[Greenbuilding] Fresnel lenses box solar cooker

[RT]

On Mon, 03 Jun 2013 09:24:34 -0400, Topher <topher at greenfret.com> wrote:

> On 6/2/2013 7:08 PM, RT wrote:
>>  he did mention "concentrating photovoltaic (CPV)" systems that were
>> becoming viable which utilise Fresnel lenses to concentrate sunlight
>> so that solar arrays could be reduced to the size of [his] thumbnail.
>
> I don't think I want one on my roof though.  My current plans are for
> about 2000 watts of cells.  That's 8000 watts or so of heat that needs
> to be dissipated.  
> I come back to the thing I have been saying for years.  If you aren't
> making solar CHEAPER, you aren't helping.

I'm not a gizmologist so I've not looked into CPV systems but I do know  
that the efficiency of PV cells in general drops as the temperatures to  
which they are subjected, increases.

As such I would imagine that the people developing CPV systems have  
addressed temperature issues.

If I were doing it, I'd certainly be looking at how to utilise the "waste"  
heat for some beneficial task, say like heating or pre-heating for a DHWH  
system.

Also, I'm pretty sure that I remember my neighbour saying that CPV systems  
are typically designed as tracking systems, my guess is that they'd be  
dual-axis tracking to maximise efficiency. If that's the case, it's  
unlikley that there'd be any contact between the PV array and the roof so  
I doubt there'd be any heat related issues WRT the roof.

 From what I've seen the major cost of any solar power plant has been the  
cost of the PV panels.

Around here, a 10 KW roof-mounted fixed array seems to cost about $40-45k.

If a CPV system can reduce the number of PV cells/panels required and  
still provide the same generating capacity, the cost of the array will be  
reduced.

I have some  (letter) page-size Fresnel lens magnifiers that I got from  
Lee Valley Tools over a decade ago.

I don't recall their being particularly pricey so I don't expect that the  
addition of Fresnel lenses to a PV array would be much of a factor in  
increasing cost.



-- 
=== * ===
Rob Tom					AOD257
Kanata, Ontario, Canada

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