But what of the volume of waste a solar powered world would create?
Research on electricity generation and land use (paper, referenced here previously), estimates that solar power to produce 100% of world electricity generation would require 5,500,000,000,000 square meters (5.5 x 10^12 m^2).
Even with thorough research, this is a number that has to be reached with a number of assumptions. Whether the panels are produced properly, whether they are functioning at their maximum efficiencies, whether they are appropriately maintained, and whether the weather is behaving and there is not an unusually cloudy year. All of these decrease production significantly. Solar panel lifetimes are about 15-30 years. We will conservatively assume that the solar panel electricity production is at its maximum production over its entire lifetime, a full 30 years.
Assuming that the land use is the approximate area of the solar panels, and that the panels are a minimum of 1 inch thick (2.54 cm), the volume of PV panels as waste would be 139,700,000,000 cubic meters.
Used nuclear fuel produced by all US reactors is 2,000 metric tons annually. This is about 100 cubic meters per year. Multiplying the amount of US nuclear electricity production to produce the same amount as worldwide electricity production (data from EIA), this becomes about 37,000 cubic meters worldwide per year. After the same 30 years, a nuclear powered world would produce 2,220,000 cubic meters of used fuel.
This means that a solar powered world produces 63,000 times the waste of a nuclear powered world.
And the solar world produces no energy at night. And used nuclear fuel actually still contains 95% of its energy- it is not just "waste". On top of this, radioactivity decreases with time, whereas solar panel components including cadmium and lead, do not go away. Yes, there is the potential for both to be recycled. There would be significant energy lost in recycling solar panels versus the energy produced from recycling nuclear fuel in fast reactors.
How to illustrate this? Nuclear waste after 30 years of powering the whole world would take up roughly 1.5 "Panamax" sized container ships (the largest container ships that can go through the Panama canal). Solar waste would take roughly 95,000 Panamax ships.
That amount of difference is near impossible to illustrate. Here's a 1/100 model of the aircraft carrier USS Enterprise, and a photo of the real Enterprise. The size of the solar waste would be the real Enterprise, and the volume of the used nuclear fuel would be maybe the size of one of the model planes on the model Enterprise. (Not to mention that the amazing achievements of the Enterprise would not be possible without nuclear power!)
Solar power could be a supplement, but never a substitute for nuclear power.
***NOTE: Alert reader Eric Hanson made a good point that the value used for nuclear density was used roughly as uranium as opposed to uranium oxide, which would reduce the multiple. The total size of all the supporting structures for solar were not taken into account either, but if we wanted to take into account the density of uranium oxide along with the geometry of the fuel- spacers, cladding, etc, the density might be closer to 3,500 kg/m3, so maybe you could divide by a factor of 6. This still leaves solar with over 10,000 times more volume of waste than nuclear. Either way, one can see that the amount of waste is significantly greater with solar than nuclear per energy produced.