three way power [RE-wrenches]

[Jeff Clearwater]

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Hi Kurt,

Nice approach though I'm not sure it's really the most "whole systems 
approach" way of thinking from a ground up standpoint.  I've done 
several multiple-residence installations with multiple inputs and I 
tend to go with centralized dual SWs for 3 wire 120/240 and then 
distribute that to the various residences.  That way you have the 
advantage of one big battery bank, centralized monitoring, economic 
efficiency of equipment (two inverters vs. three in your case) and 
easier maintenance.  You also have no need for 3 battery boxes, 3 
disconnects etc. etc.  You still get the transmission efficiency of 
240 Volt if you feed both legs to all houses and you get the surge 
power of the 2 SWs (and 240 Volt) at each house in case you have 240 
V well pumps or shop equipment, etc.  Even without the need for 240, 
small centralized systems really do win out in economic terms.

But If you have 3 battery banks and 3 inverters at the houses already 
installed and hooked up to PV, I think your solution is brilliant. 
If you continue to expand residences though, at some point you may 
seriously want to look at combining systems.

Thanks for asking -  I learned some - especially from Hugh's response.

Let us know which way you go and how it works out.

Cheers,

Jeff Clearwater
Ecovillage Design


>Kurt,
>>
>>I'd love to hear comments regarding the feasibility of sending power
>>from a shared wind generator to three homes, each about 300 feet from
>>the tower site.  Specifically I am wondering if each home could get one
>>leg of the three phase wild ac off a high voltage machine.  Each home
>>would transform the one leg down to system voltage (24) and rectify to
>>DC.  The battery, which currently has PVs at each location, would be
>>regulated with an Enermaxer.  Would this work electronically and might
>>the machine have serious problems with any uneven loading(?) of the
>>windings?
>
>This would work.  There would be some phase imbalance due to the 
>different battery voltages, and this could cause unequal currents 
>and thus the alternator to grumble if it got bad enough, but I doubt 
>if it would be noticeable.  The cost of the transformers would be 
>lower this way, than if you used 3 transformers (or a 3-ph 
>transformer) at each site.
>
>Connect the transformer primaries delta for best transmission 
>voltage.  Or connect them star (wye) to minimise harmonic currents. 
>I am not sure which wins out.  Either way the transformer turns 
>ratio has to be chosen correctly for battery voltage which may 
>require some scratching of heads.  It has to be able to cope with 
>low frequency operation, but this is OK so long as the voltage is 
>proportionately low too (compared to 60Hz, 120V or whatever the 
>transformer is rated at).
>
>In any situation where you use a transformer on a permanent magnet 
>alternator, there will be some impairment of startup due to the 
>reactive current sloshing around in the transformer at all speeds. 
>I usually try to include a cutout which disconnects the transformer 
>at low revs.  But this may not be necessary if low cut-in is not 
>critical.
>
>The battery will not work so well under these distributed conditions 
>as it would in a central location.  Some systems will be dumping 
>when others have need for charge.  Some will go flat when others 
>have energy left.  Using 3 separate batteries  helps with sharing 
>energy fairly (if that's an issue), but it would be more efficient 
>to have one big battery (and one big inverter). A centralised system 
>would need bigger cables than the system you propose but could offer 
>benefits where there is a lot of diversity in loads.
>--
>Hugh
>
>hugh at scoraigwind.co.uk
>http://www.scoraigwind.co.uk/
>
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-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Jeff Clearwater
Ecovillage Design Associates - Whole Systems Design
Community and Village Scale Renewable Energy & Water Systems

Cell: 720-480-8455
Office:  800-440-2523 (PIN-7071)
Fax:  720-528-7813
jeffc at ic.org

Council Member - Ecovillage Network of the Americas - http://www.ecovillage.org
Advisory Board - Living Routes - Ecovillage Education - 
http://www.livingroutes.org
Founder:  Ecovillage Research, Development, and Demonstration Program:
http://www.home.earthlink.net/~clrwater/RDD/rdd.html
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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