Applications & Pathways

The maritime industry is recognized as a major pollution source to the environment. The use of low- or zero-carbon marine alternative fuel is a promising measure to reduce emissions of greenhouse gases and toxic pollutants leading to net-zero carbon emissions by 2050. Hydrogen (H2 ) fuel cells particularly proton exchange membrane fuel cell (PEMFC) and ammonia (NH3 ) are screened out to be the feasible marine gaseous alternative fuels. Green hydrogen can reduce the highest carbon emission which might amount to 100% among those 5 types of hydrogen. The main hurdles to the development of H2 as a marine alternative fuel include its robust and energy-consuming cryogenic storage system highly explosive characteristics economic transportation issues etc. It is anticipated that fossil fuel used for 35% of vehicles such as marine vessels automobiles or airplanes will be replaced with hydrogen fuel in Europe by 2040. Combustible NH3 can be either burned directly or blended with H2 or CH4 to form fuel mixtures. In addition ammonia is an excellent H2 carrier to facilitate its production storage transportation and usage. The replacement of promising alternative fuels can move the marine industry toward decarbonization emissions by 2050.

There is an impetus to decarbonize transportation sector and mitigate climate change. This study examines the effect of adopting hydrogen (H2) as a fuel for Dubai Buses at different penetration scales on carbon dioxide (CO2) emissions reduction. A H2 supply-chain system dynamics model is developed to conduct life cycle cost and environmental analysis and evaluate the efficacy of different carbon prices and subsidies. Gray green and mixed H2 production scenarios were considered. The results show that gray hydrogen reduces 7.1 million tons of CO2 which is half of green hydrogen buses. Replacing diesel fleet at end of lifetime with mixed hydrogen bus fleet was the optimal approach to promote green hydrogen at pump reaching $4/kg in a decade. This gradual transition reduces 62% of the well-to-wheel CO2 emissions of the new bus fleet and creates mass for economies of scale as carbon prices and subsidies cannot promote green hydrogen alone.

In this study real voyage data and ship specifications of a general cargo ship are employed and it is assumed that diesel generators are replaced with hydrogen proton exchange membrane fuel cells. The effect of the replacement on CO2 NOX SOX and PM emissions and the CII value is calculated. Emission calculations show that there is a significant reduction in emissions when hydrogen fuel cells are used instead of diesel generators on the case ship. By using hydrogen fuel cells there is a 37.4% reduction in CO2 emissions 32.5% in NOX emissions 37.3% in SOX emissions and 37.4% in PM emissions. If hydrogen fuel cells are not used instead of diesel generators the ship will receive an A rating between 2023 and 2026 a B rating in 2027 a C rating in 2028–2029 and an E rating in 2030. On the other hand if hydrogen fuel cells are used the ship will always remain at an A rating between 2023 and 2030. The capital expenditure (CAPEX) and operational expenditure (OPEX) of the fuel cell system are USD 1305720 and USD 2470320 respectively for a 15-year lifetime and the hydrogen fuel expenses are competitive at USD 260981 while marine diesel oil (MDO) fuel expenses are USD 206435.

One of the key factors of the current energy transition is the use of hydrogen (H2 ) as fuel in energy transformation technologies. This fuel has the advantage of being produced from the most primary forms of energy and has the potential to reduce carbon dioxide (CO2 ) emissions. In recent years hydrogen or hydrogen-rich mixtures in internal combustion engines (ICEs) have gained popularity with numerous reports documenting their use in spark ignition (SI) and compression ignition (CI) engines. Homogeneous charge compression ignition (HCCI) engines have the potential for substantial reductions in nitrogen oxides (NOx) and particulate matter (PM) emissions and the use of hydrogen along with this kind of combustion could substantially reduce CO2 emissions. However there have been few reports using hydrogen in HCCI engines with most studies limited to evaluating technical feasibility combustion characteristics engine performance and emissions in laboratory settings at sea level. This paper presents a study of HCCI combustion using hydrogen in a stationary air-cooled Lombardini 25 LD 425-2 modified diesel engine located at 1495 m above sea level. An experimental phase was conducted to determine the intake temperature requirements and equivalence ratios for stable HCCI combustion. These results were compared with previous research carried out at sea level. To the best knowledge of the authors this is the first report on the combustion and operational limits for an HCCI engine fueled with hydrogen under the mentioned specific conditions. Equivalence ratios between 0.21 and 0.28 and intake temperatures between 188 ◦C and 235 ◦C effectively achieved the HCCI combustion. These temperature values were on average 100 ◦C higher than those reported in previous studies. The maximum value for the indicated mean effective pressure (IMEPn) was 1.75 bar and the maximum thermal efficiency (ITEn) was 34.5%. The achieved results are important for the design and implementation of HCCI engines running solely on hydrogen in developing countries located at high altitudes above sea level.

All diesel-only trains in the UK will be removed from services by 2040. High volumetric density rapid refuelling ability and sophisticated experience in infrastructure and logistics make ammonia a perfect hydrogen carrying fuel for rail freight which urgently requires an economically viable solution. This study conducted a novel techno-economic study of ammonia-fuelled fuel cell powertrains to be compared with current diesel engine-based system and emerging direct hydrogen-fuelled fuel cell system. The results demonstrate that hydrogen-fuelled Proton Exchange Membrane Fuel Cells (PEMFCs) and ammonia-fuelled PEMFCs (using an ammonia cracker) are more cost-effective in terms of Levelized Cost of Electricity. The ammonia fuel storage requires 61.5-75 % less space compared to the hydrogen storage. Although the ammonia-fuelled Solid Oxide Fuel Cells (SOFCs) powertrain has the highest electricity generation efficiency (56%) the overall cost requires a major reduction by 70% before it could be considered as an economically viable solution.

Liquid hydrogen (LH2) aircraft have the potential to achieve carbon neutrality. However if the hydrogen is produced using electricity grids that utilise fossil fuel they have a non-zero carbon dioxide (CO2) emission associated with their well-to-wing pathway. To assess the potential of LH2 in aviation decarbonisation an energy systems comparison of large commercial LH2 liquified natural gas (LNG) conventional Jet-A and LH2 dual-fuel aircraft is presented. The performance of each aircraft is compared towards 2050 over which three system changes occur: (1) LH2 aircraft technology develops; (2) both world average and region-specific grid electricity which is used to produce the hydrogen decarbonises; and (3) the International Air Transportation Association (IATA) emissions targets which are used to restrict the passenger-range performance of each aircraft tighten. In 2050 the emissions of all aircraft are thus constrained to 0.063 kg-CO2/p-km relative to 0.110 kg-CO2/p-km for the unconstrained Jet A fuelled Boeing 787-8. It is estimated that in this year an LH2 aircraft powered by fuel cells and sourcing world average electricity can travel 6000 km 20% further than the conventional Jet A aircraft that is also constrained to meet the IATA targets but not as far as the LNG aircraft. At its maximum range the LH2 aircraft carries 84% of the Jet A passenger demand. Analysis using region-specific hydrogen indicates that LH2 aircraft can travel further than LNG aircraft in North America only accounting for 17% of the global demand. 1.59 times the current aviation energy consumption is required if all conventional aircraft are replaced with LH2 designs. Under stricter emissions constraints than those outlined by the IATA LH2 outperforms LNG in Europe and the Americas accounting for 41% of the global demand. Also in these regions the range energy consumption and passenger capacity of LH2 aircraft can be improved upon by combining the advantages of LH2 with LNG in dual-fuel aircraft concepts. The use of LH2 is therefore advantageous within several prominent niches of a future decarbonising aviation system.

Ammonia a molecule that is gaining more interest as a fueling vector has been considered as a candidate to power transport produce energy and support heating applications for decades. However the particular characteristics of the molecule always made it a chemical with low if any benefit once compared to conventional fossil fuels. Still the current need to decarbonize our economy makes the search of new methods crucial to use chemicals such as ammonia that can be produced and employed without incurring in the emission of carbon oxides. Therefore current efforts in this field are leading scientists industries and governments to seriously invest efforts in the development of holistic solutions capable of making ammonia a viable fuel for the transition toward a clean future. On that basis this review has approached the subject gathering inputs from scientists actively working on the topic. The review starts from the importance of ammonia as an energy vector moving through all of the steps in the production distribution utilization safety legal considerations and economic aspects of the use of such a molecule to support the future energy mix. Fundamentals of combustion and practical cases for the recovery of energy of ammonia are also addressed thus providing a complete view of what potentially could become a vector of crucial importance to the mitigation of carbon emissions. Different from other works this review seeks to provide a holistic perspective of ammonia as a chemical that presents benefits and constraints for storing energy from sustainable sources. State-of-the-art knowledge provided by academics actively engaged with the topic at various fronts also enables a clear vision of the progress in each of the branches of ammonia as an energy carrier. Further the fundamental boundaries of the use of the molecule are expanded to real technical issues for all potential technologies capable of using it for energy purposes legal barriers that will be faced to achieve its deployment safety and environmental considerations that impose a critical aspect for acceptance and wellbeing and economic implications for the use of ammonia across all aspects approached for the production and implementation of this chemical as a fueling source. Herein this work sets the principles research practicalities and future views of a transition toward a future where ammonia will be a major energy player.

Electrofuels including hydrogen methane and ammonia have been suggested as one pathway in achieving net-zero greenhouse gas energy systems. They can play a role in providing an energy storage and fuel or feedstock to hard-to-abate sectors. In future energy systems their role is often studied in case studies adhering to specific region. In this study we study their role by defining multiple archetypal energy systems which represent approximations of real systems in different regions. Comparing the role of electrofuels across the cost-optimized systems relying only on renewable energy in power generation we found that hydrogen was a significant energy vector in all systems with its annual quantity approaching the classic electricity demand. The role of renewable methane was very limited. Electrofuel storages were needed in all systems and their capacity was the highest in the northern Hemiboreal system. Absence of cavern storage potential did not hamper the significance of electrofuels but increased the role of ammonia and led to average 5.5 % systemic cost increase. Systems where reservoir hydropower was scarce or level of electricity consumption was high needed more fuel storages. The findings of this study can help for better understanding of what kind of storage and generation technologies will be most useful in future carbon-neutral systems in different types of regions.

Green energy is at the forefront of current policy research and engineering but some of the potential fuels require either a lot of deeper research or a lot of infrastructure before they can be implemented. In the case of hydrogen both are true. This report aims to analyse the potential of hydrogen as a future fuel source by performing a life-cycle assessment. Through this the well-to-tank phase of fuel production and the usage phase of the system have been analysed. Models have also been created for traditional fuel systems to best compare results. The results show that hydrogen has great potential to convert marine transport to operating off green fuels when powered through low-carbon energy sources which could reduce a huge percentage of the international community’s greenhouse gas emissions. Hydrogen produced through wind powered alkaline electrolysis produced emission data 5.25 g of CO2 equivalent per MJ compared to the 210 g per MJ produced by a medium efficiency diesel equivalent system a result 40 times larger. However with current infrastructure in most countries not utilising a great amount of green energy production the effects of hydrogen usage could be more dangerous than current fuel sources owing to the incredible energy requirements of hydrogen production with even grid (UK) powered electrolysis producing an emission level of 284 g per MJ which is an increase against standard diesel systems. From this the research concludes that without global infrastructure change hydrogen will remain as a potential fuel rather than a common one.

Traditional charging stations have a single function which usually does not consider the construction of energy storage facilities and it is difficult to promote the consumption of new energy. With the gradual increase in the number of new energy vehicles (NEVs) to give full play to the complementary advantages of source-load resources and provide safe efficient and economical energy supply services this paper proposes the optimal operation strategy of a PV-charging-hydrogenation composite energy station (CES) that considers demand response (DR). Firstly the operation mode of the CES is analyzed and the CES model including a photovoltaic power generation system fuel cell hydrogen production hydrogen storage hydrogenation and charging is established. The purpose is to provide energy supply services for electric vehicles (EVs) and hydrogen fuel cell vehicles (HFCVs) at the same time. Secondly according to the travel law of EVs and HFCVs the distribution of charging demand and hydrogenation demand at different periods of the day is simulated by the Monte Carlo method. On this basis the following two demand response models are established: charging load demand response based on the price elasticity matrix and interruptible load demand response based on incentives. Finally a multi-objective optimal operation model considering DR is proposed to minimize the comprehensive operating cost and load fluctuation of CES and the maximum–minimum method and analytic hierarchy process (AHP) are used to transform this into a linearly weighted single-objective function which is solved via an improved moth–flame optimization algorithm (IMFO). Through the simulation examples operation results in four different scenarios are obtained. Compared with a situation not considering DR the operation strategy proposed in this paper can reduce the comprehensive operation cost of CES by CNY 1051.5 and reduce the load fluctuation by 17.8% which verifies the effectiveness of the proposed model. In addition the impact of solar radiation and energy recharge demand changes on operations was also studied and the resulting data show that CES operations were more sensitive to energy recharge demand changes.