Re: (ET) Solar charging, part 2 :using a stationary pack

["Pieter Litchfield" <plitch attglobal net>]

I guess I would argue that from a *purely* economic point of view, even if
the on-board charger on the ET is inefficient, it may make more sense to
sell all the solar power to the grid, then buy back only what is needed to
charge the ET when it is plugged into the wall socket.  In this way, you
could use a small capacity solar panel system with no batteries, a simpler
control system and still achieve the result of solar charging the ET.  
Since
a Kw on the grid is a generic commodity and can't be identified as solar vs
fossil generated, one could argue that as long as the output of the panels
to the grid in Kwh is greater than the use to charge the ET, then the
charging is accomplished with solar power.  You are just using the grid as 
a
big "battery bank" for the charging system, and by doing so, the capital
outlay is reduced. As a non-user, I'm not sure what the net financial 
effect
of selling power to the grid and then buying it back is, but I would assume
that would be a small variable (per Kw) cost to the charging system.

----- Original Message -----
From: "Christopher Zach" <czach computer org>
To: <jbc coate org>; "elec-trak" <elec-trak cosmos phy tufts edu>
Sent: Wednesday, April 23, 2003 9:33 AM
Subject: Re: (ET) Solar charging, part 2 :using a stationary pack


> Yes, that is another possibility. I use a 100 watt grid-tie inverter
hooked
> to my main battery pile (300amps at 24 volts) to divert surplus sun power
> from my panels into the grid. I do like inertae: it is the best way to 
> get
> efficiency out of a solar panel setup.
>
> However I will say that the efficiency of my solar charger is pretty 
> close
> to 100%. The efficiency of the Elec-Trak's on-board charger is nowhere
near
> as good (lot o' heat). Thus by using the grid-tie approach, it is not as
> efficient as charging directly from the panels.
>
> The typical "solar" way is as follows:
>
> Tractor gets top priority for charging
> Bringing the shed batteries to 25 volts gets second priority
> Rest is sold to the grid.
>
> The batteries in the shed typically get a full charge during the morning
> (the panels can put in up to 15 amps, the inverter takes out 4 tops) and
> then get discharged down to 70% or so during the afternoon. The size of
the
> battery core is large enough that I can run tools, toys, lights in the
> evening without dropping the pack below 40%.
>
> Works pretty well actually.
> Chris
>
> ----- Original Message -----
> From: "Jim Coate" <jbc coate org>
> To: "elec-trak" <elec-trak cosmos phy tufts edu>
> Sent: Wednesday, April 23, 2003 9:13 AM
> Subject: Re: (ET) Solar charging, part 2 :using a stationary pack
>
>
> >
> > Another variation is to use a grid-intertied system. For those of us
> > already on the grid, this can be done with out any stationary battery
> > pack (although won't have the blackout backup). Any solar power
> > available goes into "the grid" when the sun shines and the ET is 
> > plugged
> > in and charges from the grid (regardless of the amount of sun shine at
> > that moment). I have just two smallish panels and an intertie 
> > controller
> > (Chris Zach may have had one first that I read about??) for a 100 watt
> > system. Similar to what Jeremy and Eric and all have been saying, this
> > gets the most power possible from the panels as there is always some
> > place for it to go.
> >
> >
> > Eric wrote:
> > >    In my opinion I think charging a stationary pack instead of
directly
> > > charging the Elec-trak gives you the freedom to do more (than just
> charging
> > > the ET). Coupling together the ability to recharge the ET along with
> other
> > > uses makes the investment in solar panels a wise investment. Don't
> forget to
> > > explain to the wife how if the electricity goes off again at least we
> have a
> > > back up system to hold us over till the electricity in our area is
> restored.
> > --
> >
> > _________
> > Jim Coate
> > 1992 Chevy S10
> > 1970's Elec-Trak
> > http://www.eeevee.com
> >
> >
> >
>
>
>