Production & Supply Chain

Ammonia is an industrial chemical and the basic building block for the fertilizer industry. Lately attention has shifted towards using ammonia as a carbon-free energy vector due to the ease of transportation and storage in liquid state at − 33 ◦C and atmospheric pressure. This study evaluates the prospects of blue and green ammonia as future energy carriers; specifically the gas switching reforming (GSR) concept for H2 and N2 co-production from natural gas with inherent CO2 capture (blue) and H2 generation through an optimized value chain of wind and solar power electrolysers cryogenic N2 supply and various options for energy storage (green). These longer term concepts are benchmarked against conventional technologies integrating CO2 capture: the Kellogg Braun & Root (KBR) Purifier process and the Linde Ammonia Concept (LAC). All modelled plants utilize the same ammonia synthesis loop for a consistent comparison. A cash flow analysis showed that the GSR concept achieved an attractive levelized cost of ammonia (LCOA) of 332.1 €/ton relative to 385.1–385.9 €/ton for the conventional plants at European energy prices (6.5 €/GJ natural gas and 60 €/MWh electricity). Optimal technology integration for green ammonia using technology costs representative of 2050 was considerably more expensive: 484.7–772.1 €/ton when varying the location from Saudi Arabia to Germany. Furthermore the LCOA of the GSR technology drops to 192.7 €/ton when benefitting from low Saudi Arabian energy costs (2 €/GJ natural gas and 40 €/MWh electricity). This cost difference between green and blue ammonia remained robust in sensitivity analyses where input energy cost (natural gas or wind/solar power) was the most influential parameter. Given its low production costs and the techno-economic feasibility of international ammonia trade advanced blue ammonia production from GSR offers an attractive pathway for natural gas exporting regions to contribute to global decarbonization.

Green hydrogen—a carbon-free renewable fuel—has the capability to decarbonise a variety of sectors. The generation of green hydrogen is currently restricted to water electrolysers. The use of freshwater resources and critical raw materials however limits their use. Alternative water splitting methods for green hydrogen generation via photocatalysis and photoelectrocatalysis (PEC) have been explored in the past few decades; however their commercial potential still remains unexploited due to the high hydrogen generation costs. Novel PEC-based simultaneous generation of green hydrogen and wastewater treatment/high-value product production is therefore seen as an alternative to conventional water splitting. Interestingly the organic/inorganic pollutants in wastewater and biomass favourably act as electron donors and facilitate the dual-functional process of recovering green hydrogen while oxidising the organic matter. The generation of green hydrogen through the dual-functional PEC process opens up opportunities for a “circular economy”. It further enables the end-of-life commodities to be reused recycled and resourced for a better life-cycle design while being economically viable for commercialisation. This review brings together and critically analyses the recent trends towards simultaneous wastewater treatment/biomass reforming while generating hydrogen gas by employing the PEC technology. We have briefly discussed the technical challenges associated with the tandem PEC process new avenues techno-economic feasibility and future directions towards achieving net neutrality.

This review article deals with the challenge to identify catalyst materials from literature studies for the ammonia decomposition reaction with potential for application in large-scale industrial processes. On the one hand the requirements on the catalyst are quite demanding. Of central importance are the conditions for the primary reaction that have to be met by the catalyst. Likewise the catalytic performance i.e. an ideally quantitative conversion and a high lifetime are critical as well as the consideration of requirements on the product properties in terms of pressure or by-products for potential follow-up processes in this case synthesis gas applications. On the other hand the evaluation of the multitude of literature studies poses difficulties due to significant varieties in catalytic testing protocols.

On this episode of Everything About Hydrogen we are speaking with David Wellard Regulatory Affairs Manager at Orsted. Orsted is a global leader in renewable energy generation projects particularly when it comes to the rapidly expanding wind energy sector. Headquartered in Denmark the company has a global reach across multiple continents and technologies. David helps lead Orsted’s policy and regulatory engagement in the United Kingdom and beyond.  We are excited to have him with us to discuss how Orsted is looking at and deploying hydrogen technologies and how they expect to utilized hydrogen in a decarbonized energy future.

The podcast can be found on their website.

Much has been learned about natural hydrogen (H2) seepages and accumulation but present knowledge of hydrogen behavior in the crust is so limited that it is not yet possible to consider exploitation of this resources. Hydrogen targeting requires a shift in the long-standing paradigms that drive oil and gas exploration. This paper describes the foundation of an integrated source-to-sink view of the hydrogen cycle and propose preliminary practical guidelines for hydrogen exploration.

H2 is clean energy and an important component of natural gas. Moreover it plays an irreplaceable role in improving the hydrocarbon generation rate of organic matter and activating ancient source rocks to generate hydrocarbon in Fischer-Tropsch (FT) synthesis and catalytic hydrogenation. Compared with hydrocarbon reservoir system a complete hydrogen (H2) accumulation system consists of H2 source，reservoirs and seal. In nature the four main sources of H2 are hydrolysis organic matter degradation the decomposition of substances such as methane and ammonia and deep mantle degassing. Because the complex tectonic activities the H2 produced in a geological environment is generally a mixture of various sources. Compared with the genetic mechanisms of H2 the migration and preservation of H2 especially the H2 trapping are rarely studied. A necessary condition for large-scale H2 accumulation is that the speed of H2 charge is much faster than diffusion loss. Dense cap rock and continuous H2 supply are favorable for H2 accumulation. Moreover H2O in the cap rock pores may provide favorable conditions for short-term H2 accumulation.

In Poland hydrogen production should be carried out using renewable energy sources particularly wind energy (as this is the most efficient zero-emission technology available). According to hydrogen demand in Poland and to ensure stability as well as security of energy supply and also the realization of energy policy for the EU it is necessary to use offshore wind energy for direct hydrogen production. In this study a centralized offshore hydrogen production system in the Baltic Sea area was presented. The goal of our research was to explore the possibility of producing hydrogen using offshore wind energy. After analyzing wind conditions and calculating the capacity of the proposed wind farm a 600 MW offshore hydrogen platform was designed along with a pipeline to transport hydrogen to onshore storage facilities. Taking into account Poland’s Baltic Sea area wind conditions with capacity factor between 45 and 50% and having obtained results with highest monthly average output of 3508.85 t of hydrogen it should be assumed that green hydrogen production will reach profitability most quickly with electricity from offshore wind farms.

Alkaline electrolyzers are the most widespread technology due to their maturity low cost and large capacity in generating hydrogen. However compared to proton exchange membrane (PEM) electrolyzers they request the use of potassium hydroxide (KOH) or sodium hydroxide (NaOH) since the electrolyte relies on a liquid solution. For this reason the performances of alkaline electrolyzers are governed by the electrolyte concentration and operating temperature. Due to the growing development of the water electrolysis process based on alkaline electrolyzers to generate green hydrogen from renewable energy sources the main purpose of this paper is to carry out a comprehensive survey on alkaline electrolyzers and more specifically about their electrical domain and specific electrolytic conductivity. Besides this survey will allow emphasizing the remaining key issues from the modeling point of view.

Green hydrogen is gaining increasing attention as a key component of the global energy transition towards a more sustainable industry. Chile with its vast renewable energy potential is well positioned to become a major producer and exporter of green hydrogen. In this context this paper explores the prospects for green hydrogen production and use in Chile. The perspectives presented in this study are primarily based on a compilation of government reports and data from the scientific literature which primarily offer a theoretical perspective on the efficiency and cost of hydrogen production. To address the need for experimental data an ongoing experimental project was initiated in March 2023. This project aims to assess the efficiency of hydrogen production and consumption in the Atacama Desert through the deployment of a mobile on-site laboratory for hydrogen generation. The facility is mainly composed by solar panels electrolyzers fuel cells and a battery bank and it moves through the Atacama Desert in Chile at different altitudes from the sea level to measure the efficiency of hydrogen generation through the energy approach. The challenges and opportunities in Chile for developing a robust green hydrogen economy are also analyzed. According to the results Chile has remarkable renewable energy resources particularly in solar and wind power that could be harnessed to produce green hydrogen. Chile has also established a supportive policy framework that promotes the development of renewable energy and the adoption of green hydrogen technologies. However there are challenges that need to be addressed such as the high capital costs of green hydrogen production and the need for supportive infrastructure. Despite these challenges we argue that Chile has the potential to become a leading producer and exporter of green hydrogen or derivatives such as ammonia or methanol. The country’s strategic location political stability and strong commitment to renewable energy provide a favorable environment for the development of a green hydrogen industry. The growing demand for clean energy and the increasing interest in decarbonization present significant opportunities for Chile to capitalize on its renewable energy resources and become a major player in the global green hydrogen market.

Green hydrogen produced by water electrolysis is one of the most promising technologies to realize the efficient utilization of intermittent renewable energy and the decarbonizing future. Among various electrolysis technologies the emerging anion-exchange membrane water electrolysis (AEMWE) shows the most potential for producing green hydrogen at a competitive price. In this review we demonstrate a comprehensive introduction to AEMWE including the advanced electrode design the lab-scaled testing system establishment and the electrochemical performance evaluation. Specifically recent progress in developing high activity transition metal-based powder electrocatalysts and self-supporting electrodes for AEMWE is summarized. To improve the synergistic transfer behaviors between electron charge water and gas inside the gas diffusion electrode (GDE) two optimizing strategies are concluded by regulating the pore structure and interfacial chemistry. Moreover we provide a detailed guideline for establishing the AEMWE testing system and selecting the electrolyzer components. The influences of the membrane electrode assembly (MEA) technologies and operation conditions on cell performance are also discussed. Besides diverse electrochemical methods to evaluate the activity and stability implement the failure analyses and realize the in-situ characterizations are elaborated. In end some perspectives about the optimization of interfacial environment and cost assessments have been proposed for the development of advanced and durable AEMWE.

The demand for green hydrogen as an energy carrier is projected to exceed 350 million tons per year by 2050 driven by the need for sustainable distribution and storage of energy generated from sources. Despite its potential hydrogen production currently faces challenges related to cost efficiency compliance monitoring and safety. This work proposes Hydrogen 4.0 a cyber–physical approach that leverages Industry 4.0 technologies—including smart sensing analytics and the Internet of Things (IoT)—to address these issues in hydrogen energy plants. Such an approach has the potential to enhance efficiency safety and compliance through real-time data analysis predictive maintenance and optimised resource allocation ultimately facilitating the adoption of renewable green hydrogen. The following sections break down conventional hydrogen plants into functional blocks and discusses how Industry 4.0 technologies can be applied to each segment. The components benefits and application scenarios of Hydrogen 4.0 are discussed while how digitalisation technologies can contribute to the successful integration of sustainable energy solutions in the global energy sector is also addressed.

The need to reduce the dependency of chemicals on fossil fuels has recently motivated the adoption of renewable energies in those sectors. In addition due to a growing population the treatment and disposition of residual biomass from agricultural processes such as sugar cane and orange bagasse or even from human waste such as sewage sludge will be a challenge for the next generation. These residual biomasses can be an attractive alternative for the production of environmentally friendly fuels and make the economy more circular and efficient. However these raw materials have been hitherto widely used as fuel for boilers or disposed of in sanitary landfills losing their capacity to generate other by-products in addition to contributing to the emissions of gases that promote global warming. For this reason this work analyzes and optimizes the biomass-based routes of biochemical production (namely hydrogen and ammonia) using the gasification of residual biomasses. Moreover the capture of biogenic CO2 aims to reduce the environmental burden leading to negative emissions in the overall energy system. In this context the chemical plants were designed modeled and simulated using Aspen plus™ software. The energy integration and optimization were performed using the OSMOSE Lua Platform. The exergy destruction exergy efficiency and general balance of the CO2 emissions were evaluated. As a result the irreversibility generated by the gasification unit has a relevant influence on the exergy efficiency of the entire plant. On the other hand an overall negative emission balance of −5.95 kgCO2/kgH2 in the hydrogen production route and −1.615 kgCO2/kgNH3 in the ammonia production route can be achieved thus removing from the atmosphere 0.901 tCO2/tbiomass and 1.096 tCO2/tbiomass respectively.

Based on the concept of sustainable development to promote the development and application of renewable energy and enhance the capacity of renewable energy consumption this paper studies the design and optimization of renewable energy hydrogen production systems. For this paper six different scenarios for grid-connected and off-grid renewable energy hydrogen production systems were designed and analyzed economically and technically and the optimal grid-connected and off-grid systems were selected. Subsequently the optimal system solution was optimized by analyzing the impact of the load data and component capacity on the grid dependency of the grid-connected hydrogen production system and the excess power rate of the off-grid hydrogen production system. Based on the simulation results the most matched load data and component capacity of different systems after optimization were determined. The grid-supplied power of the optimized grid-connected hydrogen production system decreased by 3347 kWh and the excess power rate of the off-grid hydrogen production system decreased from 38.6% to 10.3% resulting in a significant improvement in the technical and economic performance of the system.

Mitigation of carbon dioxide (CO2) emission has been a worldwide concern. Decreasing CO2 emission by converting it into higher value products such as methanol can be a promising way. However hydrogen (H2) cost and availability are one of key barriers to CO2 conversion. Ethanol can be a sustainable source for H2 due to its renewable nature and easy conversion to H2-rich gas mixtures through ethanol steam reforming process. Nevertheless steam reforming of ethanol generates CO2. Hence this research is focused on different methods of H2 productions about a 1665.47 t/y from ethanol for supplying to methanol plants was performed using Aspen PLUS V10. The ethanol steam reforming process required the lowest required ethanol feed for a certain amount of H2. In contrast the ethanol steam reforming process presented significant amount of CO2 emission from reaction and electricity consumption. But the ethanol dehydrogenation of ethanol not only generates H2 without CO2 emission from the reaction but also ethyl acetate or acetaldehyde which are value chemicals. However ethanol dehydrogenation processes in case II and III presented relatively higher cost because by-products (ethyl acetate or acetaldehyde) were rather difficult to be separated.

A huge amount of organic waste is generated annually around the globe. The main sources of solid and liquid organic waste are municipalities and canning and food industries. Most of it is disposed of in an environmentally unfriendly way since none of the modern recycling technologies can cope with such immense volumes of waste. Microbiological and biotechnological approaches are extremely promising for solving this environmental problem. Moreover organic waste can serve as the substrate to obtain alternative energy such as biohydrogen (H2 ) and biomethane (CH4 ). This work aimed to design and test new technology for the degradation of food waste coupled with biohydrogen and biomethane production as well as liquid organic leachate purification. The effective treatment of waste was achieved due to the application of the specific granular microbial preparation. Microbiological and physicochemical methods were used to measure the fermentation parameters. As a result a four-module direct flow installation efficiently couples spatial succession of anaerobic and aerobic bacteria with other micro- and macroorganisms to simultaneously recycle organic waste remediate the resulting leachate and generate biogas.

Hydrogen is widely recognized as a key component of a decarbonized global energy system serving as both a fuel source and an energy storage medium. While current hydrogen production relies almost entirely on emissionsintensive processes two low-emissions production pathways – natural-gas-derived production combined with carbon capture and storage and electrolysis using carbon-free electricity – are poised to change the global supply mix. Our study assesses the financial conditions under which natural-gas-based hydrogen production combined with carbon capture and storage would be available at a cost lower than hydrogen produced through electrolysis and the degree to which these conditions are likely to arise in a transition to a net-zero world. We also assess the degree to which emissions reduction policies namely carbon pricing and carbon capture and storage tax credits affect the relative costs of hydrogen production derived from different pathways. We show that while carbon pricing can improve the relative cost of both green and blue hydrogen production compared with unabated grey hydrogen targeted tax credits favouring either blue or green hydrogen explicitly may increase emissions and/or increase the costs of the energy transition.

An energy source transition is necessary to realize carbon neutrality emphasizing the importance of a hydrogen economy. The transportation sector accounted for 27% of annual carbon emissions in 2019 highlighting the increasing importance of transitioning to hydrogen vehicles and establishing hydrogen refueling stations (HRSs). In particular HRSs need to be prioritized for deploying hydrogen vehicles and developing hydrogen supply chains. Thus research on HRS is important for achieving carbon neutrality in the transportation sector. In this study we improved the efficiency and scaled up the capacity of an on-site HRS (based on steam methane reforming with a hydrogen production rate of 30 Nm3/h) in Seoul Korea. This HRS was a prototype with low efficiency and capacity. Its efficiency was increased through thermodynamic analysis and heat exchanger network synthesis. Furthermore the process was scaled up from 30 Nm3/h to 150 Nm3/h to meet future hydrogen demand. The results of exergy analysis indicated that the exergy destruction in the reforming reactor and heat exchanger accounted for 58.1% and 19.8% respectively of the total exergy destruction. Thus the process was improved by modifying the heat exchanger network to reduce the exergy losses in these units. Consequently the thermal and exergy efficiencies were increased from 75.7% to 78.6% and from 68.1% to 70.4% respectively. The improved process was constructed and operated to demonstrate its performance. The operational and simulation data were similar within the acceptable error ranges. This study provides guidelines for the design and installation of low-carbon on-site HRSs.

Endeavors have recently been concentrated on minimizing the dependency on fossil fuels in order to mitigate the ever-increasing problem of greenhouse gas (GHG) emissions. Hydrogen energy is regarded as an alternative to fossil fuels due to its cleaner emission attributes. Reforming of hydrocarbon fuels is amongst the most popular and widely used methods for hydrogen production. Hydrogen produced from reforming processes requires additional processes to separate from the reformed gases. In some cases further purification of hydrogen has to be carried out to use the hydrogen in power generation applications. Metallic membranes especially palladium (Pd)-based ones have demonstrated sustainable hydrogen separation potential with around 99.99% hydrogen purity. Comprehensive and critical research investigations must be performed to optimize membrane-assisted reforming as well as to maximize the production of hydrogen. The computational fluid dynamic (CFD) can be an excellent tool to analyze and visualize the flow/reaction/permeation mechanisms at a lower cost in contrast with the experiments. In order to provide the necessary background knowledge on membrane reactor modeling this study reviews summarizes and analyses the kinetics of different fuel reforming processes equations to determine hydrogen permeation and lastly various geometry and operating condition adopted in the literature associated with membrane-reactor modeling works. It is indicated that hydrogen permeation through Pd-membranes depends highly on the difference in hydrogen pressure. It is found that hydrogen permeation can be improved by employing different pressure configuration introducing sweep flow on the permeate side of the membrane reducing retentate side flow rate and increasing the temperature.

The application of hydrogen energy produced by proton exchange membrane electrolyzer (PEMEC) is conducive to the solution of the greenhouse effect and the energy crisis. In order to understand the development trends and research hotspot of PEMEC in recent years a total of 1874 research articles related to this field from 2003 to 2023 were obtained from the Web of Science Core Collection (WoS CC) database. The visualization software VOSviewer is used for bibliometric analysis and the research progress hotspots and trends in the PEMEC field are summarized. It was found that in the past two decades literature in the PEMEC field has shown a trend of stable increase at first and then rapidly increasing. And it is in a stage of rapid growth after 2021.Renewable Energy previously published research articles related to PEMEC with the highest frequency of citations. There are a total of 6128 researchers in this field but core authors only account for 4.5% of the total. Although China entered this field later than the United States and Canada it has the largest number of research articles. The research results provide a comprehensive overview of various aspects in the PEMEC field which is beneficial for researchers to grasp the development hotspots of PEMEC.

Thanks to investments in diversifying the supply of natural gas Poland did not encounter any gas supply issues in 2022 when gas imports from Russia were ceased due to the Russian Federation’s armed intervention in Ukraine. Over the past few years the supply of gas from routes other than the eastern route has substantially grown particularly the supplies of liquefied natural gas (LNG) via the LNG terminal in Swinouj´scie. The growing proportion of LNG in Poland’s gas supply ´ leads to a rise in ethane levels in natural gas as verified by the review of data taken at a specific location within the gas system over the years 2015 2020 and 2022. Using measurements of natural gas composition the effectiveness of the steam hydrocarbon reforming process was simulated in the Gibbs reactor via Aspen HYSYS. The simulations confirmed that as the concentration of ethane in the natural gas increased the amount of hydrogen produced and the heat required for reactions in the reformer also increased. This article aims to analyze the influence of the changes in natural gas quality in the Polish transmission network caused by changes in supply structures on the mass and heat balance of the theoretical steam reforming reactor. Nowadays the chemical composition of natural gas may be significantly different from that assumed years ago at the plant’s design stage. The consequence of such a situation may be difficulties in operating especially when controlling the quantity of incoming natural gas to the reactor based on volumetric flow without considering changes in chemical composition.

Industry is the biggest sector of energy consumption and greenhouse gas emissions whose decarbonisation is essential to achieve the Sustainable Development Goals. Carbon capture energy efficiency improvement and hydrogen are among the main strategies for industrial decarbonization. However novel approaches are needed to address the key requirements and differences between sectors to ensure they can work together to well integrate industrial decarbonisation with heat CO2 and hydrogen. The emerging Calcium Looping (CaL) is attracting interest in designing CO2-involved chemical processes for heat capture and storage. The reversibility relatively high-temperature (600 to 900 ◦C) and high energy capacity output as well as carbon capture function make CaL well-fit for CO2 capture and utilisation and waste heat recovery from industrial flue gases. Meanwhile methane dry reforming (MDR) is a promising technology to produce blue hydrogen via the consumption of two major greenhouse gases i.e. CO2 and CH4. It has great potential to combine the two technologies to achieve insitu CO2 utilization with multiple benefits. In this paper progresses on the reaction conditions and performance of CaL for CO2 capture and industrial waste heat recovery as well as MDR were screened. Secondly recent approaches to CaL-MDR synergy have been reviewed to identify the advantages. The major challenges in such a synergistic process include MDR catalyst deactivation CaL sorbents sintering and system integration. Thirdly the paper outlooks future work to explore a rational design of a multi-function system for the proposed synergistic process.

Industrial sectors pivotal for the economic prosperity of nations rely heavily on affordable reliable and environmentally friendly energy sources. Industries like iron and steel oil refineries and coal-fired power plants while instrumental to national economies are also the most significant contributors to waste gases that contain substantial volumes of carbon monoxide (CO). CO can be converted to a highly efficient and carbon free fuel hydrogen (H2) through a well-known water gas shift reaction. However the untapped potential of H2 from waste industrial streams is yet to be explored. This is the first article that investigates the potential of H2 production from industrial waste gases. The available resource (i.e. CO) and its H2 production potential are estimated. The article also provides insights into the principal challenges and potential avenues for long-term adoption. The results showed that 249.14 MTPY of CO are available to produce 17.44 MTPY of H2 annually. This suggests a significant potential for H2 production from waste gases to revolutionize industrial waste management and contribute significantly towards Sustainable Development Goals 7 9 and 13ensuring access to affordable reliable sustainable and modern energy for all and taking decisive climate action respectively.

Plastics have become integral to modern life playing crucial roles in diverse industries such as agriculture electronics automotive packaging and construction. However their excessive use and inadequate management have had adverse environmental impacts posing threats to terrestrial and marine ecosystems. Consequently researchers are increasingly searching for more sustainable ways of managing plastic wastes. Pyrolysis a chemical recycling method holds promise for producing valuable fuel sustainably. This study explores the process of the pyrolysis of plastic and incorporates recent advancements. Additionally the study investigates the integration of reforming into the pyrolysis process to improve hydrogen production. Hydrogen a clean and eco-friendly fuel holds significance in transport engines power generation fuel cells and as a major commodity chemical. Key process parameters influencing the final products for pyrolysis and in-line reforming are evaluated. In light of fossil fuel depletion and climate change the pyrolysis and in-line reforming strategy for hydrogen production is anticipated to gain prominence in the future. Amongst the various strategies studied the pyrolysis and in-line steam reforming process is identified as the most effective method for optimising hydrogen production from plastic wastes.

This study evaluates the levelised cost of hydrogen (LCOH) dynamically produced using the two dominant electrolysis technologies directly connected to wind turbines or photovoltaic (PV) panels in regions of Australia designated as hydrogen hubs. Hourly data are utilised to size the components required to meet the hydrogen demand. The dynamic efficiency of each electrolysis technology as a function of input power along with its operating characteristics and overload capacity are employed to estimate flexible hydrogen production. A sensitivity analysis is then conducted to capture the behaviour of the LCOH in response to inherent uncertainty in critical financial and technical factors. Additionally the study investigates the trade-offs between carbon cost and lifecycle emissions of green hydrogen. This approach is applied to ascertain the impact of internalising environmental costs on the cost-competitiveness of green hydrogen compared to grey hydrogen. The economic modelling is developed based on the Association for the Advancement of Cost Engineering (AACE) guidelines. The findings indicate that scale-up is key to reducing the LCOH by a meaningful amount. However scale-up alone is insufficient to reach the target value of AUD 3 (USD 2) except for PV-based plant in the Pilbara region. Lowered financial costs from scale-up can make the target value achievable for PV-based plants in Gladstone and Townsville and for wind-based plants in the Eyre Peninsula and Pilbara regions. For other hubs a lower electricity cost is required as it accounts for the largest portion of the LCOH.

This study aims to provide a comprehensive review of the potential of geothermal energy for producing hydrogen with a focus on the Australian context where low-temperature geothermal reservoirs particularly hot sedimentary aquifers (HSAs) are prevalent. The work includes an overview of various geothermal technologies and hydrogen production routes and evaluates potential alternatives for hydrogen production in terms of energy and exergy efficiency economic performance and hydrogen production rate. Values for energy efficiency are reported in the literature to range from 3.51 to 47.04% 7.4–67.5% for exergy efficiency a cost ranging from 0.59 to 5.97 USD/kg of hydrogen produced and a hydrogen production rate ranging from 0.11 to 5857 kg/h. In addition the article suggests and evaluates multiple metrics to appraise the feasibility of HSAs geothermal reservoirs with results tailored to Australia but that can be extended to jurisdictions with similar conditions worldwide. Furthermore the performance of various hydrogen production systems is investigated by considering important operating conditions. Lastly the key factors and possible solutions associated with the hydrogeological and financial conditions that must be considered in developing hydrogen production using lowtemperature geothermal energy are summarised. This study shows that low-temperature HSAs (~100 ◦C) can still be used for hydrogen generation via supplying power to conventional electrolysis processes by implementing several improvements in heat source temperature and energy conversion efficiency of Organic Rankine Cycle (ORC) power plants. Geothermal production from depleted or even active oilfields can reduce the capital cost of a hydrogen production system by up to 50% due to the use of pre-existing wellbores under the right operating conditions. Thus the results of this study bring novel insights in terms of both the opportunities and the challenges in producing clean hydrogen from geothermal energy applicable not only to the hydro-geological and socio-economic conditions in Australia but also worldwide exploring the applicability of geothermal energy for clean hydrogen production with similar geothermal potential.