Wind, solar, hydro, natural gas and nuclear energy help meet demands.

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Every two years, Columbia Generating Station nuclear power plant goes offline for a planned refueling period. During those few weeks, about a third of the plant’s 764 nuclear fuel assemblies are replaced, having produced power in the reactor for six years. Several months before shutting down, the new fuel is delivered by truck, inspected and staged for installation in the reactor building.

Energy Northwest schedules Columbia’s refueling periods every other spring, helping to mitigate excess supplies of power during periods when the hydroelectric system and wind power are both producing at high levels.

As the third-largest generator of electricity in Washington state, Columbia is an integral part of the Bonneville Power Administration’s power resource portfolio because it is able to deliver firm, carbon-free electricity around-the-clock.

The way in which nuclear energy plants are refueled is another of their key advantages, making them mostly impervious to extreme weather conditions or related external factors. That’s not the case for other energy resources in some parts of the country.

Oh, those New England winters

In the Pacific Northwest, the power system needs to generate more electricity during the winter, when consumption is higher than in other seasons. But temperatures here often don’t come close to what New England states can encounter from December through February (remember the polar vortex?). When the temperatures drop far below freezing for extended periods of time, delivering fossil fuels to power plants can become a serious concern.

“Words such as diverse, robust, etc. do not readily come into the public debate.  Reliability is key, but people aren’t paying attention to it. They assume everything will just be reliable, because it always has been,” says Meredith Angwin, scientist, author and member of the Coordinating Committee of the Consumer Liaison Group at ISO-NE, the grid operator for New England.

ISO-NE is taking a hard look at how to maintain reliability when fuel delivery can be a challenge. One reason is that New England is becoming more and more dependent on natural gas as nuclear and coal plants are retired, sometimes prematurely. Natural gas isn’t natural to New England so it must come by land or sea, typically via pipelines or ships.

“…(T)here is a real risk that the region’s fuel-security risk could worsen to the point that the ISO would be required to take more severe emergency actions to keep the lights on and protect the power grid during winter,” an ISO-NE report recently concluded. Those actions could include voluntary conservation, brownouts or rolling blackouts, according to the agency.

“The (New England) grid is going more and more to gas-fired plants. But when they can’t get gas, substitute fuels are needed for those plants. These fuels are generally oil and liquid natural gas. Delivery of both can be problematic in bad weather. There’s a lot of drama to icebreakers, bridges open during high traffic hours to let the fuel ships go through, oil inventories at plants falling in real time,” Angwin says.

Ensuring reliability in the Northwest

To ensure reliable service to consumers, power systems must deliver adequate supplies of three types of power: energy, capacity and flexibility. Meeting the needs for all three requires having a diverse mix of generating resources. This is necessary because each type of resource has unique capabilities – no one type of resource has superior capability to produce energy, capacity and flexibility.

Energy can be defined as the production of power across a period of time, such as during the winter months.

Capacity refers to the production of power at a particular point in time. In the Northwest, the power system needs to produce more capacity during the morning and evening (especially during the winter), when electricity consumption is higher than other parts of the day.

Wind turbines produce energy and some capacity, but their production fluctuates, and often are not at full output when the region’s electricity consumption is highest.
Wind turbines produce energy and some capacity, but their production fluctuates, and often are not at full output when the region’s electricity consumption is highest.

Flexibility can be defined as the ability to increase and decrease the production of power to continuously balance the power system, including when electricity consumption fluctuates up and down.

So how does resource diversity work in practice? Nuclear and coal-fired power plants reliably produce continuous firm energy and firm capacity but offer limited flexibility. These resources, along with some hydroelectric generation, have traditionally served as the baseload workhorses in the Northwest’s power resource portfolio.

In contrast, wind and solar generation produce energy and some capacity. However, wind and solar production of energy and capacity fluctuate, and often are not at full output when the region’s electricity consumption is highest (e.g. cold winter mornings and evenings). Further, that fluctuation increases the need for flexibility from other types of power sources, such as hydro or natural gas.

Last summer, when temperatures soared throughout the Northwest, the wind generation in the BPA service area, more than 4,700 megawatts of capacity, fell to near zero. To fill the gap, hydroelectric and fossil resources ramped up. Columbia Generating Station continued producing at 100 percent power.

The Northwest power system is changing

Over the past 15 years the Northwest power system has undergone significant changes with the additions of renewable resources. More recently, owners of numerous coal-fired power plants have announced that their facilities will be closing, in large part due to increasing concerns about carbon dioxide emissions.

Coal plant retirements will remove a large portion of the region’s baseload generation and the associated firm energy and firm capacity that they provide. While additional renewable resources may partially mitigate the impacts, supplies of firm energy and firm capacity will become increasingly valuable.

These changes are being addressed by power system planners, including the Northwest Power and Conservation Council, the Pacific Northwest Utilities Conference Committee and Energy Environmental Economics. Their recent studies have found that planned coal retirements and growing concerns about CO2 emissions will create the need to add new, low- or zero-carbon generating resources.

Studies also conclude that remaining generating resources will continue to be important sources of firm energy and firm capacity. This includes Columbia Generating Station, which continues to be an excellent source of firm, non-carbon energy and capacity.

Energy Northwest develops, owns and operates a diverse mix of electricity generating resources, including hydro, solar and wind projects – and the Northwest’s only nuclear energy facility. These projects provide enough reliable, affordable and carbon-free energy to power more than a million homes.