[RE-wrenches] Battery based grid tie question.

Thu Mar 26 04:47:05 PDT 2009

Morning William,

regarding 1--

Don't know what your net-metering application form requires, but in VA the installing company has to certify/ sign off on the equipment meeting 1741. Years ago, after y2k, we had a Co-op so eager to show their support for net metering, that their people , after inspecting the system and testing the loss off grid transfer function by pulling the meter, signed the forms themselves. 

As for 2, from our experience with the local IOU, be careful when mentioning a motor-driven generator. They don't understand that the XW can't sell that power--directly-- to the grid. Since the cat is out of the bag, I think you'll need to show that the gen set only charges the battery and passes thru the XW to the dedicated loads.

May be simpler not to mention generator?

Ken
  ----- Original Message ----- 
  From: William Miller 
  To: RE-wrenches 
  Sent: Thursday, March 26, 2009 2:12 AM
  Subject: Re: [RE-wrenches] Battery based grid tie question.

  Colleagues:

  Interesting that this topic comes up at this time:

  1. We inherited a grid-tie project wherein an elderly client was sold an SW installation some years ago.  Come to find out, the installer never filed anything with the utility.  The client was caught recently back-feeding without permission by a meter reader and told to cease and desist.  We filed an application with the utility thinking this was a long shot since the client's SW inverter did not have the requisite Grid-tie Interface (GTI).  We have several GTIs sitting on the shelf, but the inverter does not have the proper interface so one could not be installed.  Lo and behold, the utility approved this installation for interconnection.

  2. We have an application to the local utility (PG&E) pending for a three XW installation with a motor-generator.  We have received multiple communications from PG&E doubting the acceptability of the XW system for use as a gird-tied battery-back up system.  We are hoping that PG&E accepts the listings from the various agencies and approves the project.

  Interesting that the old, non-complaint system receives swift approval but the latest and greatest gear hits a regulatory road block!  We'll keep you posted.

  William Miller

  At 04:56 PM 3/25/2009, you wrote:

    What year are the SWs? they have had grid inter tie for years, if the inverters were manufactured prior to I think 2001 then you do not need to have the gti box installed.  If the guys on a budget why spend  the extra $$$$? Its not the most efficient it certainly cheaper. 

      -----Original Message-----

      From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of robert ellison

      Sent: Wednesday, March 25, 2009 9:39 AM

      To: RE-wrenches

      Subject: [RE-wrenches] Battery based grid tie question.

      On a similar question to what works well together. I am rebuilding the wind side of an old off grid system that the new owner has brought the grid in. He wants to grid tie the system. Another dealer is doing the solar side of things.

      My thoughts are the 48 volt SW inverters need to go, and replace them with Outback 48 volt grid tie units and have the wind keep the battery up. Am I correct that when the batteries are full from what ever source the outbacks will grid connect and net meter any excess power to the grid? Seems that I remember that they will but almost never get a call for grid tie up here in the sticks so I figured I would ask the knowledge base.

      I would suggest he keep the SW inverters to generator charge in case of a long power outage as last I knew the Outbacks (FX) did not care for generator power.

      I could probably research it but the list is faster and probably more accurate that reading all the manuals with all my free time these days!

      Needless to say the fellow in on a budrgt and the power company brought the power into the main building not the power house. Can't make things easy......

      Thanks,

      Bob

      2009/3/23 <I2P at aol.com>

      Wrenches,

      I have been doing some experimenting --testing compatibility between brands of grid tie inverters and sign wave battery type inverters. I am hoping some of you also have  some experience here and we can compare results.

      My interest is fueled by my belief that AC coupling is the ideal way to increase system capacity  for battery based off grid systems. The primary benefit is higher system efficiency for AC loads used during the day. I realize that power management becomes important but my interest right now is just to find out who talks to who. My ultimate "power management" tool will be an electric vehicle. Charging it will undoubtedly suck up available juice.

      So far:

      SMA synchronizes to Xantrex SW (have not tested the XW yet) and Outback and of course the SMA Sunny Island

      Xantrex GT also syncs to the SW

      I started this project with Enphase as my first choice since their system is so scaleable. I have been unable to make Enphase sync. Marv at Enphase has been very helpful but to date no results.  I have, at Marv's suggestion ,used capacitors to clean the somewhat hashy SW output without results. Marv tells me he is testing Enphase and Outback. Does anyone have experience syncing Enphase to other offgrid inverters?

      Any experiences with Fronius and others.? 

      Though the SW output is not the cleanest, the results with SB and GT are very stable. They hookup early AM and its steady green light all day long. Though I use microwave, start induction motors etc, and my scope clearly shows lots of spikes during these events, the GT and SB hang in.

      What are the experiences from others regarding mix and match?. Interoperability among brands seems to be a very desirable goal to this wrench.

      Don Loweburg

      Offline Solar, Inc 

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