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Why solar is nuclear’s best friend February 19, 2013

Posted by Maury Markowitz in nuclear, solar.
Tags: ,

For reasons I’ve never fully understood, the energy world is filled with one-size-fits-all claims. You know, “we can supply all the power we need from X” or Y, all we need is some unobtainium.

But those sources that don’t enjoy widespread public support often go further; their “boosters” often actively dismiss any criticism, including any support for alternate solutions. This is most notable in the nuclear arena, where it is trivially easy to find supporters who dismiss any and all other power sources for one reason or another.

This is a bit odd, because when the obvious problems building out any sort of “nuclear economy” comes up, these arguments come back to haunt them. Having dissed their erstwhile allies, it’s almost always nuclear that ends up being dismissed by the public.

For instance…

A teeny problem…

Daily demand in Ontario varies by about 50% from the night time low to the daytime peak. Last night, for instance, the province was drawing about 16 GW of power at 3 AM, and is expected to hit about 22 GW at 6 PM later today. This graph is active, so I’m not sure what it will say when you look at it, but the pattern will remain the same.

So here’s the problem: nuclear reactors simply cannot follow this load. CANDU, in particular, has a very limited capability for “throttling”, on the order of 20%. As I write this, Pickering and Darlington are putting out 3.54 GW, about 20% below their peak 6.6 GW capability.

So that means that in order to meet peak demand, Ontario needs lots of other power. In the past we got a good chunk of that power from coal plants, but right now there’s a massive effort underway to switch over to natural gas to supply this demand, a move I’m totally in favour of.

With friends like these

As I mentioned in the lead, supporters of nuclear power – not those actually running it, just posers like myself – are largely dismissive of any and all other forms of power. Hydro is “tapped out”, solar useless, and wind bad.

Why bad? Well you see, wind and solar can’t be relied on to produce power when you need it, so you need to build some other form of power to back it up. It’s a very common argument to claim that the cost of backup isn’t factored in, so the real price of renewables is much higher than what it looks like on paper. Every watt of wind needs a watt of gas.

But wait a second, the gas plants are being built to offset nuclear’s inability to throttle down enough for night time loads. I don’t see anyone factoring that into the cost projections for Darlington B. In fact, we’ve already installed enough gas production to back up CANDU to back up all the renewables we could possibly deploy.

Can’t we all be friends?

Now here’s the irony – solar PV and nuclear are a match made in heaven (get it?). PV peaks in the day, and when you layer that on top of a flat base load, you get something that looks a whole lot like the demand curve. Here, check it out…


What you’re looking at is one week of power use in Germany, in the summer, admittedly. Notice how the peak is basically the same pattern as here in Ontario? Also notice the effect of business and industry on the power use – the weekend numbers are much smaller.

But the really obvious thing that jumps right off this graph is how perfectly solar would work with nuclear. Looking at the demand for “conventional” plants, you can see how it now varies between about 30 GW and 40 GW after the wide scale introduction of PV. This is right in the sort of scale nuclear can handle.

So why all the fussin’ and a fuedin?

When I look at graphs like these I’m baffled at the nuclear world’s dim view on PV. Here, check out comments like these, or these, where PV and wind are clearly positioned as the enemies of nuclear.

It looks like bunker mentality to me.


1. George - November 14, 2014

A teeny problem: Solar peak doesn’t coincide with peake demand.

Nuclear plants are actually capable of ramping nowadays at rates upwards of 1MW/S (EPR).

I agree nuclear and solar can get along fine, but if the goal is to decarbonized in a timely fashion then nuclear deserves far more attention.

Maury Markowitz - November 14, 2014

“A teeny problem: Solar peak doesn’t coincide with peake demand.”

Point the panels westward. Problem solved.

“ramping nowadays at rates upwards of 1MW/S (EPR).”

Some plant designs, yes, the majority of plant designs, no. CANDU plants, for instance, have less than 20% throttling on a 24 hour basis, and I believe this is greatly reduced in their current old age.

And, of course, every EPR under construction is *vastly* over-budget and over-due, so I’m not sure our political overlords with be terribly interested in that “solution”. You may want to pick another example.

Why one would *want* put put all our eggs in one basket is likewise a question that needs to be asked. Using each device source for what it is best at is clearly a good idea, for the same reason that you generally don’t remove the tops of cans with a hammer.

2. George - November 15, 2014

“Point the panels westward. Problem solved.”

Irradiance between 5-6pm not typically very strong and pointing panels westward won’t change that all that much but it will reduce harvested energy. I’m sure you know these things. Problem not solved.

The issue about nuclear ramping isn’t about if existing plants are capable of it, its about if it is practical to do in the future when expansion of flexible carbon free generation will have to take place. Fission plants are certainly capable of adequate ramping through control rod or steam bypass mechanisms, the AP1000 can similarly ramp up to 1 MW/second (wasn’t designed to operate normally in this fashion but is certainly achievable), though load following by nuclear plants would best be limited for economic rather than practical reasons – ie they are high upfront low fuel cost assets that should be run at as high of capacity as possible.

I agree we wouldn’t want to put all of our eggs in one basket, however I am not recognizing how intermittent PV becomes a major means of global decarbonization with the current suite of technologies. Being non-dispatchable and lacking a reliable correlation with elevated daytime demand or peak demand is quite an enormous disadvantage for the technology to over-come in order to achieve scaled integration.

Maury Markowitz - November 15, 2014

> I am not recognizing how intermittent PV becomes a major means of global decarbonization

Because it’s actually being installed. Nuclear power is not. There has been less nuclear power every year for the last ten. There is no sign this will change.

> be limited for economic rather than practical reasons

Didn’t you just invalidate your entire line of reasoning? If this is about economics, then there’s no argument at all.

Fission will do nothing to decarbonize if no one builds them, and as long as the price stays north of about $6, no one will build them. Based on western figures, the average CAPEX for a new plant is over $9. And guess what? No one is building them.

So you can talk about dispatchability this and load following that all you want. It’s meaningless. What’s the load following rate of a reactor that doesn’t get built because CAPEX shot over $11 so they walked away? Zero.

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