[RE-wrenches] More on AC coupling

[Steve at windandsun.co.uk]

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

Tel: 01568 -760671
Fax: 01568-760484

The latest edition of the Wind & Sun Design Guide & Catalogue is now 
available. 
This has 112 pages detailing our product range and is packed with 
information 
and advice about setting up or using a wind or solar electrical 
system.
Price is £5.00 + £1.00 p&p.

Wind & Sun Ltd
Registered in England & Wales, Company Number 3403803
VAT Number GB 448 5458 14,
Registered Office: Humber Marsh, Stoke Prior, Leominster,
Herefordshire, HR6 0NR

-------------- next part --------------
A non-text attachment was scrubbed...
Name: Eigg Inverter, voltage, frequency & SOC	22-3-08.doc
Type: application/octet-stream
Size: 114176 bytes
Desc: not available
URL: <http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org/attachments/20081126/5a6a0be8/attachment-0006.obj>