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#1
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OT free lighting
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. -- Jeff |
#2
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OT free lighting
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. |
#3
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OT free lighting
On 14/08/2013 17:59, Chris Hogg wrote:
A calculation: sunlight's composition at ground level, per square meter, with the sun at the zenith, is about 527 watts of infrared radiation, 445 watts of visible light, and 32 watts of ultraviolet radiation (from http://en.wikipedia.org/wiki/Sunlight). Call it 450 w/m^2 of visible light, or 0.045 w/cm^2, or 22.2 cm^2/w. 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. Yes, I was mistakenly basing my calculation on the approx 1000w/m^2 of total solar energy delivered perpendicularly. I hadn't taken into account that only around half is visible. I had also assumed that when the term "water bottle" was used in the article, it was referring to those large bottles found on water coolers. -- Jeff |
#4
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OT free lighting
On 14/08/2013 19:41, Jeff Layman wrote:
On 14/08/2013 17:59, Chris Hogg wrote: A calculation: sunlight's composition at ground level, per square meter, with the sun at the zenith, is about 527 watts of infrared radiation, 445 watts of visible light, and 32 watts of ultraviolet radiation (from http://en.wikipedia.org/wiki/Sunlight). Call it 450 w/m^2 of visible light, or 0.045 w/cm^2, or 22.2 cm^2/w. 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. Yes, I was mistakenly basing my calculation on the approx 1000w/m^2 of total solar energy delivered perpendicularly. I hadn't taken into account that only around half is visible. I had also assumed that when the term "water bottle" was used in the article, it was referring to those large bottles found on water coolers. Well the article does show pictures including how they are set and what the bottles are. |
#5
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OT free lighting
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... -- Cheers Dave. |
#6
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OT free lighting
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 |
#7
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OT free lighting
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. |
#8
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OT free lighting
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#9
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OT free lighting
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? |
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