[RE-wrenches] More on AC coupling

Wed Nov 26 13:32:14 PST 2008

Thanks for the report, Steve. I'm also a huge fan of the European SI. We
need to be careful when we start to compare operations across the ocean. The
US version of the SI is a bit different from the European version. SMA in
Germany decided that the full-featured SI would be too expensive for the US
market, so they sent us a stripped down, cheaper version. The US version
still has some nice features, but it has some limitations when compared to
the full-featured European version. One of the brilliant aspects of the
full-featured SI is the multi-master operation. I wrote a little bit on the
SI for AC minigrids and the multi-master operation in HP 109 - Oct/Nov 2005.
It's frustrating to me that SMA hasn't UL listed a full-featured SI for us
in the States, but they must figure it doesn't make financial sense for
them.

Dana

-- 
Dana Brandt
Ecotech Energy Systems, LLC
www.ecotechenergy.com
dana at ecotechenergy.com
360.510.0433

On Wed, Nov 26, 2008 at 10:20 AM, <Steve at windandsun.co.uk> wrote:

> Hi Tump,
>
> Yes, the SI & SB system is all it's cracked up to be!
>
> I'm not sure what is possible in the US but we've been running a 60kW
> Sunny Island system for over a year now which powers the Scottish
> Isle of Eigg and uses PV's with Sunny Boys, wind turbines with Windy
> Boys, 100kW hydro turbine & back-up diesel generation. Power is
> distributed around the island at 3.3kV three-phase using step-up &
> step-down transformers. The generation is located at various parts of
> the island (as are the houses & loads) with the Sunny Islands/Battery
> Store & back-up diesels roughly in the middle.
>
> See our website for a full description:
> http://www.windandsun.co.uk/projects_eigg.htm
>
> The Sunny Island inverters use 'Frequency Shift Power Control'  -
> variations in island grid frequency to communicate control signals to
> the generation sources and to bonus loads. If the batteries cannot
> absorb the renewable power being generated onto the network (if they
> are full, or the power generated exceeds the inverter/charger
> capacity), the Sunny Island inverters raise the system frequency.
> Sunny Boy & Windy Boy inverters are set to 'Off-Grid' mode to respond
> to this frequency rise and back off power being fed into the system.
> Other renewable generation (eg. hydro turbines) that is able to
> respond to this frequency rise to restrict their power output can
> also be incorporated in the system.
>
> The raised frequency can also be used to trigger switching on of
> bonus loads when there is surplus renewable energy output.
>
> The great thing about using this frequency shift for control is that
> no communication cabling, special circuits or dedicated switching is
> required and distance is no problem.
>
> The other great thing about using the Sunny Island system is that it
> allows use of the Sunny Webbox for remote monitoring. This means
> every morning I can check on the internet to see how the system is
> performing, view state of charge of batteries, and dial in to change
> things if needed. Furthermore, several people can do this at once -
> eg. system owners & SMA technical support - so we can all look at
> what's been happening and discuss any events. (I'm sure you all know
> how useful this can be!)
>
> As an example the attached Word document shows how the frequency
> shift works in practice (Hope it's Ok to send attachments on this
> list)
>
> Regards
> Steve Wade
>
>
>
> From:                   "Tump" <tump at hughes.net>
> To:                     "'RE-wrenches'" <re-wrenches at lists.re-wrenches.org
> >
> Date sent:              Wed, 26 Nov 2008 08:33:38 -0500 Subject:
>      Re:
> [RE-wrenches] More on AC coupling Send reply to:        RE-wrenches
> <re-wrenches at lists.re-wrenches.org>
>  <mailto:re-wrenches-request at lists.re-
> wrenches.org?subject=unsubscribe
>  >
>  <mailto:re-wrenches-request at lists.re-wrenches.org?subject=subscribe>
>
> > Matt, I have long been interested in installing the SMA SI & SBs but
> > I have a VERY tough time selling $9ks worth of inverters, just to
> > get things started. In the system below I would not of hesitated in
> > installing the SMA SI & SB! I too agree that w/this type of scenario
> > described below, I  would have given quite a bit of thought to using
> > the SMAs. Can't beat the battery charging, no charge controllers &
> > expandability.
> >  Please if there is someone out there that has had experience w/ the
> >  SMA SI
> > & SB let us know if it is all that it is cracked up to be!
> > With passport in hand, I offer my help if someone out there  has a
> > large system like this, that will be using the SI & SB/WB  type of
> > set up. TUMP
> >
>
> Wind & Sun Ltd., Humber Marsh, Stoke Prior,
> Leominster, Herefordshire, HR6 0NR.
> Web: www.windandsun.co.uk
>
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