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Downingtown, PA
·Verizon FiOS
reply to silbaco

Re: GravityLight: lighting for developing countries.

silbaco See Profile]

I get the feeling you will never be convinced but I throw this out anyway. A 10 YO study, so the LED technology has had 10 years to improve. The kerosene technology, not so much.

Summary and Conclusions

The energy use and light output of kerosene lamps vary widely depending on the type of
lantern used, maintenance of the wick, and the cleanliness of the “globe”. Moreover, our
measurements indicate that light distribution is very uneven in both the horizontal and
vertical planes, i.e. depending on the angle of view. Kerosene-based light is poor for
reading and many other tasks, particularly on horizontal surfaces.

Our estimates of useful illuminance on typical tasks show that the kerosene lamps deliver
between 1 and 6 lux (lumens per square meter), compared to typical western standards of
300 lux for reading. Light output deteriorates considerably from these already inadequate
levels within a few hours of operation (by up to 83% in our tests) as the globe becomes
soiled, requiring frequent cleaning. In contrast, “lumen depreciation” in electric lighting
systems is typically in the single-digit range after years of operation.

A competitive analysis of kerosene lanterns versus conventional electric alternatives
(both grid-based and grid-independent) and emerging white-LED alternatives shows
considerable potential for economic and environmental benefits. When evaluated in
terms of total cost of ownership (fixed and variable), the LED systems emerge as the
most cost-effective solution, with payback times from several months to two years.

»evanmills.lbl.gov/pubs/pdf/offgr ··· ting.pdf
"Facts do not cease to exist because they are ignored." - Aldous Huxley

That's an interesting read.

I have no doubt that LED light is superior to kerosene. What I doubt is the power source of this light. I can't see this light putting out enough light to be useful. Even with the most efficient LEDs on the market.