Looking for doohickey to divert excess energy

[Rob Beckers]

Someone asked me this question a little while ago and I didn't have an answer: Is there a way to divert excess energy (in this case from a wind generator, but it could also be from other sources such as solar), once the batteries are full, to be used for something like water heating.

In other words, instead of shutting down the charge controller(s) or throttling back to just meet house loads, let it deliver as much as it can and divert the rest to for example a water heater. I suppose something that simply monitors battery voltage and switches on a heating element once the voltage reaches a set "fully charged" value would do. It would then have to be switched off if one wanted to do an equalization charge. I'm pretty sure I could design/build something like this, but my question is if there's an off-the-shelf box that'll do the trick. It would seem that this is a common enough problem that there should be products out there.

Just to make sure: I realize that most wind charge controllers have just that, an automated switch that switches over to a diversion load when the batteries are full. This question came up from someone who was looking to install a Scirocco wind turbine, and those things do not use diversion loads, when their charge controller switches off they just continue spinning unloaded. The quest is to find a way to make better use of the available energy in that situation.

-Rob-

[Chuck Morrison]

Wild AC type wind generators are becoming more common and lots of folks are building their own. Just put a (three ?) rectifier in the line (to convert AC to DC) before the diversion controller.

I'm not sure about diversion controllers that will charge a 12/24/48 volt bank from a 240 volt source though. I have a 110v 3kw Jacobs that I haven't put up yet because I can't find a controller that will let me charge a 24v bank with it. If you find something I'd certainly be interested to know about it.

Chuck

[Rob Beckers]

Wild AC type wind generators are becoming more common and lots of folks are building their own. Just put a (three ?) rectifier in the line (to convert AC to DC) before the diversion controller.

I'm not sure about diversion controllers that will charge a 12/24/48 volt bank from a 240 volt source though. I have a 110v 3kw Jacobs that I haven't put up yet because I can't find a controller that will let me charge a 24v bank with it. If you find something I'd certainly be interested to know about it.

Chuck

Hi Chuck,

The diodes (rectifier) before the charge controller is not an option, the controller expects AC and very likely uses the frequency it sees to do MPPT. Did you mean using a solar controller for wind by putting a rectifier before it? I can see that working for something like a WindyBoy.

The controller in question will happily charge a 48V battery bank, so that's not an issue either. The question I had was, if there is an off-the-shelf box that can be hooked up to the batteries (or any other place) and that will switch on a load when the batteries are full, as long as they continue to be full. So that any excess energy coming from a wind generator can be put to use for something like water heating, after supplying everything else (batteries, house loads etc.). Instead of having the genny just spin idly. I hope I explained it better this time, if not, just give a shout and I'll try again.

-Rob-

[Chuck Morrison]

Hi Chuck,

The diodes (rectifier) before the charge controller is not an option, the controller expects AC and very likely uses the frequency it sees to do MPPT. Did you mean using a solar controller for wind by putting a rectifier before it? I can see that working for something like a WindyBoy.
-

What I was getting at was to use a DC based controller that does diversion control. If the controller won't do diversion, then use one that does. The only ones I know of expect DC input, but I only know of rather small ones. Bergey supplies one with the XL-1 that does just about everything, but of course it's matched to the XL-1.

I used to have a spec sheet on a european (german ?) made charge controller that might do what you're talking about up to 5kw if I remember correctly. I don't know if it used AC or DC input though. Of course I can't remember the name either...

I can't think of any apparatus that you could add to your existing setup that would supply the diversion. I would think it would have to be part of the controller.

[Rick Wesley]

Hi new to the site been reading some posts was wondering could a system be used for storing energy use the excess energy to pump water from well to a storage tank then place a water driven generator down a return well the farther down the higher the head the more power.

[Rob Beckers]

Hi new to the site been reading some posts was wondering could a system be used for storing energy use the excess energy to pump water from well to a storage tank then place a water driven generator down a return well the farther down the higher the head the more power.

Hi Rick,

What you describe is already being used at many places in the world. I've seen a hydro installation in the Austrian alps that did just that, excess energy was used to pump up water, which was then converted into electricity when needed. This lake was high up in the mountains! I've heard of similar installations in Scandinavia. Don't know about micro-hydro configurations used in this way for, say, home use. Probably it's easier and cheaper to just use batteries?

That was not what I was looking for with my initial question though. I'm simply after a device that can 'skim' power off the batteries once they are full and there's still power being generated by wind or solar (instead of throttling down the charge controllers and letting that energy go to waste).

-Rob-

[Rob Beckers]

To answer my own question: A TriStar controller in diversion mode will do what I'm looking for. It can be set to just before the charge set point of the battery charge controller, so it'll start diverting from the charge controller when the batteries are essentially full.

-Rob-