On 14/08/2013 14:04, Jeff Layman wrote:
On 14/08/2013 09:25, David Hill wrote:
Interesting item, can you find a use for it?
http://www.di-ve.com/news/invention-lights-world

Probably only for an hour or two around midday, and only on the equator.

To get 40 - 60 watts equivalent (let's say 50 for simplicity), with the
sun directly overhead, you'd need a bottle with a diameter of about 25
cm. I guess that a water bottle for a dispenser wouldn't be far off
that, so it is feasible. But it would be heavy (around 20 kg), and a
flat piece of glass with the same diameter would do just about the same
thing.

I think you need to look again at the weight.
A full 2 litre pop bottle weighs 2 kg + the weight of the bottle, and
this is the size used.