[RE-wrenches] grid tie sync with big stiff genny?

[William Miller]

Geoff:

We installed a large-ish system for the state of California 
(http://mpandc.com/Portfolio/Commercial/Cal_Trans/cal_trans_gorda.html) 
This is a location with homes, an office and workshops that has had a 
generator or two running 24/7 for decades.

The premise was that a large generator system could handle the peak loads 
and the battery based PV system would handle the off peak loads.  There was 
no load segregation, but instead the design relied on a "quick response," 
multi sync-able generator system.  The three generators were to start, sync 
and assume any loads in excess of those that the inverters were capable of 
handling.

The premise was fatally flawed.  There is no generator system that can 
respond to loads quickly enough.

There is a design philosophy that was violated on this project:  Any power 
system needs to be sized large enough to handle the maximum load that is 
possible to apply to the system.

We are now contracted to double the inverter capacity.  The load studies 
were re-run but are still inconclusive.  We agreed to the capacity of our 
installation, but we made no commitment as to the ability of our equipment 
to handle unknown loads.

Load studies are critical to every design and each power source needs to 
adhere to the results of those studies.

Good luck.

William Miller





At 06:48 PM 3/12/2009, you wrote:

>Thanks Drake and others...
>
>
>
>I will ping SMA on this... and perhaps with utility "special case" 
>approval a non-typical window could be allowed (with additional anti 
>island logic switchgear)...
>
>
>
>keep on slingin panels everyone!
>
>For a brighter energy future,
>
>Geoff Greenfield
>President
>Third Sun Solar & Wind Power Ltd.
>340 West State Street, Unit 25
>Athens, OH 45701
>
>740.597.3111     Fax 740.597.1548
>www.Third-Sun.com
>
>Clean Energy - Expertly Installed
>
>
>
>
>
>
>----- "Drake Chamberlin" <drake.chamberlin at redwoodalliance.org> wrote:
> > This should be possible.  I have discussed what it might take to set
> > up a system like that in the Gambia, with wind generators.  It would
> > take a control system with differential current sensors and other
> > features.  The UL 1741 specifications would probably need to be
> > opened up on multiple direct grid tie inverters. There would be a
> > practical limit on the percentage of feed to the generator mini grid.
> > This being said, I've not received much encouragement with this
> > idea.  There are a lot of factors to consider.
> > At 09:35 AM 3/11/2009, you wrote:
> > >Undoubtably many of us are getting interesting project requests as
> > >folks want to sprinkle magic stimulus dust on things to make solar
> > >panels grow...
> > >
> > >
> > >
> > >We have a project with a huge electrical load, pumping water for a
> > >medium sized city.  They want solar... great.  Easy.
> > >
> > >
> > >
> > >They had a power outage and kept running with 2.6 MW of diesel
> > >generators.  They are interested in solar's ability to do
> > >"backup".  I don't think that many batteries will fit in my pickup
> > >truck, and I hate working with 300/0 wire.
> > >
> > >
> > >
> > >QUESTION:  (and maybe its an easy one and the SMA guys will say,
> > >sure, we did that in Greece).  Is it viable to set up a micro-grid
> > >in this scenario and run an island-mode, with available solar
> > >reducing the genny plant demand?  Should I just say "forget it" or,
> > >at this MW scale, would the switchgear and effort be practical?
> > >
> > >
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