On May 18, 9:00*pm, Andy wrote:
Andy replies

Jim, I am using the 50K number which someone who claims to be
knowledgeable about the issue posted yesterday on this newsgroup
in a thread with a similar name. I don't know, personally, what an
installed system costs.
* *I am also using "his" allegation regarding federal subsidies and
state and municipal rebates... If I am incorrect, I'm sure that anyone
who
is pursuing the matter will want to get his own numbers anyway and
not rely on newsgroup advice.....

* *My purpose is to point out that, regardless of "subsidies" that
are
borne by the taxpayers, *there are many other factors to consider in
this
endeavor, that most people might only find out AFTER they are too
committed to back out......

* * I find it reasonable for the numbers you quote, assuming that
similar rebates apply to the user. They sure don't apply where I live,
tho..

* * And I am curious at to the 5kw system you mention. *If that is 5K
peak
watts from the array, that would only apply in "full sun", which the
tables
say averages 5.5 hours per day in the Dallas area.....
That's about 27 kwh per day, which is probably reasonable for around
here.
But for those areas that have less than 5.5 full sun hours per day,
like maybe
Seattle (as a guess), that capacity wouldn't be enough.....

* * In addition, to achieve the 27.5 kwh/day, the array would have to
be
tracked so that the sun would be "normal" to the array for the full
day.
Since I assume the array would be mounted , fixed, onto a roof, the
output would be significantly less, and would be a cosine function
for
the average value, about 64% or so (from memory), *and then only if
the roof slanted in the
proper direction..... So, you see, there is more to this than the
factory
specs, which will normally assume an optimum mounted system....
However, those are technical factors which one also finds out about
only after having the system installed, not realizing the "quoted"
potential,
and then learning the engineering behind the system....

* *Anyone who can afford 25K ( or 50K, whatever) for a system has the
ability to learn these factors and do the tradeoff for themselves
BEFORE
making the committment , since "it ain't rocket surgery". * My purpose
in the posts I have made is to encourage everyone to do so, and not
be
deterred by anyone who says "it's too complex for you to learn so you
should
just fork over the money"..... *Actually, anyone with a ham operator
license above novice class has demonstrated more electrical knowledge
than
is presented in a "PV installation class", *so while such a class
might be useful,
*(or not), ANYONE can learn to do it......

* *So, as an engineer who has done a lot of this kind of thing, I'll
simply say
that the knowledge required to hook up a PV system is insignificant
compared
to getting an engineering degree, and there's lots and lots of
engineers....
I'd compare it to changing the oil in your truck, or doing a brake
job,
which doesn't require a PhD
in mechanical engineering to accomplish, tho many many things can go
wrong......
* *Education is the key....

But thanks for your info. *It gives interested parties yet another
point of view.

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

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).
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.

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

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.

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.

A very major issue is shading. As the panels are series connected,
shade on one panel effects them all.
I cut back trees on my property to overcome this problem, later in the
day in my case.