The transition to a clean energy future will not be without bumps in the road, experts said.
The retirement of Vermont Yankee nuclear station in Vernon led to higher carbon dioxide emission rates across New England for the first time in a decade, according to the latest ISO New England Electric Generator Air Emissions Report.
ISO New England is the six-state power grid's independent system operator. Its central mission is to maintain the reliability of the power system. The organization also maintains an enormous amount of publicly-available data.
When Vermont Yankee closed in December of 2014, it removed 604 megawatts of zero-emission capacity from New England's electricity grid. Within a year, the region's power sector saw a 2.9 percent increase in its carbon emission rate, the ISO's figures show.
In all, the amount of carbon dioxide emitted by the regional power sector increased 2.5 percent in 2015, from 39,317 to 40,312 kilotons.
Carbon dioxide is one of several greenhouse gases that contribute to climate change. Nuclear power plants, while controversial, don't produce such emissions when they generate electricity.
The slight emissions increase from 2014-2015 may or may not be indicative of a trend. And it should be noted that sulfur dioxide and nitrogen oxide levels continued to decline during that period. But the upward notch in carbon dioxide has attracted attention because it followed a decade of declines.
Emission rates from the New England power sector have declined significantly in the past decade with the retirement of coal and oil plants. However, carbon dioxide emissions increased in 2015 after Vermont Yankee nuclear plant closed.ISO New England
For years, air quality improvements in New England followed the retirement of dirty oil- and coal-fired generators. The old plants, which could no longer compete in the marketplace, were largely replaced with natural gas-fired generation, which now provides more than 50 percent of the region's power.
Natural gas burns much cleaner than coal, but its emissions still contribute to climate change. Gas generators produce carbon dioxide at about half the rate of coal plants, according to the U.S. Energy Information Administration.
So, while replacing coal with a natural gas plant reduces carbon emissions, replacing a nuclear plant with natural gas-fired generation has the opposite effect.
Vermont Yankee once produced around 4 percent of New England's power. When it retired, most of its capacity was quickly replaced with natural gas generation, according to the ISO. That's despite the growing deployment of renewables, energy efficiency, and demand response measures.
The news concerning the "Vermont Yankee effect" comes as all six New England states scramble to meet aggressive emissions-reduction goals set by their state legislators and policy makers.
In addition to well-publicized problems around the long-term storage of radioactive waste from the plants, atomic power faces several market disadvantages.
While it does not directly contribute to emissions, nuclear power does not benefit from being labeled "renewable." Under renewable portfolio standards set by various states, utilities must purchase a growing portion of their electricity from renewable sources.
What's more, the aging atomic fleet must compete with new natural gas plants, which are now benefiting from historically low fuel prices.
The writing is on the wall for the future of nuclear power plants in New England. But can they be quickly replaced with energy that does not contribute to climate change?
Experts: transition to renewables won't happen overnight
Gordon van Welie, president of ISO New England, noted in a recent report that emissions did indeed tick up with the retirement of Vermont Yankee. He said the planned retirement of Pilgrim nuclear plant in 2019 is expected to have a similar effect.
At the same time, New England power plant emissions have declined significantly over the last 15 years, due in large part to natural gas replacing coal and oil. Renewables are making progress, but were not able to quickly replace the nuclear plant's capacity.
Moving into the future, the power system will still have large generators connected to the regional transmission system -- however, demand will also be met by thousands of small resources connected "behind the meter" at customers' homes and businesses, van Welie said.
Integrating large-scale renewables such as Canadian hydro will require major high-voltage transmission lines. But siting such energy infrastructure projects has proven to be difficult, he noted.
Van Welie said there is tension between New England's competitive wholesale power markets, which have attracted billions of dollars in investment, and state programs designed to provide financial supports to clean energy.
Putting a price on carbon could be the most efficient way to reduce greenhouse gases while preserving competitive markets, he said, adding that the ISO is working with stakeholders to develop market-based solutions.
All six New England states have set strong greenhouse gas emission reduction targets to combat climate change. In response, the grid is moving toward a system powered by battery-backed renewables and distributed generation such as solar.
But in the meantime, traditional sources of generation are still needed, according to Van Welie.
Steve Clemmer is director of energy research for the Union of Concerned Scientists. In a recent interview, he said when large nuclear plants suddenly retire, it can be hard to immediately replace them with renewable low-carbon resources.
"It takes time to ramp this up," he said.
Clemmer said when policy makers know far in advance that a nuclear plant is going to close, they can do a better job planning for its replacement.
In California, when Pacific Gas & Electric announced last year it would close its massive Diablo Canyon nuclear plant by 2025, the utility also announced plans to replace the capacity with a combination of energy efficiency, renewables, and storage.
Existing nuclear units in New England--Pilgrim in Massachusetts, Millstone in Connecticut, and Seabrook in New Hampshire -- now generate around 30 percent of the region's electricity.
Seabrook is licensed to operate until 2030, but has applied to keep running until 2050. Millstone won a 20-year federal license renewal in 2005. But the plant can't compete with natural gas plants, and seeks a legislative fix to stay open, reports the Hartford Courant. Pilgrim, beset with safety problems, is scheduled to close in 2019.
New York, which is not part of the ISO New England grid, plans to subsidize three aging nuclear plants while the state transitions to clean power. The bailout has prompted two lawsuits -- one from competing fossil fuel plants, and another from a coalition of environmental and consumer groups.
A similar nuclear subsidy in Illinois is also facing a legal challenge from competitors.
The prospect of building new domestic nuclear plants remains hazy. The Japan-based Toshiba announced Tuesday it would write off $6 billion and withdraw from building U.S. reactors after massive cost overruns and delays at projects in South Carolina and Georgia.
However, the Tennessee Valley Authority in October began commercial operation of its Watts-Barr nuclear plant, a 4.7 billion project completed on budget. It's the first new nuclear plant in the U.S. in 20 years.
While many oppose atomic power, saying it brings too many risks, others, including former NASA climate scientist James Hansen, insist that "next-generation nuclear" must be part of the solution to global warming.
Dave Anderson of the Energy and Policy Institute, a watchdog group, said the emissions uptick "provides further reason to ensure that retiring nuclear plants are replaced by renewable energy sources. Wind and solar power do not emit carbon dioxide when they generate electricity."
Mary Serreze can be reached at mserreze@gmail.com
