Testing of a 500W 24V VAWT

I would suggest looking at an Electronic Load of some sort... Just a generic search on Amazon:

https://www.amazon.com/s?k=electronic+dc+load+tester&crid=3NBRPRLIX0YNE&sprefix=electronic+dc+load

The actual Pmp=Vmp*Imp equation is a complex curve that has different solutions at different RPMs of the generator. An electronic load would allow you to get a more complete characterization of the genset.

Another critical feature is are the turbine blades themselves... They have their own Wind Speed vs RPM vs Torque set of curves too... Which then brings up the "other missing" parameter--Torque on the turbine/generator shaft from the "drill motor" at X rpm, y voltage, and z current (and optimizing MPPT)...

One company here (Midnite Solar), as I recall, was able to harvest (roughly?) 3x more energy from a generic wind turbine with their MPPT (maximum power point tracking) system vs just connecting a wind turbine to a battery bank with a dump load controller (i.e., pretty much fixed voltage battery charging vs MPPT variable Voltage*Current optimization system.

Could you use a GT Inverter (Grid Tied) from the generator and use the GT Inverter (usually with MPPT function) to figure out the generator parameters--Probably. But this begs the question of what are your planned loads (battery bank, GT Inverter, MPPT controller to battery, or what).

Understand that you are interested in the generator performance... But you linked to a VAWT (vertical axis wind turbine). Is this where you plans lead too? Personally, I do not believe that VAWT are capable of harvesting any useful amount of energy (they are simply not efficient at harvesting wind energy in any conditions). HAWT (horizontal axis wind turbines) have their issues--However, a well designed HAWT is a much better design (in my humble opinion).

If you are just interested in the alternator itself, perhaps search for just the alternator itself and save money on not buying the balance of system and getting hit with the shipping costs.

There is lots of information out there on turbines, alternators, and overall harvest capabilities... We have a few links here you can start with:

https://wind-works.org/ (lots of history for wind turbines)
https://forum.solar-electric.com/discussion/3638/small-windpower-a-scam-survey-says-so/p1 (government test of a bunch of different turbines)
Hugh Piggott - Scoraig Wind Electric site for tons of info
Scoraig Wind "Recipe Book" for DYI Turbines
Truth About Skystream & SWWP (a very "efficient" HAWT but had reliability issues--Went out of business, but recently resurrected).

Most of the above links are 15 years old--Not much has really changed in the Wind Business--And usually try to suggest that more solar panels and other sources of backup power (gensets, hydro, etc.) are better.

However, the DIY (do it yourself) wind turbines are probably, on average, better than most any turbine you can buy.

Your thoughts?

-Bill