For storing wind or solar not connected to the power grid, this could be a viable option. In the photo, there are several couplings from the wind turbine and the electric motor. I can't help thinking how much that lowers the efficiency. On the other hand, if 100% of the power will otherwise be wasted, then why not?
There is a person on
The Back Shed: Storing The Wind that said he has spent years using an air compressor driven by the wind.
Most sunny days my solar panels have the fork lift batteries on float by 1 pm. The charge controllers don't have a load to divert the excess energy to, so they shut the panels down. If I were to divert the load, it would be for the additional items still on grid, like the electric water heater and water well. Both of them together use about 8 kWh per day. I'm taking one step at a time...