Time 5 hrs

Difficulty Beginner
Prerequisites Thinking Like A Scientist
Departments Science
Authors Flora Lai
Groupings Pairs
Threes
Minimum Year Group None

### Blurb

Have you ever been to the wind mill on Lamma Island? In this unit, you will be building your own wind turbine and investigating how the blades could affect its efficiency.

This work is shared under the following license: Creative Commons BY-SA-NC

### Outline

 Resources What is needed to run this unit? ... Cross-Curricular Links Do not try and force this. What areas of other subjects might this reflect and/discuss language. For IB, links with ToK. ... Teacher Reflection What was successful? What needs changing? Alternative Assessments and Lesson Ideas? What other Differentiation Ideas/Plans could be used? ... Credits Any CC attribution, thanks, credit, etc. Wind turbine thumbnail image via geograph.org.uk from Oast House Archive, shared under CC BY-SA

120 mins
Building a wind turbine - background

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 flai@ichk.edu.hk 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.

There are so many possible variables, but we would like you to focus on:
● Some factors to consider: Size, Shape, Number, Material
Remember: when you change one variable, you must keep all other variables constant.

60 mins

Gather your materials and make it! You may need to make more than one set of blades for your independent variable.

Doing the experiment

You are now ready to investigate the independent variable you picked! You may want to do it more than once to ensure that your results are reliable.

When you are doing the experiments, take some photos and put them under "Observations and Results" on your google doc. Do write that any observations you make throughout the experiment too.

Put any figures or numbers into a table form.

120 mins

• Do you think your results can be presented in a more meaningful way? Such as by drawing a graph? Here is a link to the different types of graphs you may want to draw. You can also speak to your Science teacher about this.
• If you think you can draw a graph, decide on a graph type with your partner and draw it by hand.
• Take a picture of it and put it into your google doc, after your "Observations and Results" section.
• Give this section a subtitle of "Graphs".

Under another subtitle of Analysis and Conclusions, write a paragraph or 2 on the following:

• Can you see any trends or patterns on your graph?
• Why do you think there is or isn't a trend or pattern. Try and think of some Scientific reasoning for these.
• Did these match with your prediction?
• Can you write a one-sentence conclusion at the end of this seciton? E.g. "In conclusion, The elephant toothpaste produced more foam when...."

• Under a final sub-heading of Evaluation, write a paragraph on the following:
• What went well in your experiment?
• What improvements could you have if you were to do it again? Why?
• How do you think the results from your experiments could be useful in our daily lives?
• Can you think of another further experiment you could do?