New to forum, and wind power

[Travis Farmer]

Hello, first, a quick summery of my setup. due to mental health issues, financial reasons, and bad credit, i unfortunately still live with my parents. years ago, i aquired an old 29 foot camper trailer that i use as my "Man Cave". it is gutted out to house my various projects (large woodworking CNC router, and soon to have a HO scale model train layout).
my plan, electrically, is to use as little grid power in it as possible. my CNC router takes a good amount of AC power, so that will be the exception.
currently, i have a EPEver 40A MPPT charge controller (with the MT50), and only one 100W solar panel, so far. though there are several shade trees, so i am stuck there, as far as motivation to add more solar PV panels.
so, i purchased a cheap Amazon wind turbine. https://www.amazon.com/gp/product/B07STCC7KT/
i realize it may not be much, but it is just an entry level for me to experiment with. the ratings suggest the charge controller may be weak, so at some point i may swap it for a better charge controller.
my plan for the stored power is for lighting and powering the heater (Chinese diesel heater), and anything else that turns out to need 12V power.
while experimenting, i have a little lawn-tractor flooded-cell lead-acid battery, with a whopping 40Ah of capacity. will upgrade in future.

now, about the wind turbine i have ordered (hasn't arrived yet), apparently has a weak charge controller. i suspect what the issue really is, is that maybe in high wind situations, the turbine output is a bit much for the controller. my plan is to eliminate the controller, and get a bridge-rectifier. then i plan to use an Arduino to control things, such as a over-voltage disconnect, or dump relay. then i can take the output, and feed it into some sort of charge controller. i may even rig up some sort of charge controller with the Arduino.

~Travis

[Rob Beckers]

Travis, welcome to the forum!

Regarding a wind charge controller: Most wind turbines need to see a load (i.e. batteries) or they will run away and self-destruct. Just keep that in mind when you build your own. Easiest is probably to always charge the batteries, and use an Arduino to control a dump-load that siphons power from the batteries, making it so it follows a charge profile (or simply keep the batteries at "float" once you deem them fully charged).

-RoB-

[Travis Farmer]

Travis, welcome to the forum!

Regarding a wind charge controller: Most wind turbines need to see a load (i.e. batteries) or they will run away and self-destruct. Just keep that in mind when you build your own.

Hmm, i didn't think of that. makes perfect sense though. like a big truck going down a low grade hill. miss a gear when shifting, and bad things happen.

Easiest is probably to always charge the batteries, and use an Arduino to control a dump-load that siphons power from the batteries, making it so it follows a charge profile (or simply keep the batteries at "float" once you deem them fully charged).

-RoB-

that is different than what i imagined. i had assumed the dump load was used by switching off the batteries, and switching on the dump load if the wind was too strong.
clearly i have much to learn about wind power. i am now glad i purchased an inexpensive turbine to experiment with.

~Travis

[Rob Beckers]

that is different than what i imagined. i had assumed the dump load was used by switching off the batteries, and switching on the dump load if the wind was too strong.


Yup, that can work too, but is a bit harder to do. Dump loads on wind turbines walk the fine line of consuming enough power to keep the turbine from running away, but not so much that the stator windings melt.

Dumping from the batteries has the advantage that the turbine is taken care of, it's always seeing the batteries (a constant Voltage in essence) as a load. The downside is that you're in effect making what's known as a "diversion controller", another way to do a charge controller. That can interfere with other charge controllers in the system (such as solar).

-RoB-

[Travis Farmer]

Hmm, rather unfortunate. i just got a somewhat expensive solar charge controller...

if only there was a way to "feather the prop", so to speak. i highly doubt my cheap wind turbine has variable pitch blades. ;)

what if i was to use some sort of solid-state method to PWM the turbine between the batteries, and the dump load?

~Travis

[Travis Farmer]

ok, my wind turbine has arrived, and looks to be better quality than i thought. it is a 5-blade 800W 12V (with included sketchy looking charge controller). the body, that i thought was plastic, seems to be cast aluminum.

with that in mind, if i abandon my single 100W solar panel, for now, and use it (with a full-wave bridge diode), i can safely charge the battery. but i also have to regulate the wind turbine. my thinking is to use a large (car audio amplifier) storage/filter capacitor as a battery surrogate, and maintain the voltage using an arduino and some very large N-channel MOSFETs to PWM the power from the diode bridge between the dump load and the capacitor, so i should be able to roughly regulate the capacitor voltage to within the specs of the EPEver 40A MPPT charge controller. i just have to find the specs of the large capacitor i have, and verify it still works (hasn't been used in a while).

an alternative to the MOSFETs, is to slow down the PWM, and use a large SPDT relay to alternate between the cap and dump load. the issue i can see here is the constant switching of the relay, and it's lifespan.

at some point, i can setup my turbine in front of a 3-foot fan we have at work, when i am ready to test.

i think my biggest issue, will be getting the turbine into the wind. the house where i live sits on top of a small hill, and experiences some fairly good wind, when it blows. however, as it is not my house, i can't mount the turbine on the roof. so that means i need a tower. with what i have available, i will likely make the tower out of 3x 2X6 boards, pressure-treated. most likely with guy cables. and i am unfortunately limited to around 16 - 20 feet tall.
in fall and winter, this won't be too bad, as the surrounding trees have lost their wind blocking leaves. but come summer, the turbine will likely be mostly blocked.

this is mostly an experimental setup, until i can afford my own place. so power output performance is not critical, yet. just charging the battery/s in my Man Cave (formerly a 29foot camper trailer).

~Travis

[Rob Beckers]

Hi Travis,

The capacitor and MOSFET should work, but I'm not sure what you're trying to do. In essence you're building diversion controller, so why not do that straight on the main (lead-acid) batteries and forego the capacitor?

-RoB-

[Travis Farmer]

Hmm, maybe we are on the same page, but interpreting it differently...

I was trying to use the capacitor to buffer the power, and then feed it into my solar MPPT charge controller, so the very new charge controller doesn't have to go to waste.
the idea is that the charge controller does not divert unused power to a dump load. it just stops using it.

my thinking of the capacitor is to take the power from the wind turbine, but to divert power to the dump load, based on how high the voltage coming in is. but it wouldn't divert battery power, just turbine power. i have attached a very rough schematic depicting kind of what i was thinking. the battery schematic symbols depict the large capacitor. the solar MPPT charge controller would feed from the large capacitor.

so when the voltage in the capacitor is less than around 15Vdc, Q2 in the schematic activates to connect the capacitor to the turbine. once the capacitor is charged, the power is diverted through Q1, to dump the load, until the capacitor voltage drops down enough to require charging. i may step up the capacitor volts, once i know what volts it is rated for.

really, i invested a bunch into my solar MPPT controller, and would like to use it in some way. even as a solar charge controller (hybrid system), if it comes to it.

I often tend to over-complicate my thinking, so beware ;)

~Travis

[Rob Beckers]

Travis, feeding an MPPT solar charge controller from a wind turbine (capacitors or not) is not a great idea. Those solar charge controllers are designed to expect a current source on their input (that's what solar panels are), while your capacitors are a Voltage source that doesn't have a short-term current limit. Bad things could happen, depending on the firmware and hardware of that charge controller (essentially what abilities it has to limits its input/output current).

What I can see is designing something that makes an isolated diversion controller, much along the lines you sketched out; if the batteries are not full yet it charges batteries, when they're full you divert enough to keep the net-current from the turbine to the batteries down to zero. Probably need another MOSFET to switch the connection to the batteries on/off, besides the ones diverting.

-RoB-

[Travis Farmer]

ok, i won't charge with my turbine through the solar charge controller.
I revised my schematic a little, as i wasn't sure if i was depicting my idea with the MOSFETs just right. that and i had the polarity of the batteries in reverse.

so, the batteries are isolated from the wind energy by MOSFET Q2, and the dump load is isolated by MOSFET Q1. my idea is not to connect the batteries to the dump load, but to connect the turbine, through Q1. Q1 and Q2 will not be activated at the same time. the Arduino will be programed so that Q1 and Q2 will be logic opposites, and will be driven by a PWM signal. the algorithm to set the PWM signal duty cycle has not yet been figured out.

if my basic schematic is still incorrect, please let me know.

also, in regards to a maintenance/safety brake for the turbine. i have seen several people just short the three phases of the turbine together. is this correct? seems a little scary, should the turbine be turning at any good rate.

~Travis

[Rob Beckers]

Travis, look OK to me. With the right programming you can do actual 3-stage charging with this setup. The downside is that the turbine is on a dump load when the batteries are full, which I think was the situation you were trying to avoid.

Shorting out the 3 phases does work, but should really only be done when the turbine is spinning very slowly. The effect is much like sticking a piece of wood in a (spinning) bicycle wheel: The turbine stops very brutally! It's hard on all the parts and you can destroy the turbine if you short out the alternator at higher speeds (most likely it'll burn up the alternator if it doesn't stop fast enough).

To make it a bit more gradual you can add a resistor to each phase, then connect them together, just a couple Ohm should do. That will still very quickly slow down the turbine (and then you can short out the alternator completely), without the "stick in the wheel" effect.

-RoB-

[Travis Farmer]

The downside is that the turbine is on a dump load when the batteries are full, which I think was the situation you were trying to avoid.

Hmm, will do some thinking on that. the dump load is 12V, and 1200W... it will likely draw more power than the turbine can produce, so i don't think i can run 100% duty-cycle, unless i want to stall the turbine prior to stopping it. what i may be able to do is use a third MOSFET, and when the batteries are full, i can sense current coming from the turbine, and going from the battery to the dump load, and somehow match the draw to nullify the charging from the turbine.

in addition, the dump load will be producing a lot of heat. i have two 12V automotive radiator fans that i can use to cool the dump load, and they should help siphon power off the batteries.

i could also sub-divide the dump load (4 resistors), and have two 600W dump loads. maybe some redundancy, should the other one burn up? just a thought. either that, or i could use an electric water heater i have (after adding a 12V element), and use it as an emergency dump load.

~Travis

[Travis Farmer]

so... the MOSFETs i had in mind, from Digi-Key, have a 25 quantity minimum order (over $300USD). so i am thinking of using solid-state relays instead. they are more expensive, depending on where i get them, and are not very efficient at passing power (high pass-through resistance). not sure if they can handle the frequency of PWM from an Arduino, but i will give them a try.
second option, is to use large relays, and abandon the PWM. i am kind of leaning this way, due to project costs climbing.

i will likely make sure to have a fail-safe mode, to connect the turbine (rectifier) output to the dump load if everything fails (Arduino software crash, etc).
i have a small hot water electric hot water heater, and have ordered some 12Vdc elements for it. it only takes one, but good to have a spare. i will use this as my primary dump load (after the batteries), and monitor the tank temperature to turn on a circulation pump to pump hot water into a heater core, or outside radiator (depending on weather season). so this should help heat the space, as well as safely dump the load.

not sure of exact voltage levels, but here is my plan, should it work.
12.0V --> start charging the battery.
13.5V --> stop charging, dump load to water heater.
14.5V --> extra dump load needed, connect dump resistors. (high winds?)

the water heater will not be potable water, due to freezing risk, when no wind in winter. i will use a automotive antifreeze mix. the water pump will be an RV water pump, so 12V, and will be mounted after the heater core, as the water should be cooler.

~Travis

[Rob Beckers]

With all the thousands of MOSFETs available at Digikey can't you find any that are stock, with no minimum quantity?

Contactors will wear, contacts will burn in...

[Travis Farmer]

Hmm, your right. i quickly glanced at Digi-Key, and assumed the large MOSFETs all had similar min quantity restrictions.
I came across this:
https://www.digikey.com/product-detail/en/ixys/IXFH270N06T3/IXFH270N06T3-ND/6204709
looks promising, by my limited knowledge (mostly used to digital circuits, and Arduino code).
60V, 270A... could work. 10V drive, so i will have to use some trickery to get the Arduino to drive it.

~Travis

[Travis Farmer]

just realized in my first schematic, i was using N-channel MOSFETTs, high-side. i don't think that would work, so i am re-drawing for low-side.

~Travis

[Travis Farmer]

not sure if my current schematic is correct, as the batteries have an isolated ground from the rest of the circuit. in other words, my arduino will have to be powered by the wind turbine, and that may not be just right, as the arduino will reset whenever the wind falls off. but i need the isolated ground for the solar MPPT charge controller, i think.

~Travis

[Travis Farmer]

here is my attempt at moving the design forward.

R1 to R5 are still the dump loads, with R5 being the water heater element.
the MOSFETTs are low-side, as they should be, and the system should be isolated.
i have used 6N137 optoisolaters, as i have them on hand. this way, the Arduino can still be powered by the batteries, and the MOSFETTs are powered by the wind turbine.
i have ordered the MOSFETTs, hopefully they will work. seem small in size for their rated power handling, but i will see when they arrive. i ordered 10, as extra stock can't hurt, when experimenting.

so anyway, the MOSFETTs need 10V drive (at saturation), so i used a voltage divider for each channel to provide the drive volts. the voltage divider is figured for 14V, so i may want to change it, in case the wind turbine decides to really crank out some volts.

one thing i thought of, when the turbine is too slow to power the MOSFETTs, they will lose drive, and the turbine will freewheel, so it should help the turbine start up.

all 3 loads are connectable by Arduino software, so it should be adaptable when i figure out software updates.

i realize i drew circuit lines everywhere, but Eagle CAD doesn't seem to let me color the circuit lines to make it easier to read.
so, if you think it should work for me, all that is really left is to finalize the Arduino portion of the circuit, and start writing software.

i would also like to thank you very much for your help so far, as i would likely have burned something up without your guidance. :D

~Travis

[Travis Farmer]

project abandoned, wind turbine fatally damaged by sledge-hammer...

[Ralph Day]

Two s's in Hissy Wang Travis. Ask me how I know.

[Travis Farmer]

Pardon?????

[Ralph Day]

Hi Travis

I thought maybe the sledgehammer was wielded by you in frustration.

In "Canadian", Hissy Wang is a type of over reaction to a situation, often involving throwing or smashing things. I've been guilty of said reactions on occasion. Please take no offense:o

Ralph

[Travis Farmer]

you are correct, i was just unfamiliar with the terms.

[Rob Beckers]

That's my motto as well, "nothing can't be solved with a sledgehammer". :blink1:

-RoB-