Applications & Pathways

Fuel cell electric vehicles (FCEVs) can be used during idle times to convert hydrogen into electricity in a decentralised manner thus ensuring a completely renewable energy supply. In addition to the electric power waste heat is generated in the fuel cell stack that can also be used. This paper investigates how the energy demand of a compiled German neighbourhood can be met by FCEVs and identifies potential technical problems. For this purpose energy scenarios are modelled in the Open Energy System Modelling Framework (oemof). An optimisation simulation finds the most energetically favourable solution for the 10-day period under consideration. Up to 49% of the heat demand for heating and hot water can be covered directly by the waste heat of the FCEVs. As the number of battery electric vehicles (BEVs) to be charged increases so does this share. 5 of the 252 residents must permanently provide an FCEV to supply the neighbourhood. The amount of hydrogen required was identified as a problem. If the vehicles cannot be supplied with hydrogen in a stationary way 15 times more vehicles are needed than required in terms of performance due to the energy demand.

Fuel cell hybrid electric vehicles (FCEVs) are mainly electrified by the fuel cell (FC) system. As a supplementary power source a battery or supercapacitor (SC) is employed (besides the FC) to enhance the power response due to the slow dynamics of the FC. Indeed the performance of the hybrid power system mainly depends on the required power distribution manner among the sources which is managed by the energy management strategy (EMS). This paper considers an FCEV based on the proton exchange membrane FC (PEMFC)/battery/SC. The energy management strategy is designed to ensure optimum power distribution between the sources considering hydrogen consumption. Its main objective is to meet the electric motor’s required power with economic hydrogen consumption and better electrical efficiency. The proposed EMS combines the external energy maximization strategy (EEMS) and the bald eagle search algorithm (BES). Simulation tests for the Extra-Urban Driving Cycle (EUDC) and New European Driving Cycle (NEDC) profiles were performed. The test is supposed to be performed in typical conditions t = 25 ◦C on a flat road without no wind effect. In addition this strategy was compared with the state machine control strategy classic PI and equivalent consumption minimization strategy. In terms of optimization the proposed approach was compared with the original EEMS particle swarm optimization (PSO)-based EEMS and equilibrium optimizer (EO)-based EEMS. The results confirm the ability of the proposed strategy to reduce fuel consumption and enhance system efficiency. This strategy provides 26.36% for NEDC and 11.35% for EUDC fuel-saving and efficiency enhancement by 6.74% for NEDC and 36.19% for EUDC.

The steel industry is focused on reducing its environmental impact. Using the life cycle assessment (LCA) methodology the impacts of the primary steel production via the blast furnace route and the scrap-based secondary steel production via the EAF route are assessed. In order to achieve environmentally friendly steel production breakthrough technologies have to be implemented. With a shift from primary to secondary steel production the increasing steel demand is not met due to insufficient scrap availability. In this paper special focus is given on recycling methodologies for metals and steel. The decarbonization of the steel industry requires a shift from a coal-based metallurgy towards a hydrogen and electricity-based metallurgy. Interim scenarios like the injection of hydrogen and the use of pre-reduced iron ores in a blast furnace can already reduce the greenhouse gas (GHG) emissions up to 200 kg CO2/t hot metal. Direct reduction plants combined with electrical melting units/furnaces offer the opportunity to minimize GHG emissions. The results presented give guidance to the steel industry and policy makers on how much renewable electric energy is required for the decarbonization of the steel industry

Meeting the Paris Agreement will most likely require the combination of CO2 capture and biomass in the industrial sector resulting in net negative emissions. CO2 capture within the industry has been extensively investigated. However biomass options have been poorly explored with literature alluding to technical and economic barriers. In addition a lack of consistency among studies makes comparing the performance of CO2 capture and/or biomass use between studies and sectors difficult. These inconsistencies include differences in methodology system boundaries level of integration costs greenhouse gas intensity of feedstock and energy carriers and capital cost estimations. Therefore an integrated evaluation of the techno-economic performance regarding CO2 capture and biomass use was performed for five energy-intensive industrial sub-sectors. Harmonization results indicate that CO2 mitigation potentials vary for each sub-sector resulting in reductions of 1.4–2.7 t CO2/t steel (77%–149%) 0.7 t CO2/t cement (92%) 0.2 t CO2/t crude oil (68%) 1.9 t CO2/t pulp (1663%–2548%) and 34.9 t CO2/t H2 (313%). Negative emissions can be reached in the steel paper and H2 sectors. Novel bio-based production routes might enable net negative emissions in the cement and (petro) chemical sectors as well. All the above-mentioned potentials can be reached for 100 €/t CO2 or less. Implementing mitigation options could reduce industrial CO2 emissions by 10 Gt CO2/y by 2050 easily meeting the targets of the 2 ◦C scenario by the International Energy Agency (1.8 Gt CO2/y reduction) for the industrial sector and even the Beyond 2 ◦C scenario (4.2 Gt CO2/y reduction).

Ammonia a chemical that contains high hydrogen quantities has been presented as a candidate for the production of clean power generation and aerospace propulsion. Although ammonia can deliver more hydrogen per unit volume than liquid hydrogen itself the use of ammonia in combustion systems comes with the detrimental production of nitrogen oxides which are emissions that have up to 300 times the greenhouse potential of carbon dioxide. This factor combined with the lower energy density of ammonia makes new studies crucial to enable the use of the molecule through methods that reduce emissions whilst ensuring that enough power is produced to support high-energy intensive applications. Thus this paper presents a numerical study based on the use of novel reaction models employed to characterize ammonia combustion systems. The models are used to obtain Reynolds Averaged Navier-Stokes (RANS) simulations via Star-CCM+ with complex chemistry of a 70%–30% (mol) ammonia–hydrogen blend that is currently under investigations elsewhere. A fixed equivalence ratio (1.2) medium swirl (0.8) and confined conditions are employed to determine the flame and species propagation at various operating atmospheres and temperature inlet values. The study is then expanded to high inlet temperatures high pressures and high flowrates at different confinement boundary conditions. The results denote how the production of NOx emissions remains stable and under 400 ppm whilst higher concentrations of both hydrogen and unreacted ammonia are found in the flue gases under high power conditions. The reduction of heat losses (thus higher temperature boundary conditions) has a crucial impact on further destruction of ammonia post-flame with a raise in hydrogen water and nitrogen through the system thus presenting an opportunity of combustion efficiency improvement of this blend by reducing heat losses. Final discussions are presented as a method to raise power whilst employing ammonia for gas turbine systems.

In the context of the great research pulse on clean energy transition distributed energy systems have a key role especially in the case of integration of both renewable and traditional energy sources. The stable interest in small-scale gas turbines can further increase owing to their flexibility in both operation and fuel supply. Since their not-excellent electrical efficiency research activities on micro gas turbine (MGT) are focused on the performance improvements that are achievable in several ways like modifying the Brayton cycle integrating two or more plants using cleaner fuels. Hence during the last decades the growing interest in MGT-based energy systems encouraged the development of many numerical approaches aimed to provide a reliable and effective prediction of the energy systems’ behavior. Indeed numerical modeling can help to individuate potentialities and issues of each enhanced layout or hybrid energy system and this review aims to discuss the various layout solutions proposed by researchers with particular attention to recent publications highlighting the adopted modeling approaches and methods.

The overall ambition of the study has been to assess the commercial and operational viability of alternative marine fuels based on review existing academic and industry literature. The approach assesses how well six alternative fuels perform compared to LNG fuel on a set of 11 key parameters. Conventional fuels are not covered in this study however 2020 compliant fuels (HFO+scrubber and low sulphur fuels are included in the conclusion for comparative purposes.

Background: Sustainable development requires access to afordable reliable and efcient energy to lift billions of people out of poverty and improve their standard of living. The development of new and renewable forms of energy that emit less CO2 may not materialize quickly enough or at a price point that allows people to attain the standard of living they desire and deserve. As a result a parallel path to sustainability must be developed that uses both renewable and clean carbon-based methods. Hybrid microgrids are promoted to solve various electrical and energy-related issues that incorporate renewable energy sources such as photovoltaics wind diesel generation or a combination of these sources. Utilizing microgrids in electric power generation has several benefts including clean energy increased grid stability and reduced congestion. Despite these advantages microgrids are not frequently deployed because of economic concerns. To address these fnancial concerns it is necessary to explore the ideal confguration of micro-grids based on the quantity quality and availability of sustainable energy sources used to install the microgrid and the optimal design of microgrid components. These considerations are refected in net present value and levelized energy cost. Methods: HOMER was used to simulate numerous system confgurations and select the most feasible solution according to the net present value levelizied cost of energy and hydrogen operating cost and renewable fraction. HOMER performed a repeated algorithm process to determine the most feasible system configuration and parameters with the least economic costs and highest benefits to achieve a practically feasible system configuration. Results: This article aimed to construct a cost-effective microgrid system for Saudi Arabia’s Yanbu city using five configurations using excess energy to generate hydrogen. The obtained results indicate that the optimal configuration for the specified area is a hybrid photovoltaic/wind/battery/generator/fuel cell/hydrogen electrolyzer microgrid with a net present value and levelized energy cost of $10.6 billion and $0.15/kWh. Conclusion: With solar photovoltaic and wind generation costs declining building electrolyzers in locations with excellent renewable resource conditions such as Saudi Arabia could become a low-cost hydrogen supply option even when accounting for the transmission and distribution costs of transporting hydrogen from renewable resource locations to end-users. The optimum confguration can generate up to 32132 tons of hydrogen per year (tH2/year) and 380824 tons per year of CO2 emissions can be avoided.

This study analyzes the optimal sizing design of a stand-alone solar hydrogen hybrid energy system for a house in Afyon Turkey. The house is not connected to the grid and the proposed hybrid system meets all its energy demands; therefore it is considered a zero-energy building. The designed system guarantees uninterrupted and reliable power throughout the year. Since the reliability of the power supply is crucial for the house optimal sizing of the components photovoltaic (PV) panels electrolyzer storage tank and fuel cell stack is critical. Determining the sufficient number of PV panels suitable electrolyzer model and size number of fuel cell stacks and the minimum storage tank volume to use in the proposed system can guarantee an uninterrupted energy supply to the house. In this study a stand-alone hybrid energy system is proposed. The system consists of PV panels a proton exchange membrane (PEM) electrolyzer a storage tank and a PEM fuel cell stack. It can meet the continuous energy demand of the house is sized by using 10 min of averaged solar irradiation and temperature data of the site and consumption data of the house. Present results show that the size of each component in a solar hydrogen hybrid energy system in terms of power depends on the size of each other components to meet the efficiency requirement of the whole system. Choosing the nominal electrolyzer power is critical in such energy systems

The shipping industry has reached a higher level of maturity in terms of its knowledge and awareness of decarbonization challenges. Carbon-free or carbon-neutralized green fuel such as green hydrogen green ammonia and green methanol are being widely discussed. However little attention has paid to the green fuel pathway from renewable energy to shipping. This paper therefore provides a review of the production methods for green power (green hydrogen green ammonia and green methanol) and analyzes the potential of green fuel for application to shipping. The review shows that the potential production methods for green hydrogen green ammonia and green methanol for the shipping industry are (1) hydrogen production from seawater electrolysis using green power; (2) ammonia production from green hydrogen + Haber–Bosch process; and (3) methanol production from CO2 using green power. While the future of green fuel is bright in the short term the costs are expected to be higher than conventional fuel. Our recommendations are therefore as follows: improve green power production technology to reduce the production cost; develop electrochemical fuel production technology to increase the efficiency of green fuel production; and explore new technology. Strengthening the research and development of renewable energy and green fuel production technology and expanding fuel production capacity to ensure an adequate supply of low- and zero-emission marine fuel are important factors to achieve carbon reduction in shipping.

As a case study on sustainable energy use in educational institutions this study examines the design and integration of a solar–hydrogen storage system within the energy management framework of Kangwon National University’s Samcheok Campus. This paper provides an extensive analysis of the architecture and integrated design of such a system which is necessary given the increasing focus on renewable energy sources and the requirement for effective energy management. This study starts with a survey of the literature on hydrogen storage techniques solar energy storage technologies and current university energy management systems. In order to pinpoint areas in need of improvement and chances for progress it also looks at earlier research on solar–hydrogen storage systems. This study’s methodology describes the system architecture which includes fuel cell integration electrolysis for hydrogen production solar energy harvesting hydrogen storage and an energy management system customized for the needs of the university. This research explores the energy consumption characteristics of the Samcheok Campus of Kangwon National University and provides recommendations for the scalability and scale of the suggested system by designing three architecture systems of microgrids with EMS Optimization for solar–hydrogen hybrid solar–hydrogen and energy storage. To guarantee effective and safe functioning control strategies and safety considerations are also covered. Prototype creation testing and validation are all part of the implementation process which ends with a thorough case study of the solar–hydrogen storage system’s integration into the university’s energy grid. The effectiveness of the system its effect on campus energy consumption patterns its financial sustainability and comparisons with conventional energy management systems are all assessed in the findings and discussion section. Problems that arise during implementation are addressed along with suggested fixes and directions for further research—such as scalability issues and technology developments—are indicated. This study sheds important light on the viability and efficiency of solar–hydrogen storage systems in academic environments particularly with regard to accomplishing sustainable energy objectives.

This paper shows the results of an in-depth techno-economic analysis of the public transport sector in a small to midsize city and its surrounding area. Public battery-electric and hydrogen fuel cell buses are comparatively evaluated by means of a total cost of ownership (TCO) model building on historical data and a projection of market prices. Additionally a structural analysis of the public transport system of a specific city is performed assessing best fitting bus lines for the use of electric or hydrogen busses which is supported by a brief acceptance evaluation of the local citizens. The TCO results for electric buses show a strong cost decrease until the year 2030 reaching 23.5% lower TCOs compared to the conventional diesel bus. The optimal electric bus charging system will be the opportunity (pantograph) charging infrastructure. However the opportunity charging method is applicable under the assumption that several buses share the same station and there is a “hotspot” where as many as possible bus lines converge. In the case of electric buses for the year 2020 the parameter which influenced the most on the TCO was the battery cost opposite to the year 2030 in where the bus body cost and fuel cost parameters are the ones that dominate the TCO due to the learning rate of the batteries. For H2 buses finding a hotspot is not crucial because they have a similar range to the diesel ones as well as a similar refueling time. H2 buses until 2030 still have 15.4% higher TCO than the diesel bus system. Considering the benefits of a hypothetical scaling-up effect of hydrogen infrastructures in the region the hydrogen cost could drop to 5 €/kg. In this case the overall TCO of the hydrogen solution would drop to a slightly lower TCO than the diesel solution in 2030. Therefore hydrogen buses can be competitive in small to midsize cities even with limited routes. For hydrogen buses the bus body and fuel cost make up a large part of the TCO. Reducing the fuel cost will be an important aspect to reduce the total TCO of the hydrogen bus.

The development of innovative technologies based on employing green energy carriers such as hydrogen is becoming high in demand especially in the automotive sector as a result of the challenges associated with sustainable mobility. In the present review a detailed overview of the entire hydrogen supply chain is proposed spanning from its production to storage and final use in cars. Notably the main focus is on Polymer Electrolyte Membrane Fuel Cells (PEMFC) as the fuel-cell type most typically used in fuel cell electric vehicles. The analysis also includes a cost assessment of the various systems involved; specifically the materials commonly employed to manufacture fuel cells stacks and hydrogen storage systems are considered emphasizing the strengths and weaknesses of the selected strategies together with assessing the solutions to current problems. Moreover as a sought-after parallelism a comparison is also proposed and discussed between traditional diesel or gasoline cars battery-powered electric cars and fuel cell electric cars thus highlighting the advantages and main drawbacks of the propulsion systems currently available on the market.

In this paper the design of fuel cells for the main energy supply of passenger transportation aircraft is discussed. Using a physical model of a fuel cell general design considerations are derived. Considering different possible design objectives the trade-off between power density and efficiency is discussed. A universal cost–benefit curve is derived to aid the design process. A weight factor wP is introduced which allows incorporating technical (e.g. system mass and efficiency) as well as non-technical design objectives (e.g. operating cost emission goals social acceptance or technology affinity political factors). The optimal fuel cell design is not determined by the characteristics of the fuel cell alone but also by the characteristics of the other system components. The fuel cell needs to be designed in the context of the whole energy system. This is demonstrated by combining the fuel cell model with simple and detailed design models of a liquid hydrogen tank. The presented methodology and models allows assessing the potential of fuel cell systems for mass reduction of future passenger aircraft.

The hydrogen (H2) momentum affects the aviation sector. However a macroeconomic consideration is currently missing. To address this research gap the paper derives a methodology for evaluating macroeconomic effects of H2 in aviation and applies this approach to Germany. Three goals are addressed: (1) Construction of a German macroeconomic database. (2) Translation of H2 supply chains to the system of national accounts. (3) Implementation of H2-powered aviation into the macroeconomic data framework. The article presents an economy-wide database for analyzing H2-powered aviation. Subsequently the paper highlights three H2 supply pathways provides an exemplary techno-economic cost break-down for ten H2 components and translates them into the data framework. Eight relevant macroeconomic sectors for H2-powered aviation are identified and quantified. Overall the paper contributes on a suitable foundation to apply the macroeconomic dataset to and conduct macroeconomic analyses on H2-powered aviation. Finally the article highlights further research potential on job effects related to future H2 demand.

This work compares the costs of three electrolysis-based hydrogen supply systems for heavy road transportation: a decentralized off-grid system for hydrogen production from wind and solar power (Dec-Sa); a decentralized system connected to the electricity grid (Dec-Gc); and a centralized grid-connected electrolyzer with hydrogen transported to refueling stations (Cen-Gc). A cost-minimizing optimization model was developed in which the hydrogen production is designed to meet the demand at refueling stations at the lowest total cost for two timeframes: one with current electricity prices and one with estimated future prices. The results show that: For most of the studied geographical regions Dec-Gc gives the lowest costs of hydrogen delivery (2.2e3.3V/kgH2) while Dec-Sa entails higher hydrogen production costs (2.5e6.7V/kgH2). In addition the centralized system (Cen-Gc) involves lower costs for production and storage than the grid-connected decentralized system (Dec-Gc) although the additional costs for hydrogen transport increase the total cost (3.5e4.8V/kgH2).

In this seventh episode Steffan Eldred Hydrogen Innovation Network Knowledge Transfer Manager and Jenni McDonnell MBE Heating and Cooling Knowledge Transfer Manager from Innovate UK KTN discuss why using hydrogen to generate heat is so important and explore the hydrogen economy opportunities and challenges within this sector alongside their special guest Jeff House Head of External Affairs Baxi Boilers.

The podcast can be found on their website.

Thus far the adoption of hydrogen fuel cell vehicles (HCEVs) has been hampered by the lack of hydrogen fueling infrastructure. This study aimed to determine the optimal location and prioritization of hydrogen fueling stations (HFSs) in Seoul by utilizing a multi-standard decision making approach and optimization method. HFS candidate sites were evaluated with respect to relevant laws and regulations. Key factors such as safety economy convenience and demand for HCEVs were considered. Data were obtained through a survey of experts in the fields of HCEV and fuel cells and the Analytic Hierarchy Process method was applied to prioritize candidate sites. The optimal quantity and placement of HFSs was then obtained using optimization software based on the acceptable travel time from intersections of popular roads in Seoul. Our findings suggest that compliance with legal safety regulations is the most important factor when constructing HFSs. Furthermore sensitivity analysis revealed that the hydrogen supply cost currently holds the same weight as other elements. The study highlights the importance of utilizing a multi-standard decision-making approach and optimization methods when determining the optimal location and prioritization of HFSs and can help develop a systematic plan for the nationwide construction of HFSs in South Korea.

The majority penetration of Variable Renewable Energy (VRE) will challenge the stability of electrical transmission grids due to unpredictable peaks and troughs of VRE generation. With renewable generation located further from high demand urban cores there will be a need to develop new transmission pathways to deliver the power. This paper compares the transport and storage of VRE through a hydrogen pipeline to the transport of VRE through a High Voltage Direct Current (HVDC) transmission line. The analysis found a hydrogen pipeline can offer a cost-competitive method for VRE transmission compared to a HVDC transmission line on a life-cycle cost basis normalized by energy flows for distances at 1000 miles with 2030 technology. This finding has implications for policy makers project developers and system operators for the future development of transmission infrastructure projects given the additionality which hydrogen pipelines can provide in terms of energy storage.

Recently hydrogen and fuel cells have gained interest as an emerging technology to mitigate the effects of climate change caused by the aviation sector. The aim of this work is to evaluate the applicability of this technology to an existing regional aircraft in order to assess its electrification with the aim of reducing greenhouse gas emissions and achieving sustainability goals. The design of a proton-exchange membrane fuel cell system (PEMFC) with the inclusion of liquid hydrogen storage is carried out. Specifically a general mathematical model is developed which involves multiple scales ranging from individual cells to aircraft scale. First the fuel cell electrochemical model is developed and validated against published polarization curves. Then different sizing approaches are used to compute the overall weight of the hydrogen-based propulsion system in order to optimize the system and minimize its weight. Crucially this work underscores that the feasibility of hydrogenbased fuel cell systems relies not only on hydrogen storage but especially on the electrochemical cell performance which influences the size of the balance of plant and especially its thermal management section. In particular the strategic significance of working with fuel cells at partial loads is demonstrated. This entails achieving an optimal balance between the stacks oversizing and the weights of both hydrogen storage and balance of plant thereby minimizing the overall weight of the system. It is thus shown that an integrated approach is imperative to guide progress towards efficient and implementable hydrogen technology in regional aviation. Furthermore a high-performance PEMFC is analyzed resulting in an overall weight reduction up to nearly 10% compared to the baseline case study. In this way it is demonstrated as technological advancements in PEMFCs can offer further prospects for improving system efficiency.

In this episode Steffan Eldred Hydrogen Knowledge Transfer Manager and Debra Jones Chemistry Knowledge Transfer Manager from Innovate UK KTN talk about hydrogen combustion with special guest Duncan Engeham European Research and Development Director at Cummins Inc.

The podcast can be found on their website.

Hydrogen can alleviate the increasing environmental pollution and has good development prospects in power generation due to its high calorific value and low environmental impact. The previously designed hydrogen-fired combined cycle ignored water recycling which led to an inefficient application of hydrogen and the wastage of water. This paper proposes the concept of a hydrogen-fired combined cycle with water recovery to reuse the condensed water as an industrial heat supply. It was applied to an F-class combined cycle power plant. The results demonstrate that the efficiency of hydrogen-fired combined cycles with and without water recovery increased by 1.92% and 1.35% respectively compared to that of the natural-gas-fired combined cycle under full working conditions. In addition an economic comparison of the three cycles was conducted. The levelized cost of energy of the hydrogen-fired combined cycle with water recovery will be 52.22% lower than that of the natural-gas-fired combined cycle in 2050. This comparative study suggested that water recovery supplementation could improve the gas turbine efficiency. The proposed hydrogen-fired combined cycle with water recovery would provide both environmental and economic benefits.

This study presents methodology for the evaluation of appropriateness of a hydrogen generator for gas production in multiple distributed plants based on renewable energy sources. The general idea is to form hydrogen clusters integrated with storage and transportation. The paper focuses on the financial viability of the plants presenting the results of economic evaluation together with sensitivity analysis for various economic factors. The analyzed case study proves that over a wide range of parameters alkaline electrolyzers show favorable economic characteristics however a PEM-based plant is more resilient to changes in the price of electricity which is the main cost component in hydrogen generation. The study is enriched with an experimental investigation of low-pressure storage methods based on porous metal hydride tanks. The effectiveness of the tanks (β) compared to pressurized hydrogen tanks in the same volume and pressure is equal to β = 10.2. A solution is proposed whereby these can be used in a distributed hydrogen generation concept due to their safe and simple operation without additional costly equipment e.g. compressors. A method for evaluation of the avoided energy consumption as a function of the effectiveness of the tanks is developed. Avoided energy consumption resulting from implementing MH tanks equals 1.33 – 1.37 kWh per kilogram of hydrogen depending on the number of stages of a compressor. The methods proposed in this paper are universal and can be used for various green hydrogen facilities.

Green hydrogen is currently regarded as a key catalyst for the decarbonization of energy-intensive industries. In this context the pulp and paper industry stands out as one of the most demanding given the simultaneous need for large amounts of heat and electricity usually satisfied via cogeneration systems. Given the urgent need for cost-effective solutions in response to the climate crisis it is crucial to analyze the feasibility of retrofitting existing power plants to operate carbon-neutral. The aim of this work is to provide a techno-economic analysis for the conversion of a conventional cogeneration system to run on locally produced hydrogen. Building on the energy consumption of the paper mill the operation of a hydrogen-fuelled gas turbine is modelled in detail. Based on these results a multi-energy system model for the production of green fuel is presented considering production via solar-powered PEM electrolyzers storage in tanks and final use in the gas turbine. An optimal configuration for the system is defined leading to the definition of a solution that ensures a cost of 6.41 /kg for the production of green hydrogen. Finally a sensitivity analysis highlights the close dependence of the economic profitability of the Power-to-X system on the natural gas price. The results indicate that although positive performance is achieved the cost of investment remains still prohibitive for systems of this size and the high initial capital expenditure needs to be supported by incentive policies that facilitate the adoption of hydrogen in industrial applications making it competitive in the short term.

Transportation is an economic sector that contributes significantly to global warming due to its high consumption of fossil fuels and sustainably produced hydrogen is a major contender for an alternative clean energy source. Public transit is vital for environmental sustainability via reducing individual vehicle usage and traffic congestion and the prospect of powering buses using hydrogen fuel has been extensively studied lately. This paper seeks to comprehensively review the current status of research on hydrogen-powered buses considering triple bottom line sustainability perspectives. A brief technical overview of prospective environmentally benign hydrogen production processes has been presented. Technological economic and environmental findings and research trends seen in recent analyses on hydrogen-powered buses have been summarized along with the status quo of global hydrogen refuelling stations. Identified focal points for future studies include performance enhancements refuelling infrastructure propagation and policy formulation. The conclusions derived from this review will benefit the accelerated deployment of hydrogen-fuelled public transit fleets.