Re: [Biofuel] Solar Concentrator & PV Modules

[Kirk McLoren]

silicon semiconductors are not the material of choice for concentrating collectors.
Gallium arsenide stand much higher temps.

 

regular solar panels can take probably a concentration of 3 but output voltage drops as temperature rises.

Discoloration/lack of transparency can occur as well. A few years back "mud" solar panels were offered at a discount. They were removed from service in a concentrator-tracker(Carrizo). The cells were dark brown as a result of degradation of an adhesive used to bond the cells to a cover glass. I don't know if recent panels are built the same way but you need to know this before running them with more light. I assume uv was the culprit. Too bad no one has a mirror that just reflects the wavelengths the silicon uses.

 

Also concentrators destroy things if they stagnate.

 

Kirk

Logan Vilas <[EMAIL PROTECTED]> wrote:

The main concern would be thermal transfer rates of the materials that the
cell is made out of and max temp the cell can handle. I know PV are made
from silicone, but is there any more depective terms for the material? For
example all Iron is not steel and every version of it has different thermal
transfer rates. What is the maximum working temp of PV modules? From Those
two things I can calculate the maximum amount of concentration that should
work. Also approximately how large is a 50watt panel?

I can pick a PV module then based on size and material thermal transfer I
can calculate the thermal transfer it would have in BTUs. I would then
divide by 3.4 and that's the number of watts it can have aimed at it.
There's approximately 1000watts per square meter energy from the sun. The
mirrors are about 92% reflective and I would figure there it going to be
about 10% loss to heating the air between the PV and the mirrors. 82.8
percent of the energy will be transferred to the PV. That's 828watts per
square meter of mirrors. Divide the thermal transfer by 828 and that's the
max concentration that can be focused at that cell to keep it at the same
temp as the input temp of the coolant you are using.

The overall design should be engineered to keep the cell within working temp
limits without loosing much of the power gain, so under 200F (I'm guessing),
while being able to dissipate 100% of the heat that is concentrated. It
would need to dissipate all the heat because of the chance that no
electricity will be used and all the energy will become heat. When 20-30% of
the energy is being turned into electricity then the cell temp will remain
an equal percentage lower. At these temps it could be done with water and no
additives, but a closed system with relief valve would be best otherwise the
water would evaporate.

I am thinking a closed loop system of filtered and dewatered UVO. I have
firefighting material called fire blockade that can be added at 1% mixture
and that will ensure the oil is nonflamiable. That would cause the fluid to
not boil off or spontaneously combust.

Logan Vilas

-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Zeke Yewdall
Sent: Saturday, May 13, 2006 5:30 PM
To: Biofuel@sustainablelists.org
Subject: Re: [Biofuel] Solar Concentrator & PV Modules

This is exactly what I did my master's thesis on. The concept works
pretty well from a theoretical perspective. I was just investigating
using water cooling for non-concrentrating PV, but it would work even
better for concentrating PV. You shouldn't really have to deal with
1200F, at least if you are talking about water, because the maximum
working temp for a water based fluid is probably about 400F or so??
(assuming antifreeze additives and increased pressure). Depends on
how much pressure you are talking about I guess.

On 5/13/06, Jason & Katie <[EMAIL PROTECTED]>wrote:
> in theory, if one could find a way to waterproof the back of a PV cell it
> could be used as the heat-side plate in this concentrator/boiler found at
> (or after) http://www.ida.net/users/tetonsl/solar/page_46.htm you could
> safely increase the power range of a smaller PV cell without too horrible
of
> a heat loss. the problem is finding a sealing substance that wont melt or
> burn under these 1200*F temperatures.
>
>
> ----- Original Message -----
> From: "logan vilas" <[EMAIL PROTECTED]>
> To:
> Sent: Friday, May 12, 2006 4:54 PM
> Subject: Re: [Biofuel] Solar Concentrator & PV Modules
>
>
> >I am working with the idea of building my own Concentrator with about 50
> > times the mirror space then collector space. That Is why the question
was
> > asked in the first place I was wondering if placeing a 50watt solar
panel
> > at
> > the focal point would increase the power output. I've read that it is
more
> > then 100% liner increase in power output when increasing the amount of
> > light
> > on it. a normal panel at 50 watts would be 2500 watts at 50 suns. I know
> > it
> > would need to be kept cool. due to the fact that they are only 20-30%
> > efficent, but I could use the coolant to heat my biodiesel processor,
then
> > the hot water going into my home before a tankless heater. If I were to
> > get
> > a grid tied inverter It would suppliment my normal power useage and maby
> > with netmetering it might come close to canceling out my power
> > requirements
> > alltogther. a simple temp sensor could be used so if the temp is over
150f
> > in the coolant it will shut down and not collect the sun anymore. As for
a
> > solar tracker that is relative easy with very simple electronics. The
> > setup
> > to hold everything would be a simple build for most people who can make
> > their own biodiesel processor. And If I base it off a 7 meter dish I can
> > get
> > those free. I just have to use the labor to remove it.
> >
> > Logan Vilas


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