(92a) Development of a Rigorous Electrolyzer Model for Performing Robust, Dynamic Studies

In the 1990s, a push for cleaner and more efficient power-generating processes led to the development of technologies such as Integrated Gasification Combined Cycle (IGCC). They were developed to produce cleaner and more efficient electricity as well as hydrogen fuel from the gasification of coal or biomass^[1]. Throughout the 2000s, IGCC gradually improved and showed potential to compete both economically and environmentally with the alternative Natural Gas Combined Cycle (NGCC)^[2]. This trend changed in 2011 when discovery of a large natural gas source in the Marcellus Shale^[3] led to increased fracking and thus reduced natural gas prices, leaving hydrogen processes based on the existing coal supply (like IGCC) unable to compete. However, societal pressure centered around addressing rising global temperatures has created a renewed interest in pursuing the cleaner, hydrogen-fueled economy of the 2000s.

Although steam-methane reforming is the main producer of hydrogen (referred to as “blue” hydrogen), another route being investigated is hydrogen produced through the electrolysis of water^[4]. This process uses electricity from the grid to split water into hydrogen fuel and oxygen. The benefit of this approach is that the electricity can come from completely renewable sources and involves no carbon (unlike steam-methane reforming), making this a “green” hydrogen process. It is also a promising technology as it allows for the chemical storage of renewable energy in the form of fuel, an alternative to battery storage. Because these electrolyzers are connected to a renewable grid that is inherently dynamic, there is a need to develop detailed, robust, and easy-to-use dynamic models of electrolyzers.

In this work, a rigorous electrolyzer model is proposed and developed in AVEVA^TM Process Simulation’s equation-oriented environment^[5]. The electrodes for the cell are modeled as two tanks and allow for the calculation of material as well as energy holdup inside the electrolyzer. This is crucial for accurately simulating safety scenarios where the source of water is cutoff, and the water level begins to lower. Accurate energy calculations are also important as many of the material properties that determine voltage like electrical resistance are temperature-dependent^{[6], [7]}. These tanks are separated by a semi-permeable membrane where H⁺ and OH^- ions can be transferred from anode to cathode and vice versa. Lastly, a user-defined, replaceable submodel can be defined to describe the voltage of a given electrolyzer. This gives the user the ability to customize the electrolyzer model with as much detail as they require for a given study.

With this model, P&ID-level detail can be achieved for electrolyzer-focused dynamic simulations. By simply defining a voltage submodel and the design parameters of their electrolyzer, a user can quickly and seamlessly begin testing control systems, perform technoeconomic analyses, and conduct safety studies. The ability to perform such analyses is necessary for transitioning to cleaner alternative fuels like green hydrogen over the coming years.

References

[1] R. G. Lundqvist, “The IGCC demonstration plant at Värnamo,” Bioresour. Technol., vol. 46, no. 1–2, pp. 49–53, Jan. 1993, doi: 10.1016/0960-8524(93)90053-E.

[2] G. Ordorica-Garcia, P. Douglas, E. Croiset, and L. Zheng, “Technoeconomic evaluation of IGCC power plants for CO2 avoidance,” Energy Convers. Manag., vol. 47, no. 15–16, pp. 2250–2259, Sep. 2006, doi: 10.1016/j.enconman.2005.11.020.

[3] “Assessment of Undiscovered Oil and Gas Resources of the Devonian Marcellus Shale of the Appalachian Basin Province, 2011.” https://pubs.usgs.gov/fs/2011/3092/ (accessed Nov. 10, 2022).

[4] E. R. Morgan, J. F. Manwell, and J. G. McGowan, “Opportunities for economies of scale with alkaline electrolyzers,” Int. J. Hydrog. Energy, vol. 38, no. 36, pp. 15903–15909, Dec. 2013, doi: 10.1016/j.ijhydene.2013.08.116.

[5] AVEVA Group Plc., “Product Datasheet: AVEVA Process Simulation.” AVEVA, 2020. Accessed: Nov. 10, 2022. [Online]. Available: https://www.aveva.com/content/dam/aveva/documents/datasheets/Datasheet_P...

[6] O. Ulleberg, “Modeling of advanced alkaline electrolyzers: a system simulation approach,” Int. J. Hydrog. Energy, vol. 28, no. 1, pp. 21–33, Jan. 2003, doi: 10.1016/S0360-3199(02)00033-2.

[7] Z. Abdin, C. J. Webb, and E. MacA. Gray, “Modelling and simulation of an alkaline electrolyser cell,” Energy, vol. 138, pp. 316–331, Nov. 2017, doi: 10.1016/j.energy.2017.07.053.