Thursday, June 2, 2016

We can do 100% renewables. But we probably shouldn't.


 Peter Sinclair has a post up taunting "renewable haters" who are invited to be embarrassed that nuclear plants, under pressure from cheap natural gas, may require public money to stay in operation. Following hard on the heels of that, Exelon has announced the shuttering of the Clinton and Quad Cities nuclear plants, 3GW of near-zero carbon energy gone for want of $110 million in subsidy per year (which is the combined losses of the two plants in the current market.)

As an enthusiastic taunter of those I feel deserve it, I know the people Sinclair is talking about: people who position nuclear as the honest, work-a-day, practical solution, where as renewables are impractical fairy dust, a con sustained by massive public money. Which is ridiculous on all counts: nuclear energy has always required public support, with the government providing most of the R&D, permanent waste disposal at bargain prices (how's that coming, guys?), loan guarantees, even free insurance against the possibility of a meltdown. Meanwhile wind has reached 5% of US electricity production: sunny counties and regions, such as Jordan, are finding solar energy profitable without subsidies, as prices for modules continue to fall.

But the vices of nuclear advocates should not be confused with the virtues of nuclear energy. And just because we can build a 100% RE grid, does not mean we should.

Looking out into the world today, it is obviously imperative to get human civilization to net zero or net negative GHG emissions as soon as possible. Every year, every month that we don't pushes us further into the heart of a global disaster.

Renewables require careful load-balancing across large areas, storage, and dynamic demand management to begin to approach 100% of the energy supply. Contrawise, every 1% of baseload power you add makes the intermittent load easier to manage and cheaper overall. Science of Doom has a great post on the math here, and it's worth quoting his conclusion at some length:

What is the critical problem? Given that storage is extremely expensive, and given the intermittent nature of renewables with the worst week of low sun and low wind in a given region – how do you actually make it work? Because yes, there is a barrier to making a 100% renewable network operate reliably. It’s not technical, as such, not if you have infinite money..
It should be crystal clear that if you need 500GW of average supply to run the US you can’t just build 500GW of “nameplate” renewable capacity. And you can’t just build 500GW / capacity factor of renewable capacity (e.g. if we required 500GW just from wind we would build something like 1.2-1.5TW due to the 30-40% capacity factor of wind) and just add “affordable storage”.
So, there is no technical barrier to powering the entire US from a renewable grid with lots of storage. Probably $50TR will be enough for the storage. Or forget the storage and just build 10x the nameplate of wind farms and have a transmission grid of 500GW around the entire country. Probably the 5TW of wind farms will only cost $5TR and the redundant transmission grid will only cost $20TR – so that’s only $25TR.
Hopefully, the point is clear. It’s a different story from dispatchable conventional generation. Adding up the possible total energy from wind and solar is step 1 and that’s been done multiple times. The critical item, missing from many papers, is to actually analyze the demand and supply options with respect to a time series and find out what is missing. And find some sensible mix of generation and storage (and transmission, although that was not analyzed in this paper) that matches supply and demand.

What's more, baseload renewable sources such as geothermal, hydroelectric dams, and tidal power, all require large areas with appropriate geography (and geology) to be successful. Geothermal and tidal power are starting from an extremely small base, while hydroelectric dams (which have significant environmental costs of their own) are already close to their saturation point.

Compare the Exelon plants, Clinton and Quad Cities. Their combined capacity is 3GW, which at the industry-standard 0.9 capacity factor is roughly 24,000 MW-h per year. Those two plants, alone, produce more GWh of electricity than all the geothermal plants in the nation, combined. They produce more clean energy than all the utility solar plants in the nation, combined. That would be a bargain for a tiny subsidy of $100-150 million a year. It comes to about $0.05/kWh. We could subsidize our entire electrical grid to that extent and spend less than 2% of the GDP.

Nuclear energy is, by far, the largest source of low-carbon energy in the United States. Doubling or tripling our capacity could be done easily with the political will to do so. At a bare minimum, we should be maintaining the plants we have to the end of their useful life. Subsidies aren't a dirty word here. At least until we have a comprehensive carbon tax, all low-carbon energy will require subsidies or unfunded mandates, including wind and solar, especially once they reach a scale where their fluctuations necessitate storage.

Different countries and regions with different resources, relationships, and geography are going to need different mixes of sources to get to net zero. Ruling out either more RE or more nuclear seems irresponsible to me.