Many of the nuclear energy diaries I've read are perhaps even more contentious than current candidate diaries. One major issue argued over is whether renewables can provide base-load power-defined by Wikipedia as an "energy source that provides a steady flow of power regardless of demand."
A recent article in Scientific American argues that solar can be used as base-load power and that America could almost completely transition to solar over the next century. Another recent article suggests that wind turbines can also function as base-load power at about a third of their rated capacity.
The Solar Grand Plan envisions clean, renewable energy could supply almost 70% of US electricity and 35% of the total energy by 2050 if we were to construct 3000 GW of solar photovoltaic (PV) and concentrated solar plants(CSP). By the year 2100, with further construction, solar could provide 100% of the electricity and 90% of the total energy.
So, how much land would each of these solutions require? I did some calculations and have a simple slide show, similar to biodiesel bob, to illustrate the results. Image intensive!
From a purely environmental preservation standpoint, nuclear energy is the "greenest" form of electrical generation (when compared with solar and wind) currently available.
Here's where my numbers come from and how I did the calculations.
The information on solar came entirely from Scientific American's Solar Grand Plan. 53% of total solar energy is devoted to compressed air storage (based on the numbers they provide for the year 2100). The large amount needed to provide storage energy can be considered the cost of making solar energy base load. As they propose to develop 3000 GW of solar energy by 2050, we can assume that they want to provide a little under 1400 GW of base load electricity. In the article, they state that the amount of land that would need to be covered by solar panels amounts to 49,000 sq. mi, or a little more than all of Pennsylvania and Delaware.
The numbers for wind farms came from Horizon Wind. Their FAQ lists the area required to site a turbine as 3 acres or less. Maple Ridge wind farm is a 321 MW farm located on 21000 acres, of which less than one percent is devoted to turbines (assuming 0.75% this is 157.5 acres or .49 acres/MW). Wild Horse wind farm is a 230 MW farm on 8600 acres, of which 165 acres is actually occupied by wind turbines and associated infrastructure, equal to .71 acres/MW.
Based on the average from Wild Horse and Maple Ridge farms, the site requirements look to be much less than the 3 acres stated in their FAQ at about 0,6 acres per MW. I've used this lower number for the calculations and display.
According to an article (pdf) that I heard about through Gristmill, wind can, on average, supply 33% of its stated capacity as base load, assuming the wind farms are inter-connected. We therefore need to install 4200 GW of wind turbines to provide 1400 GW of base load electricity.
4200 GW x 1000 MW/GW x 0.6 acres/MW x 0.0015625 sq mi/acre = 3937.5 sq mi, or a little more than 70% of the state of Connecticut. This is the actual area required for turbines and associated infrastructure. One benefit of wind farms is that much of the land around the turbine can still be used for whatever you want (though they try and keep occupied buildings quite a distance away...rotor blades and ice can travel several hundred meters in accidents). The actual size of the area encompassing turbines would be as much as 100 times larger (10 times the size for solar), as wind turbines need to be spaced quite far apart.
The dimensions of the spent fuel storage casks come from Transnuclear, and the amount of fuel produced per plant per year is averaged from Nuclear Tourist. PWRs discharge 40 to 70 fuel assemblies and BWRs discharge 120 to 200. The common Transnuclear casks store 24 PWR assemblies or 52 BWR assemblies. I assume an average plant (1 GW) produces 3 casks per year. We would therefore need 4200 casks per year to cover our 1400 1 GW plants. The dimensions provided by transnuclear show that a horizontal storage cask is 9'8" wide (but it needs 6" on either side!) and 19'10" long. Each cask therefore occupies 128 in x 238 in = 30464 sq in * .00694444 sq ft/sq in = 211 sq. ft. One plant would therefore require 633 sq. ft. of storage per year, and 1400 would require 886,200 sq ft x 3.58700643 × 10-8 sq mi/sq ft = .031 sq mi. Assuming we store waste in dry casks for 5000 years (the approximate time it takes for the radioactivity to decay to the level of uranium ore, see Fig 16b here), we would need 159 sq. mi. of above-ground dry cask storage.
According to wikipedia (and I apologize, but I've lost the exact link or its been edited, the numbers I used are very similar however to ones provided here at AUA), an average 1300 MW nuclear plants consumes 25 t enriched uranium per year, and requires an input of 210 t of uranium oxide or 161 t uranium oxide per GW. We therefore need 225400 t uranium per year.
Output of Uranium mines comes from World Nuclear (see also inf 25 here) and McArthur River. Ranger Uranium mine produces 4026 t uranium oxide per year. It occupies 19422 acres, of which 1235 are actually in use by the mine (approx. 6% of the total lease). Olympic Dam produces 2868 t Uranium, sitting on 3358 acres of a total 44478 leased by the company (occupying around 7.5%). McArthur River mines produces 7200 t Uranium per year, and occupies 210000 acres. Taking the average "in use" numbers from the two Australian mines, we can assume McArthur has approx. 14600 acres in use. The output for these three mines then averages about 1.5 t uranium/acre. This comes to an average production of 984 t uranium per sq. mi. We would therefore need 229 sq mi of uranium mines.
The size of a nuclear power plant was based on acreage and MWs provided by EIA and is based on the average of all plants that had a listed acreage, with an average of .723acre/MW. .723 acre/MW x 1000 MW/GW x 1400 GW x 0.0015625 acres/sq mi = 1583 sq. mi. of nuclear plants to provide 1400 GW of baseload electricity. The total land required for nuclear, both front end and 5000 year back end would be 1971 sq. mi.
One thing to note is that the acreages listed at the EIA website cover the entire area owned and controlled by the nuclear power plant, of which most is not directly used; see this story on crocodiles and Turkey point for example. Calvert Cliffs, for example, sits on 2100 acres, of which only 380 is devoted to the actual power plant. Some of the smallest nuclear power plants on this list cover less than 300 acres (Indian Point Davis Besse), while the largest occupy as much as 10000 acres (Harris). If we assumed that the average amount required for power plant infrastructure was only 300 acres, only 450 sq mi would be required for all the nuclear power plants, bringing the total land down to 855 sq. mi.