Wind

Question 1

Why is wind not a sufficient energy source?

Answer 1

It is hard to predict and if substantial amounts of power are required, very large areas of wind must be intercepted.

Question 2

What is an average power coefficient for wind turbines?

Answer 2

Modern turbines have Cp of 0.45 and Betz stated Cp is unlikely to exceed 0.593

Question 3

What is the formula for tip speed ratio?

Answer 3

Lambda=Omega*R/V

Where R = the radius of the blade, Omega = angular velocity and V= linear velocity

Question 4

Clarify the differences in turbine design.

Answer 4

Horizontal and vertical axis machines. The vertical axia have two further sub groups:

1. Designs using aerodynamic drag forces (Savonius)
2. Designs using aerofoil blades to generate lift (Darrieus)

Question 5

Name the crucial parameters determining costs when building wind turbines

Answer 5

Capacity coefficient = mean power out/ rated power and the cost of borrowed capital

Question 6

How is wind speed frequency at a given site determined?

Answer 6

Wind speed measurements gathered over long periods of time are used to determine frequency of occurrence over a range of velocities. This is expressed in graph of probability of occurrence (Y axis) against wind velocity (X axis)