inverter transfer switch flexibility

[dscheckman]

Hello, I'm exploring control options for a micro hydro system I am planning. We are on the grid and will stay on for the time being. Basic question: Can a transfer switch [or other device or combination of devices] detect when batteries are low, automatically switch to grid power then back again when batteries are recharged? Object being use all available hydro generated power , switch to grid power if needed, allow batteries to recharge. Will the transfer switches built-in to inverters allow for this possibility? Hydro is not acceptable for grid-tie in our state and we are inclined to respect this [reluctantly] for various personal reasons. Thank you for any help ,

David Scheckman ,Vermont

[phil b]

Yes, with a grid tie option, Xantrex and Outback inverter/chargers can do this.

Others can as well.

http://www.xantrex.com/

http://www.outbackpower.com/

[henjulfox]

My Xantrex SW series does exactly that, right out of the box.

-Henry

[nothing to lose]

Sometimes I do things backwards.

How much power are you panning to be using? If your not expecting low batteries very often and your inverter doesn't supplie the switching option, perhaps set up a charging system for the batteries where when they fall below a certain level the grid charges them till they come back up to a preset level.

 Perhaps 11.2 volts the charger kicks on from the grid power, at 11.5 back off. In this way your always on battery power and they should never fall below 11V. Always room for the hydro to be charging them when it is available. In the meantime you have no power grid worries either like surges, brownouts, spikes, or outages. Also in the event Hydro is not working for a period of time your batteries aren't sitting there in an uncharged state becomming sulphated.

A good and expensive inverter/charger/controller may take care of all the above, but many people don't have the best of the best, in that case perhaps a grid powered charger for a backup source of charging works as well or better.

Does something effect your water source like a dam upstream, sometimes open and raging water, other times closed and slower water?? Or are you thinking seasonal like spring thaws, summer droughts? Most water flows I am familar with are fairly steady unless effected by such things.

[dscheckman]

Thanks for the responses. It's clear there are options out there that will be work, and not be too complicated. We will have seasonal flow issues and for the time being total hydro output is less than our demand although with a few changes [refrige and freezer mostly] there might be enough. Saving cash is a big priority, and I'm always drawn to simplicity. Thanks again, David

[Clifford]

Depending on your local utilty company's buyback rate...

It may be cheaper to use a grid-tie inverter that use the "grid" as the battery rather than maintaining your own.

The other thing to keep in mind...  stuff like inverters have a certain amount of waste.

If you go with 12V lighting, for instance, you wouldn't need an inverter.

[nothing to lose]

I like things to be simple also.

Another thought is run the inverter from the hydro power with it's own 120v lines wired seperately. As you see you have more water flow/more power, plug in more items to the inverter. When you see your getting less for while, plug more items into the grid.

I am still geussing even with seasonal changes then your water flow is steady for long periods of time like maybe months of high flow, months of low flow? If so it should be very simple to balance your loads as needed based on the power your getting. One nice thing about water, it runs alot steadier flow than wind.

If your getting 500watts of power that is probably for weeks or longer, not 10 minutes at a time randomly

If I had a water source here I think that's how I would use it myself. Charge batteries, load inverter for a days worth of power usage, adjust as water flow changes.

If you get 500watts (for easy figuring), over 24hours thats 12KW, and I would try to average 12kw load on the inverter for a 24hr period, thus neither over nor under charge the batteries.