@article{SternerHofrichterMeisingeretal., author = {Sterner, Michael and Hofrichter, Andreas and Meisinger, Alexander and Bauer, Franz and Pinkwart, Karsten and Maletzko, Annabelle and Dittmar, Felix and Cremers, Carsten}, title = {19 Import options for green hydrogen and derivatives - An overview of efficiencies and technology readiness levels}, series = {International Journal of Hydrogen Energy}, volume = {90}, journal = {International Journal of Hydrogen Energy}, publisher = {Elsevier}, issn = {0360-3199}, doi = {10.1016/j.ijhydene.2024.10.045}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-77756}, pages = {1112 -- 1127}, abstract = {The import of hydrogen and derivatives forms part of many national strategies and is fundamental to achieving climate protection targets. This paper provides an overview and technical comparison of import pathways for hydrogen and derivatives in terms of efficiency, technological maturity and development and construction times with a focus on the period up to 2030. The import of hydrogen via pipeline has the highest system efficiency at 57-67 \% and the highest technological maturity with a technology readiness level (TRL) of 8-9. The import of ammonia and methanol via ship and of SNG via pipeline shows efficiencies in the range of 39-64 \% and a technological maturity of TRL 7 to 9 when using point sources. Liquid hydrogen, LOHC and Fischer-Tropsch products have the lowest efficiency and TRL in comparison. The use of direct air capture (DAC) reduces efficiency and TRL considerably. Reconversion of the derivatives to hydrogen is also associated with high losses and is not achievable for all technologies on an industrial scale up to 2030. In the short to medium term, import routes for derivatives that can utilise existing infrastructures and mature technologies are the most promising for imports. In the long term, the most promising option is hydrogen via pipelines.}, language = {en} } @incollection{SternerBauerCrotoginoetal., author = {Sterner, Michael and Bauer, Franz and Crotogino, Fritz and Eckert, Fabian and von Olshausen, Christian and Teichmann, Daniel and Thema, Martin}, title = {Chemical Energy Storage}, series = {Handbook of Energy Storage}, booktitle = {Handbook of Energy Storage}, editor = {Sterner, Michael and Stadler, Ingo}, publisher = {Springer}, address = {Berlin, Heidelberg}, isbn = {978-3-662-55503-3}, doi = {10.1007/978-3-662-55504-0_8}, pages = {325 -- 482}, abstract = {Purely electrical energy storage technologies are very efficient, however they are also very expensive and have the smallest capacities. Electrochemical-energy storage reaches higher capacities at smaller costs, but at the expense of efficiency. This pattern continues in a similar way for chemical-energy storage. In terms of capacities, the limits of batteries (accumulators) are reached when low-loss long-term storage is of need. Chemical-energy storage and stocking fulfills these requirements completely. The storing itself may be subject to significant efficiency losses, but, from today's point of view and in combination with the existing gas and fuel infrastructure, it is the only national option with regards to the long-term storage of renewable energies. Chemical-energy storage is the backbone of today's conventional energy supply. Solid (wood and coal), liquid (mineral oil), and gaseous (natural gas) energy carriers are 'energy storages' themselves, and are stored using different technologies. In the course of energy transition, chemical-energy storage will be of significant importance, mainly as long-term storage for the power sector, but also in the form of combustibles and fuels for transport and heat. Not only are conventional storing technologies discussed within this chapter, but a detailed explanation is also given about the storage of renewable energies in the form of gaseous (power-to-gas, PtG) and liquid (power-to-liquid, PtL) energy carriers for electricity, heat, chemicals, and in the form of synthetic fuels.}, language = {en} } @incollection{SternerBauer, author = {Sterner, Michael and Bauer, Franz}, title = {Definition and Classification of Energy Storage Systems}, series = {Handbook of Energy Storage}, booktitle = {Handbook of Energy Storage}, editor = {Sterner, Michael and Stadler, Ingo}, publisher = {Springer}, address = {Berlin, Heidelberg}, isbn = {978-3-662-55503-3}, doi = {10.1007/978-3-662-55504-0_2}, pages = {23 -- 47}, abstract = {Energy supply always requires energy storage—either as an intrinsic property or as additional system. It is an intrinsic property of solid, liquid, and gaseous fuels, although less so of water-borne heat, but not of electricity. So to meet variable demands and supplies, heat and electricity networks usually require additional storage systems. When they are added to an energy network, should they be viewed as 'suppliers' or as 'consumers'? Who is responsible for covering the costs of storage systems? To categorize storage systems in the energy sector, they first need to be carefully defined. This chapter defines storage as well as storage systems, describes their use, and then classifies storage systems according to temporal, spatial, physical, energy-related, and economic criteria.}, language = {de} } @misc{ThemaBauerSterner, author = {Thema, Martin and Bauer, Franz and Sterner, Michael}, title = {Power-to-Gas world status report}, series = {International Renewable Energy Storage Conference, D{\"u}sseldorf 14.-16.03.2019}, journal = {International Renewable Energy Storage Conference, D{\"u}sseldorf 14.-16.03.2019}, language = {de} } @incollection{SternerBauerCrotoginoetal., author = {Sterner, Michael and Bauer, Franz and Crotogino, Fritz and Eckert, Fabian and von Olshausen, Christian and Teichmann, Daniel and Thema, Martin}, title = {Chemische Energiespeicher}, series = {Energiespeicher - Bedarf, Technologien, Integration}, booktitle = {Energiespeicher - Bedarf, Technologien, Integration}, edition = {2. Auflage}, publisher = {Springer Vieweg}, address = {Berlin ; Heidelberg}, isbn = {978-3-662-48893-5}, doi = {10.1007/978-3-662-48893-5_8}, pages = {327 -- 493}, subject = {Energiespeicher}, language = {de} } @incollection{SternerBauer, author = {Sterner, Michael and Bauer, Franz}, title = {Definition und Klassifizierung von Energiespeichern}, series = {Energiespeicher - Bedarf, Technologien, Integration}, booktitle = {Energiespeicher - Bedarf, Technologien, Integration}, edition = {2. Auflage}, publisher = {Springer Vieweg}, address = {Berlin ; Heidelberg}, isbn = {978-3-662-48892-8}, doi = {10.1007/978-3-662-48893-5_2}, pages = {25 -- 49}, subject = {Energiespeicher}, language = {de} } @techreport{SoergelLudererEmelianovaetal., author = {S{\"o}rgel, Dominika and Luderer, Gunnar and Emelianova, Polina and Koch, Otto and Timpe, Christof and Bauer, Franz and Sterner, Michael}, title = {Kopernikus-Szenarienvergleich - Robuste Eigenschaften von Klimaschutzpfaden zur Treibhausgasneutralit{\"a}t 2045 und relevante Unsicherheiten}, publisher = {Kopernikus-Projekte}, address = {Potsdam}, pages = {54 S.}, abstract = {Im Rahmen der vier Kopernikus-Projekte - Ariadne, ENSURE, P2X und SynErgie - wird die Transformation des deutschen Energiesystems hin zur Klimaneutralit{\"a}t analysiert. Im vorliegenden Bericht werden hierbei robuste Kernaussagen und relevante Unsicherheiten derjenigen Szenarien der Kopernikus-Schwesterprojekte dargestellt, die zur Zielsetzung die Klimaneutralit{\"a}t 2045 haben. Hierbei liegt der Fokus auf Indikatoren, die eine besonders hohe klimapolitische Relevanz haben.}, language = {de} } @incollection{BauerGawlikSterneretal., author = {Bauer, Franz and Gawlik, Julia and Sterner, Michael and Hamacher, Thomas}, title = {{\"U}bergreifende Energiesystemmodellierung}, series = {Optionen f{\"u}r ein nachhaltiges Energiesystem mit Power-to-X-Technologien: Transformation - Anwendungen - Potentiale. 4. Roadmap des Kopernikus-Projektes P2X, Phase II}, booktitle = {Optionen f{\"u}r ein nachhaltiges Energiesystem mit Power-to-X-Technologien: Transformation - Anwendungen - Potentiale. 4. Roadmap des Kopernikus-Projektes P2X, Phase II}, editor = {Ausfelder, Florian and Du Tran, Dinh}, publisher = {DECHEMA Gesellschaft f{\"u}r Chemische Technik und Biotechnologie e.V.}, address = {Frankfurt a.M.}, isbn = {978-3-89746-238-0}, pages = {17 -- 35}, language = {de} } @incollection{BauerGawlikSterneretal., author = {Bauer, Franz and Gawlik, Julia and Sterner, Michael and Hamacher, Thomas}, title = {{\"U}bergreifende Energiesystemmodellierung}, series = {Optionen f{\"u}r ein nachhaltiges Energiesystem mit Power-to-X-Technologien: Transformation - Anwendungen - Potentiale. 3. Roadmap des Kopernikus-Projektes P2X, Phase II}, booktitle = {Optionen f{\"u}r ein nachhaltiges Energiesystem mit Power-to-X-Technologien: Transformation - Anwendungen - Potentiale. 3. Roadmap des Kopernikus-Projektes P2X, Phase II}, editor = {Ausfelder, Florian and Dura, Hanna Ewy}, publisher = {DECHEMA Gesellschaft f{\"u}r Chemische Technik und Biotechnologie e.V.}, address = {Frankfurt a.M.}, isbn = {978-3-89746-236-6}, pages = {19 -- 33}, language = {de} } @incollection{SternerBauerHofrichter, author = {Sterner, Michael and Bauer, Franz and Hofrichter, Andreas}, title = {Systemanalyse von Power-to-X-Pfaden - Ergebnisse des Satellitenprojektes "SPIKE"}, series = {Optionen f{\"u}r ein nachhaltiges Energiesystem mit Power-to-X Technologien : Nachhaltigkeitseffekte - Potenziale Entwicklungsm{\"o}glichkeiten; 2. Roadmap des Kopernikus-Projektes "Power-to-X": Flexible Nutzung erneuerbarer Ressourcen (P2X)}, booktitle = {Optionen f{\"u}r ein nachhaltiges Energiesystem mit Power-to-X Technologien : Nachhaltigkeitseffekte - Potenziale Entwicklungsm{\"o}glichkeiten; 2. Roadmap des Kopernikus-Projektes "Power-to-X": Flexible Nutzung erneuerbarer Ressourcen (P2X)}, editor = {Ausfelder, Florian and Dura, Hanna Ewy}, publisher = {DECHEMA Gesellschaft f{\"u}r Chemische Technik und Biotechnologie e.V}, address = {Frankfurt am Main}, isbn = {978-3-89746-218-2}, pages = {145 -- 153}, language = {de} } @misc{WeberDendorferSuessetal., author = {Weber, Karsten and Dendorfer, Sebastian and S{\"u}ß, Franz and Kubowitsch, Simone and Schratzenstaller, Thomas and Haug, Sonja and Mohr, Christa and Kiesl, Hans and Drechsler, J{\"o}rg and Westner, Markus and Kobus, J{\"o}rn and Schubert, Martin J. W. and Zenger, Stefan and Pietsch, Alexander and Weiß, Josef and Hinterseer, Sebastian and Schieck, Roland and Scherzinger, Stefanie and Klettke, Meike and Ringlstetter, Andreas and St{\"o}rl, Uta and Bissyand{\´e}, Tegawend{\´e} F. and Seeburger, Achim and Schindler, Timo and Ramsauer, Ralf and Kiszka, Jan and K{\"o}lbl, Andreas and Lohmann, Daniel and Mauerer, Wolfgang and Maier, Johannes and Scorna, Ulrike and Palm, Christoph and Soska, Alexander and Mottok, J{\"u}rgen and Ellermeier, Andreas and V{\"o}gele, Daniel and Hierl, Stefan and Briem, Ulrich and Buschmann, Knut and Ehrlich, Ingo and Pongratz, Christian and Pielmeier, Benjamin and Tyroller, Quirin and Monkman, Gareth J. and Gut, Franz and Roth, Carina and Hausler, Peter and Bierl, Rudolf and Prommesberger, Christian and Ławrowski, Robert Damian and Langer, Christoph and Schreiner, Rupert and Huang, Yifeng and She, Juncong and Ottl, Andreas and Rieger, Walter and Kraml, Agnes and Poxleitner, Thomas and Hofer, Simon and Heisterkamp, Benjamin and Lerch, Maximilian and Sammer, Nike and Golde, Olivia and Wellnitz, Felix and Schmid, Sandra and Muntschick, Claudia and Kusterle, Wolfgang and Paric, Ivan and Br{\"u}ckl, Oliver and Haslbeck, Matthias and Schmidt, Ottfried and Schwanzer, Peter and Rabl, Hans-Peter and Sterner, Michael and Bauer, Franz and Steinmann, Sven and Eckert, Fabian and Hofrichter, Andreas}, title = {Forschungsbericht 2017}, editor = {Baier, Wolfgang}, address = {Regensburg}, organization = {Ostbayerische Technische Hochschule Regensburg}, isbn = {978-3-9818209-3-5}, doi = {10.35096/othr/pub-1383}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-13835}, subject = {Forschung}, language = {de} } @unpublished{MeisingerHofrichterBaueretal., author = {Meisinger, Alexander and Hofrichter, Andreas and Bauer, Franz and Sterner, Michael}, title = {Unlocking Potential Energy Partnerships in Europe: a Case Study on the Way to a Franco-German Energy Transition}, publisher = {SSRN}, doi = {10.2139/ssrn.5251699}, pages = {23}, abstract = {Global warming is already causing global destabilization. Geopolitical challenges fuel this instability and highlight the need for trusted energy partnerships to ensure energy security. To limit global warming and increase energy security, it is essential to take joint action on an international and global scale. The European Green Deal contributes to this. However, specific national actions are still needed. This research presents a way forward for a Franco-German energy transition and unlocks the potential of energy partnerships within Europe, using a cost-based, sector-coupled optimization model. Both countries are coupled via an isolated country optimization approach. Thus, the focus is on the development of each national energy system. The results highlight the increase of energy security in line with the European Green Deal. The main pillars of the energy transition are solar energy (32- 33\%), wind energy (25-38\%) and biogenic energy sources (13-27\%). Nuclear power is being phased out in Germany and France. The results show that a Franco-German energy partnership has great potential. Overall, France can cost-effectively cover 25\% of Germany's hydrogen import needs (122 TWh) in 2050. At the same time, France can also benefit from the energy partnership in terms of economic growth and joint action to mitigate climate crisis.}, language = {en} } @article{SternerGerhardtSaintDrenanetal.2010, author = {Sterner, Michael and Gerhardt, Norman and Saint-Drenan, Y. M. and Specht, M. and St{\"u}rmer, B. and Zuberb{\"u}hler, U.}, title = {Erneuerbares Methan - Eine L{\"o}sung zur Integration und Speicherung Erneuerbarer Energien und ein Weg zur regenerativen Vollversorgung}, series = {Solarzeitalter}, journal = {Solarzeitalter}, number = {1}, publisher = {Eurosolar}, organization = {Eurosolar}, issn = {0937-3802}, year = {2010}, language = {de} } @misc{SternerSchumm, author = {Sterner, Michael and Schumm, Leon}, title = {Netzpuffer - Speicher \& Kraftwerke als virtuelle Leitungen f{\"u}r mehr Versorgungssicherheit und EE-Integration in Nord und S{\"u}d}, series = {7. Smart-Grid-Fachtagung WAGO, Hannover, 29. Sept. 2021}, journal = {7. Smart-Grid-Fachtagung WAGO, Hannover, 29. Sept. 2021}, language = {de} } @techreport{SternerSchummRanketal., author = {Sterner, Michael and Schumm, Leon and Rank, Daniel and Hofrichter, Andreas}, title = {Intelligente Netzpuffer : Abschlussbericht (24.01.2021)}, language = {de} } @unpublished{SchummAbdelKhalekBrownetal., author = {Schumm, Leon and Abdel-Khalek, Hazem and Brown, Tom and Ueckerdt, Falko and Sterner, Michael and Fioriti, Davide and Parzen, Max}, title = {The impact of temporal hydrogen regulation on hydrogen exporters and their domestic energy transition}, publisher = {Research Square Platform LLC}, doi = {10.21203/rs.3.rs-4285425/v1}, abstract = {As global demand for green hydrogen rises, potential hydrogen exporters move into the spotlight. However, the large-scale installation of on-grid hydrogen electrolysis for export can have profound impacts on domestic energy prices and energy-related emissions. Our investigation explores the interplay of hydrogen exports, domestic energy transition and temporal hydrogen regulation, employing a sector-coupled energy model in Morocco. We find substantial co-benets of domestic climate change mitigation and hydrogen exports, whereby exports can reduce domestic electricity prices while mitigation reduces hydrogen export prices. However, increasing hydrogen exports quickly in a system that is still dominated by fossil fuels can substantially raise domestic electricity prices, if green hydrogen production is not regulated. Surprisingly, temporal matching of hydrogen production lowers domestic electricity cost by up to 31\% while the effect on exporters is minimal. This policy instrument can steer the welfare (re-)distribution between hydrogen exporting firms, hydrogen importers, and domestic electricity consumers and hereby increases acceptance among actors.}, language = {en} } @article{SchummBrownAbdelKhaleketal., author = {Schumm, Leon and Brown, Tom and Abdel-Khalek, Hazem and Ueckerdt, Falko and Sterner, Michael and Fioriti, David and Parzen, Max}, title = {The impact of temporal hydrogen regulation on hydrogen exporters and their domestic energy transition}, series = {Nature Communications}, volume = {16}, journal = {Nature Communications}, publisher = {Nature}, address = {London}, doi = {10.1038/s41467-025-62873-w}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-84857}, pages = {13}, abstract = {As global demand for green hydrogen rises, potential hydrogen exporters move into the spotlight. While exports can bring countries revenue, large-scale on-grid hydrogen electrolysis for export can profoundly impact domestic energy prices and energy-related emissions. Our investigation explores the interplay of hydrogen exports, domestic energy transition and temporal hydrogen regulation, employing a sector-coupled energy model in Morocco. We find substantial co-benefits of domestic carbon dioxide mitigation and hydrogen exports, whereby exports can reduce market-based costs for domestic electricity consumers while mitigation reduces costs for hydrogen exporters. However, increasing hydrogen exports in a fossil-dominated system can substantially raise market-based costs for domestic electricity consumers, but surprisingly, temporal matching of hydrogen production can lower these costs by up to 31\% with minimal impact on exporters. Here, we show that this policy instrument can steer the welfare (re-)distribution between hydrogen exporting firms, hydrogen importers, and domestic electricity consumers and hereby increases acceptance among actors.}, language = {en} } @inproceedings{SchamelAchhammerSchummetal., author = {Schamel, Marco and Achhammer, Anton and Schumm, Leon and Sterner, Michael}, title = {Harvesting Sustainability: Cost-competitiveness of Green Fertilizer Value Chains in Western Africa}, series = {Proceedings of the 2025 IEEE PES/IAS PowerAfrica Conference (PAC 2025): pioneering sustainable energy solutions for Africa's Future, 28.09-02.10 2025, Cairo, Egypt}, booktitle = {Proceedings of the 2025 IEEE PES/IAS PowerAfrica Conference (PAC 2025): pioneering sustainable energy solutions for Africa's Future, 28.09-02.10 2025, Cairo, Egypt}, publisher = {IEEE}, isbn = {979-8-3315-9850-1}, doi = {10.1109/PowerAfrica65840.2025.11289137}, pages = {6}, abstract = {The use of nitrogen fertilizers in Sub-Saharan Africa is low compared to other regions of the world, leading to inadequate crop yields. Furthermore, conventional production from fossil fuel-based ammonia is highly emissions-intensive, making decarbonization urgent. Local production using green hydrogen, sourced solely from solar energy, water, and air, could address both agricultural and climate challenges. This study focuses on Ghana, where nitrogen inputs are among the lowest globally. Using an open-source framework, we evaluate high-resolution production costs for sustainable ammonia and examine two decarbonized pathways: aqueous ammonia and urea. It is found that cost estimates with current assumptions mostly exceed historical prices. However, given their resilience to global market disruptions and expected future cost decreases of the technologies used, these sustainable approaches represent a promising pathway for development in Sub-Saharan Africa.}, language = {en} } @article{SchummHaasPeeretal., author = {Schumm, Leon and Haas, Jannik and Peer, Rebecca and Sterner, Michael}, title = {The role of hydrogen offtaker regulation in highly renewable electricity systems}, series = {Energy}, volume = {342}, journal = {Energy}, publisher = {Elsevier}, doi = {10.1016/j.energy.2025.139513}, pages = {13}, abstract = {The growing demand for green hydrogen necessitates a rapid scale-up of production and exports to meet decarbonization targets globally. However, current ramp-up efforts remain insufficient, calling for policies that unlock the potential of hydrogen as a low-carbon energy carrier. A key lever is the offtaker regulation, which impacts the pace and sustainability of export projects. This study investigates minimum renewable share requirements for hydrogen exports in countries with high renewable electricity shares. Using New Zealand as a case study, we develop a fully sector-coupled capacity expansion and dispatch model, integrating hydrogen and electricity network planning based on PyPSA-Earth. The model optimizes New Zealand's energy system under varying export scenarios, renewable electricity shares, and resulting system impacts. We find that domestic electricity demand and renewable expansion rates dominate long-term outcomes, while progressive regulation enables short-term hydrogen and Power-to-X exports. Relaxing the renewable threshold from 80\% to 60\% triples export volumes from 2.5 TWh to 8.2 TWh by 2030. We propose a two-stage requirement: an initially progressive threshold to attract investment with low consequential emissions, followed by stricter regulation to prevent high emissions, rising domestic electricity prices, and declining hydrogen competitiveness. This framework, demonstrated for New Zealand, can guide hydrogen-exporting countries worldwide.}, language = {en} } @inproceedings{UhlSchamelAchhammeretal., author = {Uhl, Julius and Schamel, Marco and Achhammer, Anton and Sterner, Michael}, title = {Sustainable Steel Production in the Desert: Economic and Technical Assessment of a Hydrogen-Powered Steel Plant in Mauritania}, series = {2025 IEEE PES/IAS PowerAfrica, 28 September - 02 October 2025, Cairo}, booktitle = {2025 IEEE PES/IAS PowerAfrica, 28 September - 02 October 2025, Cairo}, publisher = {IEEE}, doi = {10.1109/PowerAfrica65840.2025.11289120}, pages = {6}, abstract = {The global steel industry is a major contributor to climate change and faces challenges in achieving a carbon-neutral production, hinging on the availability of cost-effective hydrogen produced by renewable energy. Mauritania, with its exceptional solar and wind resources, offers some of the most competitive conditions globally for hydrogen production. Instead of focusing on hydrogen exports, this study explores the technical feasibility and economic viability of establishing a renewable-powered steel plant in Mauritania, utilizing the country's abundant iron ore reserves. The findings suggest that sustainably produced steel in Mauritania could be cost-competitive with current European prices. With ongoing declines in investment costs for emerging renewable technologies, Mauritania has the potential to become one of the world's most cost-effective steel producers.}, language = {en} } @incollection{Sterner, author = {Sterner, Michael}, title = {WBGU Gutachten - zukunftsf{\"a}hige Bioenergie und nachhaltige Landnutzung}, series = {Biomasse \& Abfall : Emissionen mindern und R{\"u}ckst{\"a}nde nutzen (Verfahren \& Werkstoffe f{\"u}r die Energietechnik ; 5)}, booktitle = {Biomasse \& Abfall : Emissionen mindern und R{\"u}ckst{\"a}nde nutzen (Verfahren \& Werkstoffe f{\"u}r die Energietechnik ; 5)}, editor = {Faulstich, Martin and Mocker, Mario}, publisher = {Dorner Printconcept}, address = {Sulzbach-Rosenberg}, isbn = {9783981039146}, pages = {23 -- 28}, language = {de} } @unpublished{AchhammerFioritiPatoniaetal., author = {Achhammer, Anton and Fioriti, Davide and Patonia, Aliaksei and Sterner, Michael}, title = {The impact of hydrogen underground storage on fair partnerships: a GIS-based integration of salt caverns into PyPSA-Earth}, publisher = {SSRN}, doi = {10.2139/ssrn.6307406}, pages = {22}, abstract = {The increasing demand for hydrogen in Europe and the development of cross-border infrastructure, such as the SoutH2 Corridorconnecting Tunisia, Italy, Austria, and Germany, underscore the importance for hydrogen storage solutions to ensure supplysecurity and competitive pricing. Without storage, producers face increased market dependency, as electrolyzers require con-tinuous operation to remain economically viable. At the same time, storage offers opportunities to strengthen domestic valuechains by securing hydrogen supply for local industries. To assess the system-level impact of underground hydrogen storageand its implications for hydrogen partnerships, we integrate GIS-based salt cavern potentials into PyPSA-Earth and apply theframework to Tunisia. Salt caverns are currently largely considered the most economical option for large-scale hydrogen storage,offering operational flexibility. Underground storage is represented as an endogenously optimised, regionally constrained option,enabling a direct comparison between scenarios with and without geological storage under identical demand, technology, andpolicy assumptions.Our results show that underground hydrogen storage enables seasonal balancing at multi-terawatt-hour scale, reshaping hydro-gen system design. Storage availability substitutes most aboveground hydrogen tank capacity, improves electrolyser utilisation,and reduces levelised hydrogen production costs by approximately 0.10 € kg-1. Moreover, it decouples hydrogen production fromshort-term electricity variability and export demand, enhancing supply stability and export competitiveness.Beyond the Tunisian case, the findings underscore the strategic role of geological storage in international hydrogen trade. Byincreasing resilience and reducing cost volatility, underground hydrogen storage strengthens the position of exporting regionsand supports more balanced and sustainable hydrogen partnerships.}, language = {en} }