<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">+1 for Maui Software. It is really helpful for finding the array-to-battery-to-generator capacity sweet spot. You can also use it to model things like the impact of various generator start/stop triggers. If you have monthly kWh meter readings for the site, you can build a daily average load profile on a month by month basis. (Better yet, monitor the daily load for a few weeks or months in the design season and use this as the basis for your model.) Then you can model system performance over a typical year and see when the generator is expected to run. <div><br></div><div>The equipment library used to be pretty thin—and probably still is—but you can add equipment to the database. Or just model performance using "similar" equipment. When I used the software it didn't have the ability to model an AC coupled system. But for a typical DC coupled system, it will produce a lot of interesting/nerdy charts that will help designers anticipate high level performance trends for a proposed system.<div><div><div><div><br><div><div>On Mar 25, 2013, at 10:18 AM, Ray Walters wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite">
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<div class="moz-cite-prefix">Also, Windy Dankoff's old spread sheet
that I adapted calculates generator run time per week, and Maui
SOlar software does a good job of calculating generator hours per
year. I've used Homer and found it to be pretty far off from off
grid reality. <br>
Any off grid application is going to benefit from inverters and
batteries to keep the generator from having to run 24/7. Next,
adding at least some PV to trickle charge the batteries is often a
no brainer. . You definitely don't need as much battery in a
hybrid system.<br>
Its not just a fuel issue, generator replacement and maintenance,
along with more esoteric considerations like noise, and smell,
need to be factored in as well.<br>
Figuring the ratio of generator run time vs. PV is a bit trickier,
but I found you can sneak up on that calculation by starting with
the generator, batteries, inverters, and smallish PV, then add
more PV incrementally while monitoring gen run time. <br>
Real performance numbers always beat computer simulations,
especially off grid, where it is often tough to characterize the
real life complexity of the loads.<br>
There is a point if your baseline 24/7 loads are large enough, a
full time generator makes sense, but unless its in Alaska, some PV
almost always makes sense as well. <br>
Also the loads will determine how much design time to put in
before hand. If your looking at a 50kw generator or up, you need
to invest in some software and/ or get an off grid design
specialist on board.<br>
<br>
<pre class="moz-signature" cols="72">R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760</pre>
On 3/25/2013 7:37 AM, Andrew Truitt wrote:<br>
</div>
<blockquote cite="mid:5A67AADE-A2C5-4933-81E9-D2A1EC19BA14@gmail.com" type="cite">
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<div>Erika - HOMER <span style="-webkit-tap-highlight-color:
rgba(26, 26, 26, 0.292969); -webkit-composition-fill-color:
rgba(175, 192, 227, 0.230469);
-webkit-composition-frame-color: rgba(77, 128, 180, 0.230469);
">(</span><span style="font-size: 15px; line-height: 19px;
white-space: nowrap; -webkit-tap-highlight-color: rgba(26, 26,
26, 0.292969); -webkit-composition-fill-color: rgba(175, 192,
227, 0.230469); -webkit-composition-frame-color: rgba(77, 128,
180, 0.230469); -webkit-text-size-adjust: none; "><a moz-do-not-send="true" href="http://www.homerenergy.com/">http://www.homerenergy.com/</a>)
is a hybrid power system modeling tool for on- or off-grid
applications. There is a 2 week free trial period and then it
costs $100 for a 6 month software license. I haven't used it
yet but have heard good things. </span></div>
<div><br>
</div>
<div>- Andrew Truitt</div>
<div><br>
<br>
Sent from my iPad</div>
<div><br>
On Mar 25, 2013, at 7:15 AM, "Erika Weliczko" <<a moz-do-not-send="true" href="mailto:Erika@RepowerSolutions.com">Erika@RepowerSolutions.com</a>>
wrote:<br>
<br>
</div>
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<div class="WordSection1"><p class="MsoNormal">Does anyone know of an efficient
calculator tool to help compare diesel /gas generator to
PV + batt + small generator for an off-grid vacation
house?<o:p></o:p></p><p class="MsoNormal"><o:p> </o:p></p><p class="MsoNormal">Regards,<o:p></o:p></p><p class="MsoNormal">Erika<o:p></o:p></p>
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