A windmill produces mechanical power according to this formula: P = 1/2rV 3 A where Z is its efficiency (assume Z = 60.%), r =

A windmill produces mechanical power according to this formula: P = 1/2ηrV³A where Z is its efficiency (assume Z = 60.%), r = density of air (1.00 kg/m³), V = wind speed in m/s (assume 5.0 m/s), and A is the cross-section of the mill that faces the wind (assume it is circular with a radius of 35.0 m).

a. How many kW does the windmill produce?

b. To load level, you have a battery storage device that can store 2.00 MWh. How long will you be charging it?

c. If the energy storage density you can achieve is 125 Wh/kg, how big is this storage battery in tonnes?