(87b) THESEUS: An Optimal Design and Downselection Framework for Energy Storage Technologies

Driven by policy efforts and technological improvements, there is currently a tremendous push to transition the current fossil-dominant energy landscape to sustainable renewable energy-based generation. This also requires measures to improve grid flexibility and ensure reliable power generation under the intermittency of variable renewable energy. Energy storage can effectively decouple the energy supply and demand profiles and improve the grid flexibility [1]. However, there exist several different types of storage technologies and the best-suited technology for a given application can differ based on the type of renewable energy farm, response time required to capture an instantaneous energy supply peak, storage duration requirement, efficiency requirements, space limitations etc. Although Li-ion battery technology is a popular storage option due to its low cost and technological maturity, it suffers from limitations such as rapid degradation, low lifetime and low storage duration, which when taken into account can increase the integration cost [2]. This makes it important to consider other types of energy storage technologies which present several benefits as opposed to the consideration of the Li-ion technology alone. For instance, sodium sulfur and vanadium flow batteries exhibit low degradation rates, long cycling lifetime along with high storage efficiency. The use of these battery technologies can also counter some of the manufacturing and recycling challenges associated with Li-ion batteries [3]. In addition, mechanical energy storage technologies provide the advantage of long-duration energy storage which can facilitate seasonal energy storage. Furthermore, thermal storage technologies have a high technological maturity and can facilitate high-efficiency energy storage with a concentrated solar power plant as well as provide large-scale and long-duration energy storage [4]. For optimal decision-making, it is important to consider the features and trade-offs among the various types of storage technologies to facilitate the determination of the best-suited technology.

To this end, we have developed a software prototype called THESEUS (TecHno-Economic framework for Systematic Energy Storage Utilization and DownSelection) which enables the user to systematically evaluate energy storage technologies for integration with various energy sources. THESEUS incorporates the detailed models of different types of storage technologies such as: (i) electrochemical energy storage in the form of lithium-ion, sodium sulfur and vanadium redox flow batteries, (ii) thermal energy storage in the form of molten salt, phase-change material and cryogenic energy storage, (iii) mechanical energy storage in the form of compressed air storage and pumped hydrostorage, and (iv) chemical energy storage in the form of hydrogen. In addition, THESEUS includes the models for solvent-based CO₂ capture as an “indirect” energy storage technology [5,6]. The detailed models of energy sources such as fossil power plants and renewable energy are also incorporated in THESEUS. A large-scale mixed integer nonlinear programming (MINLP) model which minimizes the integrated system’s cost of meeting the net power demand connects the system-level models together in a decision framework. The output of THESEUS includes the optimal selection and design of the storage technologies, a comprehensive economic analysis, visualization of the system integration configuration, and the system operational schedules. We demonstrate THESEUS for natural gas combined cycle (NGCC) and supercritical pulverized coal (SCPC) power plants across California. Our results indicate that pumped hydrostorage has the lowest levelized cost of storage (LCOS) when long duration energy storage is required, while compressed air energy storage and lithium-ion batteries show promise for short-duration energy storage and high cycling requirements. Under a futuristic carbon pricing scenario, the integration of both CO₂ capture and energy storage technologies is optimal to reduce the cycling of fossil plants by 24% as well as reduce the CO₂ emissions by 90%, while incorporating variable renewable energy. Our analysis also indicate that rather than replacing all fossil power plants with renewable energy sources, it is more economical to integrate energy storage and CO₂ capture systems with fossil plants to achieve a clean and flexible energy grid [7].

References

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[2] Zhao S, You F. Comparative life-cycle assessment of Li-ion batteries through process-based and integrated hybrid approaches. ACS Sustain Chem. Eng. 2019; 7(5): 5082–94.

[3] Schaefer S, Vudata SP, Bhattacharyya D, Turton R. Transient modeling and simulation of a nonisothermal sodium--sulfur cell. J Power Sources. 2020; 453: 227849.

[4] Peng X, Root TW, Maravelias CT. Storing solar energy with chemistry: the role of thermochemical storage in concentrating solar power. Green Chem. 2017;19(10):2427–38.

[5] Zantye MS, Arora A, Hasan MMF. Operational power plant scheduling with flexible carbon capture: A multistage stochastic optimization approach. Comput Chem Eng. 2019;130:106544.

[6] Zantye MS, Arora A, Hasan MMF. Renewable-integrated flexible carbon capture: A synergistic path forward to clean energy future. Energy Environ Sci. 2021.

[7] Zantye MS, Gandhi A, Wang Y, SP Vudata, Bhattacharyya D, Hasan MMF. Optimal design and integration of decentralized electrochemical energy storage with renewables and fossil plants. Energy Environ Sci. Under Review. 2021.