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Titel |
Jet stream wind power as a renewable energy resource: little power, big impacts |
VerfasserIn |
L. M. Miller, F. Gans, A. Kleidon |
Konferenz |
EGU General Assembly 2012
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Medientyp |
Artikel
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Sprache |
Englisch
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 14 (2012) |
Datensatznummer |
250063945
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Zusammenfassung |
Jet streams are regions of sustained high wind speeds in the upper atmosphere and are seen
by some as a substantial renewable energy resource. However, jet streams are nearly
geostrophic flow, that is, they result from the balance between the pressure gradient and
Coriolis force in the near absence of friction. Therefore, jet stream motion is associated with
very small generation rates of kinetic energy to maintain the high wind velocities, and it is
this generation rate that will ultimately limit the potential use of jet streams as a renewable
energy resource. Here we estimate the maximum limit of jet stream wind power by
considering extraction of kinetic energy as a term in the free energy balance of kinetic energy
that describes the generation, depletion, and extraction of kinetic energy. We use this balance
as the basis to quantify the maximum limit of how much kinetic energy can be extracted
sustainably from the jet streams of the global atmosphere as well as the potential climatic
impacts of its use. We first use a simple thought experiment of geostrophic flow to
demonstrate why the high wind velocities of the jet streams are not associated with a high
potential for renewable energy generation. We then use an atmospheric general
circulation model to estimate that the maximum sustainable extraction from jet
streams of the global atmosphere is about 7.5 TW. This estimate is about 200-times
less than previous estimates and is due to the fact that the common expression for
instantaneous wind power 1
2Ïv3 merely characterizes the transport of kinetic energy
by the flow, but not the generation rate of kinetic energy. We also find that when
maximum wind power is extracted from the jet streams, it results in significant climatic
impacts due to a substantial increase of heat transport across the jet streams in the
upper atmosphere. This results in upper atmospheric temperature differences of
>20 °C, greater atmospheric stability, substantial reduction in synoptic activity, and
substantial differences in surface climate. We conclude that jet stream wind power
does not have the potential to become a significant source of renewable energy. |
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