Replacing Nuclear with Solar (part 2)

I did the math (and maps) recently to compare Arizona Public Service’s (APS’s) brand new “Solana” solar power plant to the current Palo Verde Nuclear power plant.

The Solana plant is one of the most efficient solar thermal plants in the US today and it has thermal energy storage to be able to continue to produce power when the sun goes down.   It is so new, I was unable to locate a Google map to display it, so I’ve just represented it as an orange box to compare the area.  Here is how it roughly compares with the Palo Verde Nuclear power plant (outlined in blue) in area.


It doesn’t look too bad right?  The nuclear plant takes up roughly 1.5+ square miles including the nearby cooling ponds to the east, and the solar plant is 3 square miles.

However, where it gets interesting is when you compare Wikipedia for the total annual output in GWh (gigawatt-hours).  On your electric bill, power is paid for and measured in kWh.  1 million kWh = 1 GWh, so that should give you a sense of scale.

The Solana plant is expected to produce 944 GWh per year!  Amazing.

The Palo Verde plant will produce 29,250 GWh in the same year.  Oh.  Its about 31x more than the solar plant even though the nuclear plant is about half the size of the solar plant.  That’s about 60x less space for the same power.

If you wanted to build 31 Solana’s (at about $2 billion x 31 total cost), you could then equal the output of the Palo Verde plant (which cost $6 billion in 1988).  It would take up roughly 100 square miles.  Here is what that looks like comparing the current nuclear plant (blue), the solar plant size (orange) with the required equivalent solar (yellow).    Note the size of Phoenix to the east.  The blue box is hard to see at this scale. PVvsSolarThermal


It depends on where you say Phoenix ends and the suburbs begin, but I’d say it would need to be quite a bit larger than the city of Phoenix in size.

Speaking earlier of costs, APS is to lease the power from Solana for about 14c/kWh, or put simply higher in cost than the current price of electricity consumers pay in Phoenix.  That means the costs for electricity will be going up, and/or it will be coming out of tax subsidies.  The nuclear plant generates energy for less than 2c/kWh.

The nuclear plant is cheaper than coal and about 7x cheaper than solar thermal, and takes up less than 60x the space for the same yearly energy output.

 Coming soon – I visited the Palo Verde Energy Education Center in Buckeye (located between Phoenix and the plant).  I took some video…


One thought on “Replacing Nuclear with Solar (part 2)

  1. I love how clearly this demonstrates the difference in cost and land use.

    Last line “takes up less than 60x the space for the same yearly energy output” should be “takes up less than 1/60th the space for the same yearly energy output”.

    A LFTR wouldn’t need any cooling ponds. Though the fission products for U233 are very similar to those for U235, with a molten fueled reactor they can be separated from the fuel and put in any radiation-storage container to decay and cool. 1/35 the amount of waste, water is one storage method but storing in molten salt is a better one.

    No water for cooling ponds, no water for the reactors, no water that could explode the reactor vessel so no large steam containment building needed.

    No water use in a desert is a big benefit.

    Without the uranium and fuel rods any LWR site stores, the storage space would be much smaller. (LWR store 35,000 kg to make 1 gigawatt-year electricity, only 1,000kg of that is fission products; LFTR fissions over 99% of the fuel, 1,000 kg of fission products is the total to store.)

    Many of the fission products have extremely short half-lives, some measured in seconds. But even if we don’t separate the fission products by storage time, except for the few that have 35 year half-lives, the rest get stored only 10 years before they are below background radiation levels. Extremely little, 170kg per gigawatt-year (8765 gigawatt-hours), to store longer than 10 years.

    A LFTR site could be much smaller than any LWR site.

    (Other types of Molten Salt Reactor could use as fuel the waste from LWR. Mechanically shred the fuel rods, acid to separate the fuel from pellets and rods, chemically convert the uranium oxide to uranium fluoride, and put in the MSR. Turn 1000kg long-term waste into 1GW-year electricity and 830kg 10-year waste and 170kg 350-year waste. Probably could be done inside the Palo Verde steam containment buildings, and use the existing electric infrastructure.)

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