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| Titel |
The problem of the second wind turbine – a note on a common but flawed wind power estimation method |
| VerfasserIn |
F. Gans, L. M. Miller, A. Kleidon |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
2190-4979
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| Digitales Dokument |
URL |
| Erschienen |
In: Earth System Dynamics ; 3, no. 1 ; Nr. 3, no. 1 (2012-06-08), S.79-86 |
| Datensatznummer |
250000851
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| Publikation (Nr.) |
 copernicus.org/esd-3-79-2012.pdf |
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| Zusammenfassung |
| Several recent wind power estimates suggest that
this renewable energy resource can meet all of the current
and future global energy demand with little impact on the
atmosphere. These estimates are calculated using observed
wind speeds in combination with specifications of wind turbine
size and density to quantify the extractable wind power.
However, this approach neglects the effects of momentum
extraction by the turbines on the atmospheric flow that would
have effects outside the turbine wake. Here we show with a
simple momentum balance model of the atmospheric boundary
layer that this common methodology to derive wind
power potentials requires unrealistically high increases in
the generation of kinetic energy by the atmosphere. This
increase by an order of magnitude is needed to ensure momentum
conservation in the atmospheric boundary layer. In
the context of this simple model, we then compare the effect
of three different assumptions regarding the boundary
conditions at the top of the boundary layer, with prescribed
hub height velocity, momentum transport, or kinetic energy
transfer into the boundary layer. We then use simulations
with an atmospheric general circulation model that explicitly
simulate generation of kinetic energy with momentum
conservation. These simulations show that the assumption of
prescribed momentum import into the atmospheric boundary
layer yields the most realistic behavior of the simple model,
while the assumption of prescribed hub height velocity can
clearly be disregarded. We also show that the assumptions
yield similar estimates for extracted wind power when less
than 10% of the kinetic energy flux in the boundary layer
is extracted by the turbines. We conclude that the common
method significantly overestimates wind power potentials by
an order of magnitude in the limit of high wind power extraction.
Ultimately, environmental constraints set the upper
limit on wind power potential at larger scales rather than detailed
engineering specifications of wind turbine design and placement. |
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