(710c) Harnessing Flexibility from Inflexible Systems: A Case Study in Electrolysis

Electrochemical devices, such as electrolysis units and batteries, can play a critical role in providing flexibility to the power grid.^1,2 Specifically, demand flexibility provided by these devices can help absorb strong fluctuations in wind and solar power supply, ultimately making the grid more resilient.^1,3 However, there exists an inherent and poorly understood trade-off between device flexibility and durability, which hinders the participation of electrochemical devices in power grid markets and operations. Specifically, adjusting the power load of devices in order to follow highly dynamic electricity market signals can accelerate device degradation.^4-6

To overcome these challenges, this work proposes to combine parallel electrochemical devices that operate using structured operating protocols of limited flexibility (e.g., periodic ON/OFF programs with different duty cycles). The key observation is that the use of structured operating protocols can help mitigation degradation, while the coordination of parallel protocols results in a mixing effect that enables a flexible total response signal. Using electrolysis systems as a case study, we formulate an optimization model that, given a family of predefined structured operating protocols, determines the optimal time-varying mixing of these protocols that maximizes total profit. Our findings show that the total profit obtained by mixing a sufficiently large number of devices converges to the optimal profit of a fully flexible device. Our studies explore behavior in different electricity markets (day-ahead and real-time markets) and under different types of structured protocols (e.g., triangular-wave protocols, squared-wave protocols, and bell-shaped/Gaussian protocols).

We also provide the mathematical justification of why mixing devices with structured protocols can help harness flexibility; specifically, we show that structured protocols can be seen as basis functions that, when mixed, enable the recovery of demand signals of any form. As such, our results pave the way to a new perspective on how to think about the design and operation of grid-connected devices.

(1) Mallapragada, D. S.; Dvorkin, Y.; Modestino, M. A.; Esposito, D. V.; Smith, W. A.; Hodge, B.-M.; Harold, M. P.; Donnelly, V. M.; Nuz, A.; Bloomquist, C.; Baker, K.; Grabow, L. C.; Yan, Y.; Rajput, N. N.; Hartman, R. L.; Biddinger, E. J.; Aydil, E. S.; Taylor, A. D. Decarbonization of the Chemical Industry through Electrification: Barriers and Opportunities. Joule 2023, 7 (1), 23–41. https://doi.org/10.1016/j.joule.2022.12.008.

(2) Wang, R.; Ma, J.; Sheng, H.; Zavala, V. M.; Jin, S. Exploiting Different Electricity Markets via Highly Rate-Mismatched Modular Electrochemical Synthesis. Nat. Energy 2024. https://doi.org/10.1038/s41560-024-01578-8.

(3) Mallapragada, D. S.; Junge, C.; Wang, C.; Pfeifenberger, H.; Joskow, P. L.; Schmalensee, R. Electricity Pricing Problems in Future Renewables-Dominant Power Systems. CEEPR.https://ceepr.mit.edu/workingpaper/electricity-pricing-problems-in-futu… (accessed 2025-01-25).

(4) Alia, S. M.; Stariha, S.; Borup, R. L. Electrolyzer Durability at Low Catalyst Loading and with Dynamic Operation. J. Electrochem. Soc. 2019, 166 (15), F1164. https://doi.org/10.1149/2.0231915jes.

(5) Jung, H. Y.; Jun, Y. S.; Lee, K.-Y.; Park, H. S.; Cho, S. K.; Jang, J. H. Effect of Ramping Rate on the Durability of Proton Exchange Membrane Water Electrolysis During Dynamic Operation Using Triangular Voltage Cycling. J. Electrochem. Sci. Technol. 2024, 15 (2), 253–260. https://doi.org/10.33961/jecst.2023.00948.

(6) Schofield, L.; Paren, B.; Macdonald, R.; Shao-Horn, Y.; Mallapragada, D. Dynamic Optimization of Proton Exchange Membrane Water Electrolyzers Considering Usage-Based Degradation. AIChE J. 2025, 71 (1), e18635. https://doi.org/10.1002/aic.18635.