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Bob-O,<br>
<br>
I neither subscribe to the notation that cheaper is better nor the
notion that more expensive is better. Adding more wire until 1%, or
any other arbitrary percent loss figure is attained, does not
necessarily make a project better. It will make the project more
efficient to increase the wire size. But without considering the value
delivered by the extra efficiency, how do you decide when to stop
adding wire? The installed cost per watt (or watthr/per year)
delivered is a reasonable metric to use for making the decision to use
more wire or not. That is in fact the metric you and I both use to
decide that using MPPT technology is a smart choice. We know MPPT
technology is worth using because we get more for our dollar. If a FM
60 was the only MMPT charge controller on the market and it cost $1500,
neither of us would use them as often.<br>
<br>
Since neither you nor any other wrench on this list offered an answer
to my previous question, I'll rephrase it. If 1% loss is a good
design, then why isn't 1/2% loss better? Why stop at 1%?<br>
<br>
I'd like to point out an error in your reasoning that extra cost is
recovered over time as power prices increase. There is a point to be
made there, but as you stated your argument the comparison was between
future value and present value. That's an incorrect economic
comparison; you have to determine the present day value of future
benefits and compare that to present cost.<br>
<br>
It is unfortunate that there are getting to be fewer and fewer choices
for PV modules that aren't entirely or largely made in China. It's
criminally ironic that BP Solar is predicting 50% growth in PV sales at
the same time they are closing their manufacturing facility in
Maryland, <a
href="http://www.pv-tech.org/news/_a/bp_solar_closes_frederick_facility_hopes_to_improve_product_costs/">see
article</a>. I wonder how many of those 320 newly unemployed workers
will be in the market for PV systems. And how many more such jobs can
be sent to China for short term corporate greed before no one in the
U.S. will be able to buy one.<br>
<br>
Kent Osterberg<br>
Blue Mountain Solar, Inc.<br>
<br>
<br>
<br>
Bob-O Schultze wrote:
<blockquote
cite="mid:C81BCC75-1767-4C81-8908-C18B4A1B786E@electronconnection.com"
type="cite">Of course it's not a practical solution, which is why we
strived for (but rarely got) 2% VD on low voltage situations as I said
in my first post. The obvious reply to this post is that your scenario
isn't real world anymore. MPPT controllers fixed that. Or perhaps you
advocate that MPPT controllers are just too expensive too? I could
easily come up with a scenario where a C40 and big wire is less
expensive than using MPPT and smaller wire. But is that good design? I
don't think so.
<div>My point -and one which you apparently dismiss out of hand- is
just that cheaper is not always better. Good design and best practices
rarely go hand in hand with cheaper.</div>
<div>Waste is waste. Along those same lines, I'll repeat something a
friend of mine recently said, "If you like getting your oil from Saudi
Arabia, you're gonna love getting your PV from China. " It's cheaper,
right?</div>
<div>Ya know?</div>
<div>Bob-O</div>
<div><br>
<div>
<div>On Apr 10, 2010, at 9:22 AM, Kent Osterberg wrote:</div>
<br class="Apple-interchange-newline">
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Here's my challenge to all of you that want to design for 1% or 1.5%
voltage drop all the time:<br>
Take a 50-ft circuit carrying 40 amps at 12 volts, going to a C40
charge controller, select your wire size for 1% or 1.5% loss. You know
that's not a practical solution. I know that it makes more sense to
replace the charge controller and run the PV circuit at a higher
voltage.<br>
<br>
<b>At % loss did it become impractical?</b> Ray's answer and my
answer
is "when there is a cheaper alternative -- lower cost per watt out or
lower cost per kWh over the project life." And that answer works even
when you are considering a 400-kW PV array that is 1000 feet away.<br>
<br>
Kent Osterberg<br>
Blue Mountain Solar, Inc.<br>
<br>
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