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• Egeland-Eriksen, Torbjørn & Sartori, Sabrina (2024). Techno-economic analysis of the effect of a novel price-based control system on the hydrogen production for an offshore 1.5 GW wind-hydrogen system. Energy Reports. 11, s. 2633–2655. doi: 10.1016/j.egyr.2024.02.016. Fulltekst i vitenarkiv Vis sammendrag

  The cost of green hydrogen production is very dependent on the price of electricity. A control system that can schedule hydrogen production based on forecast wind speed and electricity price should therefore be advantageous for large-scale wind-hydrogen systems. This work presents a novel price-based control system integrated in a techno-economic analysis of hydrogen production from offshore wind. A polynomial regression model that predicts wind power production from wind speed input was developed and tested with real-world datasets from a 2.3 MW floating offshore wind turbine. This was combined with a mathematical model of a PEM electrolyzer and used to simulate hydrogen production. A novel price-based control system was developed to decide when the system should produce hydrogen and when it should sell electricity to the grid. The model and control system can be used in real-world wind-hydrogen systems and require only the forecast wind speed, electricity price and selling price of hydrogen as inputs. 11 test scenarios based on 10 years of real-world wind speed and electricity price data are proposed and used to evaluate the effect the price-based control system has on the levelized cost of hydrogen (LCOH). Both current and future (2050) costs and technologies are used, and the results show that the novel control system lowered the LCOH in all scenarios by 10-46%. The lowest LCOH achieved with current technology and costs was 6.04 $/kg H2. Using the most optimistic forecasts for technology improvements and cost reductions in 2050, the model estimated a LCOH of 0.96 $/kg H2 for a grid-connected offshore wind farm and onshore hydrogen production, 0.82 $/kg H2 using grid electricity (onshore) and 4.96 $/kg H2 with an off-grid offshore wind-hydrogen system. When the electricity price from the period 2013-2022 was used on the 2050 scenarios, the resulting LCOH was approximately twice as high.

• Oosterkamp, Antonie & Egeland-Eriksen, Torbjørn (2024). Flow assurance of offshore hydrogen pipelines - a review, Proceedings of the Thirty-fourth (2024) International Ocean and Polar Engineering Conference - ISOPE 2024. International Society of Offshore and Polar Engineers. ISSN 9781880653784. s. 4360–4367. Fulltekst i vitenarkiv Vis sammendrag

  This paper reviews some of the specific issues of flow assurance in the design and operation of large-scale offshore pipeline transport of hydrogen. An estimated thirty thousand km of hydrogen pipelines are planned in the next ten years. The effect of the different fluid properties compared to natural gas, especially the effect of transport properties and speed of sound on fluid behavior inside the pipeline under dynamic operation were studied. Case studies of dynamic behavior of hydrogen and natural gas pipelines were modelled and compared within the context of offshore export pipelines. The results show both the similarities and differences for both fluids with respect to pipeline capacity, flow conditions and response to flow transients

• Egeland-Eriksen, Torbjørn & Oosterkamp, Antonie (2024). Electricity transport vs. hydrogen production from future offshore wind farms, Proceedings of the Thirty-fourth (2024) International Ocean and Polar Engineering Conference - ISOPE 2024. International Society of Offshore and Polar Engineers. ISSN 9781880653784. s. 4353–4359. Fulltekst i vitenarkiv
• Egeland-Eriksen, Torbjørn; Jensen, Jonas Flatgård; Ulleberg, Øystein & Sartori, Sabrina (2023). Simulating offshore hydrogen production via PEM electrolysis using real power production data from a 2.3 MW floating offshore wind turbine. International Journal of Hydrogen Energy. ISSN 0360-3199. 48(74), s. 28712–28732. doi: 10.1016/j.ijhydene.2023.03.471. Fulltekst i vitenarkiv Vis sammendrag

  This work presents simulation results from a system where offshore wind power is used to produce hydrogen via electrolysis. Real-world data from a 2.3 MW floating offshore wind turbine and electricity price data from Nord Pool were used as input to a novel electrolyzer model. Data from five 31-day periods were combined with six system designs, and hydrogen production, system efficiency, and production cost were estimated. A comparison of the overall system performance shows that the hydrogen production and cost can vary by up to a factor of three between the cases. This illustrates the uncertainty related to the hydrogen production and profitability of these systems. The highest hydrogen production achieved in a 31-day period was 17 242 kg using a 1.852 MW electrolyzer (i.e., utilization factor of approximately 68%), the lowest hydrogen production cost was 4.53 $/kg H2, and the system efficiency was in the range 56.1–56.9% in all cases.

• Hajizadeh, Amin; Sartori, Sabrina & Egeland-Eriksen, Torbjørn (2021). Hydrogen-based systems for integration of renewable energy in power systems: Achievements and perspectives. International Journal of Hydrogen Energy. ISSN 0360-3199. 46, s. 31963–31983. doi: 10.1016/j.ijhydene.2021.06.218. Fulltekst i vitenarkiv Vis sammendrag

  This paper is a critical review of selected real-world energy storage systems based on hydrogen, ranging from lab-scale systems to full-scale systems in continuous operation. 15 projects are presented with a critical overview of their concept and performance. A review of research related to power electronics, control systems and energy management strategies has been added to integrate the findings with outlooks usually described in separate literature. Results show that while hydrogen energy storage systems are technically feasible, they still require large cost reductions to become commercially attractive. A challenge that affects the cost per unit of energy is the low energy efficiency of some of the system components in real-world operating conditions. Due to losses in the conversion and storage processes, hydrogen energy storage systems lose anywhere between 60 and 85% of the incoming electricity with current technology. However, there are currently very few alternatives for long-term storage of electricity in power systems so the interest in hydrogen for this application remains high from both industry and academia. Additionally, it is expected that the share of intermittent renewable energy in power systems will increase in the coming decades. This could lead to technology development and cost reductions within hydrogen technology if this technology is needed to store excess renewable energy. Results from the reviewed projects indicate that the best solution from a technical viewpoint consists in hybrid systems where hydrogen is combined with shortterm energy storage technologies like batteries and supercapacitors. In these hybrid systems the advantages with each storage technology can be fully exploited to maximize efficiency if the system is specifically tailored to the given situation. The disadvantage is that this will obviously increase the complexity and total cost of the energy system. Therefore, control systems and energy management strategies are important factors to achieve optimal results, both in terms of efficiency and cost. By considering the reviewed projects and evaluating operation modes and control systems, new hybrid energy systems could be tailored to fit each situation and to reduce energy losses.

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• Oosterkamp, Antonie & Egeland-Eriksen, Torbjørn (2023). State of the art for transport systems for hydrogen-based energy carriers. Internal Report. Fulltekst i vitenarkiv Vis sammendrag

  This report is a review of the state of the art within transport systems for hydrogen, either as pure hydrogen or as a component of a hydrogen carrier. The various transport methods, including transport by truck, pipeline or ship in the form of pure hydrogen or in a hydrogen carrier, are described. More than 50 scientific articles and technical reports published in the last five years are then reviewed, and the results and conclusions from these are summarized and discussed.

• Vestrheim, Magnus; Oltedal, Velaug Myrseth; Egeland-Eriksen, Torbjørn & Fernø, Martin (2022). Offshore hydrogen production from floating offshore wind - a study of UNITECH Zefyros. Universitetet i Bergen. Fulltekst i vitenarkiv Vis sammendrag

  The aim of this thesis is to review design considerations and study the effect of a variable power supply of offshore hydrogen production by an electrolyser inside the turbine tower of a floating offshore wind turbine. To achieve this, UNITECH Zefyros, previously known as Hywind Demo, the world’s first floating offshore wind turbine, has been studied for the possibility of hydrogen production. Historical 2020 wind and power data collected by Zefyros are used for calculations in the thesis. The thesis is divided into two cases, shown below. • Case 1 An in-turbine electrolyser to show the feasibility of hydrogen production at UNITECH Zefyros. • Case 2 A large-scale hydrogen production system to study the effect of an intermittent power supply from wind power on an electrolyser. The chosen electrolyser must comply with the space constraints in the turbine tower, resulting in a low-rated electrolyser, less than 1 % of the turbine’s rated power. Hence, the electrolyser will operate at its rated load if the turbine generates power and cannot be used to study how variable power influences the electrolyser. A second hydrogen production system is thus proposed, where the constraints regarding space inside the turbine tower are not considered. This facilitates for an electrolyser that can use all available energy from Zefyros for hydrogen production, making the load profile dynamic. For case 1, an in-turbine hydrogen production system is proposed, where the components are reviewed for compatibility in an offshore environment. Safety considerations introduced by in-turbine hydrogen production are identified. Zefyros’ responses to 1- and 10-year seas are estimated to identify what displacement and accelerations an in-turbine electrolyser would experience. The annual hydrogen yield in 2020 from the in-turbine electrolyser is estimated. For case 2, a model is developed in which the electrolyser’s energy efficiency is estimated through the cell voltage. The energy efficiencies throughout 2020 and the annual hydrogen yield are estimated to show the effect a variable power source has on an electrolyser.

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