Solar Radiation available for CPV vs Flat pannel

[Thaddeus Ward]

Hello all,

I think this is an important point for the overall ROI and production
of any CPV product. In the last posting Greg was saying that direct
radiation is generally at about 85% of the total available. This may
be the case. I have data from the US showing radiation available to a
CPV 2 axis tracking system vs fixed panel flatties ranging from
60%-85% in a high-latitude (44N), high-humidity location to 98% to
128% in a lower-latitude (35N), very-low-humidity environment. I
should also note that it is a very different picture for 2 axis
tracking on flatties. This is based on data from the NREL data base
here in the US.

In either case CPV can still be a better investment, but each project
needs to check its ROI assumptions carefully. I believe differences
in direct ray vs. diffuse radiation need to be considered.

I may also be off-base here so if there are alternative approaches
please let me know.

-TW

[Greg Watson]

Hi Thaddeus,

Yes the ratio does vary a bit but generally as the 2 axis concentrator DNI
drops, so to does the fixed latitude tilt flattie global drop as the
predominate energy is the direct component.

Then you need to factor in that silicon based flat panels suffer a
significant conversion efficiency drop as the available global energy drops
below 200 W/m2. Their conversion efficiency versus W/m2 is not very flat and
really drops into a hole as the W/m2 declines. This is why some decide to
use thin film as it offers a somewhat flatter conversion efficiency versus
W/m2 at low W/m2 levels but then you need to ask why as there is really very
little energy to be had from global at 150 W/m2 and lower.

So sure flat panels can generate SOME power using only diffuse but the cost
of that energy is very expensive as you are talking about global inputs of
around 150 W/m2 times say 5% conversion efficiency yielding 7.5 W/m2 of
delivered energy. Not what I would spend my money on.

So for both flat panels and CPV you need direct beam to make it pay.
Generation power from diffuse is salesman's spin.

All the best,
Green and Gold Energy Pty., Ltd
Greg Watson, CEO
7 Provident Avenue, Glynde, 5070
South Australia, Australia, +61 8 8365 5844
http://www.greenandgoldenergy.com.au

"SunCube" and "SunBall Solar Battery" are
trademarks of Green and Gold Energy Pty Ltd

> --
> You received this message because you are subscribed to Green-India
> to discuss India's Energy Future and Sustainable Living.
>
> Green-India
> http://groups.google.com/group/green-india
>
> Posting Guidelines
> http://groups.google.com/group/green-india/web
>
> To unsubscribe, send email to
> green-india...@googlegroups.com
>