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| Fig. 1: Land use Efficency in Watts per square meter (left) compared between solar and wind power for climate optimal and average conditions. Land area required for equivalent power generation (right) with values in square kilometers. [1,2] (Image source: D. Merrell) |
Solar and wind power are both commonly presented as alternatives to hydrocarbon-based power generation. Unlike more traditional forms of power, both solar and wind rely on ideal weather patterns and large tracts of land for stable and maximal generation. Despite these similarities, they operate in very different climates, on very different scales, and with very different technology. The question presents itself: Is one source of power clearly superior to the other?
The criteria for superiority considered here is lower cost for energy ($/MWh) and higher energy production per area (W/square meter). For solar, obtaining both parameters is relatively simple. The National Renewable Energy Laboratory (NREL) reports that, averaging over a whole year, 250 Watts per square meter of solar radiation makes it to the surface of the Earth, assuming clear weather. Current solar cells operate at 20% efficiency, meaning that with optimal packing solar panel fields can at most generate 50 W per square meter with optimal weather. The average incident power per square meter in the United States is closer to 25 W per square meter. The average cost of solar energy in 2020 was $25/MWh. [1]
Wind power is much more difficult to approximate theoretically. Fortunately, Enevoldsen et al. considered this very question and recovered a maximum possible land use efficiency of 21.7 W per square meter and average efficiency of 6.60 W per square meter for wind turbines located on land in the United States. [2] The average cost of wind energy in 2022 was $24/MWh, but has been volatile, hitting as high as $60/MWh. [3]
In the final analysis, the cost per production of energy is quite similar, with wind holding a slight lead, meaning the overall favorability of either power source will come down to other factors, such as location. Solar energy is much more efficient in terms of land use, meaning if investment is limited by land availability, solar can provide a much higher total power output (and profit) per square meter as demonstrated in Figure 1. This would especially apply to regions where other industries are land-intensive, such as agriculture or to local generation such as for single- family homes. In an increasingly interconnected world, power generation can be localized to regions where these considerations are moot, such as the deserts for solar, and transported to regions where demand is high. In conclusion, both sources of power generation result in similar cost per energy. Despite this, solar has an advantage in overall power generation when land area is the limiting factor in scaling production.
© Devin Merrell. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] "Solar PV Energy," Center for Sustainable Systems, University of Michigan, Pub. No. CSS07-08, October 2024.
[2] P. Enevoldsen and M. Z. Jacobson, "Data Investigation of Installed and Output Power Densities of Onshore and Offshore Wind Turbines Worldwide," Energy Sustain. Dev. 60, 40 (2021).
[3] "Wind Energy," Center for Sustainable Systems, University of Michigan, Pub. No. CSS07-09, August 202e.