AC versus DC

[maykmayk]

Hi there I'm new to posting on this forum though I have been in the back ground for a while. I need some help regarding an already functioning back up system. I run my pumps on a fish farm using AC pumps connected to 2 x 7.5 KVA inverter/chargers (SUKAM Brand) the inverter DC side operates of a 120 vdc 495ah battery bank (30 x 12v 165ah batteries connected in series and parallel) my total load is about 6kw continuous and the system is used as a backup. I charge with a 13kva AC diesel generator set. As I have had to use this system quite often I would like to get a more efficient system either by charging with a DC generator for faster charging or by using DC pumps etc Any ideas available on what would make up the most efficient system. I still consider the solar option to be quite expensive as I would need quite a few solar panels and more so when I expand.

[ghurd]

I believe a DC motor will use less power.

It seems the bigger the better.

Converterd box fans, 75W AC to 5W DC.

Water pumps not quite so shocking, but still a huge change.

Etc.

Check the power to CFM of DC40 and DC20.

Couple stories that may be related...

http://www.fieldlines.com/story/2007/3/10/212941/303

http://www.fieldlines.com/story/2007/3/10/23942/1876

G-

[wpowokal]

Lets see if I get the question, you are on mains power but need back up power for fish ponds, that part is understandable.

Now you have a large battery bank and two adequatly sized inverter chargers with a 6Kw load. You top up the batteries during mains outages by a 13kva gen set, and your power outages are frequent, and have no source of renewable energy.

Just quickly, when the gen set is running supply your 6Kw load and charge the batteries, changing to DC motors or generator does not make sence to me. Manage the battery discharge and start the genset when an acceptable discharge level is reached, when the mains returns use that to finish charging the batteries if necessary.

Any better answer would require more detailed information. There was another question recently about fish ponds running off a gen set.

allan down under