A Wind Turbine can be used to change wind power into electrical power. We will be looking at the Science behind how generators work in a later unit, but the Math behind this is quite complicated, as you can see:
P = 0.5 x rho x A x Cp x V^3(cubed) x Ng x Nb
● P = power in watts (746 watts = 1 hp) (1,000 watts = 1 kilowatt)
● rho = air density (about 1.225 kg/m3 at sea level, less higher up)
● A = rotor swept area, exposed to the wind (m2)
● Cp = Coefficient of performance (.59 (Betz limit) is the maximum theoretically possible, .35 for a good design)
● V = wind speed in meters/sec (20 mph = 9 m/s)
● Ng = generator efficiency (50% for car alternator, 80% or possibly more for a permanent magnet generator
or grid-connected induction generator)
● Nb = gearbox/bearings efficiency (depends, could be as high as 95% if good)
To make our investigation simpler, we will skip the complicated bit and instead determine the power by measuring how long it takes the wind turbine to wind up a piece of string.
Write a plan on a google doc for investigating how one aspect of the blade design could affect the speed at which the turbine turns.
Have a look at this website which shows you one way to create a wind turbine model.
Here is a list of what you need to include in a plan again:
- Research Question - A question you want to find an answer for through your experiment
- The variables - you can find out what these are here.
- Prediction/Hypothesis - try and make a guess as to what you think will happen, with reasons.
- Materials list - a list of materials that you need for the experiment.
- Method - a step-by-step guide to how the experiment will be done.
When you are ready. Email Ms Lai at firstname.lastname@example.org to get your plan approved. Also ask them if they have your materials. While you are waiting for a reply, you can look up some videos on wind turbines in different countries, write some notes in your google doc.
A note about your independent variable (which is your one aspect of blade design):
There are so many possible variables, but we would like you to focus on:
● Blade Design : without blades, your turbine wouldn’t produce any electricity.
● Some factors to consider: Size, Shape, Number, Material
Remember: when you change one variable, you must keep all other variables constant.