On 14/08/2013 21:46, Chris Hogg wrote:
On Wed, 14 Aug 2013 20:28:47 +0100 (BST), "Dave Liquorice"
wrote:

On Wed, 14 Aug 2013 17:59:31 +0100, Chris Hogg wrote:

If a bottle delivers say 50 watts of light, then each bottle will have
to have a cross-sectional area of 50/0.045 = 1110 cm^2, or a diameter
of about 37.6 cm. So they'd have to be even bigger than Jeff
suggested, which makes me think the estimate of 40-60 watts is
somewhat exaggerated.

I think you are missing an efficiency factor. I suspect the light you
get from the pop bottle is similar in level to that which you get
from a 40-60 watt tungsten incandescent bulb. Incandescent light
bulbs are horribly inefficient, less than 5%.

Reversing the calculation, a 2 litre pop bottle has a diameter of
about 9.5 cm, so a cross sectional area of about 71 cm^2, and would
give a visible light output of 71x0.045 = 3.2 watts.

3.2 Watts of real light or 64 Watts of incandescent assuming 5%
efficiency.
Most incandescent bulbs won't be that efficient...

Sorry Dave. I didn't see your post before I fired off mine. We think
alike.

Well I have a large sectional concrete garage that has limited windows
and no way of adding more without major deconstruction work, It needs re
roofing so I may try to set s few of those into the new roof when I get
round to that job.
Problem is the roof runs North to South, so should I put them all on the
East slope?
I don't think it would be feasible to set them into the ridge.
David @ a damp side of Swansea bay

In article ,
says...

On Wed, 14 Aug 2013 23:21:19 +0100, David Hill
wrote:


Well I have a large sectional concrete garage that has limited windows
and no way of adding more without major deconstruction work, It needs re
roofing so I may try to set s few of those into the new roof when I get
round to that job.
Problem is the roof runs North to South, so should I put them all on the
East slope?
I don't think it would be feasible to set them into the ridge.
David @ a damp side of Swansea bay

Why just limit it to the East side? You'll get just as many hours of
sunlight on the West side. But why use what appears to be essentially
a third world solution to the problem, where resources are scarce? You
could easily and probably more effectively put several skylights in,
and with less risk of leaking.

Or reroof it with the rigid profile panels used on farm buildings
using some metal and some plastic .. (same profile but it lets in
light).

Janet

On 15/08/2013 08:01, Chris Hogg wrote:
On Wed, 14 Aug 2013 23:21:19 +0100, David Hill
wrote:


Well I have a large sectional concrete garage that has limited windows
and no way of adding more without major deconstruction work, It needs re
roofing so I may try to set s few of those into the new roof when I get
round to that job.
Problem is the roof runs North to South, so should I put them all on the
East slope?
I don't think it would be feasible to set them into the ridge.
David @ a damp side of Swansea bay

Why just limit it to the East side? You'll get just as many hours of
sunlight on the West side. But why use what appears to be essentially
a third world solution to the problem, where resources are scarce? You
could easily and probably more effectively put several skylights in,
and with less risk of leaking.

Well the wife only drinks Pop so I have so many 2 litre bottles being
recycled, and no shortage of water and I can spare a little bleach.
As for leaking, the bottles she has have a slight depression 3/4 of the
way up the bottle so mastic in this will hold the bottle in place and
seal it.
If it doesn't work I can still put in skylights, but for the price of a
couple of tubes of mastic why pay for skylights?

On Wed, 14 Aug 2013 23:21:19 +0100, David Hill wrote:

Well I have a large sectional concrete garage that has limited windows
and no way of adding more without major deconstruction work, It needs re
roofing so I may try to set s few of those into the new roof when I get
round to that job.

Reroofing with what? I'd look at onduline (corogated reinforced
bitumen sheeting) and use a few clear plastic sheets to let the light
in. If tiles, I think you can get matching glass ones.

Make the holes and reliably sealing around a pop bottle is not going
to be that easy.

Problem is the roof runs North to South, so should I put them all on the
East slope?

Is the west slope shaded by the house or something? I'd put them of
both sides a lot of light is scattered light and these things will
"collect" that as well as direct sunlight.

--
Cheers
Dave.