Environmental Engineering Reference
In-Depth Information
25 kW
40 kW
60 kW
80
70
60
50
40
30
20
10
0
2
4
6
8
10
12
14
16
18
20
Wind Speed, m/s
figure 8.8
Power curves for Enertech 44 with different sized generators.
The availability was good, even though it was a prototype unit and there were several component
failures. The downtime was estimated at 1% for routine maintenance and service, 1% for repair of
component failures, and 1% for weather-related events, mainly icing. The other downtime was for
replacing gears in the gearbox and installing different generators. Notice that 1992 was a low year
for wind power. The unit was down over 2 months as a yaw bearing was replaced in 1995, down
for 1.5 months for a major oil leak in 1996, and down for 2.5 months as a soft start was installed
to reduce the loads on the motor/generator. After that the unit was connected part of the time to a
wind-diesel test bed (a village grid), so it would not have the same connect time and energy produc-
tion. The unit was down 0.5 month in 1999 due to control failure due to lightning. A report on the
reliability is available from USDA-ARS, which includes causes for all downtimes for 20 years of
operation. The unit is still in operation as of 2008.
With the small generator, the capacity factor is higher, but the annual energy production is bet-
ter with the larger-sized generators. However, the energy differences between the 40 and 60 kW
generators were not significant. The power curves (Figure 8.8) include all efficiencies, from wind
to electric output. The same information is presented by the power coefficient curves (Figure 8.9).
25 kW 40 kW 60 kW
0.50
0.40
0.30
0.20
0.10
0.00
2 4 6 8 10 12 14 16 18 20
Wind Speed, m/s
figure 8.9
Power coefficient curves for Enertech 44 with different size generators.
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