Renewables and the vortex

Sounds like something from the Harry Potter universe, doesn't it.  But it's about how the US NE grid coped during the polar vortex.

In the depths of the deep freeze late last month, nearly every power plant in the Eastern and Central U.S. that could run was running.

Energy analysts saw a useful experiment in that week of extreme cold: What would have happened, they asked, if the power grid had relied exclusively on renewable energy—just how much battery power would have been required to keep the lights on?

Using energy production and power demand data, they showed how a 100 percent renewable energy grid, powered half by wind and half by solar, would have had significant stretches without enough wind or sun to fully power the system, meaning a large volume of energy storage would have been necessary to meet the high demand.

"You would need a lot more batteries in a lot more places," said Wade Schauer, a research director for Wood Mackenzie Power & Renewables, who co-wrote the report.

How much is "a lot"?

Schauer's analysis shows storage would need to go from about 11 gigawatts today to 277.9 gigawatts in the grid regions that include New England, New York, the Mid-Atlantic, the Midwest and parts of the South. That's roughly double Wood Mackenzie's current forecast for energy storage nationwide in 2040.

Energy storage is a key piece of the power puzzle as cities, states and supporters of the Green New Deal talk about a transition to 100 percent carbon-free energy sources within a few decades. The country would need to transform its grid in a way that could meet demand on the hottest and coldest days, a task that would involve a huge build-out of wind, solar and energy storage, plus interstate power lines.

During the Jan. 27 – Feb. 2 polar vortex event, the analysts test case of 50 percent wind, 50 percent solar would have had gaps of up to 18 hours in which renewable sources were not producing enough electricity to meet the high demand, so storage systems would need to fill in.

The grid would have to be designed to best use wind and solar when they're available, and to store the excess when those resources are providing more electricity than needed, a fundamental shift from the way most of the system is managed today.

[Read more here]

A couple of points:

• Notice how much solar production there even in the middle of winter
• There were 18 hour gaps when there would not have been enough generation.  So 18 hours of storage would have been enough to guarantee supply, even in this extreme situation.  Of course, to be safe, 24 hours of storage plus some seasonal storage would be necessary.  This is consistent with modelling elsewhere.
• Having a grid more skewed to wind would require less storage (at this latitude and in this season).  Note that the major variability of supply comes from the solar portion. From the graph, the wind supply (between the solar peaks) is much less variable than solar.  In winter, reliance on solar requires at least 12 hours of storage, because demand may peak at night when it's coldest.  In summer, because demand peaks during the day, less storage is needed.