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How do we make the electrical grid more resilient?

This week, a US federal commission said “no” to a proposed rule that would have paid a premium to coal and nuclear power plants. The rule, put forward by Energy Secretary Rick Perry with the goal of protecting the electricity grid from power outages, was controversial. Critics said it unfairly favored two flailing industries over renewable energy. Perry argued, though, that only power plants capable of storing at least 90 days’ worth of fuel onsite—in other words, coal and nuclear—are reliable enough to keep the US grid resilient through the worst winter storms.

The Federal Energy Regulatory Commission, composed of five Trump-appointed commissioners, unanimously rejected Perry’s proposal. But the fact is, he was right about at least one thing: The US electrical grid does have a resiliency problem, and is periodically at risk of plunging millions of Americans into frozen darkness. Perry’s proposal wasn’t perfect, but it could have mitigated the risk. With his idea off the table, how should energy providers and regulators think about bolstering the system? To answer that question, it helps to understand how heat and electricity are delivered.

If you live in the continental United States, you have likely experienced some cold weather lately. Beginning around Christmas, it was unseasonably chilly as far south as Florida and Texas, while the Midwest and New England saw temperatures far below freezing for days on end. Fortunately, natural gas has done an outstanding job of meeting the public’s heating needs. In recent weeks, pipelines delivered around the clock, with no widespread gas outages, showing just how critical fossil fuels remain for sustaining people under difficult circumstances.

That said, the regional transmission organizations responsible for delivering power to every home and business get nervous during severe cold snaps. During the 2014 Polar Vortex, parts of the country were barely able to meet the need for electricity. During a deep freeze, demand for natural gas and other fuels spikes, and stormy, frigid weather can physically block delivery of both fuels and electricity.

Heat when you need it. Natural gas has been our cheapest dispatchable energy source—the kind that can be turned on and off quickly—since prices for it crashed in late 2008. About half of US homes use natural gas for heating and hot water, but it is also used by power plants to generate electricity—in 2016, natural gas provided about 34 percent of US electricity generation. (The commercial, industrial, and transportation sectors use it too.) Most of the year, these competing demands are not a problem, but when the need for home heating peaks, it can divert the supply of natural gas that might otherwise go to power plants.

Natural gas is not stored where it is used, but rather comes to our homes and power plants through pipelines, arriving just as we need it for heating, cooking, or electricity production. This is called “just-in-time” delivery. Not too long ago, the system was different. My home, built in 1937, has a coal chute. A truck would drive up and dump a load of coal into the basement, and the owner could heat the house for as long as it lasted. Homes heated with wood or fuel oil still work the same way, as do the coal-powered generators that have provided electricity for much of the last 70 years. These plants keep enormous coal piles, stored as a reserve in case of a delivery problem caused by accident or bad weather.

There are problems with both of these supply methods. Given the energy density of fossil fuels, it requires a lot of land to store a significant reserve supply. It is also dangerous for non-professionals to store large quantities of flammable material in their homes. But just-in-time delivery has its own issues. For one thing, if there is a disruption in the system, there is no back up; homeowners simply have to wait until service is restored. There is also a limit to the amount of gas that can be delivered to a region and ultimately an end user. The pipelines have a fixed capacity, so the only way to deliver more natural gas is to build more pipelines.

When demand for natural gas peaks, power plants that use it cannot get the amount they need from pipeline operators. (For obvious reasons, home heating takes priority over electricity generation.) As a result, the regional operators that control the grid have to do a lot of maneuvering to try to ensure a continuous flow of electricity. During this month’s cold snap, the grid manager in New England, ISO-NE, turned to power plants that burn fuel oil to ensure continuity. While normally oil makes up only a tiny percent of the fuel mix in that region, on January 5th it made up 36 percent of the electrical fuel mix, as the below screenshot from the ISO-NE website shows.

Spiking demand for fuel oil is a potential problem: Legal restrictions on emissions limit oil use, there is a limit to the amount of fuel that can be stored onsite, and as Bloomberg reported on January 2nd, power plants start to run short on fuel oil after multiple days of cold. When they do run out, plants will shut down and homes will go cold. As we continue to convert the US grid toward natural gas and away from coal-fired generation, I expect that these efforts to keep the power on during extreme weather will become even more challenging.

A role for coal. Prolonged cold events are relatively rare. On the other hand, the one we experienced from December 25, 2017 to January 8, 2018 was the third of its kind since 2011. During the 2014 Polar Vortex, a cold front descended on the eastern and central United States. This created high demand for natural gas for heating, but also record electrical demand in the winter. (US consumers normally use less electricity in the winter than in the summer.) Natural gas redirected for residential heating could not be used for electricity generation. Fortunately, fuel-secure generators—those with onsite fuel supply, both nuclear and coal—were online or could be brought online to provide electricity for the 65 million customers of PJM Interconnection, the regional transmission organization serving 13 states and the District of Columbia. Many of the coal and nuclear plants that prevented catastrophe during the polar vortex have now been permanently closed, so can no longer come to the rescue when electricity supplies are tight.

Read full article at The Bulletin of the Atomic Scientists