On Jul 15, 2008, at 6:07 PM, R C Macaulay wrote:
Whoa! Michel... say that again.. I'm missing something. My feeble
mind cannot grasp the physics of attaining anywhere near this
output.. unless.. well.. err...wez talkin about Dime Box saloon
poker playing rules where both cards and whiskey can stretch the
imagination.
Richard
It is pretty simple Richard. A "2300 sun system" uses mirrors or
lenses to focus light to 2300 times full sunlight, i.e. to 2,300,000
watts per square meter, which is 230 watts per square centimeter
(there are 10,000 cm^2/m^2). Here is a perfect example from IBM:
http://www.renewableenergyworld.com/rea/news/story?id=52541
It uses a lense to focus the light. Many cells are more efficient at
higher insolations, and the focusing devices, mirrors and lenses,
including sun tracking, are cheaper than silicon.
Very coincidentally, the IBM system above produces 70 watts/cm^2.
Hmmm... that number 70 does get around, almost as much as the number
2300! Must be nice to be popular.
----- Original Message ----- From: "Michel Jullian"
<[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Tuesday, July 15, 2008 8:13 PM
Subject: [Vo]:Re: 70% solar panels
Nope, 1000 W per m^2 at normal incidence is all there is to it. Per
square centimeter that's 1000/(100*100) = 0.1 W, so as the wiki you
quote says (quite clearly I would have thought) you need 2300 times
that, which you can obtain e.g. by focussing sunlight with a
concentration factor of 2300:1, to get 230W on a square centimeter...
Michel
The above all makes perfect sense. Brian, OTOH, appears to be
completely confused.
----- Original Message ----- From: "Brian Prothro"
<[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Wednesday, July 16, 2008 2:02 AM
Subject: RE: [Vo]:Re: 70% solar panels
Now in my meager understandings in this area, I thought the
1000watts per
square meter is defined as a narrow "1 nm bandwith" of sunlight
and is "a
measuring standard" not the full power falling on the surface of
the Earth.
(The bands defined from below 400nm to 1700nm.)
The test measurement is partially described as;
"The ASTM G173 spectra represent terrestrial solar spectral
irradiance on a
surface of specified orientation under one and only one set of
specifed
atmospheric conditions. These distributions of power (watts per
square meter
per nanometer of bandwidth) as a function of wavelength provide a
single
common reference for evaluating spectrally selective PV materials
with
respect to performance measured under varying natural and
artifical sources
of light with various spectral distributions..."
The above describes the method of measuring the solar *spectrum*. It
does not state or imply that the resulting measurements produce
anything remotely close to 1000 watts per square meter per nanometer
of bandwidth. That 1000W/m^2 is divided up across a bunch of 1 nm
wide buckets. The power to *all* the buckets summed together make
1000 W/m2.
"
So, if a panel absorbs multiple bands and is more efficient, as
DBK seem to
have resolved thru engineering, then there is more power.
Yes, but the sum of *all* the buckets for a square meter is 1000W.
It is true that the more buckets you include the bigger the sum, but
the sum can never be more than 1000W even if each bucket is captured
with 100% efficiency - which is also impossible.
I also saw
mentioned they work well in low light? (might be poor rcall on my
part.)
Now I am not an expert here, but the wiki says the power per square
centimeter is 230 watts:
"One sun" is a measurement equal to the solar power incident at
noon on a
clear summer day. I.e. in a 2300 sun system, approximately 230
watts per
square centimeter are concentrated onto the cell system.[14]
You have to understand what a "2300 sun system" is. It involves a
cell on which the light is focused by mirrors or lenses to 2300 times
maximum solar brightness.
Does the Additional multiple junction solar technology not tend to
be far
higher in production that the normal 15%? DBK claims Five levels.
It doesn't matter if there are 50 levels. You can't get more power
out than goes in, unless there is a storage battery or capacitor on
board. In any case you can't get more total energy out long term
than the total energy that goes in from the sun.
I will ask DBK this directly...
It will be most interesting to hear the answer!
Best regards,
Horace Heffner
http://www.mtaonline.net/~hheffner/
