As an increasing number of states increase their renewable portfolio requirements, a key question is whether their transmission and distribution grids can handle the intermittent nature of renewables. And the follow on question to that is whether there is ample generation in utility's portfolio that can kick in quickly when the sun is not shining or the wind is not blowing.
Those are two separate questions to be addressed here. As to the relationship between renewables and natural gas, it is a close one and become closer. That's because more natural gas is used to firm up wind and solar, all in a moment's notice.
One of the points that detractors of renewables have made is that such back up generation is typically fired with fossil fuels. But natural gas plants still produce emissions, which can't be avoided unless battery technologies improve to the point where wind and solar electrons can be stored and keep operations running. (Right now, storage is mostly used to smooth out blips in voltage, or to keep the lights from flickering out.)
Wartsila, a Finnish maker of electric generators, produces such natural gas generators. (And, in the interest of full transparency, this writer spoke at its conference a few years ago on this subject.) The advent of some of these modern generators has generally meant that coal plants are not used. But if they are, those coal plants are not ideally suited to such tasks and can even increase overall emissions as they take a while to rev up and down.
But until storage technologies reach their full potential, the relationship between natural gas and renewables is symbiotic.
“All other things equal, a 1% percent increase in the share of fast reacting fossil technologies is associated with a 0.88% percent increase in renewable generation capacity in the long term,” says a study published in the National Bureau of Economic Research. “Our paper calls attention to the fact that renewables and fast-reacting fossil technologies appear as highly complementary and that they should be jointly installed to meet the goals of cutting emissions and ensuring a stable supply.”
The next question is whether the grids can handle this intermittency. Even in California, grid experts have expressed concern, especially as renewable requirements have increased. California, for example, has a 50 percent mandate by 2030.
"When you started getting into those ranges at least five or six years ago when they were doing it, it got to be sort of expensive in the 25 to 30 percent range," says Ron Litzinger, president of the Edison Energy Group, at a symposium moderated by this journalist. "I think that’s come down a lot. I see the same trend as we go to 50 percent. Using the grid as storage, I think what I basically meant by think about is as you as an individual customer are either producing or consuming electricity going back and forth two ways on the grid, you’re relying on that grid to do the equivalent of what a battery would do for you.
"And so it’s not that the grid itself has batteries that are accommodating it ... is starting to take place at both the distribution and the transmission level," adds Litzinger, who spoke at an Edison Energy conference. "But through smart communications and quick communications and control, the other generators on the system are adjusting accordingly to make up for your fluctuation."
So it’s really the way the grid operates as a storage device is if you think of a network of streets, it’s a system of streetlights and synchronized streetlights that make the traffic flow smoothly -- all controlled by cloud-based technology, he notes.
As to California's 50 percent mandate, the National Energy Renewable Laboratory is looking into that: "Not only did we find, from an engineering standpoint, that you could easily operate the grid with that much renewable energy, but that it’s actually quite affordable provided that you’re making investments in helping that underlying grid become more flexible.
"The big challenge that you see out there ... is you’ve now got more variability and supply on the other hand. And then with customers becoming more interactive, you’ve got variability of demand on the other side," says Bryan Hannegan, director of the National Renewable Energy Lab in Golden, Colo., at the same conference.
To achieve that, though, he says that the "one-way distribution system" must be modernized and allow for more flexibility -- the ability for utilities to communicate with their customers to adjust energy usage during peak periods. That would ease the constraints and allow all electrons to pass through, avoiding brownouts.
