MPPT arrays in different directions [RE-wrenches]

Rob Wills RWills at AdvancedEnergy.com
Wed Mar 27 14:02:09 PST 2002


Hi Jay & Doug - sorry about the late response but I've been on the road.
I talked this over with Gary at length, and concluded, as others have, that
the simplest solution is the best - just connect all three arrays into the
MM-5 DCDC converter.  There will be some power loss, but the peak power vs.
voltage curve is typically pretty broad.

The main reason for keeping simple, and not using other suppliers MPPT
converters into the battery, is that there is no easy way to coordinate
their voltage control with the MM, and with temp compensation by the MM,
this is a moving target.  You would find that sometimes the MM would export,
others it might import and turn the additional charge controllers off..

I suggested that Gary try connecting each sub-array in turn when the system
is operating to get a measure of the power loss.

Regards

Rob Wills

-----Original Message-----
From: jay peltz [mailto:jay at asis.com]
Sent: Tuesday, March 19, 2002 8:56 PM
To: RE-wrenches at topica.com
Subject: Re: MPPT arrays in different directions [RE-wrenches]


Hi Gary,

I don't know for sure, but my gut tells me that I'd go with different
controllers to get MAX power from the situation.  Given this you could go
with
either inverter as you will have to add MPPT's to it.

If you are willing to ( or the customer) to probably sacrifice a bit of
power
for the ease of install, then just hook them up to the MM-5.

Maybe the AEI guys could respond to this?

jay

peltz power

"Gary Higbee, Solutions from the Land" wrote:

> Hi Wrenches,
>
> I'd appreciate your thoughts on a large install I'm working on. We've got
> about 5kW of PV, though it is divided into South, East, and West fixed
roof
> arrays. Not optimum, but the architect got to my client before we did.
>
> We're setting up a 48-volt grid-tied system with battery backup. The only
> viable inverter solutions I'm aware of for almost immediate delivery are
the
> Vanner RE48-4500 and the AEI MM-5000. I love the way the MM-5000 is
packaged
> (built-in 5kW MMPT, ground fault, etc.) but I am concerned about using one
> MPPT unit on three different PV orientations. I think I heard that each
> different orientation should have its own MPPT controller. Is this true?
>
> If I use the Vanner I'll need 5 combiner boxes, 5 Solar Boost 3048 units,
> and all the ground fault and main breakers (the 5 units encompassing 3
> directions and current limitations). I'd likely use two Outback DC boxes
and
> mount the PV controllers in a row above a raceway. I think this could be
> done in a clean manner, but the AEI is sure attractive.
>
> So, what do you think--lump the whole roof (East, South, West) into one
> giant array with one MPPT and go with the AEI, or break down the roof and
> MPPT each direction, using the Vanner/Outback solution?
>
> THANK YOU!
>
> Gary
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>            Gary Higbee  (ghigbee at efn.org)
>               (541)607-1818 (Eugene)
>              (541)902-8544 (Florence)
> Solar, wind, and hydro site analysis and system design
>     Components dealer and installation assistance
>               ~Solutions from the Land~
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
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