[RE-wrenches] diesel vs. solar

[Ray Walters]

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.
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.
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.
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.
Real performance numbers always beat computer simulations, especially 
off grid, where it is often tough to characterize the real life 
complexity of the loads.
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.
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.

R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760

On 3/25/2013 7:37 AM, Andrew Truitt wrote:
>
> Erika - HOMER (http://www.homerenergy.com/) 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.
>
> - Andrew Truitt
>
>
> Sent from my iPad
>
> On Mar 25, 2013, at 7:15 AM, "Erika Weliczko" 
> <Erika at RepowerSolutions.com <mailto:Erika at RepowerSolutions.com>> wrote:
>
>> 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?
>>
>> Regards,
>>
>> Erika
>>
>> _______________________________________________
>> List sponsored by Home Power magazine
>>
>> List Address: RE-wrenches at lists.re-wrenches.org 
>> <mailto:RE-wrenches at lists.re-wrenches.org>
>>
>> Change email address & settings:
>> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
>>
>> List-Archive: 
>> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
>>
>> List rules & etiquette:
>> www.re-wrenches.org/etiquette.htm 
>> <http://www.re-wrenches.org/etiquette.htm>
>>
>> Check out participant bios:
>> www.members.re-wrenches.org <http://www.members.re-wrenches.org>
>>
>
>
> _______________________________________________
> List sponsored by Home Power magazine
>
> List Address: RE-wrenches at lists.re-wrenches.org
>
> Change email address & settings:
> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
>
> List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
>
> List rules & etiquette:
> www.re-wrenches.org/etiquette.htm
>
> Check out participant bios:
> www.members.re-wrenches.org
>

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org/attachments/20130325/55cb5510/attachment-0003.html>