8.5 Wind Power

Question 1

Where is wind power useful?

Answer 1

For isolated area and for agricultural use.

Question 2

How much energy can a modern large wind turbine produce?

Answer 2

A few megawatts of power.

Question 3

How can the scale of energy transfer in a wind power be estimated?

Answer 3

Consider a mass of air moving at wind velocity v that in time delta t passes through the cross sectional area A spanned by the blades of a wind turbine. This is equal of a tubular volume of length vdelta. If p is the density of air this mass is pAvdeltat. The kinetic energy of this mass of air is 0.5(pAvdeltat)v^2 = 0.5pAdeltatv^3
The rate at which this energy passes through the blades is P = 0.5pAv^3

Question 4

What are the advantages of wind power?

Answer 4

Essentially unlimited energy supply
No extraction costs
Clean
Practical for remote locations away from other energy sources

Question 5

What are the disadvantages of wind power?

Answer 5

Works only if there is wind
Visually intrusive in large numbers
Low frequency operating noise intrusive for some people
High maintenance costs due to wind stresses