how to plot the mppt curve for a custom low rpm drag VAWT?

[turbinebuildernewb]

I am building a low rpm drag type VAWT with a rather simple yet high output setup.

I think I can design this turbine and alternator in such a way it can output 48vdc + 30% at rather low wind speeds. But that also makes me worried that when we do get rather high wind things can get over 250VocAC rather easy.
It might be the dunning-kruger effect here in where the less I know the more I think I know but I think I believe it.

Here is an image of an older 4m diam 2.44 height prototype turbine.
[attach=1]
The current version is 5.2mm diam.

The goal is that it has a low rpm yet putting out a rather high Voc.

Now how should I go about to plot this mppt curve so that I can input the data into a midnite classic 250 mppt curve?

[Vic]

Hi turbinebuildernub,  welcome to the Forum.

Have you looked at this Video?:
https://www.midnitesolar.com/video/videoPlay.php?video_ID=65&videoCat_ID=18

You can also Search this forum, using a search term, like  'programming Classic wind curve  ', or similar.

I know nothing of turbines.   Good Luck, Vic

[turbinebuildernewb]

yes thank you for the response.
I have infact seen that video already. The video assumes one has measured all the data points already.

My question is, how do I go about collecting the data points given the type of turbine I am making.

[Vic]

I suggest that you use the Classic Topic of this Fourm,  as your post here might limit the attention from those here, who have experience in wind programming:

https://midniteftp.com/forum/index.php?board=2.0

Using quotation marks in your seach terms will help limit the number of hits which result from portions of words.  AND,  believe, that searching inside the Classic Topic will limit searches to just that topic  ...  this is the way that the Searches used to work, anyway,  and is easy to test.

All that I know of wind turbins,  is that I know NOTHING about them.

Good Luck.  Member,  '  kitestrings  ', seems to have experience with turbins   ...   FWIW,  Vic

[boB]

Normally, you would start with the lowest cut-in speed (voltage) it produces that it can be loaded with when it connects to the Classic, then at higher output currents, (higher power), you step the voltage up a bit, the next step a bit, etc. 

The question of course is how much is "a bit" ?

I would start incrementing in say, 3 to 5 volts increments at every couple of output amps and see how that goes.

You can save curves, or the last curve you tried and see if the newer one is any better.  It takes time  unless you know how the turbine behaves at higher wind speeds.  The wind never sits still of course like it would in a wind tunnel. A wind tunnel is the best way but those aren't readily available.  It may be that with a VAWT, the voltage does not have to be brought a lot higher than the battery voltage.

Battery voltage bound, dump load regulated turbines work so you should get some power out of it that way as long as the curve starts at the right voltage above battery V by a few volts typically

But if you have a lot of wind, and the batteries are full, then unless you have a clipper of some sort connected to the input to keep the turbine loaded down, it could possibly over-voltage the Classic input.  I kind of doubt that you would have that problem vith the VAWT but ya just never know unless you measure the unloaded turbine voltage in high wind.... 

Or just put a clipper on it.  A proper clipper will not load down the actual DC input to the Classic.  It can, but the best option is to load the raw 3-phase AC output of the turbine, if it is available.

boB

[turbinebuildernewb]

Thank you for taking a stab at this. I'd like to dive a little deeper into this as to make sure I understand

Normally, you would start with the lowest cut-in speed (voltage) it produces that it can be loaded with when it connects to the Classic, then at higher output currents, (higher power), you step the voltage up a bit, the next step a bit, etc. 

Did you mean hook up the turbine/alternator to the classic and then the classic to my 48Vdc battery array? And then measure what voltage is flowing over the wires to the classic or
should I be reading anything from the classic display?

How does one step up the voltage a bit? The only way I know how the voltage can increase is when the wind speed increases. But I have no control over the wind speed so I am not sure how I can step up the voltage a bit.

It may be that with a VAWT, the voltage does not have to be brought a lot higher than the battery voltage.

Could you elaborate a bit? This sounds very interesting as it will help me with the target voltage the alternator should put out at the lower bounds of our average wind speeds

[boB]

Thank you for taking a stab at this. I'd like to dive a little deeper into this as to make sure I understand

Normally, you would start with the lowest cut-in speed (voltage) it produces that it can be loaded with when it connects to the Classic, then at higher output currents, (higher power), you step the voltage up a bit, the next step a bit, etc. 

Did you mean hook up the turbine/alternator to the classic and then the classic to my 48Vdc battery array? And then measure what voltage is flowing over the wires to the classic or should I be reading anything from the classic display?

How does one step up the voltage a bit? The only way I know how the voltage can increase is when the wind speed increases. But I have no control over the wind speed so I am not sure how I can step up the voltage a bit.

It may be that with a VAWT, the voltage does not have to be brought a lot higher than the battery voltage.

Could you elaborate a bit? This sounds very interesting as it will help me with the target voltage the alternator should put out at the lower bounds of our average wind speeds

By "step up the voltage" I mean the voltage in the next step of the wind curve.   To start with, make the wind curve go up in voltage only a small small amount.  2 volts per step maybe.

But start the first step (cut in voltage) just above the highest voltage the battery needs to be charged at.  Remember that there is a certain minimum amount of voltage that the cut-in voltage (the first step) should be above the highest battery voltage you expect to charge at.

If your battery needs to be charged to say, 60 volts maximum, you should set cut in voltage (step one) to some mid 60V range.  That is, unless the turbine needs to cut in at even some higher voltage, say, 80 volts or something.  Then each step can be a couple volts above the previous step up to the last step.

You don't have any control over the wind speed, BUT you have control over what the Classic presents to your turbine AT that wind speed.  For a typical HAWT, if you give it too low of voltage, the turbine can stall.   Others have used the Classic with VAWT but I do not remember much about what they had to do to make them work well.

The worst you can do is to keep the turbine running just above battery voltage.  The best you can do is to present the turbine with the best wind speed vs. input voltage wind curve.  That curve is hard to reliably guess at and it can't be done quickly, normally.  It can take quite a while.

The problem with finding a good wind power curve is that the wind doesn't always cooperate with what you want it to do.

boB