[beardicus]

> You need to lift a 10KG weight about 2 kilometres to get a teaspoon of kerosene's energy, so it's not a great replacement on that front

This says nothing of light output. If you want light, and most of kerosene's output is heat, your energy calculation is not helpful.

> and having 10KG weights dangling around at variable points between ceiling and floor sounds if anything even more of a liability than a lamp with a naked flame

This seems like an incredibly contrived "problem". What's the liability? Somebody may bump into a somewhat heavy object that is moving downwards at a barely perceptible clip? Somebody may tweak their back lifting the weight? That seems lower risk than my housing burning down with me in it.

[hanoz]

Okay, okay, you are right of course, the light efficiency is very different, although the heat may not be an altogether unwanted by-product in many cases. There are also more efficient ways of getting light from petroleum than sticking a wick in it. But if you do want the benefits of LEDs, there are better ways of getting the energy than lifting sacks to the ceiling. It's still 180 meters for a pair of AA rechargeables.

I genuinely don't think the hazards are at all contrived, and range from the grave if unlikely to the mild but virtually certain. You are surely going to knock your head on this massive hovering, albeit reasonably well lit, object on a regular basis, and it might not be as soft and rounded as the illustration. On the floor, in dark mode, you'll be tripping over it, which doesn't always end comically. Reasonable precautions not withstanding it's not impossible that it could crush or smother something beneath it even at its snail's pace, but more likely it could come down hard through overloading, wear or misuse. It's really not something I'd want in a family home.

It is a nice idea and obviously of the very best intentions but I'm afraid it's simply misguided and efforts would be far better directed towards battery plus solar. Sorry.

[prewett]

I would say the hazards of this device sure beat the hazards of kerosene lamps (fire, mostly). [1] lists a series of accidents with kerosene lamps in a three year period in a small town. I think a horse kicking over a kerosene lantern started one of the big Chicago fires. There's even a possibility that a kerosene lamp caused a deadly fire in modern USA [2]. And I'm guessing that fire would be a serious problem in small, dense areas such as the slums (not intended pejoratively) in the third world nations that are likely to have the most use for this.

Solar plus battery might be better than this, but this looks like a whole lot better than a kerosene lamp.

[1] http://www.thelampworks.com/lw_lamp_accidents.htm

[2] http://www.chicoer.com/20120322/kerosene-lamp-may-have-cause...