I see this.
http://mwands.com/store/freedom-ii-hydro-pmg-permanent-magnet-generator?search=hydro900 rpms to charge at 48v and is rated for 2800 watts the electric 1/4 hp motor does 1750 rpms
I just so happen to have a 48v golf cart next to 4 mining rigs running on a 230v PDU consuming 13.3 amps (~3000 watts).. would be pretty easy to test this..
Planning on adding solar / wind eventually so will use components for that..
atleast you comprehend if you look at the chart in the link you posted you will see in the picture the wind speed to power conversion now convert that wind speed to rpm and you will know at what rpm the generator will need to spin at to get the desired output wattage at its rated voltage you will need approximately 47 mph wind speed to produce 2000 watts convert 47 mph to rpm and use an electric motor with a pulley drive ratio to achieve that rpm for example a motor with 1725 rpm at 1 to 3 would result in 5175 rpm