(710f) Impact of Battery and Thermal Energy Storage on the Operation of Electric Heating Processes

With increased renewable contributions to the power generation portfolio, power grids face more volatility in electricity supply. Increasing the operational flexibility of large electricity consumers, such as chemical plants, to adjust production and energy consumption in response to daily changes in electricity generation and demand rates (reflected in time-varying electricity prices) is an option to overcome this challenge.[1] It allows a reduction in operating costs on the user end and contributes to the overall grid reliability from the perspective of the grid operators, whose critical mission is to ensure that power supply and demand are balanced at all times.[2] The effects of these actions, also known as demand side management, have been widely studied for energy-intensive chemical processes, such as air separation units[3], chlor-alkali plants[4], ammonia plants[5], glass furnaces[6], and other heavy industries[7]. The flexibility of process operations can further be supported by implementing storage systems for heat or electricity.[8] The cost of batteries for electricity storage is dropping, while thermal systems that use storage materials with high heat capacity, such as firebricks, have gained attention for their potential to provide industrial heat at a relatively low cost.[9,10]

Electrification of process heating in manufacturing processes has emerged as a pathway for the decarbonization of the industrial sector.[11,12] It mainly focuses on modifying the source of heating by replacing combustion-based heating with electric heating, such as resistive heating, inductive heating, heat pumps, etc. Electric process heating shows potential benefits in operation and control beyond its decarbonization potential, such as more precise temperature control and faster response time.[13] In our previous work,[14] we showed that the transition from conventional, combustion-based heating (using a byproduct “tail gas” as the fuel) to electric heating in reaction/separation/recycle processes alters the system dynamics. Specifically, we noted a de-integration behavior that removes the feedback effect present due to the recycle of tail gas. Moreover, we pointed out that electric heating offers an additional degree of freedom for control. On the other hand, electrifying process heat will give rise to numerous large loads on the grid, likely exacerbating the grid balancing challenges highlighted earlier.[14] Conversely, plants with electric heating are expected to provide flexibility and be available to engage in demand side management to support grid operations.

Motivated by the above, we present a formulation of the optimal operation problem for processes with high electric heating demand that accounts for the intermittency and availability of a highly renewable power grid. The time-dependent availability of electricity due to the intermittency of renewable sources is incorporated into the optimization framework as an additional optimization constraint. Models that capture essential dynamic features and constraints of thermal and electrical storage systems, along with the appropriate cost correlations, are also incorporated.

Using a previously introduced electrified ethylene cracker model,[14] we present a case study probing the effects of flexibility and installation of energy storage systems. The results confirm the potential of exploiting the flexibility of energy-intensive electrified processes for demand-side management and load shifting. It is found that firebrick-based thermal storage systems that store energy as heat and discharge heat can provide additional benefits in reducing electricity costs to the chemical process, relative to electricity-based energy storage systems. Additional operational considerations for thermal energy storage systems, including the heat transfer-driven discharge mechanism of heat discharge from the thermal batteries impacting the plant operation, were identified and analyzed for the future adoption of thermal batteries for industrial heating.

[1] Cegla, M.; Semrau, R.; Tamagnini, F.; Engell, S. Flexible Process Operation for Electrified Chemical Plants. Current Opinion in Chemical Engineering 2023, 39, 100898. https://doi.org/10.1016/j.coche.2023.100898.

[2] Zhang, Q.; Grossmann, I. E. Enterprise-Wide Optimization for Industrial Demand Side Management: Fundamentals, Advances, and Perspectives. Chemical Engineering Research and Design 2016, 116, 114–131. https://doi.org/10.1016/j.cherd.2016.10.006.

[3] Kelley, M. T.; Pattison, R. C.; Baldick, R.; Baldea, M. An MILP Framework for Optimizing Demand Response Operation of Air Separation Units. Applied Energy 2018, 222, 951–966. https://doi.org/10.1016/j.apenergy.2017.12.127.

[4] Otashu, J. I.; Baldea, M. Demand Response-Oriented Dynamic Modeling and Operational Optimization of Membrane-Based Chlor-Alkali Plants. Computers & Chemical Engineering 2019, 121, 396–408. https://doi.org/10.1016/j.compchemeng.2018.08.030.

[5] Kelley, M. T.; Do, T. T.; Baldea, M. Evaluating the Demand Response Potential of Ammonia Plants. AIChE Journal 2022, 68 (3), e17552. https://doi.org/10.1002/aic.17552.

[6] Seo, K.; Edgar, T. F.; Baldea, M. Optimal Demand Response Operation of Electric Boosting Glass Furnaces. Applied Energy 2020, 269, 115077. https://doi.org/10.1016/j.apenergy.2020.115077.

[7] Golmohamadi, H. Demand-Side Management in Industrial Sector: A Review of Heavy Industries. Renewable and Sustainable Energy Reviews 2022, 156, 111963. https://doi.org/10.1016/j.rser.2021.111963.

[8] Misra, S.; Maheshwari, A.; Gudi, R. D. Optimal Energy Storage System Design for Addressing Uncertainty Issues in Integration of Supply and Demand-Side Management Approaches. Renewable Energy Focus 2024, 49, 100552. https://doi.org/10.1016/j.ref.2024.100552.

[9] Stack, D. C.; Curtis, D.; Forsberg, C. Performance of Firebrick Resistance-Heated Energy Storage for Industrial Heat Applications and Round-Trip Electricity Storage. Applied Energy 2019, 242, 782–796. https://doi.org/10.1016/j.apenergy.2019.03.100.

[10] Jacobson, M. Z.; Sambor, D. J.; Fan, Y. F.; Mühlbauer, A. Effects of Firebricks for Industrial Process Heat on the Cost of Matching All-Sector Energy Demand with 100% Wind–Water–Solar Supply in 149 Countries. PNAS Nexus 2024, 3 (7), pgae274. https://doi.org/10.1093/pnasnexus/pgae274.

[11] Thiel, G. P.; Stark, A. K. To Decarbonize Industry, We Must Decarbonize Heat. Joule 2021, 5 (3), 531–550. https://doi.org/10.1016/j.joule.2020.12.007.

[12] Zheng, L.; Ambrosetti, M.; Tronconi, E. Joule-Heated Catalytic Reactors toward Decarbonization and Process Intensification: A Review. ACS Eng. Au 2024, 4 (1), 4–21. https://doi.org/10.1021/acsengineeringau.3c00045.

[13] Wismann, S. T.; Engbæk, J. S.; Vendelbo, S. B.; Bendixen, F. B.; Eriksen, W. L.; Aasberg-Petersen, K.; Frandsen, C.; Chorkendorff, I.; Mortensen, P. M. Electrified Methane Reforming: A Compact Approach to Greener Industrial Hydrogen Production. Science 2019, 364 (6442), 756–759. https://doi.org/10.1126/science.aaw8775.

[14] Rho, J. H.; Baldea, M.; Endler, E. E.; Heredia, M. A.; Bojovic, V.; Pajand, P. Probing the Impact of Electric Heating on the Design, Dynamics, and Operation of Integrated Chemical Processes. Ind. Eng. Chem. Res. 2025, 64 (11), 6043–6059. https://doi.org/10.1021/acs.iecr.4c03397.