Wind Turbines

[skomadina2]

Trying to set up experiment conclusions.
IV - Wind (Fan speed)
DV - Height of Turbines
CV - 3 Turbines, 3 different heights all facing the fan

Question asked: Why do some turbines turn faster than others?

Most will answer this question with the wind being the answer. However, it is also dependent on the height of the turbines, since shorter turbines will have obstruction of wind flow due to trees, hills sides, etc. I am having trouble measuring the results, other than eyeing the fact that the taller one turns on a consistant basis, the smaller may turn faster at times, but not consistantly. My results will tell me the taller is most effiecient, but how do I chart this? How do I put on paper the measurement?
Thank you for your time.
sandy

[davidkallman]

Hi sandy,

One way to plot the values when you can't measure the absolute numbers is to use qualitative observations. The observations are assigned numeric values, which can be plotted. As an example, you could use:

very slow = 1
slow = 2
medium = 3
fast = 4
very fast = 5

It's not perfect, but may serve what you're looking for.

[ChrisG]

Hi,
Another possibility would be to measure the number of rotations per second or per minute for each of the turbines. There are a variety of ways to do this, and we can provide additional help if you need it.
Good luck!
Chris

[davidkallman]

Hi sandy and Chris,

Re-reading sandy's post, there are two issues:

1. How to calculate the speed for a windmill that's turning "too" fast.
2. How to handle variable speed data, which we haven't addressed.

Re 1: Chris, you mention there's a way to do the calculation. I'm curious, how?
Re 2: One way to handle this is to plot average data over several observations. One could also plot maximums and minimums, if there is any significant data here.

[ChrisG]

Dave, I was thinking of methods such as video recording or electronic or mechanical counters to address the basic issue of how to quantify the experimental results. I think your ranking scheme is also feasible. It's hard to know what would be appropriate without knowing more about the Sandy's experience, grade level, and experimental design. So, Sandy, if you would like to discuss further, please let us know!
Thanks,
Chris

[davidkallman]

Chris,

Thanks for the explanation.

[skomadina2]

Thanks for your responses and general information. I have decided to put a black dot on one blade and count the number of times it revolves in one minute. I did this 3 times x 3 and came up with a median for each one.
In research of this project I found that it was not just the wind speed but another factor is the height of the turbine. So each turbine is a different height.
My question now is in the presentation. Before I started this, I assumed like others it was the wind speed that caused the turning. In the books they say it is also the height since the lower to the ground it is, the more chance of the wind being blocked by hills, homes, etc. The experiment did show that the taller turbine was slower, but consistant in the turning. The smaller would start out fast then slow and even stop waiting to catch it again. The medium height was the slowest of all.
So, knowing this through research, do I tell them my research in the conclusion? or do I explain somewhere in the background or what do you think?
Thanks, Sandy

[agm]

Hi Sandy,

Generally any information you read that helped you understand your topic, design your experiment, develop a hypothesis, etc, should be thoroughly discussed in your introduction or 'research paper' section. This usually comes after the abstract but before your method, results, and conclusions. Then, when you are discussing what you observed and how to make sense of it, it's good to reference this outside information briefly. But, you probably shouldn't be presenting background research for the first time in the conclusion section.

Here are pages from our guide for reference -- if you've been given a list of sections to include in your paper that differs slightly, follow that.
http://www.sciencebuddies.com/science-f ... ndex.shtml
http://www.sciencebuddies.com/science-f ... port.shtml
http://www.sciencebuddies.com/science-f ... aper.shtml
http://www.sciencebuddies.com/science-f ... ions.shtml

Amanda

[ChrisG]

Hi Sandy,
It sounds like you found a good solution to your problem. With respect to the issue of wind speed versus height, you might need to give some additional clarification in your presentation.

Before I started this, I assumed like others it was the wind speed that caused the turning.

I think that "wind speed" here refers to the wind speed measured at the ground surface. This is an important distinction that should be made clear. Otherwise, your audience might get confused, or think that you have misunderstood the concepts when you also state:

In the books they say it is also the height since the lower to the ground it is, the more chance of the wind being blocked by hills, homes, etc.

This is another way of saying that air velocity (or wind speed) is higher at the elevation of taller windmills. The higher air velocities tend to result in faster rotation.

For your own experiment, it seems as though you are using the rate of rotation of your turbines as indicators of air velocity. The question becomes whether the air velocities in your experiment are similar to the real-world scenario described by the books, where obstacles & friction result in lower air velocities close to the ground (or table top, or whatever you used). If your velocities do not match the expected relations (it sounds like the taller turbine was not the fastest?), why not? Did you lack tall obstacles? Did you use a fan that might direct air in a certain direction? What implications does that have for your experiment and for real world use of wind turbines? These are examples of the sorts of issues you can raise in your presentation. Also if you identify a flaw in your experiment while considering these sorts of questions, you might be able to rerun your experiment to correct the flaw.

I hope that helps!
Good luck.
Chris