Replacing Nuclear with Solar

You sometimes hear:  “We should use the nuclear station in the sky for all of our power needs”

I did some interesting math to look at the environmentalist idea of replacing all of our current power plants with solar plants.

In Pickering, Ontario, Canada, is the “Pickering Generating Station” consisting of 8 CANDU reactors, each producing about 0.5 GW.  Put together they are over 4.1 GW.  I wondered how much space this would take up as solar panels…

The picture shows clearly the efficiency between a 4.1GW nuclear plant and its equivalent in solar.  To actually replace solar in Pickering would actually take up twice the space shown, since the solar radiation is about half of what was used in the calculation.  In short, you would have to cover the entire town in solar panels, to do what one plant can do (see the light blue box in the lower right corner).

Proof (warning, MATH!)

To give this a fighting chance, I imagined that the solar is put in Phoenix AZ (well known for its 300+ days of sun/year), and looked up the solar “insolation” – a measurement of the average power of the sun in an area over a year.  Phoenix is about 6.5 kWh per square meter.

With 15% efficient panels (normal) and ignoring all other losses, it results in about 1 kWh.  Multiplying by 365, gives about 365 kWh of output every year, per square meter.

The nuclear plant on the other hand is 4.1 GW of output, all day, every day, or 4.1 GW x 365 x 24 hrs x 1 million kWh per GWh = 36 thousand million kWh = 36,000,000,000 kWh per year from the plant.
Divide this by 365 kWh per year: 36,000,000,000 / 365 = 100,000,000 square meters, or 100 square km (roughly).



The purple line drawn is 10×10 km to make 100 square km.  In reality, if you replaced the actual Pickering plant, and put the panels in Pickering, you would need about 200 square km of them, since the solar insolation is about half that of phoenix, and don’t even get me started on the snow removal on 200 square km of solar panels.

Consider also the cost of building and installing and maintaining 100-200 square km of solar panels, or the environmental damage of that much shade (if you built it somewhere remote).  Or, consider that they will need to be replaced about every 30 years, or that there is only power generated when the sun shines.

The original technology for the CANDU reactor used in this example (sitting operating in Pickering), is over 40 years old.  It isn’t even a thorium LFTR reactor, which would be about 100x more efficient than the CANDU or about 300x more efficient than the standard US based light-water reactors.

The math took care to use an average number for the year, but unless you don’t mind either huge costly energy storage solutions, or not having power at night – other solutions must also be added in.  It is just too bad we don’t have:  something that is on 24/7, doesn’t use vast amounts of resources, and doesn’t emit greenhouse gases – like nuclear power.  Hmm!  How about that – We do!  And with thorium and LFTR, it could be better.