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Windmill, rectifiers, battery, inverter, heater...control system
By kww, Section Homebrewed Electricity Posted on Mon Sep 29th, 2003 at 08:31:05 AM MST
Trying to see if I got this right.

I want to make heat with my windmill, but it's looking complicated to do the way I was planning on doing it(windmill straight to heater). However, from what I think I've recently learned using a battery and inverter isn't such a terrible thing :-), but I thought I'd check and make sure I got this all right. To start, I hook my windmill(which is in construction) up to rectifiers so I can charge a battery. Since the battery will maintain a certain level of voltage it keeps the windmill that it's hooked to free from "electrical drag" until a certain rpm is reached, helping the windmill build enough rpms to make some power in low winds. My question here is: Would one small(car sized battery) be okay with a windmill capable of sending 1000 watts, maybe even more, of power into it? Basically I'll just be using the battery as a control to allow for easy windmill startup. The next thing I wanted to know: Is the low battery cutoff feature that some/most/all(?)inverters have effective in keeping batteries alive over time? My new current plan(which changes like the wind blows :-) is to use one small battery(to start with) with an inverter capable of powering my heat source(s). I'm thinking that when the wind picks up and charges the battery enough the inverter will kick on, cutting on the heat source(s) and when the wind dies, letting battery voltage drop, the inverter will shut down along with the heart source(s) to give me a simple, automatic, still somewhat cheap(I know a 1000 watt inverter is going to cost a bit) control system. Is this the way it would all work? Also, would I kill the inverter and/or battery prematurely by using them like this?

Windmill, rectifiers, battery, inverter, heater...control system | 21 comments (21 topical, 0 editorial)

Re: Windmill, rectifiers,etc (none / 0) (#1)
by troy on Mon Sep 29th, 2003 at 12:48:54 PM MST
(User Info)

I'm just working from memory here, but many inverters use a low voltage cutoff of around 11 volts. That's pretty deep discharge and will kill a car battery in short order. A true deep cycle battery would tolerate that better, but deep discharge is tough on all lead acid batteries. It's better to keep an eye on bat voltage and disconnect the load to prevent premature battery death.

The really nice solution is to use an amp/hour meter. This is as close as you can get to a gas gauge for your battery. It measures how many amphours go into the battery, how many go out of the battery, and most of them can tell you your battery's state of charge or discharge. Of course, they're not cheap and will cost between 100 and 200+ bucks.

But using some kind of low voltage disconnect (like the inverter) is better than running the bat into the ground if you're not around to keep an eye on it.

Hope that helps, keep asking questions!

Best regards,

troy

Re: Windmill, rectifiers,etc (none / 0) (#2)
by JW on Mon Sep 29th, 2003 at 01:12:29 PM MST
(User Info)

kww,

I was out crusing around on the net and I found something that might help. Inverters, I found a site with some pretty good prices, for example they have got a 400watt inverter on there for 25 bucks. the site is http://www.techbuys.net I found a 3000watt model for $300.00, no kidding.

-JW

[ Parent ]

Re: Windmill, rectifiers,etc (none / 0) (#3)
by Larsanderss (larsanderss@brevet.nu) on Mon Sep 29th, 2003 at 03:34:45 PM MST
(User Info)

I have had som plans also about direct heating....... Would it not (after some studies of available effect versus rpm) be possible to use Hugh Piggots triac circuit(s) to step by step connect more and more load when rpm is rising and disconnect when rpm is falling. And have no load connected until appropriate rpm is reached.... and the turbine furling out in other end of it..?

Good evening everybody

Lars A

[ Parent ]

Re: Windmill, rectifiers,etc (none / 0) (#7)
by kww on Tue Sep 30th, 2003 at 05:46:28 PM MST
(User Info)

Lars, I think what you're wanting to do would work, from what I remember reading, but I'm far from being an expert on this stuff.

[ Parent ]

Re: heater...control system (none / 0) (#4)
by J Steele (Jvsinthai@yahoo.com) on Mon Sep 29th, 2003 at 03:37:25 PM MST
(User Info)

I'm working on a similar layout. I want to make heat and avoid the battery and other components. So I'm going to run the mill's AC into a rectifier but only use the resulting DC to power a control circuit. When the control detects enough voltage it will pull in a relay which will connect the heater wire straight to the mill's AC output. The control circuit may end up being as simple as a relay coil that is too weak to pull in the relay until a certain voltage. That should be interesting to work the bugs out of.
John

Re: heater...control system (none / 0) (#5)
by Dave B on Tue Sep 30th, 2003 at 09:18:29 AM MST
(User Info) http://www.madbbs.com/users/bruggelog

Just my 2 cents worth on the relay. Simple yes but it will be cycling hundreds of thousands of times and is mechanical. I'm leaning toward electronic switching and trying (very little time) to design the variable load step (switching) circuit. I know Hugh and the electronic guys out there can figure this out quite easily with their combined talent. I guess this is a cry for help or challenge to anyone interested in drawing up a functional circuit switching AC direct to 2 maybe 3 progressive loads (heating elements) depending on RPM / voltage / windspeed. I'm playing and not lazy, been working with a LM3915 display driver chip (yes, it's logrithmic not linear) and a 10 segment LED. I'm half way there, the chip works great and I can adjust the sensitivity of the display to indicate a variable output at any level. I just need more time. I've been distracted lately with tower options. Fun stuff, Dave B.

[ Parent ]

Re: heater...control system (none / 0) (#6)
by kww on Tue Sep 30th, 2003 at 05:43:37 PM MST
(User Info)

Thanks for all the info. and ideas guys, sounds like there's a market out there for a variety of simple relatively cheap windmill power control equipment(got to do a search on that). If anyone comes up with something that works well I may be interrested in paying you to make me one as electronics aren't my thing, at least not yet. :-)

[ Parent ]

Re: heater...control system (none / 0) (#8)
by JW on Wed Oct 1st, 2003 at 02:50:50 PM MST
(User Info)

Dave B,

The mechanical relay could easily be replaced by a solidstate one, in fact for AC voltage control they are much more available and cheaper, compared to DC. check this part# from McMaster Carr, 7456K14 , its on page 816 in the 109 catalog. whatever circuit you had in mind could be prototyped with a mechanical relay, or three relay's in progresive stages. then once you got that how you like it just switch over to solid state. it will use 3-30 vac or dc to actuate. The load side will handle 25amps@300vac. I'm not quite sure how you going to determine the "neutral"(white). but you should switch "hot" lead(black). I guess with a WYE connection instead of DELTA. Also it would be neat to know if you can parallel the three(hook together) and get your "hot" lead and tap the center of the "wye" connection to get "neutral". but mostly I am curious about the hot leads, all three phases should be "hot" most likely (watch for sparks) its okay to connect them.

Another point thats interesting is rectifing some dc for the control circuitry. I would suggest some form of regulator circuit, since depending on wind speed voltage is going to vary. and your LM3915 is not going to like this. But on the otherhand you may be able to ditch the regulator, and the LM3915, by using zenier diodes hooked in to the dc rectified part, and the voltage surges, from more wind will be enough to actuate the solidstate relay and the zeiner together. pop a led in each relay circuit and you have some indicator of whats happening.

when I say "switch" the hot lead I am refering to the switching leads of the relay or load circuit.

just tossing some ideas around

-JW

[ Parent ]

Re: heater...control system (none / 0) (#9)
by Dave B on Wed Oct 1st, 2003 at 10:45:22 PM MST
(User Info) http://www.madbbs.com/users/bruggelog

JW,
Thank you for your comments and suggestions. I'm looking for a simple circuit and your idea with the zenier diodes after the regulator circuit could be the ticket to a simpler way to go. I'll check out the part number for the solid state relay and see how this might work. Switching a variable AC voltage to different loads seems like a very simple application, I just need a little time to play and I'll make it work. Thank you again and if you have any circuit sketches or ideas that you think might work I sure would be interested to see them. Dave B.

[ Parent ]

Re: heater...control system (none / 0) (#10)
by JW on Thu Oct 2nd, 2003 at 10:15:29 AM MST
(User Info)

Dave B,

The zeiner diodes are definitly worth a try for what you are doing. I think Xeroid brought these up on the board before. I believe he was using one to transfer a dump load from the charging circuit, once the battery was full. I think he was working with a pure DC circuit.

If you are trying to make DC power, I think its best to use a Delta wired stator and the six rectifier diode arrangement. But in this case you are intending to make and use AC power. This is why I brought up a WYE connection for the stator. this will accomodate a neutral leg. But its probably not as efficient as a Delta connection. And the delta connection will not give you a neutal. I am pretty sure STAR and WYE are the same type of connection, but not absolutly sure.

Now, with a WYE connected stator you should have a total of 4 leads, from the three phase arrangement of the coil connection. three of these leads should be hot and the center tap should be neutral. At this point you are going to have to do some bench testing with your windmill generator. Isolate the four leads comming from the connection. note the three that are suposed to be hot, and the one, thats suppose to be neutral. spin up the generator to a speed you feel comfortable with. then try to short any two, of the three hot leads, and dont mess with the neutral. check to see if there is a negative effect when shorting the hot leads together. If there is, or the geny loads up or slows down this may not be that good of an idea. However... if you short any or all the hot leads to the neutral the geny should slow down from load. this is triky business, observe all safety practice while trying this. In the event that shorting the hot leads together does not cause any problems, then this is very do-able.

On to the hybred AC/DC circuit. assuming you can hook the hot leads together plus the neutral, you should only have two leads. this is your main AC output circuit. since you are using this output for simple heating and water could be involed, WIRE IN A GFCI, or ground fault interupter. then take the neutral and connect it straight to all your loads. all you have to do from this point is hook up the hot lead and complete the circuits to your loads. use your relays (single position single throw should be all you need) to make the hot connections to your loads.

The DC part. before your GFCI you have your AC output, connect a simple run of the mill bridge rectifier here. now you have some DC to power your ziener diodes and relay coil circuit. the zieners are wired in series with the relay coil, the ziener is placed in the circuit backwards so it will not conduct, until its activation voltage is reached, then it will conduct in both directions. and thats pretty much it. I think some serious playing will be in order by the time you reach this stage. remember ziener doides have all kinds of activation voltages many to choose from. current should not be a major selection factor since you are only activating a small load "ie" relay coil, or solidstate relay. the solid state relay may be obtained for less then ten dollars from http://allelectronics.com . but Im pretty sure your ziener rating will be very different from mechanical to solidstate relay coil activation.

the GFCI is where you will get your main ground that can be connected to the water tank. I would love to make a schmatic for this, but the computer I do that with is having some problems. but more importantly is the question if you can connect the three "hots" from the WYE connection.

-JW

[ Parent ]

Re: heater...control system (none / 0) (#11)
by Dave B on Thu Oct 2nd, 2003 at 03:15:23 PM MST
(User Info) http://www.madbbs.com/users/bruggelog

JW,
Great information, thank you. I need to clarify my alternator setup. It is single phase (18 coils awg 18 at 100 turns each and 18 magnets) and at present all connected in series to give me approx. 110 VAC @ 400 rpm. I may find I want to try different series / parallel combinations of the coils for higher current / lower voltage but for now testing seems to be very positive as is. All I'd like to do is switch this AC output in 2 or 3 steps into progressive loads (IE: heating elements) depending on the alternator rpm / voltage. This will allow easy start up (unloaded) and best utilize the output available by stepping (switching) to match the load. This should also help keep the alternator moving as some or all of the load is switched off as the rpm decreases. Sounds very simple, I think tapping off a couple coils to rectify for the DC control and the zenier diodes / solid state relay combination seems like it would work quite well. No need to complicate things but it would also be nice to incorporate some hysterisis into the circuit for delaying the time on or off of the load, I think this could be more efficient for gusty conditions. What do you think ? Anyone else feel free to chime in also, thank you. Dave B.

[ Parent ]

Re: heater...control system (none / 0) (#12)
by JW on Fri Oct 3rd, 2003 at 09:56:04 AM MST
(User Info)

Dave B,

I was hopeing you would specify your coil wiring arrangment. Sounds fine to me the way it is, seems you already have a two wire output. This is very good news, you should not have to allocate any coils for DC voltage production. Use them all to generate AC.

The start up and run features that you are aiming for will not be a problem. Upon further thought, you will be able to run AC to the house, and do all the DC buisness at the point/place of use or load.

My suggestion is this, at your tower install the GFCI. Take your two wire AC output run it to a small box at the bottom of the tower, get a GFCI type outlet mount it in there and hook the output from the genny into the GFCI outlet, then ground the GFCI to the tower. now you have a grounded outlet at the bottom of your tower. use a grounded (three prong) extention cord to get the AC to the load, house, whatever. I would set up a reciever box with a pig tail, cut off the male end of an extention cord to make a pigtail, make sure it has a ground pin. take the three wires and run them into a box of some sort to keep things neat, use a terminal block in there to recieve the three wires.

Now, wire out to your loads and include your relays in series. its best to worry about these circuts one at a time.(meaning output or control) I would start with your ground, first hook that to your water tank. then feed all the relays (solidstate or mechanical) with what you designate as your hot. the neutral can go strait to your heaters. by the way as you are hooking up your GFCI "it" will determine for you, which hot and neutral, depending on the direction your mill spins. in other words when you hook up the GFCI it will "pop" automatically when the mill spins if you need to reverse the wires(of the two AC output) but it may not pop either way, in any case the outlet will have a wider and slimer pin or spade, the wider one is hot. now lets say you gought this far, and your mill is connected to everything. the loads should be all wired up at this point. the whole AC part should be done, hooked to the relays and loads. lets say you used three solid state relays. and each of these completes the circuit to each of the three heaters. since control is not energized the relays should be open and no load on the mill, no power to the heaters.

take a 9 volt battery and energize the "control" side of the solid state relay. It should turn on, and energize the heater. I was thinking about an indicator for this. you could use a small neon "bulb" conected in parallel with the heater its self. these neon bulbs are commonly used in aqaurium heaters, its the strange type of light bulb that has two strait bars in side, usually they turn orange or yellow when they light up. cheap or old style AC contiuity testers use this form of illumination also. so if the heater is seeing power the neon bulb will light. you can get these neon bulbs at radio shack for like a buck. neon bulbs use raw AC power to work. then check the other relays with the 9v battery and make sure the AC circuit works as it should. at this point you should have manual control.

DC, ok go back to the reciever box at the house, wire in a bridge rectifer. now you should have the rectifer block wired in parallel with the AC, and DC comming out of the rectifier. At this point your DC output should be a bit out of control. and will vary greatly from 5vdc to 80vdc, depending on wind speed. use a resistor to cut down the voltage, again some playing is in order here. you will probably be best off using 1 watt resistors for this, not the very small 1/4 watt type you see in circuit boards. but then agian you should be able to get away with alot, since your solidstate relay control takes practically no current. but it is the impeadance or ohm's that will drop the voltage. wattage is its current rating, ohms is what actually drops voltage. at maximium mill rpm you must not make more than 25 or 30vdc, this includes furling. if you make more than 32vdc you can damage your solidstate relay control circuit. remember you can still activate the solid state relay at 3.5v .

Zieners, you should have one main resistor to drop the dc comming out of the rectifier, this will put you in a range of maximium potental for your control circuit. then you will need an additional resistor for each relay with a different ohm value. its going to take some time to work out all these values, but you will be able to use the same value of the zeiner for all relays. Id pick a ziener with a 5v break down voltage, and use it for all three relays. then switch resistor values on each relay to get the different heater activation rpm's. wiring is very easy at this point, negative on the rectifier can go to all the relays directly. positive gets a main resistor(you may not need this) and then goes into three branches one for each relay, use the resistor and the zeiner in series with the final connection for each relay. remenber if the ziener is in place correctly, it keeps the circuit open until it goes over 5v(in my example)the the diode conducts in both directions.

-JW

[ Parent ]

Re: heater...control system (none / 0) (#13)
by Dave B on Fri Oct 3rd, 2003 at 10:12:17 PM MST
(User Info) http://www.madbbs.com/users/bruggelog

JW,
Thank you for that very detailed write up on the control circuit. I followed every step the first read through (maybe you should write tech. manuals or teach ?) Great idea with the GFI as basically a protection / disconnect prior to the house. I can use any total number of coils to provide a low enough AC voltage to rectify for a control voltage under the max. trip voltage of the solid state relay. This could eliminate the main voltage dropping resistor. I have played with this already, works fine. The only problem that I can see so far is that the specs. on the solid state relays indicate a minimum operating frequency. (I'm assuming this is the minimum frequency of the AC switched voltage) I think I was reading 50 HZ or something like that. Anyway, if that's the case obviously I would be below that at the lower switched voltages. Right now I measure nearly 60 HZ exactly at 110 VAC 400 rpm. very nice. Are you familiar with the minimum frequency spec. on these relays ? I really would like to use the solid state set up. Thank you again for your great write up, I just need more time to play and I'll have it bread boarded and tested. Let me know about the frequency thing if you know anything. Dave B.

[ Parent ]

Re: heater...control system (none / 0) (#14)
by JW on Mon Oct 6th, 2003 at 07:01:01 AM MST
(User Info)

Dave B,

Im gathering your worried about the output freq of your genny, with respect to the load control side of the solidstate relay. the best thing to do is just try it out and see what happens. I think you should be ok. these AC controling relays use an SCR to switch the load. so if your output is even at 4hz it should switch on and off. If you try to switch DC with one of these you will find it will never disengauge. however for AC this is not a problem since it goes +/-. as long as its ac at all it will shut off like it should, regardless if its over 60hz or under it. Interesting you found a minimum spec for AC frequency requirement on the relay. This could be for the control side if it does not have DC capability like it should from 3 to 32vdc.
-JW

[ Parent ]

Re: heater...control system (none / 0) (#15)
by JW on Tue Oct 7th, 2003 at 07:39:09 AM MST
(User Info)

Dave B,

I want to thank you for your kind words and suggestions. I hope this project works out for you as best as possible. And I must tell you using hot water as energy storage is a really cool idea. The way I figure it, as long as your water tank is grounded to that GFI (or ground fault circiut interupter)the worst case scenario is reseting the GFI. other than that as far as designing the circuit goes, I feel the sky is the limit. I look forward to seeing a future post here about your progress, please include some pictures.

-JW

[ Parent ]

Re: heater...control system (none / 0) (#16)
by JW on Tue Oct 7th, 2003 at 07:50:07 AM MST
(User Info)

when I said future post, I mean a whole new posting, it will be neat to see how you bring all this together, and I for one am very interested. something about the idea of making heat from cold wind is very efficient.
-JW

[ Parent ]

Re: heater...control system (none / 0) (#17)
by kww on Tue Oct 7th, 2003 at 10:22:35 AM MST
(User Info)

Thanks for all this great info. JW, it's what I think I've been looking for too. I may be able to figure it all out now, just got to get the windmill finished.
Kevin

[ Parent ]

Re: heater...control system (none / 0) (#18)
by JW on Tue Oct 7th, 2003 at 02:16:01 PM MST
(User Info)

More than welcome, Kww. thanks for chimeing in.
-JW

[ Parent ]

Re: heater...control system (none / 0) (#19)
by Dave B on Thu Oct 9th, 2003 at 05:08:43 PM MST
(User Info) http://www.madbbs.com/users/bruggelog

Hi there,
I've been out of town a few days for work but now a little break and it's great to see more responses to the hot water idea. I did question the low frequency spec. on the solid state relay and wondered like you if maybe it just wasn't specified that this was only for AC as the activation voltage which I would say could make sense. I will be purchasing at least one of these relays soon to experiment with the zener switching circuit you described previously. Just not enough time. Here's a photo of the beast and my test setup that runs this up to 400 rpm and 110 vac, I can't wait to start playing again and I'll be sure to keep everyone up to date with photos too as things progress. Thanks for all of your help and words of encouragement. Dave B.

[ Parent ]

Re: heater...control system (none / 0) (#20)
by JW on Mon Oct 13th, 2003 at 03:40:04 PM MST
(User Info)

DaveB,

when you mentioned that about a freq reqiurement on the load side of a AC solidstate relay, its makes sence that AC power has freq. but 1hz should be sufficient. my understanding of these AC switching solidstate relays, is that they use an SCR, silicon controlled rectifier. And you cant use an SCR to switch DC because the gate never de-energises hence it wont un-latch. A MOSFET on the otherhand frys when you try to switch AC with it. MOSFET's are used for DC solidstate swithing relays, and SCR's are used for AC solidstate switching relays. I could be wrong/ perhaps for applications where conditioned AC loads are used a special type of AC solidstate relay is used that will automatically disconnect if the ac quality isnt up to snuf, the relay kicks out as a protective device, maintaining quality of power. Stay away from this type of device, your needs have variable freq output, besides were just talking about a simple resitive load here, not some hi-tech cpu-app. read up on SCR's and you'll see what I mean. Hell Its very possible you could use an SCR if you heat sink it correctly, but then you have to build control circuitry that will turn the scr on and off with DC, thats what makes a DC controlled AC load switching solidstate relay so nice, besides you cant use the zieners without DC control on the solid state relay..

I see your having fun keep at it, cant wait till you get to the water tank and radiator part.

-JW

[ Parent ]

Re: heater...control system (none / 0) (#21)
by Dave B on Thu Oct 16th, 2003 at 09:59:52 AM MST
(User Info) http://www.madbbs.com/users/bruggelog

I've got a couple of these solid state relays on the way so at least I'll have the stuff here when I get a chance to work on the switching circuit. Wish I had more time to play. Dave B.

[ Parent ]

Windmill, rectifiers, battery, inverter, heater...control system | 21 comments (21 topical, 0 editorial)

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