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"
<er...@repowersolutions.com <mailto:er...@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
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