(373at) Electrolyzer Plant Scheduling for Hydrogen Production and Power Market Participation in Frequency Containment Reserves

Hydrogen is a pivotal contributor to the transition towards green energy, although fossil fuels remain the primary source, accounting for 80% of global production. Green hydrogen plants, comprising renewable resources and electrolyzers, emerge as an attractive option to reduce the carbon footprint of hydrogen production. Europe is a good example of the recent efforts aimed at expanding the green hydrogen capacity. Here, it is mentioned that the EU targets 6 GW of electrolyzer capacity to produce up to 10 Mt of hydrogen by 2030 (EU Commission, 2020). However, the high production cost is the major barrier to the large-scale deployment of this technology. Electricity consumption represents 50% of the overall cost of green hydrogen yielding a price that is twice as high as Steam Methane Reforming (SMR-based) hydrogen (IRENA, 2021). Therefore, there is a need to explore alternative schemes that can make electrolyzers a competitive option. One of them is their participation in the markets of frequency control ancillary services.

This work explores the economic implications for an electrolyzer plant participating in electricity markets as a power consumer as well as a reserve provider while satisfying the hydrogen requirements of a manufacturing site. In this work, we develop a modeling and optimization framework for the operation of the electrolyzer. The resulting multi-period scheduling model accounts for: (i) the power consumption from the grid, (ii) the plant’s participation in the day-ahead market as a load, and (iii) the plant’s participation in the power grid as real-time Frequency Containment Reserve (FCR), when there is an imbalance in the power grid, such as excess demand or supply, leading to a frequency deviation (that, if left unmitigated, can lead to power outages).

To demonstrate this modeling and optimization approach, we applied this methodology to the Australian National Electricity Market (NEM). This market comprises 10 FCR markets, with 6 being technically feasible for the electrolyzer to participate (Carter et al., 2020). The latter include regulation raise/lower, raise/lower 60s, and raise/lower 5 min. The FCR bids consist of a reserve capacity and a forecasted price and must be submitted by 12:30 on the day before the day for which the bid applies (AEMO, 2023). This stage is called reserve contraction. The proposed scheduling model is optimized at any time before the bid submission so that the electrolyzer owner can determine the optimal reserved capacity to be committed. The electrolyzer plant model includes an alkaline water electrolyzer (AWE) and assumes a non-linear relationship between the hydrogen produced and the power consumed. For this purpose, the electrolyzer stacks and the rest of the balance of the plant (i.e., compressors, and heat exchangers) were modeled using Aspen HYSYS® (Aspen Technology, 2024a). Based on this first-principles model, we created a non-linear surrogate model using Aspen AI model builder® (AIMB) (Aspen Technology, 2024b). consider four dependent variables: hydrogen and oxygen production, total power consumption (by the electrolyzer and the auxiliary process equipment), and total heating and cooling requirements. This model formulation also considers: (i) the three states of the electrolyzer operation (ON, STANDBY, OFF), as well as (ii) the effect of the modular aspect of the electrolyzer operation that enables the partial load utilization in the participation to the FCR markets.

This work proposes an improved representation of the hydrogen-producing electrolyzer assets and demonstrates that the use of non-linear models not only improves the accuracy and optimality of the results but also avoids the use of piecewise linearization, a common approach taken by some authors (Baumhof et al. 2023).

International energy agency (IEA). 2021. Global hydrogen review 2021. Available at: https://iea.blob.core.windows.net/assets/5bd46d7b-906a-4429-abda-e9c507a62341/GlobalHydrogenReview2021.pdf

EU Commission. 2020. Communication from the commission to the European Parliament, the council, the European Economic and Social Committee, and the committee of the regions. A hydrogen strategy for a climate-neutral Europe. Available at: https://energy.ec.europa.eu/system/files/2020-07/hydrogen_strategy_0.pdf

International Renewable Energy Agency (IRENA). 2021. Making the breakthrough. Green hydrogen policies and technology costs. Available at: https://www.irena.org/-/media/Files/IRENA/Agency/Publication/2020/Nov/IRENA_Green_Hydrogen_breakthrough_2021.pdf?la=en&hash=40FA5B8AD7AB1666EECBDE30EF458C45EE5A0AA6

Carter, N., Osullivan, T., Nolan, T., Saba, E. 2020. Flexibility of hydrogen electrolysers. Opportunities in the Australian National Electricity Market. Available at: https://www.macquarie.com/assets/macq/perspectives/Flexibility-of-Hydrogen-Electrolysers-Interactive.pdf

Austrlian Energy Market Operator (AEMO). 2023. Guide to ancillary services in the national electricity market. Available at: https://aemo.com.au/-/media/files/electricity/nem/security_and_reliabili...

Baumhof, M. T., Raheli, E., Johnsen, A. G., & Kazempour, J. (2023). Optimization of hybrid power plants: When is a detailed electrolyzer model necessary?. In 2023 IEEE Belgrade PowerTech (pp. 1-10). IEEE.

Aspen Technology 2024a. Aspen HYSYS. https://www.aspentech.com/en/products/engineering/aspen-hysys

Aspen Technology. 2024b. Aspen Hybrid models. https://www.aspentech.com/en/solutions/aspen-hybrid-models