Scasper,
The simple answer is no (yes it is possible, but not practical). Mppt controllers must have a reference like Kenny said. If the windmill is turning sufficient to generate energy, the charge controller would not know what to do with that energy. There are electronics that could help, but it is far easier to use a battery.
Here are the reasons: Your charge controller would need a reference. SO let's say you attach a windmill to the charge controller and fire up the windmill without a battery or dump load, the energy must go somewhere. As the windmill turns faster and faster, the voltage will try to increase. With no place to put the energy, the charge controller would convert the energy and the amps would continue to climb until it burned up the system. Also, when the windmill stops, the system would go unpowered. No problem there, but when the windmill starts up, the voltage sag would also harm equipment.
Using a windmill usually requires a dump load to have a place for the energy to go if your battery is full and you have no working load, or not enough working load. Charge controllers that can talk to a dump load to properly protect the system are a little more complicated but not much more. There are windmills out there that have "okay" charge controllers. But a battery is expected to be in the system.
Try this. Look for a windmill that is the right size for your system and then look for the compressor you need to do the job. Then see if you can find that pump in 24 or 48 volts. If you can it will be easier to setup and work longer.
Then look at the requirements and build the right system.
All this said, yes it is possible, but you will have to have the right equipment to deal with all the issues, or you can build a system with a battery.
Does any of this help?
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