Publications

Currently transitioning from fossil fuels to renewable sources of energy is needed considering the impact of climate change on the globe. From this point of view there is a need for development in several stages such as storage transmission and conversion of power. In this paper we demonstrate a simulation of a hybrid energy storage system consisting of a battery and fuel cell in parallel operation. The novelty in the proposed system is the inclusion of an electrolyser along with a switching algorithm. The electrolyser consumes electricity to intrinsically produce hydrogen and store it in a tank. This implies that the system consumes electricity as input energy as opposed to hydrogen being the input fuel. The hydrogen produced by the electrolyser and stored in the tank is later utilised by the fuel cell to produce electricity to power the load when needed. Energy is therefore stored in the form of hydrogen. A battery of lower capacity is coupled with the fuel cell to handle transient loads. A parallel control algorithm is developed to switch on/off the charging and discharging cycle of the fuel cell and battery depending upon the connected load. Electrically equivalent circuits of a polymer electrolyte membrane electrolyser polymer electrolyte membrane fuel cell necessary hydrogen oxygen water tanks and switching controller for the parallel operation were modelled with their respective mathematical equations in MATLAB® Simulink®. In this paper we mainly focus on the modelling and simulation of the proposed system. The results showcase the simulated system’s mentioned advantages and compare its ability to handle loads to a battery-only system.

Energy plays a crucial role in the sustainable development of modern nations. Today hydrogen is considered the most promising alternative fuel as it can be generated from clean and green sources. Moreover it is an efficient energy carrier because hydrogen burning only generates water as a byproduct. Currently it is generated from natural gas. However it can be produced using other methods i.e. physicochemical thermal and biological. The biological method is considered more environmentally friendly and pollution free. This paper aims to provide an updated review of biohydrogen production via photofermentation dark fermentation and microbial electrolysis cells using different waste materials as feedstocks. Besides the role of nanotechnology in enhancing biohydrogen production is examined. Under anaerobic conditions hydrogen is produced during the conversion of organic substrate into organic acids using fermentative bacteria and during the conversion of organic acids into hydrogen and carbon dioxide using photofermentative bacteria. Different factors that enhance the biohydrogen production of these organisms either combined or sequentially using dark and photofermentation processes are examined and the effect of each factor on biohydrogen production efficiency is reported. A comparison of hydrogen production efficiency between dark fermentation photofermentation and two-stage processes is also presented.

As countries seek ways to meet climate change commitments hydrogen fuel offers a low-carbon alternative for sectors where battery electrification may not be viable. Blending hydrogen with fossil fuels requires only modest technological adaptation however since combustion is retained nitrogen oxides (NOx) emissions remain a potential disbenefit. We review the potential air quality impacts arising from the use of hydrogen–diesel blends in heavy-duty diesel engines a powertrain which lends itself to hydrogen co-fuelling. Engine load is identified as a key factor influencing NOx emissions from hydrogen–diesel combustion in heavy-duty engines although variation in other experimental parameters across studies complicates this relationship. Combining results from peer-reviewed literature allows an estimation to be made of plausible NOx emissions from hydrogen–diesel combustion relative to pure-diesel combustion. At 0–30% engine load which encompasses the average load for mobile engine applications NOx emissions changes were in the range 59 to +24% for a fuel blend with 40 e% hydrogen. However at 50–100% load which approximately corresponds to stationary engine applications NOx emissions changes were in the range 28 to +107%. Exhaust gas recirculation may be able to reduce NOx emissions at very high and very low loads when hydrogen is blended with diesel and existing exhaust aftertreatment technologies are also likely to be effective. Recent commercial reporting on the development of hydrogen and hydrogen–diesel dual fuel combustion in large diesel engines are also summarised. There is currently some disconnection between manufacturer reported impacts of hydrogen-fuelling on NOx emissions (always lower emissions) and the conclusions drawn from the peer reviewed literature (frequently higher emissions).

Split hydrogen direct injection (SHDI) has been proved capable of better efficiency and fewer emissions. Therefore to investigate SHDI deeply a numerical study on the effect of second injection timing was presented at a gasoline/hydrogen spark ignition (SI) engine with SHDI. With an excess air ratio of 1.5 five different second injection timings achieved five kinds of hydrogen mixture distribution (HMD) which was the main factor affecting the engine performances. With SHDI since the HMD is manageable the engine can achieve better efficiency and fewer emissions. When the second injection timing was 105◦ crank angle (CA) before top dead center (BTDC) the Pmax was the highest and the position of the Pmax was the earliest. Compared with the single hydrogen direct injection (HDI) the NOX CO and HC emissions with SHDI were reduced by 20% 40% and 72% respectively.

Beyond its typical usage as an economical fuel for creating ammonia methanol and petroleum refineries hydrogen has become a modern form of energy. Energy-scarce advanced countries like Japan and Korea are concerned about energy privacy and environmental responsibility. Many wealthy countries have been fervently building hydrogen networks and renewable energy sources to fulfil their main goals or the growing requirement for energy. In this study we concentrate on proton-exchange membrane fuel cells (PEMFCs) generally viewed as financially viable for vehicle industries especially for automobiles demanding less hydrogen infrastructure facilities like fleets of cabs buses and logistical automobiles. This overview includes all of the significant PEMFC components focusing on the reaction gas diffusion and polymer. Without question the equipment necessary for a consistent supply of ultra-pure hydrogen is essential for the effectiveness of PEMFC in extensive requests.

Authored by the Hydrogen Council in collaboration with McKinsey and Company Global Hydrogen Flows addresses the midstream challenge of aligning and optimizing global supply and demand. It finds that trade can reduce overall system costs.

In doing so it provides a perspective on how the global trade of hydrogen and derivatives including hydrogen carriers ammonia methanol synthetic kerosene and green steel (which uses hydrogen in its production) can develop as well as the investments needed to unlock the full potential of global hydrogen and derivatives trade.

Our hope is that this report offers stakeholders – suppliers buyers original equipment manufacturers (OEMs) investors and governments – a thorough and quantitative perspective that will help them make the decisions required to accelerate the uptake of hydrogen.

Key messages from the report:

Hydrogen and its derivatives will become heavily traded: 400 out of the 660 million tons (MT) of hydrogen needed for carbon neutrality by 2050 will be transported over long distances with 190 MT crossing international borders.

In a cost-optimal world around 50% of trade uses pipelines while synthetic fuels ammonia and sponge iron transported on ships account for approximately 45%. Europe and countries in the Far East will rely on imports while North America and China are mostly self-reliant.

Trade has huge benefits: It can lower the cost of hydrogen supply by 25% or as much as US$6 trillion of investments from now until 2050. This will accelerate the hydrogen transition which can abate 80 gigatons of CO2 until 2050.

The paper can be found on their website.

The development of low-carbon fuels from renewable resources is a key measure to reduce carbon dioxide emissions and mitigate climate change. Biomass gasification with subsequent gas processing and purification is a promising route to produce low-carbon hydrogen. In the past decade simulation-based modelling using Aspen Plus software has supported the investigation of future potential industrial applications of this pathway. This article aims to provide a review of the modelling and economic assessment of woody biomass gasification-based hydrogen production with focus on the evaluation of the model accuracy in predicting producer gas composition in comparison with experimental data depending on the approach implemented. The assessment of comprehensive models which integrate biomass gasification with gas processing and purification highlights how downstream gas processing could improve the quality of the syngas and thus the hydrogen yield. The information in this article provides an overview of the current practices challenges and opportunities for future research particularly for the development of a comprehensive pathway for hydrogen production based on biomass gasification. Moreover this review includes a techno-economic assessment of biomass to hydrogen processes which will be useful for implementation at industrial-scale.

In this paper we implement a long-term multi-sectoral energy planning model to evaluate the role of green hydrogen in the energy mix of Chile a country with a high renewable potential under stringent emission reduction objectives in 2050. Our results show that green hydrogen is a cost-effective and environmentally friendly route especially for hard-to-abate sectors such as interprovincial and freight transport. They also suggest a strong synergy of hydrogen with electricity generation from renewable sources. Our numerical simulations show that Chile should (i) start immediately to develop hydrogen production through electrolyzers all along the country (ii) keep investing in wind and solar generation capacities ensuring a low cost hydrogen production and reinforce the power transmission grid to allow nodal hydrogen production (iii) foster the use of electric mobility for cars and local buses and of hydrogen for long-haul trucks and interprovincial buses and (iv) develop seasonal hydrogen storage and hydrogen cells to be exploited for electricity supply especially for the most stringent emission reduction objectives.

One of China’s ambitious hydrogen strategies over the past few years has been to promote fuel cells. A number of hydrogen refueling stations (HRSs) are currently being built in China to refuel hydrogen-powered automobiles. In this context it is crucial to assess the dangers of hydrogen leaking in HRSs. The present work simulated the liquid hydrogen (LH2) leakage with the goal of undertaking an extensive consequence evaluation of the LH2 leakage on an LH2 refueling station (LHRS). Furthermore the utilization of an air curtain to prevent the diffusion of the LH2 leakage is proposed and the defending effect is studied accordingly. The results reveal that the Richardson number effectively explained the variation of plume morphology. Furthermore different facilities have great influence on the gas cloud diffusion trajectory with the consideration of different leakage directions. The air curtain shows satisfactory prevention of the diffusion of the hydrogen plume. Studies show that with the increase in air volume (equivalent to wind speed) and the narrowing of the air curtain width (other factors remain unchanged) the maximum flammable distance of hydrogen was shortened.

In the modern world zero-carbon society has become a new buzzword of the era. Many projects have been initiated to develop alternatives not only to the environmental crisis but also to the shortage of fossil fuels. With successful projects in automobile technology hydrogen fuel is now being tested and utilized as a sustainable green fuel in the aviation sector which will lead to zero carbon emission in the future. From the mid-20th century to the early 21st numerous countries and companies have funded multimillion projects to develop hydrogen-fueled aircraft. Empirical data show positive results for various projects. Consequently large companies are investing in various innovations undertaken by researchers under their supervision. Over time the efficiency of hydrogen-fueled aircraft has improved but the lack of refueling stations large production cost and consolidated carbon market share have impeded the path of hydrogen fuel being commercialized. In addition the Unmanned Aerial Vehicle (UAV) is another important element of the Aviation industry Hydrogen started to be commonly used as an alternative fuel for heavy-duty drones using fuel cell technology. The purpose of this paper is to provide an overview of the chronological development of hydrogen-powered aircraft technology and potential aviation applications for hydrogen and fuel cell technology. Furthermore the major barriers to widespread adoption of hydrogen technology in aviation are identified as are future research opportunities.

As the European Union intensifies its response to the climate emergency increased focus has been placed on the hard-to-abate energy-intensive industries. Primary among these is the steel industry a cornerstone of the European economy and industry. With the emergence of new hydrogen-based steelmaking options particularly through hydrogen direct reduction the structure of global steel production and supply chains will transition from being based on low-cost coal resources to that based on low-cost electricity and therefore hydrogen production. This study examines the techno-economic options for three European countries of Germany Spain and Finland under five different steel supply chain configurations compared to local production. Results suggest that the high costs of hydrogen transportation make a European steelmaking supply chain cost competitive to steel produced with imported hydrogen with local production costs ranging from 465-545 €/t of crude steel (CS) and 380-494 €/tCS for 2030 and 2040 respectively. Conversely imports of hot briquetted iron and crude steel from Morocco become economically competitive with European supply chains. Given the capital and energy intensive nature of the steel industry critical investment decisions are required in this decade and this research serves to provide a deeper understanding of supply chain options for Europe.

Hydrogen can play a key role in the gradual transition towards a full decarbonization of the combustion sector e.g. in power generation. Despite the advantages related to the use of this carbon-free fuel there are still several challenging technical issues that must be addressed such as the thermoacoustic instability triggered by hydrogen. Given that burners are usually designed to work with methane or other fossil fuels it is important to investigate their thermoacoustic behavior when fueled by hydrogen. In this framework the present work aims to propose a methodology which combines Computational Fluid Dynamics CFD (3D Reynolds-Averaged Navier-Stokes (RANS)) and Finite Element Method (FEM) approaches in order to investigate the fluid dynamic and the thermoacoustic behavior introduced by hydrogen in a burner (a lab-scale bluff body stabilized burner) designed to work with methane. The case of CH4 -air mixture was used for the validation against experimental results and benchmark CFD data available in the literature. Numerical results obtained from CFD simulations namely thermofluidodynamic properties and flame characteristics (i.e. time delay and heat release rate) are used to evaluate the effects of the fuel change on the Flame Response Function to the acoustic perturbation by means of a FEM approach. As results in the H2 -air mixture case the time delay decreases and heat release rate increases with respect to the CH4 -air mixture. A study on the Rayleigh index was carried out in order to analyze the influence of H2 -air mixture on thermoacoustic instability of the burner. Finally an analysis of both frequency and growth rate (GR) on the first four modes was carried out by comparing the two mixtures. In the H2 -air case the modes are prone to become more unstable with respect to the same modes of the case fueled by CH4 -air due to the change in flame topology and variation of the heat release rate and time delay fields.

As the global energy landscape transitions towards a more sustainable future hydrogen has emerged as a promising energy carrier due to its potential to decarbonize various sectors. However the economic competitiveness of hydrogen production by water electrolysis strongly depends on renewable energy source (RES) availability. Thus it is necessary to overcome the challenges related to the intermittent nature of RESs. This paper presents a comprehensive techno-economic analysis of complementing green hydrogen production with grid electricity. An evaluation model for the levelized cost of hydrogen (LCOH) is proposed considering both CO2 emissions and the influence of RES fluctuations on electrolyzers. A minimum load restriction is required to avoid crossover gas. Moreover a new operation strategy is developed for hydrogen production plants to determine optimal bidding in the grid electricity market to minimize the LCOH. We evaluate the feasibility of the proposed approach with a case study based on data from the Kyushu area in Japan. The results show that the proposed method can reduce the LCOH by 11% to 33% and increase hydrogen productivity by 86% to 140% without significantly increasing CO2 emission levels.

Hydrogen is an emerging technology changing the context of heating with cleaner combustion than traditional fossil fuels. Studies indicate the potential to repurpose the existing natural gas infrastructure offering consumers a sustainable economically viable option in the future. The integration of hydrogen in combined heat and power systems could provide residential energy demand and reduce environmental emissions. However the widespread adoption of hydrogen will face several challenges such as carbon dioxide emissions from the current production methods and the need for infrastructure modification for transport and safety. Researchers indicated the viability of hydrogen in decarbonizing heat while some studies also challenged its long-term role in the future of heating. In this paper a comprehensive literature review is carried out by identifying the following key aspects which could impact the conclusion on the overall role of hydrogen in heat decarbonization: (i) a holistic view of the energy system considering factors such as renewable integration and system balancing; (ii) consumer-oriented approaches often overlook the broader benefits of hydrogen in emission reduction and grid stability; (iii) carbon capture and storage scalability is a key factor for large-scale production of low-emission blue hydrogen; (iv) technological improvements could increase the cost-effectiveness of hydrogen; (v) the role of hydrogen in enhancing resilience especially during extreme weather conditions raises the potential of hydrogen as a flexible asset in the energy infrastructure for future energy supply; and finally when considering the UK as a basis case (vi) incorporating factors such as the extensive gas network and unique climate conditions necessitates specific strategies.

Proton Exchange Membrane Fuel Cells (PEMFCs) are seen as an alternative for heavy-duty transportation electrification. Powered by a green hydrogen source they can provide high efficiency and low carbon emissions compared to traditional fuels. However to be competitive these systems require high reliability when operated in real-life conditions as well as safe and efficient operating management. In order to achieve these goals the X-in-the-loop (also called model-based design) methodology is well suited. It has been largely adopted for PEMFC system development and optimisation as they are complex multi-component systems. In this paper a systematic analysis of the scientific literature is conducted to review the methodology implementation for the design and improvement of the PEMFC systems. It exposes a precise definition of each development step in the methodology. The analysis shows that it can be employed in different ways depending on the subsystems considered and the objectives sought. Finally gaps in the literature and technical challenges for fuel cell systems that should be addressed are identified.

Acceleration of the hydrogen economy is being observed on a global scale. It is considered to be a potential solution to the problems with high-carbon energy industry and transport systems. The potential of production cost-competitiveness and opportunities are currently being investigated to provide insights to policymakers researchers and industry. In this context this study makes a quantitative assessment of the competitiveness of hydrogen storage compared to Li-ion batteries based on price arbitrage in the day-ahead market. Two scenarios that form the boundaries of rational decision-making regarding the charging and discharging of energy storage are considered. The first one assumes the charging and discharging of energy storage facilities over the same hours throughout the entire year. The selection of these hours is based on historical electricity prices. The second scenario assumes charge and discharge during historical daily minimum and maximum prices. The results show that NPV is below zero for both technologies when current values of investment expenditure are assumed. The outcomes of sensitivity analysis indicate that only a substantial reduction of investment expenditure could improve the financial results of the Li-ion batteries (NPV>0). The investigation also shows that even simplified charge and discharge over the same hours allows one to achieve 47% (hydrogen) and 70% (Li-ion batteries) of the maximum operating profit when the perfect foresight of prices is applied. In each case NPV for Li-ion technology is significantly higher than for hydrogen; for example for a 1 MWh and 1 MWout storage system NPV is EUR -4.85 million in the case of hydrogen and with Li-ion NPV is EUR -0.23 million. Consequently the application of expensive decision support systems in small systems may be unprofitable. The increase in profits may not cover the cost of developing and introducing such a system.

Renewable energy (solar and wind) sources have evolved dramatically in recent years around the globe primarily because they have the potential to generate environmentally friendly energy. However operating systems with high renewable energy penetration remain challenging due to the stochastic nature of these energy sources. To tackle these problems the authors propose a state machine-based energy management strategy combined with a hysteresis band control strategy for renewable energy hybrid microgrids that integrates hydrogen storage systems. By considering the power difference between the renewable energy source and the demand the battery’s state of charge and the hydrogen storage level the proposed energy management strategy can control the power of fuel cells electrolyzers and batteries in a microgrid and the power imported into/exported from the main grid. The results showed that the energy management strategy provides the following advantages: (1) the power supply and demand balance in the microgrid was balanced (2) the lifespans of the electrolyzer and fuel cell were extended and (3) the state of charge of the battery and the stored level of the hydrogen were appropriately ensured.

Using photovoltaic (PV) energy to produce hydrogen through water electrolysis is an environmentally friendly approach that results in no contamination making hydrogen a completely clean energy source. Alkaline water electrolysis (AWE) is an excellent method of hydrogen production due to its long service life low cost and high reliability. However the fast fluctuations of photovoltaic power cannot integrate well with alkaline water electrolyzers. As a solution to the issues caused by the fluctuating power a hydrogen production system comprising a photovoltaic array a battery and an alkaline electrolyzer along with an electrical control strategy and energy management strategy is proposed. The energy management strategy takes into account the predicted PV power for the upcoming hour and determines the power flow accordingly. By analyzing the characteristics of PV panels and alkaline water electrolyzers and imposing the proposed strategy this system offers an effective means of producing hydrogen while minimizing energy consumption and reducing damage to the electrolyzer. The proposed strategy has been validated under various scenarios through simulations. In addition the system’s robustness was demonstrated by its ability to perform well despite inaccuracies in the predicted PV power.

In the context of the European decarbonization strategy hydrogen is a key energy carrier in the medium to long term. The main advantages deriving from a greater penetration of hydrogen into the energy mix consist in its intrinsic characteristics of flexibility and integrability with alternative technologies for the production and consumption of energy. In particular hydrogen allows to: i) decarbonise end uses since it is a zero-emission energy carrier and can be produced with processes characterized by the absence of greenhouse gases emissions (e.g. water electrolysis); ii) help to balancing electricity grid supporting the integration of non-programmable renewable energy sources; iii) exploit the natural gas transmission and distribution networks as storage systems in overproduction periods. However the hydrogen injection into the natural gas infrastructures directly influences thermophysical properties of the gas mixture itself such as density calorific value Wobbe index speed of sound etc [1]. The change of the thermophysical properties of gaseous mixture in turn directly affects the end use service in terms of efficiency and safety as well as the metrological performance and reliability of the volume and gas quality measurement systems. In this paper the authors present the results of a study about the impact of hydrogen injection on the properties of the natural gas mixture. In detail the changes of the thermodynamic properties of the gaseous mixtures with different hydrogen content have been analysed. Moreover the theoretical effects of the aforementioned variations on the accuracy of the compressibility factor measurement have been also assessed.

There is renewed interest in hydrogen as an alternative fuel for aero engines due to their perceived environmental and performance benefits compared to jet fuel. This paper presents a cycle thermal performance energy and creep life assessment of hydrogen compared with jet fuel using a turbofan aero engine. The turbofan cycle performance was simulated using a code developed by the authors that allows hydrogen and jet fuel to be selected as fuel input. The exergy assessment uses both conservations of energy and mass and the second law of thermodynamics to understand the impact of the fuels on the exergy destruction exergy efficiency waste factor ratio environmental effect factor and sustainability index for a turbofan aero engine. Finally the study looks at a top-level creep life assessment on the high-pressure turbine hot section influenced by the fuel heating values. This study shows performance (64% reduced fuel flow rate better SFC) and more extended blade life (15% increase) benefits using liquefied hydrogen fuel which corresponds with other literary work on the benefits of LH2 over jet fuel. This paper also highlights some drawbacks of hydrogen fuel based on previous research work and gives recommendations for future work aimed at maturing the hydrogen fuel concept in aviation.

Decarbonisation of heavy haul rail is an essential contributor to a zero-emissions future. However the transition from diesel to battery locomotives is not always practical given the unique characteristics of each haul. This paper demonstrates the limitations of state-of-the-art batteries using real-world data from multiple locomotives operating in Australian rail freight. An energy model was developed to assess each route’s required energy and potential regenerated energy. The tractive and regenerative battery energy mass and cost were determined using data from the energy model coupled with battery specifications. The feasibility of implementing lithium iron phosphate (LFP) nickel manganese cobalt (NMC) and lithium titanium oxide (LTO) chemistries was explored based on cost energy density cycle lifespan and locomotive data. LFP was identified as the most suitable current battery solution based on current chemistries. Further examination of the energy demands and associated mass/volume constraints concluded that three platforms are required for heavy haul rail decarbonisation i) a battery electric locomotive for low-energy demands which can be coupled with either ii) a battery electric tender for medium energy demands or iii) a hydrogen fuel cell electric tender for higher energy demands. A future-looking techno-economic assessment of battery and hydrogen fuel cell platforms concludes that the lowest cost solution for low-energy hauls is a battery-only system and for high-energy hauls a battery-hydrogen system.

Green liquid hydrogen (LH2) could play an essential role as a zero-carbon aircraft fuel to reach long-term sustainable aviation. Excluding challenges such as electrolysis transportation and use of renewable energy in setting up hydrogen (H2) fuel infrastructure this paper investigates the interface between refueling systems and aircraft and the impacts on fuel distribution at the airport. Furthermore it provides an overview of key technology design decisions for LH2 refueling procedures and their effects on the turnaround times as well as on aircraft design. Based on a comparison to Jet A-1 refueling new LH2 refueling procedures are described and evaluated. Process steps under consideration are connecting/disconnecting purging chill-down and refueling. The actual refueling flow of LH2 is limited to a simplified Reynolds term of v · d = 2.35 m2/s. A mass flow rate of 20 kg/s is reached with an inner hose diameter of 152.4 mm. The previous and subsequent processes (without refueling) require 9 min with purging and 6 min without purging. For the assessment of impacts on LH2 aircraft operation process changes on the level of ground support equipment are compared to current procedures with Jet A-1. The technical challenges at the airport for refueling trucks as well as pipeline systems and dispensers are presented. In addition to the technological solutions explosion protection as applicable safety regulations are analyzed and the overall refueling process is validated. The thermodynamic properties of LH2 as a real compressible fluid are considered to derive implications for airport-side infrastructure. The advantages and disadvantages of a subcooled liquid are evaluated and cost impacts are elaborated. Behind the airport storage tank LH2 must be cooled to at least 19 K to prevent two-phase phenomena and a mass flow reduction during distribution. Implications on LH2 aircraft design are investigated by understanding the thermodynamic properties including calculation methods for the aircraft tank volume and problems such as cavitation and two-phase flows. In conclusion the work presented shows that LH2 refueling procedure is feasible compliant with the applicable explosion protection standards and hence does not impact the turnaround procedure. A turnaround time comparison shows that refueling with LH2 in most cases takes less time than with Jet A-1. The turnaround at the airport can be performed by a fuel truck or a pipeline dispenser system without generating direct losses i.e. venting to the atmosphere.

Hydrogen gas will be an essential energy carrier for global energy systems in the future. However non-renewable sources account for 96% of the production. Food wastes have high hydrogen generation potential which can positively influence global production and reduce greenhouse gas (GHG) emissions. The study evaluates the potential of food waste hydrogen-based power generation through biogas steam reforming and its environmental and economic impact in major Ghanaian cities. The results highlight that the annual hydrogen generation in Kumasi had the highest share of 40.73 kt followed by Accra with 31.62 kt while the least potential was in Tamale (3.41 kt). About 2073.38 kt was generated in all the major cities. Hydrogen output is predicted to increase from 54.61 kt in 2007 to 119.80 kt by 2030. Kumasi produced 977.54 kt of hydrogen throughout the 24-year period followed by Accra with 759.76 kt Secondi-Takoradi with 255.23 kt and Tamale with 81.85 kt. According to the current study Kumasi had the largest percentage contribution of hydrogen (47.15%) followed by Accra (36.60%) Secondi-Takoradi (12.31%) and Tamale (3.95%). The annual power generation potential in Kumasi and Accra was 73.24 GWh and 56.85 GWh. Kumasi and Accra could offset 8.19% and 6.36% of Ghana's electricity consumption. The total electricity potential of 3728.35 GWh could displace 17.37% of Ghana's power consumption. This electricity generated had a fossil diesel displacement capacity of 1125.90 ML and could reduce GHG emissions by 3060.20 kt CO2 eq. Based on the findings the total GHG savings could offset 8.13% of Ghana's carbon emissions. The cost of power generation from hydrogen is $ 0.074/kWh with an annual positive net present value of $ 658.80 million and a benefit-to-cost ratio of 3.43. The study lays the foundation and opens policy windows for sustainable hydrogen power generation in Ghana and other African countries.

The production storage and use of hydrogen for energy purposes will become increasingly important during the energy transition. One way to use hydrogen is to apply it to power vehicles. This green technological solution affects low-emissions transport which is beneficial and important especially in cities. The authors of this article analyzed the use of hydrogen production infrastructure for bus propulsion in the city of Katowice (Poland). The methods used in the study included a greedy algorithm and cost methods which were applied for the selection of vehicles and identification of the infrastructure for the production storage and refueling of hydrogen as well as to conduct the economic analysis during this term. The article presented the complexity of the techno-economic analysis of the infrastructure and its installation. The key element was the selection of the number of vehicles to the hydrogen production possibilities of an electrolyser and capabilities of the storage and charging infrastructure.

Technical economic and environmental assessments of projected power-to-gas (PtG) deployment scenarios at distributed- to national-scale are reviewed as well as their extensions to nuclear-assisted renewable hydrogen. Their collective research trends outcomes challenges and limitations are highlighted leading to suggested future work areas. These studies have focused on the conversion of excess wind and solar photovoltaic electricity in European-based energy systems using low-temperature electrolysis technologies. Synthetic natural gas either solely or with hydrogen has been the most frequent PtG product. However the spectrum of possible deployment scenarios has been incompletely explored to date in terms of geographical/sectorial application environment electricity generation technology and PtG processes products and their end-uses to meet a given energy system demand portfolio. Suggested areas of focus include PtG deployment scenarios: (i) incorporating concentrated solar- and/or hybrid renewable generation technologies; (ii) for energy systems facing high cooling and/or water desalination/treatment demands; (iii) employing high-temperature and/or hybrid hydrogen production processes; and (iv) involving PtG material/energy integrations with other installations/sectors. In terms of PtG deployment simulation suggested areas include the use of dynamic and load/utilization factor-dependent performance characteristics dynamic commodity prices more systematic comparisons between power-to-what potential deployment options and between product end-uses more holistic performance criteria and formal optimizations.