Trace gridtied [RE-wrenches]

[sunwise at win.bright.net]

Jason Fisher wrote:
> 
> Greetings wrenches,
> 
> I had a question which is based on:
> 
> Kurt Nelson wrote:
> 
> > the Trace is left in the LBX mode, which is a lot less efficient than
> > grid-tied.

I've been considering shying away from the sell mode and using
> the LBX mode for clients who are willing to get more hands on with their
> system.

	This is kurt again and I'm actually in agreement with you Jason.  A
number of factors come into play, but the biggest is the size of the
back-up battery.  The Trace not only keeps it topped of with PV all day,
it keeps it topped off with grid at night.  LBX systems can be designed
that are more efficient, though if you factor in battery longeviety and
if the battery get abused by (uneducated) owners?  I'm finishing up a
system as we speak that is a grid-tied LBX.  We are switching a couple
home appliances back and forth between the grid and solar, based on
battery voltage, using the SW series AUX relays and thirty amp two throw
contactors.   The frig will go solar when the battery voltage comes up
in the morning and drop off early in the evening as the voltage drops to
about 25.2 (12.6).  This also allows for the inverter to really sleep at
night, as the frig has a defrost timer that would keep it up (DC nite
lites).  The addition of a small 120vac relay with the contactor's coil
wired thru keeps the frig on the solar if utility power fails.  In some
ways I am suprised that the Trace gets wired exactly the same in a LBX
as in a Sell, and only a menu button keeps a LBX from becoming truely
utility interactive (that nobody has expressed concern).  Does anyone
know of any utilites expressing concern over this or with them having a
problem with the type of system described above?
> >
> 
> Why is this?  I have a bunch of net-metered systems selling away and I'm
> not too sure about the performance of the Trace and battery versions.
> While the sell mode is the most hands-off and convenient for a grid-tied
> backup system, I'm dubious as to how good it is at selling that power.
> In the typical system with battery backup, I have a 4 kW or even 5.5 kW
> inverter selling around 1.5 kW worth of PV for most of the day.  I've
> been planning on setting up a monitored system to get some hard results
> but based on what I've witnessed, and what I've heard from others, the
> overall efficiency of the unit in this mode seems to be in the 70% range
> or so.  I've been considering shying away from the sell mode and using
> the LBX mode for clients who are willing to get more hands on with their
> system.  This way I can put the inverter back in search mode and be
> confident that the PV will be used to its full capacity so long as the
> batteries aren't at float.  This also gets rid of that daily float
> charge cycle that they set up in the sell mode, this must waste some
> juice.  The big drawback is of course that most people want more backed
> up loads than the PV they bought can handle on a daily basis but that
> could be worked out.  The thing I like about it is that it keeps the
> consumption issue out in front, instead of blurring it behind a slightly
> smaller utility bill.  I also thought it should be better for the
> typical flooded batteries to see some use.  What do you all think?
> 
> Keep it up.
> --
> Jason Fisher
> 
> Aurora Energy
> 86 Conduit St.
> Annapolis, MD 21401
> USA
> 
> Voice/ Fax: 410-268-3088
> email: aurora at toad.net
> 
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for info contact: <michael.welch at homepower.com>
_________________________________________________________
Enlighten your in-box.         http://www.topica.com/t/15