Applications & Pathways

The transition from traditional petrol-based combustion engines to hydrogen-powered systems represents a promising advancement in sustainable and clean energy solutions. This review paper explores the intricacies of converting a conventional internal combustion engine to operate on hydrogen gas. Key topics include the performance limitations of hydrogen engines the role of water injection in combustion modulation and the investigation of direct injection and port injection systems. This review also examines challenges associated with lean and rich mixtures risks of backfire and pre-ignition and the conversion’s overall impact on engine performance and longevity. Additionally this paper discusses hydrogen lubrication to prevent mechanical wear and addresses emission-related considerations.

Hydrogen valleys are encompassed within a defined geographical region with various technologies across the entire hydrogen value chain. The scope of this study is to analyze and assess the different hydrogen technologies for their application within the hydrogen valley context. Emphasizing on the coupling of renewable energy sources with electrolyzers to produce green hydrogen this study is focused on the most prominent electrolysis technologies including alkaline proton exchange membrane and solid oxide electrolysis. Moreover challenges related to hydrogen storage are explored alongside discussions on physical and chemical storage methods such as gaseous or liquid storage methanol ammonia and liquid organic hydrogen carriers. This article also addresses the distribution of hydrogen within valley operations especially regarding the current status on pipeline and truck transportation methods. Furthermore the diverse applications of hydrogen in the mobility industrial and energy sectors are presented showcasing its potential to integrate renewable energy into hard-to-abate sectors.

Hydrogen (H2) offers a green medium for storing the excess from renewables production instead of dumping it thus being crucial to decarbonisation efforts. Hydrogen also offers a storage medium for the grid’s cheap electricity to be used during grid peak demand or grid power cutoffs. Funded by the Scottish Government’s Emerging Energy Technologies this paper presents the design and performance analysis of a hydrogen uninterruptible power supply (H2GEN) for Cygnas Solutions Ltd. which is intended to enable continuity of supply in the residential sector while eradicating the need for environmentally and health risky lead–acid batteries and diesel generator backup. This paper presents the design optimal sizing and analysis of two H2Gen architectures one powered by the grid alone and the other powered by both the grid and a renewable (PV) source. By developing a model of each architecture in the HOMER space and using residential location weather data the home yearly load–demand profile and the grid yearly power outages profile in the developed models the optimal sizing of each H2Gen design was realised by minimising the costs while ensuring the H2Gen meets the home power demand during grid outages To enable HOMER to optimise its selection the sizes technical specifications and costs of all the market-available H2GEN components were added in the HOMER search space. Moreover the developed models were also used in assessing the sensitivity of the simulation outputs to several changes in the modelled system design and settings. Using a residential home with frequent power outages in New Delhi India as a case study it was found that the optimal sizing of H2Gen Architecture 1 is comprised of a 2 kW electrolyser a 0.2 kg type-I tank and a 2 kW water-cooled fuel cell directly connected to the AC bus offering an operational lifetime of 14.3 years. It was also found that the optimal sizing of Architecture 2 is comprised of a 1 kV PV utilised with the same 2 kW electrolyser 0.2 kg type-I tank and 2 kW water-cooled fuel cell connected to the AC bus. While the second design was found to have a higher capital cost due to the added PV it offered a more cost-effective and environmentally friendly architecture which contributes to the ongoing energy transition. This paper further investigated the capacity expansion of each H2GEN architecture to meet higher load demands or increased grid power outages. From the analysis of the simulation results it has been concluded that the most feasible and cost-effective H2GEN system expansion for meeting increased power demands or increased grid outages can be realised by using the developed models for optimally sizing the expanded H2Gen on a case-by-case basis because the increase in these profiles is highly time-dependent (for example an increased load demand or increased grid outage in the morning can be met by the PV while in the evening it must be met by the H2GEN). Finally this paper investigated the impact of other environmental variables such as the temperature and relative humidity on the H2GEN’s performance and provided further insights into increasing the overall system efficiency and cost benefit through utilising the H2GEN’s exhaust heat in the home space for heating/cooling and selling the electrolyser exhaust’s O2 as a commodity.

To reduce carbon dioxide emissions from the steel industry efforts are made to introduce a steelmaking route based on hydrogen reduction of iron ore instead of the commonly used cokebased reduction in a blast furnace. Changing fundamental pieces of steelworks affects the functions of most every system unit involved and thus warrants the question of how such a transition could optimally take place over time and no rigorous attempts have until now been made to tackle this problem mathematically. This article presents a steel plant optimization model written as a mixed-integer non-linear programming problem where aging blast furnaces and basic oxygen furnaces could potentially be replaced with shaft furnaces and electric arc furnaces minimizing costs or emissions over a long-term time horizon to identify possible transition pathways. Example cases show how various parameters affect optimal investment pathways stressing the necessity of appropriate planning tools for analyzing diverse cases.

Fuel cell electric vehicles are getting deployed exponentially in Europe. Hydrogen fuel quality regulations are getting into place in order to protect customers and ensure end-users satisfactory experiences. It became critical to have the capability to sample and analyse accurately hydrogen fuel delivered by hydrogen refuelling stations in Europe. This study presents two separate comparisons: the first bilateral comparison between two sampling systems (H2 Qualitizer) and (“H2 Sampling System” of Air Liquide) and the interlaboratory comparison between NPL and Air Liquide on hydrogen fuel quality testing according to EN 17124. The two sampling systems showed equivalent results for all contaminants for sampling at 70 MPa hydrogen refuelling stations. The two laboratories showed good agreement at 95% confidence level. Even if the study is limited due to the low number of samples it demonstrates the equivalence of two sampling strategies and the ability of two laboratories to perform accurate measurement of hydrogen fuel quality.

This paper aims at the development and validation of a computational fluid dynamic (CFD) model for simulations of the refuelling process through the entire equipment of the hydrogen refuelling station (HRS). The absence of such models hinders the design of inherently safer refuelling protocols for an arbitrary combination of HRS equipment hydrogen storage parameters and environmental conditions. The CFD model is validated against the complete process of refuelling lasting 195s in Test No.1 performed by the National Renewable Energy Laboratory (NREL). The test equipment includes high-pressure tanks of HRS pressure control valve (PCV) valves pipes breakaway hose and nozzle all the way up to three onboard tanks. The model accurately reproduced hydrogen temperature and pressure through the entire line of HRS equipment. A standout feature of the CFD model distinguishing it from simplified models is the capability to predict temperature non-uniformity in onboard tanks a crucial factor with significant safety implications.

Optimal design and performance analysis of renewable energy system to serve the cruise ship main and auxiliary power in Stockholm Sweden is presented in this paper. The goal is to integrate renewable energy systems in small and large ships for greener and sustainable marine transport. The power load for the cruise ship was determined and modeling and simulation analysis was used to investigate the daily and annual performance of the power system architectures including the efficiency and capacity factors of the energy conversion systems. The total electrical power generated from the solar PV PEM fuel cell and Diesel generator; the cost of electricity; and the greenhouse gas and particulate matter PM emissions were determined. The proposed renewable energy system offers a good penetration of renewable energy system (13.83%) and greenhouse gas and particulate emissions reduction (9.84% emissions reduction compared to baseline system using Diesel engines). The integration of renewable and clean power systems such as solar PV and PEM fuel cell (high electrical efficiency) is very attractive solution for onboard ship power generation. They are economically viable (reduce the cost of Diesel fuel) cleaner than the conventional gas turbine and internal combustion engines and reduce the dependency on fossil fuel.

Nowadays integrating renewable energy sources (RESs) poses significant challenges due to the deterioration of performance indices especially in cold-climate unbalanced microgrids. Beyond network unbalance harsh conditions with low irradiance weak wind speeds and low temperatures necessitate hydrogen storage systems (HSSs) to address seasonal mismatches between RES generation and demand. This paper proposes a two-stage multi-timescale planning framework that integrates RESs plug-in electric vehicles (PEVs) battery energy storage systems (BESSs) seasonal HSSs and a dynamic demand response (DDR) program. In the short term BESSs are coordinated under slow and fast charging/discharging modes for responding to daily load shifting and peak shaving or sudden demand fluctuations. Smart converters with active/reactive power control are equipped with RES and BESS for local voltage regulation. Furthermore the proposed DDR program which combines load reduction and valley filling strategies enables consumer flexibility based on real-time market signals across seasonal variations. Seasonal HSSs are designed to store excess hydrogen produced from RESs for long-term use across different seasons. The proposed strategy is validated in two stages. The first stage guarantees multitimescale coordination of BESSs seasonal HSSs and the DDR. In turn the second stage optimally plans RESs BESSs and HSSs in a unified manner to reduce voltage unbalance and line congestion while maximizing microgrid RES hosting capacity. Simulation results for six interconnected microgrids demonstrate a 12.5% reduction in voltage unbalance 21% alleviation of line congestion and a 108% increase in hosting capacity highlighting the effectiveness of the proposed planning approach for unbalanced RES-rich microgrids.

Hydrogen fuel cell electric trucks and battery electric trucks can significantly contribute to the decarbonisation of the heavy-duty vehicles transport segment. Nonetheless a paucity of hydrogen refuelling and fast-charging stations can represent a hindrance to the development of zero-emission vehicles. This work aims to provide a techno-economic analysis with a view to comparing the costs of hydrogen refuelling and electric charging and evaluating their effects on the total cost of ownership of zero-emission trucks. Thus a comprehensive analysis has been conducted on off-site compressed (CH2) cryo-compressed subcooled hydrogen refuelling stations in conjunction with a fast-charging station. The resulting levelized costs of hydrogen and charging have been incorporated into the total cost of ownership analysis. Thus it has been demonstrated that battery electric trucks are more costeffective than hydrogen-fuel cell electric trucks. The findings of this study indicate that the costs associated with electric charging and hydrogen refuelling are comparable and the economic profitability is contingent upon a number of techno-economic variables. Therefore it is not possible to determine a priori whether one solution is more economically competitive than the other. A mixed infrastructure can represent an opportunity for the transport sector decarbonisation whereby electric-charging and hydrogen-refuelling are not mutually exclusive.

Proton exchange membrane fuel cells (PEMFCs) present great potential for the decarbonization of the maritime sector but their durability in harsh marine environments remains a critical challenge. This review focuses on post-mortem analysis techniques as a tool to understand the degradation mechanisms of PEMFCs under stressors relevant to marine applications. In further detail the application of various imaging (SEM TEM) structural (XRD) electrochemical (CV) and elemental analysis (EDS) methods to characterize the effects of key stressors such as salt spray mechanical vibration and operational cycling was examined. By analyzing degraded PEMFC components post-mortem analysis reveals critical insights into catalyst layer degradation membrane damage and the impact of impurities enabling the identification of failure modes and the development of effective mitigation strategies for the establishment of PEMFCs in the maritime sector.