Production & Supply Chain

This research models a 20 MW PEM hydrogen plant. PEM units operate in the 60 to 80 ◦C range based on their location and size. This study aims to recover the waste heat from PEM modules to enhance the efficiency of the plant. In order to recover the heat two systems are implemented: (a) recovering the waste heat from each PEM module; (b) recovering the heat from hot water to produce electricity utilizing an organic refrigerant cycle (ORC). The model is made by ASPEN® V14. After modeling the plant and utilizing the ORC the module is optimized using Python to maximize the electricity produced by the turbine therefore enhancing the efficiency. The system is a closed-loop cycle operating at 25 ◦C and ambient pressure. The 20 MW PEM electrolyzer plant produces 363 kg/hr of hydrogen and 2877 kg/hr of oxygen. Based on the higher heating value of hydrogen the plant produces 14302.2 kWh of hydrogen energy equivalents. The ORC is maximized by increasing the electricity output from the turbine and reducing the pump work while maintaining energy conservation and mass balance. The results show that the electricity power output reaches 555.88 kW and the pump power reaches 23.47 kW.

In an effort to bridge the gap between academic research and industrial application this study investigates the integration potential of steam methane reforming and Co-electrolysis for the efficient conversion of refinery offgases into high-purity syngas. Experimental work was conducted under conditions representative of industrial environments using platinum- and nickel-based catalysts in steam reforming to assess methane conversion and H2 /CO ratio at varying temperatures and gas hourly space velocities (GHSV). Co-electrolysis was evaluated in solid oxide electrolysis cells (SOECs) across a range of gas compositions (H2O/CO2 /H2 /CO) including pure CO2 electrolysis as a strategy for pre-electrolysis hydrogen removal. Electrochemical performance was analyzed using impedance spectroscopy distribution of relaxation times (DRT) and current–voltage characterization. Results confirm the superior stability and performance of the Pt catalyst under high-throughput conditions while Ni-based systems were more sensitive to operational fluctuations. In the SOEC increased H2O content accelerated reaction kinetics whereas CO2 concentration governed polarization resistance. To enable optimal SOEC operation the addition of steam downstream of the reformer is proposed as a means of adjusting the reformate composition. The findings demonstrate that tuning reforming and electrolysis conditions in tandem offers a promising route for sustainable syngas production using renewable electricity. This work establishes a foundation for further development of integrated thermo-electrochemical systems tailored to industrial gas streams.

In this study the electrolysis of water by using ammonium chloride (NH4Cl) as an electrolyte was investigated for the production of hydrogen gas. The assembled electrochemical cell consists mainly of twenty-one stainless-steel electrodes and a direct current from a battery ammonium chloride solution. In the electrolysis process hydrogen and oxygen are developed at the same time and collected as a mixture to be used as a fuel. This study explores a technic regarding the matching of oxyhydrogen (HHO) electrolyzers with photovoltaic (PV) systems to make HHO gas. The primary objective of the present research is to enable the electrolyzer to operate independently of other energy origins functioning as a complete unit powered solely by PV. Moreover the impact of using PWM on cell operation was investigated. The experimental data was collected at various time intervals NH4Cl concentrations. Additionally the hydrogen unit consists of two cells with a shared positive pole fixed between them. Some undesirable anodic reaction affects the efficiency of hydrogen gas production because of the corrosion of anode to ferrous hydroxide (Fe(OH)2). Polyphosphate Inhibitor was used to minimize the corrosion reaction of anode and keep the efficiency of hydrogen gas flow. The optimal concentration of 3M for ammonium chloride was identified balancing a gas flow rate of 772 ml/min with minimal anode corrosion. Without PWM conversion efficiency ranges between 93% and 96%. Therefore PWM increased conversion efficiency by approximately 5% leading to a corresponding increase in hydrogen gas production.

Industrial alkaline water electrolysis systems face challenges in maintaining hydrogenin-oxygen impurity within safe limits under fluctuating operating conditions. This study aims to characterize the dynamic response of hydrogen-in-oxygen concentration in an industrial 10 kW alkaline water electrolysis test platform (2 Nm3/h hydrogen output at 1.6 MPa and 90 ◦C) and to identify how operating parameters influence hydrogen-inoxygen behavior. We systematically varied the cell current system pressure and electrolyte flow rate while monitoring real-time hydrogen-in-oxygen levels. The results show that hydrogen-in-oxygen exhibits significant inertia and delay: during startup hydrogen-inoxygen remained below the 2% safety threshold and stabilized at 0.9% at full load whereas a step decrease to 60% load caused hydrogen-in-oxygen to rise to 1.6%. Furthermore reducing the pressure from 1.4 to 1.0 MPa lowered the hydrogen-in-oxygen concentration by up to 15% and halving the alkaline flow rate suppressed hydrogen-in-oxygen by over 20% compared to constant conditions. These findings provide new quantitative insights into hydrogen-in-oxygen dynamics and offer a basis for optimizing control strategies to keep gas purity within safe limits in industrial-scale alkaline water electrolysis systems.

The coupling of renewable energy sources with electrolyzers under standalone conditions significantly enhances the operational efficiency and improves the costeffectiveness of electrolyzers as a technologically viable and sustainable solution for green hydrogen production. To address the configuration optimization challenge in hybrid electrolyzer systems integrating alkaline water electrolysis (AWE) and proton exchange membrane electrolysis (PEME) this study proposes an innovative methodology leveraging the morphological analysis of Pareto frontiers to determine the optimal solutions under multi-objective functions including the hydrogen production cost and efficiency. Then the complementary advantages of AWE and PEME are explored. The proposed methodology demonstrated significant performance improvements compared with the single-objective optimization function. When contrasted with the economic optimization function the hybrid system achieved a 1.00% reduction in hydrogen production costs while enhancing the utilization efficiency by 21.71%. Conversely relative to the efficiency-focused optimization function the proposed method maintained a marginal 5.22% reduction in utilization efficiency while achieving a 6.46% improvement in economic performance. These comparative results empirically validate that the proposed hybrid electrolyzer configuration through the implementation of the novel optimization framework successfully establishes an optimal balance between the economy and efficiency of hydrogen production. Additionally a discussion on the key factors affecting the rated power and mixing ratio of the hybrid electrolyzer in this research topic is provided.

Hydrogen production via water electrolysis and renewable electricity is expected to play a pivotal role as an energy carrier in the energy transition. This fuel emerges as the most environmentally sustainable energy vector for non-electric applications and is devoid of CO2 emissions. However an electrolyzer´s infrastructure relies on scarce and energyintensive metals such as platinum palladium iridium (PGM) silicon rare earth elements and silver. Under this context this paper explores the exergy cost i.e. the exergy destroyed to obtain one kW of hydrogen. We disaggregated it into non-renewable and renewable contributions to assess its renewability. We analyzed four types of electrolyzers alkaline water electrolysis (AWE) proton exchange membrane (PEM) solid oxide electrolysis cells (SOEC) and anion exchange membrane (AEM) in several exergy cost electricity scenarios based on different technologies namely hydro (HYD) wind (WIND) and solar photovoltaic (PV) as well as the different International Energy Agency projections up to 2050. Electricity sources account for the largest share of the exergy cost. Between 2025 and 2050 for each kW of hydrogen generated between 1.38 and 1.22 kW will be required for the SOEC-hydro combination while between 2.9 and 1.4 kW will be required for the PV-PEM combination. A Grassmann diagram describes how non-renewable and renewable exergy costs are split up between all processes. Although the hybridization between renewables and the electricity grid allows for stable hydrogen production there are higher non-renewable exergy costs from fossil fuel contributions to the grid. This paper highlights the importance of nonrenewable exergy cost in infrastructure which is required for hydrogen production via electrolysis and the necessity for cleaner production methods and material recycling to increase the renewability of this crucial fuel in the energy transition.

As a result of international agreements on the reduction of CO2 emissions new technologies using hydrogen are being developed. Hydrogen despite being the most abundant element in Nature cannot be found in its pure state. Water is one of the most abundant sources of hydrogen on the planet. The proposal here is to use energy from the sea in order to obtain hydrogen from water. If plants to obtain hydrogen were to be placed in the ocean the impact of long submarines piping to the coast will be reduced. Further this will open the way for the development of ships propelled by hydrogen. This paper discusses the feasibility of an offshore installation to obtain hydrogen from the sea using ocean wave energy.

Today hydrogen (H2) is overwhelmingly produced through steam methane reforming (SMR) of natural gas which emits about 12 kg of carbon dioxide (CO2) for 1 kg of H2 (∼12 kg-CO2/kg-H2). Water electrolysis offers an alternative for H2 production but today’s electrolyzers consume over 55 kWh of electricity for 1 kg of H2 (>55 kWh/kg-H2). Electric grid-powered water electrolysis would emit less CO2 than the SMR process when the carbon intensity for grid power falls below 0.22 kg-CO2/kWh. Solar- and wind-powered electrolytic H2 production promises over 80% CO2 reduction over the SMR process but large-scale (megawatt to gigawatt) direct solar- or wind-powered water electrolysis has yet to be demonstrated. In this paper several approaches for solar-powered electrolysis are analyzed: (1) coupling a photovoltaic (PV) array with an electrolyzer through alternating current; (2) direct-current (DC) to DC coupling; and (3) direct DC-DC coupling without a power converter. Co-locating a solar or wind farm with an electrolyzer provides a lower power loss and a lower upfront system cost than long-distance power transmission. A load-matching PV system for water electrolysis enables a 10%–50% lower levelized cost of electricity than the other systems and excellent scalability from a few kilowatts to a gigawatt. The concept of maximum current point tracking is introduced in place of maximum power point tracking to maximize the H2 output by solarpowered electrolysis.

This study investigates the potential for establishing a self-sufficient renewable hydrogen production facility utilising a floating photovoltaic (FPV) system on an artificial irrigation reservoir located in a small municipality in southern Italy. The analysis examines the impact of different system configurations and operating conditions on the technical economic and environmental performance with a particular focus on hydrogen production and water conservation resulting from reduced evaporation. Different sizes of the FPV plant are considered with and without a tracking system. The electrolyser performance is evaluated under both fixed and variable load conditions also considering the integration of battery storage to ensure consistent operation. The findings indicate that the adoption of the largest FPV plant can result in the conservation of approximately 1.87 million m3 of water annually while simultaneously producing up to 4199 tons of hydrogen per year in variable load mode—more than twice the output compared to fixed load conditions. Although battery integration increases hydrogen production it also leads to higher investment and maintenance costs. Therefore the variable load operation emerges as the most economically viable option reducing the levelized cost of hydrogen (LCOH) to €13.18/kg a 26 % reduction compared to fixed load operation. Moreover the implementation of a vertical axis tracking system leads to only marginal LCOH reductions (maximum 2.2 %) and does not justify the additional complexity. In all tested scenarios the system proves to be self-sustaining. Given the case study’s location in southern Italy—where a pilot project for fuel cell–battery hybrid trains is underway—the hydrogen produced is assumed to be used for railway applications as a possible offtaker. The analysis shows that the potential of the system in terms of hydrogen production is much higher (tens of times) than the estimated demand of the present hydrogen railway configuration thus suggesting that a significant expansion of the number of trains and routes served could be considered. Although this work is based on a specific case study its key findings are potentially replicable in other contexts—particularly in Mediterranean or semi-arid regions where water scarcity may otherwise act as a limiting factor for the deployment of hydrogen production systems.

The applications and need for large-scale long-duration electrical energy storage are growing as both the share of renewable energy in energy systems and the demand for flexibility increase. One potential application is the renewable hydrogen industry where temporal matching of renewable electricity generation and hydrogen production will be required in the future according to the new European Union regulations. In this paper a case study of electrical energy storage utilization in hydrogen production is conducted in the Nordic context with a high share of wind production. The storage is used in the hydrogen production process for temporal matching. The levelized cost of storage of three medium- to long-term storage technologies is assessed using an Excel-based model with four case approaches. In the first case approach the electrolyzer load is inflexible while the other approaches explore how the flexibility of the electrolyzer and the increase in renewable production capacity affect the size and cost of the storage. Electro-thermal energy storage based on sand as storage material presented the lowest levelized cost of storage (114-198 €/MWh) due to its low energy-related investment cost. However the results show that additional usage purposes for all examined storage technologies are required to avoid high investment costs. Additionally flexibility from the electrolyzer load and over-investing in renewable capacity is required. In conclusion storage should not be the only component providing flexibility in the studied system and it should be used to integrate multiple assets in the wider energy system to reach cost-effectiveness. This paper brings novelty by expanding on the storage technology options considered in previous literature and deepening the perspective of storage as a component in renewable hydrogen production. Future research should assess the effect of electricity prices and emissions allowance prices from the regulatory perspective which could further reduce the storage investment.