Help set power curve on Classic 150 for the Istabreeze I-2000 wind turbine

[SPAXIO]

Good morning everyone,

a few days ago I bought my first Midnite Charge Controller Classic 150,
and in a few days I will receive an Istabreeze i-2000 wind turbine,

https://it.istabreeze.store/products/generatore-eolico-serie-istabreeze%C2%AE-i-2000?variant=41564827451580

I kindly ask on what values of Volt and Ampere I have to set 16 values of the power curve?

I have attached the curve of the power delivered vs. wind speed of the Ista breeze I-2000 wind turbine

Thanks in advance

Francesco

[boB]

Unless there is a power curve published for this turbine to be used with a curve tracking inverter/controller like the Classic, you will be in for a bit of playing around to get it close.   That can be enjoyable though. 

Since you have a 48V battery, then the first point on the left side of the Classic turbine curve will be some small amount above whatever your battery voltage is at the time and the power or output current will be very low.  Say, 60 volts.

The curve normally shown and what I believe you have shown is with the turbine connected directly to the battery.  So, one thing you could start with is a curve that is just slightly slanted from left to right in order to make the Classic's input voltage rise when the power/current rises as the wind picks up speed.  As long as the curve's voltage is somewhat constant (but rising) above the battery voltage, but sticking close to the battery voltage, then you should get about what they are showing in the original power curve you posted.

The Classic's power curve shows battery output current vs. Classic turbine input voltage which pretty much follows the same thing as power vs wind speed in your graph.  What you would like to see is the turbine voltage starting where the power is zero and wind speed is zero.  Then as the wind speed rises and the power rises, you would like the  Classic input voltage to rise as well.

HOW the voltage rises with power (battery current) is the big question.  But in the typical wind turbine power curve, the turbine voltage *IS* the battery voltage and isn't allowed to rise with wind speed.

If you are going to fill in 16 data points and keep its input voltage sort of close to just above battery voltage (it cannot work below the battery voltage) then just try to make the  voltage points fairly close together as the current (power) rises.

Since you have a 48V battery, assume the battery voltage is say, 60 volts which would be about the highest you would expect the battery to rise.  The Classic will have not trouble operating this close or this far voltage-wise from the actual battery voltage at any time.  Even if the battery voltage at the time is sitting at around 10 to 15 volts below that 60 volts.

A 2000 watt turbine, if that is the maximum it will put out when tied to a battery is  around 42 amps.  You might expect this turbine to put out more than this at higher wind speeds and low battery state of charge so you might want to limit the right side of the curve to something like 50 amps or so to start with.

If you are not adding a Clipper to the system which is highly recommended for any type of turbine using MPPT, then you will have to make sure that the turbine does not run too high of voltage that WILL happen when the battery cannot accept the current of if the Classic should reset or over-current when you have high wind speeds.

I seem to remember this turbine though and it just might be an alright turbine to use.

A true wind power and voltage curve is measured using a wind tunnel which  is hard to come by and even then, not cheap at all !

You may want to try using one of the already built in power curves in the Classic that kind of replicate  your situation too to make this easier.

The MidNite "Local App" has a nice little wind power curve editor to make this easier but the one in the Classic MPGP remote isn't all that difficult either.

boB 🌜

PS, others certainly welcome to chime in here as they may be more up to date with this particular turbine or similar

[SPAXIO]

Hi boB,

many thanks for the very rapid and articulate reply, I will read it carefully,

at the moment I have two 12 V 100 Ah AGM batteries in series,

do you think it is better to put 2 more in series for 48 volts total ?


Thanks again!

Francesco

[boB]

AHA !   So you are set up for 24V inverter etc ?

That is fine.  In fact, that's better I would say than using a 48V turbine with a 48V battery.  It makes sure there is a higher input voltage to work with to start with !

If you are set up for 24V now, you can just leave it there.  The Classic should work well with that.

Just watch it to make sure that the turbine doesn't show up with too much power and then have the Classic shut off (go to Absorb or Float) as it would be more or less unloaded and create a high voltage that over-voltages the Classic's input.

It looks like this turbine might be a furling type which would be good in that it can only go so fast and turn itself away from the wind.  When wind kicks up, be prepared to brake the turbine unless it can safely be run unloaded and disconnected from the Classic's input.

If that turbine is 3-phase AC and your 3-phase rectifier is down-stairs, then you can easily brake the turbine by using two circuit breakers  to short out all 3 phases of the turbine without shorting the DC input of the Classic.  You want to avoid shorting the input of the Classic especially if it is running and converting power.   Shorting or loading down the turbine on its AC side is the best way to go to do that.

boB 🌜

[kitestrings]

Francesco,

Welcome.  I would just emphasize boB's suggestion to consider having some place for the power from the turbine to go once the batteries are full (float).  You mentioned that your battery bank is 200 Ah.  Assuming lead-acid, you have really about half of that available without discharging more the 50%.  That is not a lot of capacity.  When they get full, the controller will unload the turbine unless you have a dump load to divert to.  It could be just sending the excess to an air or water element triggered off one of the Aux outputs (thru a relay), but you are going to need something.

Good luck, ~ks

[SPAXIO]

Hi Kitestrings,

Thanks to you for the welcome,
I appreciate your advice and I will put it into practice.

I am trying to put in the Classic the right values in the Volt-Ampere curve of my Ista Breeze I-2000 turbine,

starting from the manufacturer's performance chart, that I have attached

I graphically interpolated the turbine output power values with respect to the wind speed 

I put them in an excel table and I assumed that the nominal voltage of the turbine (48 V) occurs at a speed of 12 m / s

since Lenz's law E = Blv establishes that the voltage E of an alternator is linear respect to the speed v,

where :
B = Magnetic Field
l = length of the wire
are fixed in the alternator

dividing power by voltage as a linear ramp
I obtained the current values that in the next few days they fed into the Classic.

Do you think my reasoning is correct?


I will contact the turbine manufacturer in the next few days to ask for a turbine V-A curve.

See you soon and have a good fun


Francesco

[ralph day]

I would 2nd boB's suggestion about a Clipper.  I tried to run my Bergey XL with just some electric heaters.  It worked, but put a lot of load on the inverter, and it wasn't terribly fast in reaction time.  The Clipper is infinitely better, setable, fast reacting, and a Midnite product.

Ralph

[boB]

It doesn't HAVE to be a MidNite Clipper but if one doesn't have expertise in building such things then, it can be bought.

They just aren't cheap.

There MAY be situations where they are not needed, but you really need to be careful about not using one.  Have to really know your turbine.

A Clipper can also reduce turbine noise as well as wear and tear on turbine bearings.   The MidNite Clipper along with the Classic's Aux software can keep the turbine spinning just fast enough to keep the battery in Absorb or Float when full power isn't needed.

boB 🌜

[kitestrings]

I am trying to put in the Classic the right values in the Volt-Ampere curve of my Ista Breeze I-2000 turbine,

...

Do you think my reasoning is correct?

No.  I'm not disputing your theory Francesco, but you should check out the midnite video on programming a wind curve.  The voltage for the power curve that you are programing is voltage in to the Classic from the turbine/rectifier; the amperage is the current out of the Classic to the batteries.

You also want a little bit of 'headroom' above your battery voltage; space for the Classic to work in -

So on the far left, if your system is 48V, your first step will be -0- amps and maybe 58V.  This is just near where you want the thing to wake up, it should be somewhere near the cut-in of the turbine.  You are correct that the voltage and speed rise linearly.  On the far right you will probably not want to be more than 2.5-3x the starting voltage without having "helicopter" level noise.  The current, will be near the full output, so as boB says maybe 40A (40A x 56V = 2,200 watts); your last step maybe a bit higher to start.

Step 2-15 will be somewhat linear to start, and you can tweak them, but the voltage should rise from start to end.

I found a couple curves folks have published for a HY2000, which I think is a 2,000 watt Chinese built turbine.  It goes (I, V): 0,62...17,66...20,70...23,73...ending at 78,120.  This one the current is probably too high on the early steps, but voltage may be about right.

Another, a 10' axial homebuilt went (I,V): 0,50...4,56...8,62...12,68...and ends at 60,135.  This one the current rises more modestly, but the voltage would allow it to spin up pretty fast at higher winds.

Hopefully this helps.

[SPAXIO]

Hi Kitestrings,

Thank you so much for your help,

I have read what you wrote and my ideas are clearer.

So I update the table of currents that the midnite controller delivers to the batteries,
inserting two columns relating to the current that the Midnite could deliver to 24 and 48 Volt batteries,

therefore regarding the programming curves I will do some tests with both: the data in the updated table and with those indicated by you.


Thanks also a boB and Ralph suggestion about a insert Clipper on my system.


The problem is that the Clipper is very expensive and that I also, buying it from Italy, have to pay customs taxes on it,
for now I try the turbine only in my presence,

I plan to install in the system a circuit with a micro-controller that I am planning that, in case of very strong wind and / or fully charged batteries,
inserts a suitable load with auxiliary rectifier bridge and Mosfet, the circuit is programmed with a decreasing resistance ramp up to the short circuit.

Thanks again!

Francesco

[boB]

Francesco,  your wind power voltage and current table is nice to have.

It should work for a 24V battery but won't work too well with those settings for wind turbine voltages below around 25V or so because the voltage from the turbine would be below the battery voltage.

Does not look like this would work at all for a 48V battery except for the highest wind speeds.

For 24V battery, you will have to start the curve at say, 30V and the second curve step would be around 9 amps as shown in your table.

Wondering how you got these table numbers ?  Did the turbine manufacturer supply that ?

Maybe they have a turbine that is wound with a higher output voltage that would be more suitable for 24V and especially 48V batteries ?

PS...   Where did that PCB come from ?

boB

[SPAXIO]

boB,

about the table attached :

Hi Kitestrings,

starting from the manufacturer's performance chart, that I have attached

I graphically interpolated the turbine output power values with respect to the wind speed 

I put them in an excel table and I assumed that the nominal voltage of the turbine (48 V) occurs at a speed of 12 m / s

since Lenz's law E = Blv establishes that the voltage E of an alternator is linear respect to the speed v,

where :
B = Magnetic Field
l = length of the wire
are fixed in the alternator

dividing power by voltage as a linear ramp

according to what written by Kitestrings :

The voltage for the power curve that you are programing is voltage in to the Classic from the turbine/rectifier; the amperage is the current out of the Classic to the batteries.

I added two columns that indicate the current sent by the controller Midnite Solar 150 for the 24 and 48 V batteries,
the table is a starting point, in the next few weeks I try to verify on the turbine the output voltage at the various wind speeds.

The PCB is a programmable electronic load that I am designing (I hope to find the time to finish the job),
designed to experimentally search for the optimal turbine load curve,
with additional parts I will try to use it as a turbine protection circuit "Clipper like"

Francesco

[boB]

I added two columns that indicate the current sent by the controller Midnite Solar 150 for the 24 and 48 V batteries,
the table is a starting point, in the next few weeks I try to verify on the turbine the output voltage at the various wind speeds.

The PCB is a programmable electronic load that I am designing (I hope to find the time to finish the job),
designed to experimentally search for the optimal turbine load curve,
with additional parts I will try to use it as a turbine protection circuit "Clipper like"

Francesco

This is great that you are making this clipper !    Please let us know how that works !

What are you using for the power clipping ?   Triacs ?   FETs ?

Good deal on the table.   It looks like this turbine would be perfect for a 12V battery though using the Classic.

boB

[SPAXIO]

Thanks boB,

What I am designing is a programmable electronic load to study the power produced by the turbine at various wind speeds,
it measures voltage and current in real time, it has 3 Mosfets in parallel, adequately cooled,

to make it work as a clipper I will have to implement a task in the firmware that when a voltage is reached (which can be set by the user),
it reduces the resistance of the mosfets (consequently the voltage is also reduced) making them dissipate the excess energy,

the work is still long even for the short time I have available, however I will keep you informed on the progress

Francesco

[boB]

OK, thanks.

It will be interesting to see how that works out.

You will most likely have to make it so that the transistors share.  With FETs, at least as one gets hot, its resistance increases which allows the others to take more current and hopefully equalize their temperature.

I prefer to switch FETs on and off and use a power resistor to do the dissipation but that cannot be switched very fast because of the inductance of the power resistors.