Posted by RF on July 22, 2008, 11:34 pm
http://www.independent.co.uk/news/science/new-windows-double-as-solar-panels-865592.html
New windows double as solar panels
By Steve Connor, Science Editor
Friday, 11 July 2008
Organic solar conccentrators
Donna Coveney/MIT
By collecting light over their full surface and
concentrating it at their edges, these devices
reduce the required area of solar cells
A new type of solar panel that allows light to
pass through it like a pane of glass has been
invented by scientists who said that it is 10
times more powerful than conventional methods of
producing energy from sunlight.
The discovery raises the prospect of using
ordinary domestic windows to generate electricity
with minimum structural alterations, although
scientists have not yet worked out how much it
would cost to convert a domestic home to a
solar-powered generator.
Instead of coating the entire solar panel with
solar cells - the expensive semiconductor devices
that turn the energy of sunlight into electricity
- the new solar panel works on the principle of
concentrating the light, and the energy, at the
edges of a pane of glass where it can be collected
by the solar cells.
Scientists from the Massachusetts Institute of
Technology (MIT) in Boston said that the “solar
concentrator” is made from a film of organic
molecules that can be coated on to glass window
panes or other surfaces exposed to sunlight. This
allows light to pass straight through the window
even though it is being used to generate power.
It also means that the expensive solar cells need
only be placed around the edges of the collecting
area, so that there is little need to track the
movements of the Sun for generating maximum power,
as well as reducing overall costs.
“Light is gathered over a large area [like a
window] and gathered, or concentrated, at the
edges. The cost of photovoltaic power can be
reduced with organic solar concentrators,” said
Professor Marc Baldo, the leader of the research
team at MIT.
Existing solar concentrators using in commercial
solar generators have to track the movements of
the Sun during the day to generate the highest
optical intensities. This often involves expensive
mobile mirrors and are difficult to maintain,
Professor Baldo said.
“In addition, solar cells at the focal point of
the mirrors must be cooled, and the entire
assembly waste space around the perimeter to avoid
shadowing neighbouring concentrators,” he said.
The MIT solar concentrator involves a mixture of
two or more dyes that are painted onto a pane of
glass or plastic. These dyes absorb light across a
range of different wavelengths, which is then
re-emitted at a different wavelength and
transported across the pane to the waiting solar
cells at the edges.
Jon Mapel, one of the MIT scientists who worked on
the project, said that the trick was to improve
the efficiency of the process, which ultimately
leads to better performance and lower costs.
“We made it so the light can travel a much longer
distance. We were able to substantially reduce
light transport losses, resulting in a tenfold
increase in the amount of power converted by the
solar cells,” Dr Mapel said.
Solar power is seen as one of the greenest sources
of energy but it has been dogged by the relatively
high costs of installing photovoltaic cells on
houses and buildings, which can take years to pay
off in terms of energy savings.
Their efficiency in low-light conditions is also a
problem for countries such as Britain were
sunlight is a rare commodity in the coldest months
of winter.
Posted by Morris Dovey on July 23, 2008, 8:57 am
RF wrote:
> By collecting light over their full surface and concentrating it at
> their edges, these devices reduce the required area of solar cells
Your post would probably have been on-topic in news:alt.solar.photovoltaic
--
Morris Dovey
DeSoto Solar
DeSoto, Iowa USA
http://www.iedu.com/DeSoto/
Posted by RicodJour on July 23, 2008, 3:29 pm
On Jul 23, 11:18 am, david.willi...@bayman.org (David Williams) wrote:
> -> Scientists from the Massachusetts Institute of
> -> Technology (MIT) in Boston said that the “solar
> -> concentrator” is made from a film of organic
> -> molecules that can be coated on to glass window
> -> panes or other surfaces exposed to sunlight. This
> -> allows light to pass straight through the window
> -> even though it is being used to generate power.
> This sounds like voodoo, or having your cake and eating it too. There
> must be some loss. Less light would pass through the window than would
> pass through ordinary glass. How much less? And is the window
> transparent or just translucent? Can you see through it, or just get
> illumination from it? And how long will it last? Do the organic dyes
> that are exposed to full sunlight get degraded over time?
> I'm sceptical...
Voodoo? I would imagine it's closer to someone with bushings in their
wheels commenting that ball bearings were magic. ;) They're
manipulating the light with wave guides - moving the light around
instead of the apparatus to track the light.
One of your questions is answered in the posted article, or at least
hinted at.
"These dyes absorb light across a
range of different wavelengths, which is then
re-emitted at a different wavelength and
transported across the pane to the waiting solar
cells at the edges."
So when you say how much light passes through the window, are you
asking about visible light, or all wavelengths that can be considered
light? I know from applying solar films to windows that visible light
transmission can be reduced substantially and most be people won't
notice the difference at all.
Of course there are questions and it's good to be skeptical, but it is
an interesting approach. Other articles with some added information:
http://www.photonics.com/content/news/2008/July/11/92377.aspx
MIT's Technology Review
http://www.technologyreview.com/Energy/21066/
Lateral Aperture
http://research.atspace.org/030Solar.html
R
Posted by O Solar Mio on July 23, 2008, 7:40 pm
ups.com:
>> This sounds like voodoo, or having your cake and eating it
>> too. There must be some loss. Less light would pass
>> through the window than would pass through ordinary glass.
>> How much less? And is the window transparent or just
>> translucent? Can you see through it, or just get
>> illumination from it? And how long will it last? Do the
>> organic dyes that are exposed to full sunlight get
>> degraded over time?
I may be all wrong about this but these plastic windows remind
me of the fluorescent dyes used with nitrogen laser: The
nitrogen laser emits in the ultraviolet wavelenght (invisible)
and uses different chemical dyes to turn this UV emission into
various visible wavelenght. These lasers are often used in night
clubs since they are not limited to a single color.
Solar light also contains a lot of UV...
Posted by RicodJour on July 23, 2008, 11:16 pm
On Jul 23, 10:15 pm, david.willi...@bayman.org (David Williams) wrote:
Please have the courtesy to quote with attribution. It takes no more
effort.
> -> One of your questions is answered in the posted article, or at least
> -> hinted at.
> -> "These dyes absorb light across a
> -> range of different wavelengths, which is then
> -> re-emitted at a different wavelength and
> -> transported across the pane to the waiting solar
> -> cells at the edges."
> -> So when you say how much light passes through the window, are you
> -> asking about visible light, or all wavelengths that can be considered
> -> light? I know from applying solar films to windows that visible light
> -> transmission can be reduced substantially and most be people won't
> -> notice the difference at all.
> Fluorescent materials absorb light at some wavelength, or range of
> wavelengths, and re-emit the energy at longer wavelengths, i.e. lower
> photon energies. So it's plausible to guess that the stuff they're
> using absorbs visible light, probably toward the blue end of the
> spectrum, and re-emits it as infrared or reddish visible. I doubt that
> the emitted light is initially directed. They're probably relying on
> some of it being trapped between the two surfaces of the window and
> travelling to the edges. So some of the emitted light escapes. If it's
> visible, this would give a reddish hue to the window, which would also
> absorb some of the blue. So there would be substantial colour
> distortion of the scene as viewed through the window.
Well considering what has been done with tweaking the light from
fluorescent light bulbs, and that the researchers are looking at
modifying windows, I think it's just as plausible that the researchers
are not planning on people looking out their windows on a Martian red
landscape.
> They say that this stuff would be useful in places like Britain, where
> (especially in wintertime) daylight is scarce. Having lived there for
> 30+ years, I am sure that any significant absorption of light by the
> window *would* be noticed. It would probably lead to people switching on
> lights when they otherwise wouldn't, so at least some of the electrical
> energy produced by the window would be used by the lights.
> Also, of course, there will have to be some PV stuff around the edges
> of every window pane, which must reduce its effective area.
Insufficient information for a meaningful response.
> I agree that it's an intriguing technology, but I am still sceptical of
> its usefulness. It seems far more practical to me to put PV panels on
> surfaces of the building that are *not* windows, so the daylighting
> through windows is not reduced at all.
The energy code specifies maximum areas of windows in all climate
zones and the difference in area allowed in a particular climate zone
is based on heating, not cooling - substantially more fenestration is
allowed in hot climates. Hot climates have substantial areas of glass
that require shading and are often shaded with curtains or something
similar. You are assuming a disadvantage. It's one thing to be a
skeptic without suitable information, and another thing to be a
pessimist.
R
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> their edges, these devices reduce the required area of solar cells