Institutional - Wind Energy: Renewable Energy and the Environment - page 224

source if it did not buy power from the qualifying facility. Avoided cost reflects the cost from new
power plants, not the average cost from plants already installed. The avoided cost includes not only
present but also future costs.
However, many utilities said they did not need any new generation; therefore, avoided costs
were only the fuel adjustment cost. Utilities may set a standard purchase rate for qualifying facili-
ties under 100 kW capacity. Contact your public regulatory body for more information on small
power production. In the 1980s, the California Public Utilities Commission (PUC; now CEC) set
the avoided costs and types of contracts for qualifying facilities [4]. Standard Offer 4 set the avoided
costs for a period of 10 years, while Standard Offer 1 was variable, depending on the cost of fuel.
One of the reasons wind farms started in California was the high avoided costs set by the PUC.
The fuel adjustment cost for Southwestern Public Service in the Texas Panhandle in January
1994 was $0.02/kWh. The company was consolidated with a company in Colorado and Minnesota,
now called Xcel Energy, and in 2008 the avoided cost is still the fuel adjustment cost. However,
it has risen to around $0.05/kWh due to the increase in the price of natural gas. Therefore, some
utilities now consider wind as a hedge against future volatility of natural gas costs and are actively
seeking wind farms.
11. 2 UTILIT Y CONCERNS
For a few wind turbines on a large utility grid there would be no problems with the amount of power.
It would be considered as a negative load, a conservation device that is the same as turning off a
load. For large penetration, 20% and greater, other factors such as the variability of the wind and
dispatching become important. The utilities are concerned with safety and power quality due to any
wind turbines on their grid.
11.2.1 S AFETY
Safety is a primary consideration. This includes energizing a dead utility line, grounding of equip-
ment, and lightning. This issue has been resolved, as large numbers of wind turbines have been con-
nected safely to the utility line. Induction generators have to be energized by the utility line, so when
there is a fault on the line they do not operate. Inverters have sensors for loss of load to disconnect
them from the utility line.
Of course, safety in installation and operation is of concern, as with any other industrial enter-
prise. High voltages, rotating blades and machinery, large weights, and working at heights of 50 to
100 m make for a hazardous workplace. Safety is the first consideration for working around wind
turbines. Never climb a met tower or a turbine tower if you are the only person at the site. Although
the large wind turbines have taller towers, it is easier to climb inside a tubular tower than on a truss
or met tower, especially in inclement weather.
There is a summary and full list of wind turbine accidents up to March 31, 2008, which includes
accident type, turbine, date, and location [5]. The summary notes 482 accidents that include 49
fatalities, with the most common cause being falls from turbines. Thirty-five of the fatalities were
industry workers and fourteen were public fatalities, of which three were from road accidents attrib-
uted to driver distraction. Surprisingly, four people were killed when an airplane crashed into a
wind turbine during a fog. The largest number of accidents was from blade failure, and the second
most common accident was from fire. It is clearly understood that the data, especially early data,
are not comprehensive.
For example, AEI and USDA have tested over sixty prototype wind turbines with a number
of failures, from lost blades to complete destruction, which are not in the database. The longest
distance for a blade failure was 56 m from a small wind turbine, 4 kW, which is quite a bit shorter
than the documented 400 m distance noted in the summary. However, the top of a forklift hit a