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We examined bird and bat mortality at a new 89-turbine windfarm constructed in an environmentally sensitive area in north-central Iowa. The windfarm became operational in November 2001. It is located in cropland between three Wildlife Management Areas (WMA's) with historically high bird use. In the past, migrant and resident waterfowl, shorebirds, raptors, and songbirds moved between the WMA's through the area now occupied by the windfarm. Studies of bird collision mortality in California and elsewhere raised concerns about the possibility of mortalities in this area. From April 15, 2003 and December 15, 2003 we searched for dead animals under 26 randomly selected turbines. Six 76.2 m by 3.0 m transects were maintained...
Ecological processes of low-productivity ecosystems have long been considered to be driven by abiotic controls with biotic interactions playing an insignificant role. However, existing studies present conflicting evidence concerning the roles of these factors, in part due to the short temporal extent of most data sets and inability to test indirect effects of environmental variables modulated by biotic interactions. Using structural equation modeling to analyze 65 years of perennial vegetation change in the Sonoran Desert, we found that precipitation had a stronger positive effect on recruitment beneath existing canopies than in open microsites due to reduced evaporation rates. Variation in perennial canopy cover...
We examined bird and bat mortality at a new 89-turbine windfarm constructed in an environmentally sensitive area in north-central Iowa. The windfarm became operational in November 2001. It is located in cropland between three Wildlife Management Areas (WMA's) with historically high bird use. In the past, migrant and resident waterfowl, shorebirds, raptors, and songbirds moved between the WMA's through the area now occupied by the windfarm. Studies of bird collision mortality in California and elsewhere raised concerns about the possibility of mortalities in this area. From April 15, 2003 and December 15, 2003 we searched for dead animals under 26 randomly selected turbines. Six 76.2 m by 3.0 m transects were maintained...
Tall wind turbines, with hub heights at 80 m or above, can extract large amounts of energy from the atmosphere because they are likely to encounter higher wind speeds, but they face challenges given the complex nature of wind flow and turbulence at these heights in the boundary layer. Depending on whether the boundary layer is stable, neutral, or convective, the mean wind speed, direction, and turbulence properties may vary greatly across the tall turbine swept area (40 to 120 m AGL). This variability can cause tall turbines to produce difference amounts of power during time periods with identical hub height wind speeds. Using meteorological and power generation data from a West Coast North American wind farm over...
Very detailed models often hinder the ability to develop a broad, highlevel understanding of system behavior. A system-of-systems perspective combined with a policy analysis approach offers an alternative approach for policy decision-making. This paper specifies the elements of the energy system-of-systems using this new approach and illustrates its use via an example from the Dutch residential sub-sector. The resulting comprehensive problem representation provides meaningful insights into the interdependencies of relevant factors and values among different levels of the system-of-systems covering both the supply and demand side. The paper also shows that despite the high complexity of the energy sector, an energy...