Offshore Wind Will Add Power When New England Needs It Most

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Last Christmas Eve, in the middle of an historic cold snap, the New England power grid came close to going dark. Thirty-six different power plants failed to deliver promised energy, and grid operator ISO-New England (ISO-NE) was forced to implement emergency operating procedures, stopping just a few steps short of asking the public to help by voluntarily cutting back on electricity use.

ISO-NE was not the only grid operator to face unexpected power plant outages that day, but in a region where electric rates had recently skyrocketed, the appeal for customers’ help would have been particularly frustrating; rates had been driven up specifically to accommodate an expensive fuel-subsidy arrangement that the ISO claimed was necessary to keep the grid running smoothly during cold weather.  

The good news for New Englanders is that a more effective solution for winter reliability is finally within reach. The first of several large-scale offshore wind projects planned for off our coast, Vineyard Wind 1, will soon begin delivering power to the grid. Wind energy in this region is strongest in the winter months, and–as anyone who has ever been out on the water or walked on a New England beach in January knows firsthand–offshore wind is particularly strong. Even better, offshore wind is consistently strongest when temperatures are the coldest. This means that adding more of this resource to our generation mix will bolster the reliability of our power system during cold spells and help to reduce the risk of close calls like the one we had on December 24, 2022.

To understand how offshore wind will support the grid in winter, we can use ISO-NE wind speed data to see how much power Vineyard Wind and other projects would have contributed if they had been online last Christmas Eve. But first, let’s look more closely at what went wrong that day.

What went wrong on December 24, 2022?

Early morning: temperatures plummet and gas becomes scarce

The trouble began in the pre-dawn hours of the 24th, when an Arctic air mass moved into the region and temperatures fell into the teens. Across New England, millions of gas furnaces had to burn more fuel than usual to keep homes and businesses warm. This meant that less gas than usual was available for gas-fired power plants because they typically rely on “non-firm” contracts that entitle them only to the gas that is left over after heating needs are met. In other words, whenever cold weather moves into New England, gas power plants lose access to their fuel in direct proportion to the depth of the cold.

The region’s wholesale electricity markets had already factored in the forecast for extreme cold on December 24th, along with the expectation that gas would be scarce—and expensive. A day earlier, in the Day Ahead energy market run by ISO-NE, gas-fired power plants had been forced to offer their power at exceptionally high prices to cover their anticipated fuel costs. Oil-fired power plants, which are usually more expensive to run than gas plants, suddenly became the more economical option, and based on those results the ISO scheduled them to run throughout the day on Christmas Eve. 

Mid-day: aging oil plants struggle to fill in for gas plants

In a subsequent report to 11 New England Senators who had expressed concern about the Christmas Eve event, ISO-NE president and CEO Gordon van Wylie explained how the switch to oil plants exposed the grid to an unusual type of risk:

“During very cold weather when the gas pipelines into New England are constrained and natural gas prices are high, the market shifts to older, oil-fired generators, which do not run very often.… Given the age and infrequent operation of these facilities, they tend to have higher outage rates when called upon to start than most resources in the fleet.” (Emphasis added.)

The “tendency” of oil plants to struggle at startup was on full display on December 24th. As the day unfolded, an extraordinary number of them encountered mechanical and other problems that led to partial or full outages. Before noon, 1,245 megawatts of outages occurred, followed by 340 megawatts between noon and 4 pm, and another 150 megawatts out before 4:30 pm. In the meantime, the demand for power was rising, with the total demand or “peak load” of 17,510 megawatts forecasted to occur from 5 to 6 pm. 

4:30 pm: ISO-NE declares Emergency Alert

The unexpected and rapid failure of so many power plants, so close to the peak hour, left the grid operator in a difficult position. While an additional 8,000 megawatts of power was theoretically available from other plants that had been paid to be on stand-by status, none of those plants could start up on short notice, meaning that ISO-NE could not call on them to help meet the peak load that was less than an hour away. 

At 4:30 pm, the ISO determined there would be enough power to serve the peak load, but not enough to maintain the full amount of operating reserves required by grid reliability standards. 

Below, a simplified illustration of power system conditions that afternoon shows how the combination of oil plant outages and the unavailability of other plants led to a reserve shortfall, or “capacity deficiency,” for the peak hour:

Offshore Wind Will Add Power When New England Needs It Most

The ISO promptly implemented “Operating Procedure #4”, which authorizes emergency actions during a capacity deficiency, and declared an “Energy Emergency Alert Level 1” to inform neighboring grid operators of the reserve shortfall. Proceeding under this emergency authority, the ISO then took several preliminary steps to restore the supply of operating reserves. Shortly thereafter, another 540 megawatts of outages occurred, and the grid operator was forced to take additional emergency actions to keep reserves from running out.

Finally, after 6 pm, the demand for electricity began to decrease slightly, and imports from Quebec (which was also in the midst of a deep-freeze) began to rebound, eliminating the reserve shortfall and allowing the ISO to cancel all emergency actions at 7 pm. 

In the end, the ISO had not needed to issue public appeals for conservation or resort to “load-shedding” (i.e. rolling blackouts), but the scarcity of gas, the outages at oil plants, and the inability of other power plants to respond quickly had all contributed to a very close call.

How would offshore wind have helped New England last year?

To see how offshore wind would have helped in this situation, we need to back up two days to December 22, 2022, when forecasters began warning of “strong to damaging winds” that were predicted to arrive the following day. The National Weather Service issued high wind warnings for eastern Massachusetts and Rhode Island through the night of the 23rd, and NWS meteorologist Bill Leatham added the practical advice that, “anyone who has placed holiday decorations on their homes or in their lawns should bring them inside or make sure they are well-secured so they don’t blow away.” 

It was not a coincidence that strong winds preceded the cold snap. As Boston Globe meteorologist Dave Epstein explained, “The contrast between the comparatively warm air and the [incoming] Arctic air is producing a large pressure gradient and, in turn, a lot of wind. Wind is nature’s way of trying to balance all of this out.”  

In other words, wind at offshore sites ramped up ahead of the cold.

Thanks to an ISO-NE database of historical meteorological data, we can see exactly what the wind speeds were at the Vineyard Wind and other offshore wind project sites during this time period. We can also see the ISO’s estimate, based on that wind speed data, of the amount of power that each project would have produced if it had been operating. 

As the chart below shows, the power output from Vineyard Wind would have ramped up dramatically on December 22nd and 23rd and stayed strong throughout the day on December 24th

During the critical peak hour on Christmas Eve, Vineyard Wind would have delivered more than 700 megawatts to the grid—enough to eliminate the reserve shortage and create a “capacity surplus.” Another project that will be located nearby and is scheduled to come online in 2025, Revolution Wind, also would have made a substantial contribution, delivering more than 600 megawatts during the peak hour:

Adding offshore wind will improve winter reliability

Events like the reserve shortfall on December 24th illustrate just how vulnerable the New England grid is to extreme cold weather—and by the same token, how valuable the energy from projects like Vineyard Wind and Revolution Wind will be. 

Unlike gas-fired power plants, which have less access to fuel the colder it gets, and unlike oil-fired power plants, which can struggle to start up quickly, offshore wind projects can be counted on to perform exceptionally well in periods of extreme cold, because–as the data for December 22nd-24th shows–their supply of “fuel” automatically ramps up for such events.

The ISO’s own studies have borne this out. From analyses of specific weather events to probabilistic energy modeling based on 70 years of historical data, the results have shown that offshore wind energy is reliably strong across a broad range of cold weather conditions. And during the rare wintertime “lull” in offshore wind speeds, these studies show that solar power picks up the slack.

So far, with the exception of the 30 megawatt Block Island project, the offshore wind in all these studies has all been hypothetical. But this winter, with Vineyard Wind connected to the grid, the reliability contribution of a large-scale offshore wind project will become real. With the addition of Revolution Wind soon after, our region will begin to experience the benefits of both projects ramping up their production during extreme cold weather, adding power when we need it most, just as they would have done last December. 

ISO-NE predicts that wintertime demand for electricity will grow dramatically over the next decade, which means that solutions to the winter reliability problem will become even more critical. Rather than continuing to spend exorbitant sums to prop up the performance of gas- and oil-fired power plants during the winter months, only to see them fail to deliver during the coldest hours, we should focus on adding more offshore wind in New England as the best solution for winter reliability.