Inefficient windmills are older than calculus. Efficient windmills need aerodynamic theory to calculate a good blade design. It's quite difficult to do that. It took several decades to scale up windmills.

(A small wind turbine is like a propeller in reverse. A large wind turbine is not, because wind speed varies across the blade circle enough that those stresses dominate the design. It took decades to debug this, and make large wind turbines stable under high winds.)