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Dual Voltage system


By wdyasq, Section Diaries
Posted on Sat Apr 5th, 2008 at 12:29:49 AM MST
High voltage to 24V and 48V system thoughts

I have been asked to help design a system to be completely off-grid. The system will start with 8 'golf cart batteries' and a small diesel charging them with a 24V alternator as needed. This will supply a freezer, chest type refrigerator, lights, domestic water and part time internet connection by satellite. The refrigerator and freezer may be the only "120V" loads.

This system will eventually 'morph' into a larger system. Planned upgrades are a high-voltage 15 pole 3PH turbine feeding a 3HP transformer that may be custom wound. Thoughts are it will transform the high voltage to charge a 48V battery bank of considerable size. I am thinking at low wind-speed one may be able to get a bit of 24V charging off the mill and feed the 24V system if it were low. There will need to be some sort of switching to cut power to the low voltage system once the batteries are full.

If considerable wind is available, there will be plenty of places to 'dump' power in this system. A large shop will be nearby that will be able to use any excess once water is pumped and a large chunk of ice is frozen for supplemental refrigeration.

If all wind decides to play somewhere else, one could 'fall back' to the 24V system and the small diesel. This would allow one to 'exist in style' and still not use much purchased fuel. If almost any wind were available, the 24V system should charge first. The 48V bank could be kept to voltage if necessary by the small diesel and some intelligent thinking.

Now, I am looking for thoughts on practicality of such a system and what I am overlooking. I think this will keep the system simple and still affordable. And, yes, there will be some PV panels in the mix as the system matures, MPPT, and panel tracking will be employed on that system.

'Picture so some can color their screen with crayons'.

Ron

Dual Voltage system | 5 comments (5 topical, 0 editorial)

Re: Dual Voltage system (3.00 / 0) (#1)
by PaulJ on Sat Apr 5th, 2008 at 04:37:37 AM MST
(User Info)

   Finances permitting, I'd skip the 24V system and move straight to 48V. My old 24V gear is gathering dust, maintaining battery banks at two different voltages is a PITA, and the 24V system wouldn't even cut it as a backup now (living here full time, 3 kids, not to mention I wouldn't dare run the fancy new fridge on the old 24V MSW inverter).

   If parts of the proposed 24V system already exist it might be a different story, I'd still be tempted to scrap/sell it and start again with a 48V system even if it meant borrowing money though, in my case it would have been cheaper in the long run.

   Paul.
   (Off-grid 3 years).



Re: Dual Voltage system (3.00 / 0) (#2)
by Flux on Sat Apr 5th, 2008 at 07:41:37 AM MST
(User Info)

I would avoid the 15 pole turbine.

Flux

[ Parent ]



Re: Dual Voltage system (3.00 / 0) (#3)
by Old F on Sat Apr 5th, 2008 at 08:56:53 AM MST
(User Info) http://www.oldf.homestead.com

Ron have you seen this site  http://www.backwoodssolar.com

This is something  like BT was working with a wile back
Mite save some on refrigeration

Old F




Re: Dual Voltage system (3.00 / 0) (#4)
by Old F on Sat Apr 5th, 2008 at 09:01:23 AM MST
(User Info) http://www.oldf.homestead.com

Oops  
Go to Our online catalog an click on refrigeration.
Old F


[ Parent ]


Re: Dual Voltage system (3.00 / 0) (#5)
by richhagen (richhagen (a t) Juno.com) on Sat Apr 5th, 2008 at 04:43:27 PM MST
(User Info)

I tend to think that by using a two voltage system you are adding unnecessary complexity.  I would probably aim for an all 48V system, and then shed loads as the voltage drops, so that only essential loads were powered when the least energy was available and generator use required.  Rich
'A Joule saved is a Joule made'


Dual Voltage system | 5 comments (5 topical, 0 editorial)
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