efficiency is only a factor of two; that's well within the range of making reasonable adjustments in the weight and/or height.
As far as voltage/amperage is concerned, I would expect the generator to be low voltage DC, matched to some voltage in the range the LED light could support. AFAIK LED lights are fairly tolerant of a range of low DC voltages, so I don't see this as a major issue.
I've not seen a generator (quite likely 'cause I've never gone looking), but I've seen model plane motors claiming almost 95% efficiency (a quick hunt found this one claiming 94% max efficiency: http://www.astroflight.com/index.php?main_page=product_info&... )
I'm guessing that's pretty reversible - if you spun that motor backwards with the right speed and torque and loaded the output up in just the right fashion, I think you'd get 94% of the energy you put in out as electricity.
The problem I see is that a slowly falling weight is unlikely to provide "the right speed and torque" without some sort of lossy gearbox in between - there's the physical equivalent of an impedance mismatch there. If I had to imagine a motor/generator that'd be likely to work on a direct-drive to a falling weight it'd probably be several feet in diameter. (For model plane motors, the diameter of the motor is a significant factor in the kV constant and the rpm at max efficiency. Small diameter motor spin fast, large diameter motors spin slow.)
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Link to a generator with 95% efficiency please.
> I think the reason this contraption is valuable is that LEDs don't need much power to produce enough light
Actually, that contraption cannot produce enough light, unless you have a crazy weight, a lot of elevation, and a magical efficient system that converts energy to electricity, and then transforms it to whatever voltage/amperage appropriate for you LED lights.
As posts upthread have shown, the light output will be comparable to a kerosene lamp, which is what these lights are supposed to replace. It doesn't take a "crazy weight" or "a lot of elevation". And the difference between 50% efficiency and 100% efficiency is only a factor of two; that's well within the range of making reasonable adjustments in the weight and/or height.
As far as voltage/amperage is concerned, I would expect the generator to be low voltage DC, matched to some voltage in the range the LED light could support. AFAIK LED lights are fairly tolerant of a range of low DC voltages, so I don't see this as a major issue.
I've not seen a generator (quite likely 'cause I've never gone looking), but I've seen model plane motors claiming almost 95% efficiency (a quick hunt found this one claiming 94% max efficiency: http://www.astroflight.com/index.php?main_page=product_info&... )
I'm guessing that's pretty reversible - if you spun that motor backwards with the right speed and torque and loaded the output up in just the right fashion, I think you'd get 94% of the energy you put in out as electricity.
The problem I see is that a slowly falling weight is unlikely to provide "the right speed and torque" without some sort of lossy gearbox in between - there's the physical equivalent of an impedance mismatch there. If I had to imagine a motor/generator that'd be likely to work on a direct-drive to a falling weight it'd probably be several feet in diameter. (For model plane motors, the diameter of the motor is a significant factor in the kV constant and the rpm at max efficiency. Small diameter motor spin fast, large diameter motors spin slow.)