Discussion and Sources of Error

Table of Contents

Discussion

This was a really interesting project and I enjoyed working on it. I wanted to do a project that was important and relevant to society. Since last spring, there have been numerous newspaper articles on the rising cost of electricity, the Kyoto Protocol and increasing interest in wind energy technology. Until I started researching this project, I did not realize how much pollution and greenhouse gases are created in the production of electricity from fossil fuels.

"Torque it Up" started out as a very simple "what if a second rotor was added" question and grew into the fourteen rotor variations I tested. There are many more possibilities of rotor placement and size I could have evaluated.

I chose to use three bladed rotors because they seem to be the industry standard. I would have liked to try the testing with some two bladed rotors, alone or in combination with rotors of different blade configurations.

This project allowed me to learn how to use some measuring devices such as the anemometer and tachometer. The experiments taught me how careful I had to be in positioning the instruments to obtain consistent readings. In all, I collected 1260 observations.

I learned a lot more about spreadsheet programs and how to use them to analyze and present the data collected. I also learned some basics about statistics and how they can be used to assess the quality of the testing performed.

This novel idea of adding a second rotor appears to be worthwhile pursuing. A third or even more additional rotors, may be even more efficient. I will pursue some of these ideas in "Torque it Up", Phase 2.

If the answer is blowing in the wind, why don't we see wind turbines everywhere?

Although wind turbines are gaining in popularity and becoming more cost effective, there are still opponents to the use of wind energy. The following is a list of some of the main concerns:
· Decreases property values
· Causes noise pollution
· Unattractive to landscapes
· Sun reflection off blades
· Harms passing birds and disturbs wildlife habitat

Proponents for wind energy make the following statements:
· Wind is the fastest growing source of electricity in the world.
· The more electricity generated from wind power, the less need for electricity produced from dirty sources such as coal.
· There are health benefits in reducing emissions of carbon dioxide, nitrous oxide and sulphur dioxide, especially for those with lung problems, such as asthma.
· At 250 metres, turbines produce noise levels of 42-43 decibels, lower than noise levels in urban residential neighbourhoods.
· Research shows bird mortality to be less than two birds per turbine per year, less than those killed colliding with buildings, houses and communication towers.

A commitment to a cleaner environment through the use of renewable energy sources will require a great deal of public education and investment in these technologies. Governments are being forced to reduce greenhouse gas emissions, by signing the Kyoto Protocol. We can all do our part by being open to the ideas of new technology and doing our share to reduce our electricity consumption.

Sources of Error

The experiment was designed to keep sources of error to a minimum but not every aspect could be perfectly controlled.

1. Although the same three speed fan was used for all tests, the wind speed measurements at each speed were not exactly the same. However, the wind speed data at each speed was analyzed using statistics and there did not appear to be a significant variation.

2. The bearings were used to support the axis in a friction free way. However, the weight of the rotors, especially when there was more than one, probably did create a small amount of friction that would reduce the torque and RPM measurements obtained. When I continue with the next phase of this project, I will likely use a larger diameter axis that will be more rigid.

3. The most difficult measurement to perform was weight. Great care had to be taken to ensure that the fishing line wound around the axis in a consistent way and finished winding with the line directly below the hanging weigh scale. In the next phase of the project, I plan to generate and measure electricity and will eliminate the need to measure weight.

4. I used 60 cm of fishing line for all weight measurements. It seemed to allow enough time for the rotors and axis to reach maximum torque and speed before it became taut and stopped the rotation. A longer line might have reduced some error, but would have been more difficult to control adding a different source of error. Some sort of guiding mechanism would have helped.

5. The wind speed, RPM and torque measurements could not be done simultaneously. The anemometer was held between the fan cage and rotor and the position interfered with the wind flow to the rotor, meaning that RPM measurements would not be valid. Obviously, the weight measurements stopped the axis from rotating, making it impossible to measure RPM. I compromised and consistently first measured RPM at low, medium and high, followed by wind speed at high, medium and low fan speeds. The rotor was then stopped and the axis held so that the fishing line could be taped to the axis.

6. The anemometer had a stated accuracy of +/- 3 % or +/- 0.1 m/s.

7. The tachometer had a stated accuracy of +/- 0.05 %.

8. The spring scale had a stated accuracy of +/- 0.8 % or +/- .02N.

Applications/Phase 2