Wind and Water Powerpp. 322-326

Wind generators

Horizontal Axis—higher positioning of rotor blades

Vertical Axis—catches wind closer to the groundClick picture for source (Fiddler’s

Green)

Power from Wind Dependent on the mass of air moving through the

turbine every second. What do we need to know to determine power?

Need to know area through which the rotor blades sweep Need to know the density of air Need to know the speed of the wind

Volume passing through blades in 1 sec = speed of the wind x Area swept out by blades

Mass = density x volume Power = change in energy as air passes through

blades each second

Wind Power Maximum (theoretical) power that can

be extracted from the wind occurs when:

the wind that passes through the blades and comes to a stop (vf = 0) Volume of air per second = speed * area Mass = density * volume

𝑃=∆𝐸𝑘=12𝑚𝑣2=12 (𝜌 ∙𝑣 ∙ 𝐴 ) (𝑣2 )

𝑃=12 𝜌𝜋 𝑟

2 ∙𝑣3

Wind Power Power that can be extracted from the

wind can be calculated by determining the speed of the wind before reaching the turbine and the speed of the wind after passing through the blades:

𝑃=12 𝜌𝜋 𝑟

2 ∙𝑢3− 12 𝜌𝜋 𝑟2𝑣3