On May 19, 1:45*pm, Andy wrote:
On May 19, 1:20 am, harry wrote:

There is a number for your area. *In my case it is 830. *This is the
number of Kwh generated per year per kwp installed. You need to find
out what your number is, (prob. around 1000 fir you).

**** Thanks haarry. *A back of the napkin calculation says my
number is more like 1200 for Dallas *(1.0 x 5.5 X 365 X 64% ), but
I'd
need to look up the specific criteria used in your number to
see if I left anything out.

Thers additionally a chart that shows % reduction in output as the
array deviates from due South and from the optimum angle (to the
ground).
My optimum angle is 35 degrees, it will be more like 10 degrees in
Texas I should think.

**** I agree. * My latitude is about 36 deg N...... *and I don't
remember
the sun path deviation thru the year. ( I should, since celestial
nav was once a hobby, but that was a long time ago :)) *)



This is all for fixed arrays. *The cost of rotators is not generally
viable.

***** Perhaps some mechanical guy will come up with something
eventually. But, in Texas, we need to practically weld the panels
to the roof since we are subject to large hail, tornadoes, and , at
the very least, high winds.... I don't think you have those
environmental variables in the UK..... On the other hand, on my
trips to south England, I don't think I've ever seen the
sun * :))))))

The current technology is silocone but they are not all a like. Some
perform better in lower light conditions than others, ie in the
shoulder period. *So while they have the same Kwp, they generate more
Kw because they perform better during the shoulder periods.
Most power is generated between 10.00h and 14.00h.

*** I guess you are using GMT...... Ok, that is consistent with the
cosine function I was talking about, with "local noon" being 0 deg.
The panels I used were amorphous silicon, by UniSolar. *I recently
google them again, and they have some interesting new items, including
"solar shingles".... *They are just lain on top *of the normal
asphalt
shingle and a couple holes bored in the roof to bring two wires thru,
and the interconnection done in the attic...... It would be a bitch
to replace the roof shingles....



So you need to look at the graphs of power generated/available light.
The less"peaky" the curve the more power you get in any given day.

**** Like I mentioned, Dallas is rated at 5.5 hrs of "faverage ull
sun" per day.
For other readers, that means that the power generated is the same
as if the sun were directly overhead at optimun angle for 5.5 hours.
It averages out things like clouds but I don't think it averages out
the
sun movement and seasonal angle , and assumes a tracked array.....
*I guess I need to check on that.....

A very major issue is shading. *As the panels are series connected,
shade on one panel effects them all.

**** *In my experimental system, I used blocking diodes and paralleled
the
output to the charge controller. Shading, in that case, applied to
individual
panels. * I understand that some panels are manufactured with
"shading
diodes" to minimize this, *but I don't know if they work well since
I've
never tried them...

I cut back trees on my property to overcome this problem, later in the
day in my case.

****** I live in a wilderness area with lots and lots of trees, and
the south
side of my house has some blocking. But in the afternoon, when the
sun is in the west, it's pretty clear already. *Plus, I have a high ,
sloped
roof, if I were to mount it there.... Actually, that would shade the
roof a
bit more and cut down on the heat in my attic...... hmmmmm.....

** Thanks for the reply Harry. *It's nice to be able to learn from
someone who
actually has an installation and has the skills to evaluate the
performance.
So I have a couple questions :

*1) What is your system capacity and how much did it cost ?
My systemi s 3.88Kwp.It cost £14,500 installed (=$23.000?). I think
most stuff is cheaper in America though than here..

*2) Did it meet the manufacturer's literature, or was the output
* * *less due to "other circumstances" *???
It frequently hits or exceeds the rated output. This is apparently
normal with a new array. I t will fall back ina few weeks to rated
power apparently

*3) What is the cost of electricity per kwh in your area?
* * * ( Around here , it is about 10.5 cents per kwh )
I pay around £0.12/Kwh (= $0.20/Kwh)
.. However I am paid £0.41/Kwh for everything generated whether I use
it myself or export it. I get an additional £0.03/Kwh for exported
power.
All is tax free and inflation linked for 25 years.
It works out at 11.5% return on capital, which these days is a really
good deal.
The thing has been runnining for three weeks now, I have generated
530Kwh.

*4) *Did the cost make your real estate tax go up, and your
* * * house insurance premium go up ?
Our tax system is different to yours. No extra taxes. Yet.
I have notified my house insurance company, they don't want any more
money. I suspect when they get their heads round the business, this
might change.

BTW,by shading I meant things like trees and chimneys casting a shadow
on the array.

* * * *(I don't know how it works in the UK, but here in Texas the
typical
* * * * * yearly tax is about 2% of the appraised value of the
* * * * * property and about 0.5% of the replacement value for
* * * * * homeowner insurance)

* *Thanks again , Henry. *I'm sure that most of those who post
here will have an interet in your first hand experience...

* * * * * * * * * * * Andy in Eureka, Texas