Michener 1
Nathaniel Michener
EK131 Wind Energy, Prof. Grace
Museum of Science Data Analysis Project
10/1/12
The Boston Museum of Science plays host to a number of wind turbines of varying types. They are all small and offer the potential for a
small business or home user to use them. This report discusses data made available by the Museum regarding the performance of the
Skystream 3.7 model, built by Southwest Windpower. The data covers a 2-month period from January 1, 2010 to February 26, 2010. Data was
recorded every 10 minutes regarding minimum, maximum, and average wind speed, output power, and wind direction. Statistics on the
Skystream turbine, as well as the “POWER” graph, are taken from Southwest Windpower’s brochure about their product and information made
available by the Museum of Science about their wind turbine projects.
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Average Wind Speed vs. Time of Day
16.000
14.000
Avg Wind Speed in m/s
12.000
10.000
8.000
Skystream
Avg Wind
Speed
6.000
4.000
2.000
0.000
0
5
10
15
Time of Day in Hours
20
25
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Histogram of Average Wind Speed, 1/1 - 2/26
2500
Number of Instances
2000
1500
Skystream Avg
Wind Speed
1000
500
0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Wind Speed in m/s
When examining the scatterplot of Average Wind Speed vs. Time of Day, it is hard to see any trends for the Museum of Science’s testing period
of January 1 to February 26, 2010. There seems to be little variance in the wind speeds, but when looked at as a whole, the scatter plot shows a
higher density of wind speed measurements at certain times of the day. Generally speaking, the morning hours from around 3AM to 8AM
experienced the lowest speeds (under 4 meters per second), while the higher speeds were recorded in the afternoon, from 12PM to 4PM, with
many speeds between 2 meters per second and 6 meters per second. The evening experienced a reduction in wind speeds to back under 4
meters per second. The histogram of this data reflects these conclusions; most average wind speeds were close to 3 meters per second, and
almost none were over 7 meters per second.
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Max Wind Speed vs. Time of Day
30
25
Max Wind Speed in m/s
20
15
Skystream
Max Wind
Speed
10
5
0
0
5
10
15
Time of Day in Hours
20
25
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Histogram of Max Wind Speed,
1/1 - 2/26
3000
2500
Number of Instances
2000
1500
Skystream
Max Wind
Speed
1000
500
0
0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
Wind Speed in m/s
The Max Wind Speed graph reflects very similar trends; the maximum speeds of around 10 meters per second were centered around the midday
hours, while the lower times were during the morning and late night hours. The histogram of maximum wind speed is curious because the
turbine’s power is rated at 11 m/s, but that speed is hardly ever reached. Most maximum speeds did not reach past 6 or 8 m/s.
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Wind Direction vs. Time of Day
400
350
Wind Direction in Degrees from North
300
250
200
Skystream
Wind
Direction
150
100
50
0
0
5
10
15
Time of Day in Hours
20
25
Michener 7
Histogram of Wind Direction,
1/1 - 2/26
1600
1400
Number of Instances
1200
1000
800
Skystream
Wind
Direction
600
400
200
0
0
30
60
90
120
150
180
210
240
270
300
330
360
Wind Direction in Degrees from North (Read "30" as "0 to 30")
The Wind Direction scatter plot is more difficult to interpret. The points are very scattered, but again the density of points can show that the
wind directions were generally between 150 and 250 degrees from north. The histogram is a much better model of the data, since there is
hardly any noticeable change in the wind direction data based on the time of day. Predominantly, the winds came from a southerly or southwesterly direction, with another spike in the graph from the northeast. While the turbines are set rather low to be affected by prevailing winds,
the placement of the museum close to the river and ocean could expose it to shore-based winds.
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Average Power vs. Average Wind Speed
2500
Average Power in Watts
2000
1500
Skystream Avg Power
1000
500
0
0.000
2.000
4.000
6.000
8.000
10.000
12.000
14.000
16.000
Average Wind Speed in m/s
The Average Power vs. Average Wind Speed also tells a perplexing story. The Skystream turbine’s manufacturer rates its cut-in speed at 3.0 m/s,
but in some cases the average wind speed reached 6 or even 8 m/s while the turbine’s power was zero. Likewise, the turbine sometimes
generated electricity while the average wind speed did not reach the rated cut-in value. This makes sense (perhaps the wind at times reached
cut-in speed even the average value for the 10-minute interval was below cut-in). However, the first situation is less easily explained. If the
average value of the wind speed for the time interval was above cut-in speed, then electricity should have been generated. This could be
explained by maintenance down-time, or perhaps the cut-in speed value is not cut-and-dry.
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Michener 10
Power vs. Wind Speed
4000
3500
3000
Power in Watts
2500
2000
Skystream Avg Power vs. Avg Wind Speed
Skystream Max Power vs. Max Wind Speed
1500
1000
500
0
0.000
5.000
10.000
15.000
20.000
25.000
30.000
Wind Speed in m/s
Finally, the graphed power curves compared with the company’s power curves show that the turbine’s performance is, if anything, better than
expected. The curve of Average Power vs. Average Wind Speed almost exactly matches the company’s curve, and the Max Power vs. Max Wind
Speed curve shows that the turbine can reach up to 500 watts over its expected performance levels.
Michener 11
During the 2-month testing period, the Museum of Science’s turbine generated about 224.42 kWh of electricity. Compared to the home energy
audits conducted at the beginning of the course, this would be about enough to power my home for 1/3 of a month (or, for example’s sake, a
refrigerator for 7 ½ months). 17% overall power coverage seems fairly effective, but could take an extremely long time to cover the $10,000
price tag. It also does not come close to matching the predicted 40-90% coverage. Thus, the Skystream is only marginally effective in the
relatively low-wind setting that the Museum of Science has it set up in.