Question

(ii) (a) Why do wind turbines have three blades? [2 marks] (b) Compare and contrast your answer if you choose to use two blades or [4 marks] four blades instead of three blades.

Answer 1

Why do wind turbines have 3 blades?

Answer:

There are many wind turbines which dont have 3 as number of blades. There are many reasons for the wind turbine to have 3 blades and few are mentioned below :

1. Balance : One of the main reasons is the balance of the system, In a 3 blade system there is a more balance of weight.

2.Cost : The cost of a 3 blade wind turbine is comparitively less than that of other blade systems.

3.Perfomance : The design of the 3 blade wind turbine is a bit easier to design and manufacture compared to the other designs.

4.Conditons : Based on the winds in a particular place taking on an average, the 3 blade wind turbines are more useful. It means the 3 blade design is good to work in most of the weather conditons.

Comparision between the other designs and 3 blade wind turbine?

Answer:

Wind turbines design have to deal with two conflicting parameters.
Less number of blades reduce the spinning mass of the system and drag

As we increase the number of blades the torque generated is more and there is a good spinning mass balance.

2 Blade design:

The main problem with this design is, They should be designed very strong because they should rotate at a very high speed for a given power output. When they rotate at high speeds they are prone to failure because of the vibrations and fatigue. The operating speeds should be very high for the optimum usage of wind turbines.

These 2 blade designs are economical only in regions where there are strong winds, which is not possible in all geographical conditions.

4 Blade design:

The main problem with 4 blade design is the cost of the wind turbines. There is an advantage of more mass balance, but at the expense of an increased cost. Each blade of the wind turbines weigh in tonnes. So as the number of blades increases it increases the material cost and the manufacturing costs too. The installation costs also gets increased as the number of blades increased.

With the use of the 4 blade design the power extraction is effected by the wake of each blade. We end in loss of capital by using 4 blade design because of the high manufacturing and maintenance costs.

NOTE:

Please do comment to get clarified in any part of the solution. There are many factors but I shared you the most important ones.

Thank you.