Hi Rod. You could just connect it up, and probably what will happen is the turbine will run at half speed, making it very inefficient, but it would still charge the battery. (The battery would clamp the voltage to around 12V-14V as long as it is not fully charged.)
An alternative is a DC-DC converter, which takes in 24V and puts out 13.6V or so. They use this in trucks (which run on 24V) to run things like 12V music systems.