3 KW+ wind - dump load and how ?

[Dave B]

  I will soon be charging batteries with my 16' axial that currently I am heating water with direct. It outputs 3KW before furling in approx. 25 MPH winds. I have purchased a Trace DR3624 inverter/charger and will in time be winding a new stator for 24 volts.

  My question is to those who are charging batteries with machines capable of 3KW plus. Possibly 16-20'+ diameter ?  What type of diversion load control are you using after your batteries are fully charged ? It seems to me that the controllers available are limited in the diversion mode to 60 and possibly 80 Amps at 24 volts.

  Control seems to be a topic of discussion lately but I have not found any clear cut answers for diversion control for those who have larger machines capable of higher outputs of say 2KW and above. It would be great to hear from those successfully charging batteries and diverting these higher outputs. Thank you,  Dave B.    

[ruddycrazy]

Hi Dave,

        Ages ago I made up a shunt contoller designed by RossW and it's working perfect on my array but to switch 3Kw will just mean some decent fets in parrallel. In the last day or so Oztules has made up what to me looks like a perfect dumpload for large currents - Just using twitching wire to make a resistor.

       Now as you say you are/were using the genny to directly heat water so a suitable sized mains water immersion element might be your best bet. The LM358 based shunt controller will do the switching nicely and I'll let the guru's suggest the right fets to use, I reckon the problem your facing is an easy fix.

Regards Bryan

[imsmooth]

Rudy,

Do you have the schematic for your shunt controller? Is it simply divert power to the shunt, or does it use a PWM driver for a duty cycle through the FETs?

[jmk]

 Hi Dave, Your going to need two controllers. One has to be set to a slightly higher voltage than the other.  

[theantivawt]

Dave,

I have 2500 watt machine. Have had good luck using two Morningstar TS-60's for diversion. Diverting into a wirewound resistor bank.  Used the Trace C-40's prior, didn't like how slow they were to react.

Kevin

[Dave B]

Hi Kevin,

  Thank you for your reply. If I were to use 2 (purchased) controllers such as the Morningstar or Zantrex are these just parralleled some how to double their capacity ? Obviously I am not familiar yet with the controller aspect of diversion load switching.

  How do you set these up so there is no confusion with the inverter / charger also ? My head spins the more I read the manuals, there just does not seem to be a straight forward explanation or schematic for setting up what I want to do. That's a 24 volt system with my DR3624 and diversion for at least 3 KW at times. Thank you for your help,  Dave B.

[vawtman]

Hi Dave,

 My question is, Why are you switching from direct drive and accepting the losses?What is the the problem with your current system?

 Sorry if i missed something.

Mark

[Dave B]

Hello Mark,

  There is nothing wrong with my system as a direct AC hot water heater. I have learned much from this system and most importantly that it was not as simple to dial in as it may appear especially using no controller.

  If it's turning it's pre-heating and with a good 24 hour cycle of wind there is plenty of hot water for a long shower without any heating from the grid. I have proven the concept to work even with just a 16' machine.

  I have crunched the numbers and with our grid power at about 20 cents / KWH including all the taxes and delivery etc. I am earning about a dollar a day if the wind averages 10 MPH. Not earth shaking but enough to know that a 20'+ machine could be very practical for hot water heating. (future plan)

  It's time to put my machine to new use as a charging system. I am certain I will learn plenty from this also and look forward to it. I am finding out there apparently are not too many out there charging batteries with axial machines capable of 3 KW and over. If there are I would really like to hear how they are diverting their power when the batteries are fully charged.

  Thank you again for your reply,  Dave B.  

[jmk]

 Hi Dave, I will try to tell how I set up my system for 27 volts. I have the The SW 40/24 Xantrex inverter. It might function differently than yours. I also set my system up a couple of years ago and found that it was real confusing too. It takes care of itself now I haven't had to tweak it for a long time so I hope I don't say anything wrong. You will have to watch your system work threw every aspect and make sure that you don't have any problems like mentioned before, your dump tuning on when you are feeding grid power. I use charge control mode. In this mode first I had to calculate what amount of amps I could charge my battery with. If you have a small battery bank, which I think is the way to go, you don't want to be throwing 30 amps of charge at it in the bulk charge mode. I have four L - 16's so I think I set the inverter to 10 amps max charge at 120 volts. You don't want to boil your batteries hard! If for some reason you turn off your dc breaker than turn it back on you will need to reset this voltage. Next I set the float voltage to 26. 27 is normal for a 24 volt bank, but cut in is a tad earlier on my machine this way and I have more control, plus it leaves room for the voltages on the charge controllers. I set the bulk on the inverter to 28 ( I think it's been a while) When I turned on the inverter for the first time it ran a bulk charge. It will run a bulk charge every time you set it in charge mode if the voltage is below in my case 28 volts. I don't want my C- 40 to turn on while the inverter is in bulk, so I set the C - 40 to dump at 30 volts. I also have The C - 40 floating at 27 volts. Now when my inverter switches to float it will clamp the battery at 26 volts. I use a load that is slightly higher than what my wind turbine will produce on average. This way the inverter has to feed power to the battery every now and then to keep the voltage at 26. When the wind picks up the voltage will start to fluctuate between 26 and 30. when it hits 30 the C - 40 feeds power to a resister. It makes a buzzing noise then stops when the voltage goes below 30. In your case you would have another controller set to like 31, or you can go 29, and 30. What ever you will have to play with it so they are high enough that they don't turn on when your inverter is bulk charging. So, yours would hit say 29 volts first dump load would start buzzing. Its dumping power but not enough to clamp the voltage of the battery to 29 and the voltage goes up to 30. Then the second one kicks in and now they are both buzzing. The first one will not hit its max amps of dumping at 30 volts with the other controller dumping too. Then they will shut off in reverse order. I had my machine braked when ever I wasn't able to watch it for a long time till I could trust the system. I would turn it on preferably when the voltage is above 28 so it doesn't do a bulk charge and watch it go through the cycles. Now that I got my machine furling and have had confidence in my controls I leave her go at night and when I am at work except when a big storm is coming. Then I shut everything down and unplug the battery from the tower, and the bank. I pulled the furnaces off the grid in a way so I can plug them into an outlet feed by the R/E, or unplug them from there and plug them back into an outlet that goes back to the grid breaker. I hope this was helpful and I remembered what I did corectly . In all watch your system get to now it keep reading your manuals, tweak your system, and be safe. Than on the way have the fun, John.  

[Dave B]

John,

  Thank you for taking the time to explain your system and how it works. As you have been through it you know it can get a bit complicated and it certainly takes time to work through it.

  I think my DR3624 will adjust the same way and to be safe it looks as if I will end up with 2 controllers. I would like to set it all up on the bench with a variable DC supply and loads plenty safe to dial in it's proper switching with charge and dump voltages etc.

  My next purchase will be batteries and controller(s) but before that I need to figure my space requirements and lay everything out. Are your batteries inside or out ? I really would like to have them inside (I have a full basement) but the venting is a concern. Either way they will be in an enclosure and close to the inverter. I'm in Western NY and we get real Winter here and good winds, battery enclosure prices seem out of sight just to purchase.

  Thank you again for explaining all this, I have been reading the manuals and things are starting to make more sense as to how this equipment can be tweaked to dial in the system. Any other suggestions or ideas from you or anyone else out there is greatly appreciated.  Dave B.

[jmk]

 Dave, I have my set up in the garage. It is hazardous to have them in your garage or house. I think if done right it can be safe. I built a box out of 3/4 plywood. At the bottom of the box is plastic, and it has a sprinkler pex hose to catch any acid and divert it to the outside ground if there ever was a leak. I built a tray under the lid so all the gasses will go up slope to another piece of 1" pex that goes outside too to vent the gasses. It would be a good idea to keep all flammable material away from battery area, and to have an adequate fire extinguisher. It was a good thing that I did the bottom drain too. One of my batteries has a small scrape on the plastic casing. I am actually in the process today of fixing or trying to fix the case. I thought that if If they were standing all together and  with thier wieght that they would be ok in the bac of my van. I had to break hard on the freeway and they all tiped over. I had to pull over and pick them all back up real quick. Just what a guy needs to happen with a grand of batteries. Make sure you secure yours so that doesn't happen. The drain worked and all is well. The acid feel onto the clay ground outside the house. At least its 3/4 of the way to the top of the battery. As you know the gasses are very corrosive and explosive if you don't vent them you could have problems down the road, and god bless if they explode or catch on fire. I had an R/E installer tell me that they had to go in a fire proof box to pass code. I never have seen anyone do that though. Some guys put fans in their battery boxes to make sure there is adequate ventilation. Tom said he uses a small computer fan and hooks it so it runs when his voltage is high and the batteries are bubbling. I feel fine with the fact that hydrogen floats to the top and wants to keep on going up. That's just what my venting system does to, goes upward. last year I had to ad a little bit of water to that cell in that battery. This year I noticed that the charger was giving bigger zaps when trying to float the battery so I figured some thing was up. I looked at the end of the drain tube and saw where it had changed the color of the dirt below. I turned everything off and pulled that battery. I had a small dab of clear silicon on it and it held for a couple of years. I tried J-B weld and it didn't like the acid. It started to bubble, so I cleaned it up again put a dab of silicone on and tomorrow I am going to put a coat of resin over that. I may need to get a new battery? Two hundred a pop I think I will try and fix this one first. The nice thing about charge mode is the batteries don't get run down and get abused as offten. They will be fully charged until you loose grid power. Don't make your load to big that they will drain fast if you loose power.

[ruddycrazy]

DaveB,

      Forget the commercial controllers as when they go wrong bad things happen to you RE equipment. As I posted above the RossW shunt controller works fine with a few people and here is the schematic.

With the fet output you can parrallel them and i'm sure this this simple circuit it will cater for your needs.

 Dave if your electronics challenged I or other people will help if required.

 Just as your system is big doesn't mean a simple controller can't do the job and if you want to equalize the batteries just turn the pot when you want too..

Too easy...

But this is from an Ozzie

Cheers Bryan

[GWatPE]

Hi Dave,

I have designed and built diversion loading controllers for Skystream 3.7 windmills on RE Off grid battery systems using a PL20 as the battery maintenance control, with AC loading at 240VAC with bar radiators.  These work with an inverter/charger system.  The On/Off output does place considerable loading on electrical components.

On my personal windmills, I use a PL20 still, and I have used the PWM output to  regulate, with an interface, into a grid connect inverter as a diversion load, [PVE1200].  This is not at the 3kW level though, but could be parallel scaled to suit.  The PL20 changes the regulation voltage, depending on the battery requirements and the battery state of charge, automatically.  This system with the interface can directly provide proportional AC loading if a VFD is used.  This would be a more expensive option, but allows cheap bar heaters to be used.

These power levels do present some challenges.

Gordon.

[Dave B]

Gordon,

  I don't know what a PL20 is and because of this I cannot follow your own controller explanation. I will be running a 24 volt charging system capable of over 3 KW and need to have a reliable way of dumping this much power when my batteries are fully charged. If you or anyone else have working sytems doing this I would appreciate hearing from you along with the details of how you accomplish this. Thank you for your reply.  Dave B.

[GWatPE]

Hi Dave,

Do you have a grid connection available?  If yes, would you consider grid feeding surplus power?

You have been heating water in the past.  Would you consider still doing this?

What battery capacity did you have in mind?

What capacity inverter do you intend connecting to the battery?

Do you have any budget limits?

I presume the windmill will be connected to the battery without a converter, apart from rectifiers!

I would preferably use a PWM system, to load proportional to the windmill power surplus.  Alternatively, I would load/brake the mill with a separate rectifier with ON/OFF control, set from the battery controller. [I use a PL20, made by plasmatronics, or a similar unit]  

The control electronics cct as provided by bryan, in a post above would work, with a separate rectifier and mosfets, to brake the mill.  The currents, would dictate power ratings of components.  

Dissipating many kW in mill rated power resistors allows the mill to continue operating.  Unless there is PWM control, the full loading resistance will still stop the mill in low wind conditions when the battery is full, and in windy conditions, the mill may continue to provide full power to this load.

There are some questions to answer, before a useful solution can be given.

Gordon.

[ghurd]

Why not a TS-45 for all the bells and whistles (3 stage, PWM, temp comp),

dump output to center tapped non-inductive wound power resistors carrying large current,

center tap to IGBTs with on-board drivers,

IGBTs to the load.

Morningstar's other solar controllers run under 400Hz on my meters.  Usually 359Hz+/-2.

I never tested a TS-X for Hz.  They don't publish it anywhere I looked.  Plenty slow enough if under 400Hz?

Grid tie sounds good for 3+KW.

G-

[Dave B]

 Thanks to all trying to help with ideas and suggestions. I have many ideas of my own and have built a controller in the past using 2 LM3914's driving 15 LED's with select LED's (voltage levels) triggering 50A solid state relays for chosen RPM. Many ideas of this similar theme I understand can be done.

 I was hoping for someone to chime in who is actually running a diversion load of 3KW plus with a battery charging system utilizing an axial alternator and an explanation of how they are doing this.

 It is becoming apparent that not many out there fit this criteria. Right now I'm leaning toward manufactured controllers which when adjusted properly seems like a fairly safe bet to use with my DR3624 inverter / charger.

 Thanks again for the suggestions and ideas.  Dave B.

   

[dlenox]

Dave,

Not sure how much help I can be, as I am grid-tied with my 17' 3kw wind turbine.

99.9% of the time the grid is up, and when batteries are charged any excess power that I make and don't consume goes out to the grid (my big battery bank).

The only time that dump load is an issue is when grid goes down, then just have to dump the excess power to my dump load.  Currently have a .6ohm 6kw power resistor for that purpose. I used to use it as inline resistor, but recently changed how I'm using it.

With my Xantrex XW-6048 one thing I absolutely have to do is keep below 70 volts or the inverter will drop off line, so ideally the load would have about .6ohms to keep the voltage in check.

Ideally I would like to install a dedicated water heater to use a diversion load, would like to have a circuit that triggers off my TS-60 diversion controller and work in 2 stages: first stage 'kicks in' when diversion controller goes off - heating one element, as excess current is available 2nd stage 'kicks in' powering 2nd element.

I'm told that the circuit ideally would use scr's and solid state relays, but I am electrically challanged...

Dan Lenox

[Dave B]

Hi Dan,

  So you are charging a 48 volt battery bank and grid tied besides ? How much does the grid charge you for 1 KWH including delivery charges and tax etc. ? How much less per KWH do they charge you if you send any back to the grid ? Or put another way, if you are not using any grid power for say 1 hour and you sent back 1000 watts for this hour how much would the grid pay you for providing 1 KWH of power to them ? I think you get what I mean.

  Here the grid averages about 20 cents per KWH including all delivery charges and tax etc. At first glance the incentives to grid tie seem attractive but it's certainly a money maker here for the State of NY. Personally I will keep what I make either stored in batteries, hot water or both and use what I want, when I want, as needed.

  I have experimented with the hot water heating for a few years now and it works. Now it's time to combine a battery bank with hot water as a dump load and figure a happy balance between the 2 for my needs. Small battery bank dumping often to hot water or larger battery capacity and less pre-heated water etc. It's exciting and it works.

  Grid tie around here might eventually sell more but for now it's more for those who also have purchased their "Green Statement" by driving a "hybrid" Caddy SUV instead of an old VW diesel running vegie oil. Any awareness is good though and times are a changing.

  Now if I can just figure a simple and safe way to dump 3 KW+ to hot water to protect my batteries I'll be all set. Thanks for the input and I look forward to your posts, you have a great project there.  Dave B.

[jmk]

 Dave most of the grid tie systems that I know of charge batteries. My Xantrex SW 4024 If selling back to the grid would need to be in charge mode and set to sell in section 9 on the menu screen. Their are different ways to sell power too. You can dump your battery down to a certain voltage at any preset time of the day, like peak hours for the grid. Another way is to use the grid like a battery and set sell to your float voltage and then your battery will be floating at like 27 volts and anything coming in that wants raise your voltage higher will be dumped into the grid. Keep in mind that it will have to reach a point above what your house is using before you are actually selling power back. The best grid set up is when they allow you to spin your meter backwards and then when there is no wind it spins back forward. This way you are still using your power you made and your meter still hasn't rose much higher in usage. Not to many electric co offer that, but down the road from me their grid system works that way. I found it to be to many bells and whistles to grid tie, so I just use charge control mode. It works almost the same except you have to dump power to a dump load more often. It cost extra in equipment, and inspections with grid tying too. Plus you are responsible for their equipment and men if your system does any damage.    

[dlenox]

Dave,

Price is about the same here for 1kwh.

As far as pushing power into the grid, think of it as a debit card, what ever I push into the grid (for free) I can pull from the grid (for free) at a later date.  No money exchanges hands.

This is why I consider the grid to be my big battery bank, rather than trying to store all of it locally in my own batteries and taking efficiency hits pushing the power in/out from the battery bank.

So in total by pushing power into the grid I take less of a hit on losses.

My battery bank here is fairily small 8 - 12v batteries for total of 220ah. The inverter requires the battery bank and it allows me power for when the grid does go down so that I can still have minimal power.

Dan

[Dave B]

JMK & Dan,

  Thank you for the information on grid tie. Dan, with your grid tie do you have 2 meters and the power company pays you for a surplus or are you spinning your single meter backwards ? I don't quite understand how you monitor your savings by being grid tied.

 JMK, as with you there are many hoops to jump through here for grid tie and it is a moey maker for the power companies for sure. I will store any and all of my power in batteries or hot water or both from wind and or solar. I'll be reporting soon on my solar hot air collectors I am building also. Thanks again for the information, this is fun stuff.  Dave B.

[dlenox]

Dave,

Actually the power company has been dragging their butts since April!  It just so happens that this Friday (12/12) they are finally coming out to install new meter, and at same time my electrician will install the external disconnect switch.

I am the first one for the power company to do net metering, so it is pretty new to them. Yes - they are installing a dual meter, one to measure usage and the other for output.

Up till now my existing meter just ran backwards when I put power into grid and by doing so deducted from my total consumption. So up till now my electric power bill has gotten lower.

Again to clarify - the power company does NOT pay for power I put into the grid. It is more like a debit card, I have 12 month revolving time period to pull out any excess power that I put into the grid - at no charge. If I do not pull out the power I loose the credit after 12 months.  Kinda like a medical flexible spending plan, if you don't use it you loose it.

Dan

[Dave B]

Dan,

  That's interesting and spinning your meter backwards was great, true even up payment for your power back. Be careful of the 2 meter set up. I know you are certain of how it is proposed to work but this monitoring will allow the power company to juggle numbers around. In certain areas the power company reads your contribution back to the grid and pays you a price per KWH, this is often less than what you pay them per KWH. Unlike the "even up" way you had previously of spinning your meter backwards KWH for KWH. Just some thoughts based on research here, it sure could be different for you there.  Dave B.

[imsmooth]

WHy is there a rectifier diode, 1N4004, on the resistive dump load?  I can see this if it were an inductor, but I don't see what purpose it is serving here.