Solutions to the Duck Curve

Solutions to the Duck Curve

NuScale’s multi-module plant, with its NuFollow™ load-following capability, adds the flexibility needed to a grid system that has renewables integrated to balance power supply on the grid, no matter what time of day, the season, or what the weather forecast is.

NuScale and the 2020 California "Duck Curve"

NuScale and the 2020 California Duck Curve

The graphic above shows that a NuScale nuclear power plant has ramp rates that meet California Duck Curve requirements. As previously discussed, an increase in power demand in the evenings coincides with a loss of solar power production. A NuScale plant can respond to meet the power generation demand in the evenings by ramping from 20% to 100% power in 96 minutes, without exceeding fuel limits (and significantly faster than conventional nuclear power). This remarkable NuScale plant capability provides a flexible, cost-effective solution within the Energy Imbalance Market (EIM). The EIM is a tool that dispatches lowest cost resources to address energy imbalances, while maintaining reliability.

NuScale’s NuFollow is central to the EIM and represents a significant advancement in nuclear plant load following capability. NuScale developed an intuitive human-system interface (HSI) and flexible power operation automation process to assist the control room operators in: (1) accessing information, (2) selecting units to maneuver, (3) identifying the most appropriate modes of load following, and (4) initiating the plant maneuvers in a safe, reliable, and efficient manner. Our highly automated control room constantly monitors and evaluates key parameters to determine what SMR units are best suited to accomplish power maneuverability. This NuFollow automation utilizes information such as rate of load change, final load, duration of load change, core age, power history, Xenon level, and control rod margin to enable safe and efficient automated load following and frequency stabilization.

The U.S. Office of Energy Efficiency & Renewable Energy also suggests increasing the geographic area across which the power supply for a grid can be balanced. The scalable nature of NuScale’s SMR plants means they can fit more locations and meet the energy needs of any area, rural or urban, making it possible for regions with smaller electrical grids and limited infrastructure to add new electrical capacity in appropriate increments. These features allow utilities to consider siting NuScale plants at a broader range of distributed locations to accommodate increasing amounts of renewable generation on the grid and balance overall power supply.

An alternative solution to wasting excess capacity through curtailment is to use the power1, either as electricity or steam, to support non-grid applications such as water desalination, hydrogen production, district heating, and more. A NuScale power plant is specifically designed to accommodate diverse applications such as these, since each module within a 12-SMR plant can be designated to different functions as needed. A hybrid energy system approach that combines renewable generating capacity with a NuScale nuclear plant can be optimized to meet grid demand and balance it by yielding additional valued products— all without requiring the NuScale plant to vary its reliable baseload output.

There are other solutions proposed, such as shifting solar generation to the evening by storing solar power earlier in the day (i.e., using batteries, etc.). However, this storage capability has yet to be successfully implemented at scale and recent research by Energy and Environmental Economics (E3) shows that it would be extremely costly and impractical to replace all carbon-emitting firm baseload generation capacity with solar, wind, and storage, due to the very large quantities of these resources that would be required2. E3 found that for storage to provide reliable capacity during multi-day and multi-week stretches of low renewable energy production, it must have a fleetwide duration of 100-1000 hours. However, in current storage technology such as lithium-ion, flow batteries, or pumped hydro cannot provide this duration economically, and most only have a 1 to 10-hour duration.

In the meantime, NuScale’s cost-effective SMR technology provides a unique, carbon free, and reliable solution to the challenging economics of integrating renewables into the grid and will continue to support the expansion of renewables on the grid as renewable energy storage capabilities evolve and come online. NuScale has experienced growing domestic and international interest in the flexible and scalable features of its technology, especially for integration of nuclear power and renewables, because these features are also what makes NuScale nuclear energy so cost competitive.

NuScale looks forward to new opportunities to work with renewable energy influencers and utilities everywhere to provide clean, abundant, carbon-free energy to support the low-carbon energy sector and improve the lives of people around the world.


1Vox News. (May 9, 2019). The ‘Duck Curve’ is Solar Energy’s Greatest Challenge. YouTube video.
2Olson, A. & Ming, Z. (January 2019). Resource Adequacy in the Pacific Northwest: Serving Load Reliably under a Changing Resource Mix. Study by Energy and Environmental Economics, Inc. (E3).