Wind and solar power generation have grown dramatically, yet they still generate only a small fraction of electricity or of primary energy. In 2017, for example, wind and solar generated 6.0% and 1.8% respectively of US electricity. Wind and solar, like all energy systems, occupy land, displacing natural systems, agriculture, and human communities. Power density, the energy generation rate per time per unit ground area (expressed here as We m−2), is one important measure of the land use of energy systems. Existing power density estimates for wind and solar are inconsistent. As an example of the implications of these results, consider Germany and its ambitious energy transformation policy. If US wind power density was applicable to Germany, then devoting all German land to wind power would meet about 40% of Germany's total primary energy consumption.
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