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Abstract:
The availability of wind power for renewable energy extraction is ultimately limited by how much kinetic energy
is generated by natural processes within the Earth system and by fundamental limits of how much of the wind
power can be extracted. Here we use these considerations to provide a maximum estimate of wind power availability
over land. We use several different methods. First, we outline the processes associated with wind power generation and
extraction with a simple power transfer hierarchy based on the assumption that available wind power will not geographically
vary with increased extraction for an estimate of 68TW. Second, we set up a simple momentum balance model to estimate
maximum extractability which we then apply to reanalysis climate data, yielding an estimate of 21TW. Third, we perform general circulation model simulations in which we extract different amounts of momentum from the atmospheric
boundary layer to obtain a maximum estimate of how much power can be extracted, yielding 18–34TW. These
three methods consistently yield maximum estimates in the range of 18–68TW and are notably less than recent estimates
that claim abundant wind power availability. Furthermore, we show with the general circulation model simulations that
some climatic effects at maximum wind power extraction are similar in magnitude to those associated with a doubling of
atmospheric CO2. We conclude that in order to understand fundamental limits to renewable energy resources, as well as
the impacts of their utilization, it is imperative to use a “topdown” thermodynamic Earth system perspective, rather than
the more common “bottom-up” engineering approach.
