Battery or non-battery UI? [RE-wrenches]

[Kirk Herander, VT Solar]

Hello Jeff,

I  lean more towards battery-based UI. Once I explain to customers that they will have zero power for
critical loads in a non-battery system
should the power fail, most don't care about the economics or efficiency. They want critical load
power to bridge the blackout.  They value this peace of mind more, and often bring up the "ice storm"
of a few years ago to reinforce their own opinion. Because if you live out in the boonies, it may be
days before power is restored after a bad winter storm, especially in a rural state such as Vermont.

I don't have data to back this up, but I think that battery UI using a MPPT controller can make up a
good bit of the efficiency losses in cool / cold (i.e. low panel temp) conditions if the controller
is never allowed to leave bulk charge (by programming inverter sell voltage well below the bulk
charge setting). Granted, MPPT efficiency varies from season-to-season, but it can help to justify
battery-UI depending on application.

regards, Kirk, Vt. Solar

"Jeffrey Wolfe, Global Resources" wrote:

> Based on the above, I have taken a very strong inititative to try to keep
> on-grid people from buying a battery system. If they are living without
> backup power now, I try to keep it that way. If they need backup power, I
> look for options. (Computer UPS's are very cheap.) However, as we all know,
> battery backup is a big selling point. (Here we are in marketing again!) So
> we're spending time educating people. I've done the comparisons on cost.
> For a small system, you're looking at about a 30-40% material adder, plus
> more shipping and installation costs. (This is based upon using the new
> Trace SL line tie inverters, versus those FETful SW's).)
>
> The only way you can touch a 15 year payback is with energy costs in the
> mid teens per kWh, interest rate at 0%,  a direct grid tie batteryless
> system, and a lot more sun than we get in Vermont. If you can make those
> numbers work, give me a peak at them!
>
> Jeff
>
> Jeffery D. Wolfe, P.E.
> Global Resource Options, LLP
> A Woman-Owned Vermont Limited Liability Partnership
> 4 Kibling Hill Road
> P.O. Box 51
> Strafford, VT 05072
> 802/765-4632
> 802/765-9983 (Fax)
> global at sover.net
> www.globalresourceoptions.com
>
> T

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