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Marco,<br>
<br>
Three components of power delivered by the utility company: Watts,
volt-amps-reactive (VAR), and apparent power or volt-amps (VA). Power
factor is the ratio of the watts to the volt-amps. PF = Watts/VA.<br>
<br>
To see how this works: draw a right triangle with 8 kW as the
horizontal leg, 6 kVAR as the vertical leg, and 10 kVA as the
hypotenuse. The power factor is 8 kW/10 kVA = 0.8. Now put in a 4-kW
solar system. The 6 kVAR reactive load doesn't change So the solar
system reduces the real power delivered by the utility by 50%, the
reactive power by 0%, and the apparent power by 28%. The power factor
afterwards is PF = 4 kW/7.21 kVA = 0.55. The power factor did get
worse! To see how that all works just draw a new hypotenuse starting
from the midpoint of the 8-kW horizontal leg. Hardly seems worthy of a
paper. But the utility doesn't like to supply power for a load with a
power factor less than 0.8 because the out of phase current still
causes I-squared x R losses or line losses. <br>
<br>
<br>
Joel,<br>
<br>
The utility company isn't responsible for the power factor. The
customers' loads determine the power used and the power factor. The
utility company is responsible for the power quality, which is really
poor in lots of locations.<br>
<br>
Kent Osterberg<br>
Blue Mountain Solar, Inc.<br>
<br>
<br>
<br>
Marco Mangelsdorf wrote:
<blockquote cite="mid:00da01ca908b$43394100$c9abc300$@com" type="cite">
<pre wrap="">According to an article, written by a utility engineer on O'ahu, PF can be
worsened at the site where a substantial PV system is located.
If there is a poor or wavering PF due to an abundance of inductive loads at
a particular site, having a large inverter, in relation to the overall power
consumption of the facility, can actually make the PF worse.
I can track down that piece for anyone interested.
Marco
ProVision Solar
-----Original Message-----
From: <a class="moz-txt-link-abbreviated" href="mailto:re-wrenches-bounces@lists.re-wrenches.org">re-wrenches-bounces@lists.re-wrenches.org</a>
[<a class="moz-txt-link-freetext" href="mailto:re-wrenches-bounces@lists.re-wrenches.org">mailto:re-wrenches-bounces@lists.re-wrenches.org</a>] On Behalf Of Joel
Davidson
Sent: Thursday, January 07, 2010 5:42 AM
To: RE-wrenches
Subject: Re: [RE-wrenches] Power Factor and Grid Tied PV
We worked on dozens of commercial PV systems in Southern California Edison
(SCE), Los Angeles Department of Water & Power (LADWP), and San Diego Gas &
Electric (SDG&E) territories. We installed Xantrex, SMA, and SatCon
inverters and measured power factor on both the grid and the inverters. In
every case, inverter power factor was 1. In almost every case LADWP's power
factor was less than 1 and in older parts of Los Angeles power factor was
often 0.75. SCE and SDG&E generally has pretty good power factors. In
general, PV inverters do not worsen grid power factor. In general, newer
sections of the grid are better designed and better managed than older grid
sections. When utility companies or anyone says PV causes grid problems, ask
for proof.
Joel Davidson
----- Original Message -----
From: "Darryl Thayer" <a class="moz-txt-link-rfc2396E" href="mailto:daryl_solar@yahoo.com"><daryl_solar@yahoo.com></a>
To: "RE-wrenches" <a class="moz-txt-link-rfc2396E" href="mailto:re-wrenches@lists.re-wrenches.org"><re-wrenches@lists.re-wrenches.org></a>
Sent: Wednesday, January 06, 2010 9:39 PM
Subject: Re: [RE-wrenches] Power Factor and Grid Tied PV
I recently spoke with an inverter manufacture and I left with the following
opinion. Normally the inverter takes the unity power factor load and leaves
the reactive load. making the power factor worse. However the power factor
could be corrected by the inverter, However this would add cost to the
inverter and would not appear to have value to the solar industry. There
are variable reactance devices existing that can correct power factor, is
there need for another device?
Darryl
</pre>
<blockquote type="cite">
<pre wrap="">Hello Wrenches,
Commercial power customers often are penalized for low
power factors.
Looking for other info I came across this article, which
seems to
cover the subject from an academic standpoint.
<a class="moz-txt-link-freetext" href="http://tinyurl.com/ye5pzrw">http://tinyurl.com/ye5pzrw</a> Does anyone
have real world data which
might shed light on the impact of a DGT PV system on power
factor.
With Regards
Carl Adams
SunRock Solar, LLC.
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