Potential of Hydrogen Flexibility for Flattening the Duck Curve

In 2013, the California Independent System Operator (CAISO) published a chart depicting the effects of large-scale deployment of solar PV. This chart illustrates the difference in electricity demand and amount of available solar energy over a 24-hour period for a March day in California. During periods of sunshine, solar power inundates the market then wanes during the evening when a demand ramp is observed. Due to its distinct pattern and uncanny resemblance to fowl, this chart was named the duck curve. 

The duck curve poses balancing of supply and demand challenges for utility companies. From the supply-side perspective, excessive solar generation causes system operators to curtail or shed the residual. In contrast, as the sun sets, power production from PV updates and electricity generators are required to quickly ramp up (which can be expensive) to satisfy demand. Depending on the magnitude of these ramps, the potential of grid congestion increases. 

Electricity Demand and Available Solar Energy in March 2013

(Source: California Independent System Operator)

In the near future, system operators will likely be required to contend with issues of voltage quality and congestion management on a more frequent basis given that both the installed capacity of solar power and demand ramps (due to electrification of sectors such as transport and heating) are only expected to increase. The duck curve is not specific to California. This phenomenon has also been observed in places such as the Netherlands and Australia.

Hydrogen as a Solution to the Duck Curve

A promising solution for addressing the duck curve is to increase flexibility in the electric grid. Demand response and energy storage are effective mechanisms to increase the flexibility of the power system. Although it does have its skeptics and currently high production costs, a promising solution for flattening the duck curve could be hydrogen production. Electrolyzers are capable of consuming excess solar power for splitting water into its constituent molecules of hydrogen and oxygen. The produced hydrogen can be stored over long seasonal durations, thereby reducing the need for solar curtailment during the summers, and can be dispatched over the winter months for heating, transport, or supporting the electric grid. Through their functioning as controllable loads, electrolyzers increase demand side flexibility and provide grid balancing services. 

This controllable nature of hydrogen electrolyzers additionally aid in assuaging another complication of the duck curve, the ramping of generators. By drawing power for electrolysis, electrolyzers relax the stringent ramping requirements on generators. For example, power generation from NuScale’s modular nuclear reactors is consumed for hydrogen production in the presence of excessive solar, which is then ramped in accordance with demand. 

With its potential to store excessive power and dispatch it even over long seasonal durations, hydrogen has garnered attention from governments, industry, and environmental organizations. In addition to accommodating the duck curve, hydrogen produced through electrolysis paves the path for the decarbonization of sectors such as steel manufacturing and transportation.