I also like Bill Brooks' test. I use a Daystar irradiance meter to determine
light levels through glazing or PV modules by measuring the light throughout
the day and at the distance from the glazing and height of whatever is being
illuminated.
----- Original Message -----
From: Ray Walters
To: RE-wrenches
Sent: Thursday, November 03, 2011 11:54 AM
Subject: Re: [RE-wrenches] Bifacial modules
Geez Joel, we need to start a solar museum for all the cool old stuff you
have.
I just did a bit of research, and it seems lux is a weighted measure based on
visible light present, while irradiation is more a total power measurement. I
guess we really need to have two different meters to measure how much light
passes through a module.
If we were to go a step further and characterize the quality of light
present, we might need a spectral analyzer to determine whether its "cool
white" or "daylight", etc. As always, the more you think about something, the
more complicated it becomes.
Ray Walters
On 11/3/2011 11:39 AM, Joel Davidson wrote:
See-thru solar cells have been around for decades. Arco Solar made 4%
efficient amorphous silicon modules and car sunroofs in 1984 that were tinted
brown like sunglasses. I got a 12-inch square see-thru laminate that still
works.
I also have a 6.75-inch square sample of MSK Corp's amorphous silicon PV-TV
solar panels. They were developed in conjunction with Kaneka and Japanese
architects Taiyo Industries. The full-size glass panels, measure 1-meter
square. In addition to producing electricity, they provide thermal insulation,
solar heat gain protection and protection from ultra violet rays. During the
manufacturing process, a laser inscribes a series of ultra fine lines onto the
panel to allow 10 percent of visible light to be transmitted through the glass,
enough for sufficient light to enter a building even during cloudy conditions
while protecting against excessive solar gain. Amorphous silicon solar cells
with 10 percent, 5 percent or 1 percent transparency are placed between two
sheets of glass to generate power. This solar panel is called PV-TV because it
is also used as a display screen on the outside of buildings. See
http://www.metropolismag.com/story/20040727/pv-tv-a-multifunctional-eco-friendly-building-material
The Tiger Woods Learning Center in Anaheim and other buildings have
see-thru Schott solar modules with different amounts of transparency. See
http://www.solardesign.com/library/pdf/tiger-woods-solar-curtain-wall.pdf
Also, opaque cell solar modules are manufactured with various cell spacings
for BIPV applications.
I have a Mastech Light Meter LX1010B in my tool kit for measuring lux. This
handy tool costs around $20.
Joel Davidson
----- Original Message -----
From: Keith Cronin
To: Phil Undercuffler ; RE-wrenches
Sent: Wednesday, November 02, 2011 9:50 PM
Subject: Re: [RE-wrenches] Bifacial modules
Thanks everyone for the feedback!
Thinking that the manu's can space cells accordingly on the surface of
the glass and create whatever % light the end user wants to seep through.
The % of light must slide between 5-15%, depending on manu's specs.
Architecture can meet solar and increase the applicability of the products.
Perhaps someday, they can make the cells see-through (or almost), like
glass.......? Now that opens up possibilities!
Aloha,
Keith
--------------------------------------------------------------------------
From: Phil Undercuffler <[email protected]>
To: Keith Cronin <[email protected]>; RE-wrenches
<[email protected]>
Cc: Bill Brooks <[email protected]>
Sent: Wednesday, November 2, 2011 9:18 AM
Subject: Re: [RE-wrenches] Bifacial modules
We've got an array of Silicon Energy modules "out back," and in the
interests of scientific discovery and procrastinating from what I really am
supposed to be doing, Kelly, Seth and I just ran a few experiments to see if we
can quantify the amount of irradiation that makes it through the array.
Using a Kyocera module as our reference, we measured ISC with the module
in the plane of the array, then moved the module to the same orientation but
approximately 12 feet behind and in the shade of the SE array, and again
measured ISC. Sun conditions were light wispy clouds, guesstimated 800 W/M2
(pretty darned good for Arlington WA this time o' year), 10:30 local time. We
measured 5.9A ISC in front of the array, and 610 milliamps when in the shade
the array, leading us to say that just over 10% of the available sun will make
it to your orchids.
It should be noted that there is a opaque backing behind each SE cell, so
the only light that makes it through is through the intercell gaps. I've used
Sanyo doubles before, and in those modules the cells are slightly translucent,
so the sun is somewhat visible through the body of the cell itself as well --
sort of like looking through very dark sunglasses. In either case, the
illumination on objects behind the array is a dappled, dynamic light. As Bill
says, it's pretty cool from an aesthetic point of view. My personal .02 is
that there is no finer place to put an array than a shade structure using clear
modules. It keeps everything off the roof, gives shade and makes for a premium
installation option.
Phil
-----------
"When we learn how to store electricity, we will cease being apes
ourselves; until then we are tailless orangutans. You see, we should utilize
natural forces and thus get all of our power. Sunshine is a form of energy, and
the winds and the tides are manifestations of energy. Do we use them? Oh, no!
We burn up wood and coal, as renters burn up the front fence for fuel. We live
like squatters, not as if we owned the property.
There must surely come a time when heat and power will be stored in
unlimited quantities in every community, all gathered by natural forces."
-- Thomas Edison --
On Tue, Nov 1, 2011 at 7:48 PM, Keith Cronin <[email protected]>
wrote:
Bill
Appreciate the feedback. One of the questions that I'm seeking to
determine- how much light will filter through the spaces between the cells to
the surface below?
Lets say for someone that wants to grow orchids- they need low light,
as an example.
Wondering how much light is diffused through the panels to be able to
do things like grow orchids and or have filtered light to work?
As an example: Do any of you have irradiance measurements on any
carports that have done bifacials and determined how many watts sq m are below?
Keith
------------------------------------------------------------------------
From: Bill Brooks <[email protected]>
To: 'Keith Cronin' <[email protected]>; 'RE-wrenches'
<[email protected]>
Sent: Tuesday, November 1, 2011 11:44 AM
Subject: RE: [RE-wrenches] Bifacial modules
Keith,
This is easy to test. Simple take an irradiance sensor, turn it
upside-down and test the irradiance on the bottom surface of any PV array. It
will vary greatly based on exposure to reflected light and so on, but it will
rarely be above 100 W/m^2. 10% improvement is an absolute maximum for any
bifacial technology, and that is on the high side. Any claims above 10% are
ignoring the physics of sunlight, reflectance of typical materials, and PV.
Nothing wrong with bi-facials. They are beautiful to look at. I would
buy them based on aesthetics, not on performance.
Bill.
From: [email protected]
[mailto:[email protected]] On Behalf Of Keith Cronin
Sent: Tuesday, November 01, 2011 1:04 PM
To: RE-Wrenches
Subject: [RE-wrenches] Bifacial modules
Hi
Was wondering if any of you have installed bifacial modules and know
what the % of light that comes through to a surface below the modules?
Looking for a canopy type of installation/ application and wondered if
you have any #'s?
Thank you~
Aloha,
Keith
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