15Kw hydro control

[simonbrookes]

I have a friend that had already a 1.5kw wind turbine connected to a 48v 900Ah battery bank. He has a lake and weir, which he wants to put in a hydro plant. He has seen a 220V ac 50 hz 15kw unit. The distance from the lake to the batteries is about 300 yards.  Would it be possible to connect it to a transformer at the batterers to get it to 48v and then put it through a bridge rectifier? Then use this to charge the batteries. If so what should the step down be to reach a charge voltage? And does the transformer have to be over rated. Thanks.

[Flux]

Not a lot of details to work on but yes that would be possible. You don't say whether this is single phase or 3 phase. Neither do you say whether he has the water available to produce the 15kW.  I can't imagine trying to feed the whole output to batteries at 300A. If so then it will need a monster transformer and if it is single phase you may not get a high % of the full 15kW. If you want a decent battery charger than starting with 3 phase is a better proposition.

Not sure what you mean about the transformer being over rated, it depends on the charge you want to get into the battery.

To reach charge voltage the transformer will need  a secondary voltage in excess of 38v. How much more you need depends on many factors. I personally would use a choke filter after the rectifier to increase the conduction angle and that would require nearer 70v ac but few do things this way.

I can't offer you detailed advice with so little information.

Flux

[simonbrookes]

Thanks for that. I don't have a lot of details yet as he has not got the turbine yet. It is from China and until we see it we really have not idea. It is single phase. He has a large house and swimming pool and intends to connect large dump heaters off the batteries to heat the water in the pool. He has go 24Kw 220V of inverters off the batteries for feed the house and out buildings. They are 3 x 8000Kw Xtender Combi  units in parallel. http://www.barden-uk.com/inverter-charger-combi-units.html . He has go plenty of water head for the hydro nearly 50 feet and a flow area of 4 feet wide by 2 feet deep falling 50 feet. We don't know the gallons per minute but it is a lot.

So we thought that we would just keep charging the batteries with the hydro and when the batteries got full then switch in heating elements to the pool until the voltage drops again. We were going to use a 1kw, 2kw, 4kw, 4kw, 4kw so we can switch them in 1kw loads.

[Flux]

Can't see any sense in using batteries for a heating system. Why not run the heaters direct at 220v from the turbine.

Flux

[simonbrookes]

The heating is a secondary part. The main use is the ac out to the house and the small wood work shop hence the large inverters. The hydro system comes with a dump heater that is local to the hydro plant and sits in the stream. He thought that it would be a waist to dump the heat into the stream when he has to pay for oil to heat the pool so was going to dump any spare capacity into the pool. He expects the house and work shop will pull nearly all the power the hydro produces. On the system there is also a generator. So with a hydro at 220V a generator at 415v three phase and the inverters we thought that to bring everything into 48v would make it easier to control. These inverter combi are linked to make 3 phase so we can only use the three phase 415v ac generator to charge. The three phase from the inverters is needed for the workshop. So we don't have to buy a large charger for the hydro we were going to make a simple one.