Publications

Proton-Exchange Membrane-Fuel Cells (PEM-FC) are regarded as one of the prime candidates to provide emissions-free electricity for propulsion systems of aircraft. Here a turbocharged Fuel Cell Power System (FCPS) powered with liquid H2 (LH2) is designed and modelled to provide a primary power source in retrofitted Cessna 208 Caravan aircraft. The proposed FCPS comprises multiple PEM-FCs assembled in stacks two single-stage turbochargers to mitigate the variation of the ambient pressure with altitude two preheaters two humidifiers and two combustors. Interlinked component sub-models are constructed in MATLAB and referenced to commercially available equipment. The FCPS model is used to simulate steady-state responses in a proposed 1.5 h (∼350 km) mission flight determining the overall efficiency of the FCPS at 43% and hydrogen consumption of ∼28 kg/h. The multi-stack FCPS is modelled applying parallel fluidic and electrical architectures analysing two power-sharing methods: equally distributed and daisy-chaining. The designed LH2-FCPS is then proposed as a power system to a retrofitted Cessna 208 Caravan and with this example analysed for the probability of failure occurrence. The results demonstrate that the proposed “dual redundant” FCPS can reach failure rates comparable to commercial jet engines with a rate below 1.6 failures per million hours.

Non-catalytic thermal methane cracking (TMC) is an alternative for hydrogen manufacturing and traditional commercial processes in small-scale hydrogen generation. Supplying the high-level temperatures (850–1800°C) inside the reactors and reactor blockages are two fundamental challenges for developing this technology on an industrial scale (Mahdi Yousefi and Donne 2021). A regenerative reactor could be a part of a solution to overcome these obstacles. This study conducted an experimental study in a regenerative reactor environment between 850 and 1170°C to collect the conversion data and investigate the reactor efficiency for TMC processes. The results revealed that the storage medium was a bed for carbon deposition and successfully supplied the reaction’s heat with more than 99.7% hydrogen yield (at more than 1150°C). Results also indicated that the reaction rate at the beginning of the reactor is much higher and the temperature dependence in the early stages of the reaction is considerably higher. However after reaching a particular concentration of Hydrogen at each temperature the influence of temperature on the reaction rate decreases and is almost constant. The type of produced carbon in the storage medium and its auto-catalytic effect on the reactions were also investigated. Results showed that carbon black had been mostly formed but in different sizes from 100 to 2000 nm. Increasing the reactor temperature decreased the size of the generated carbon. Pre-produced carbon in the reactor did not affect the production rate and is almost negligible at more than 850°C.

On today’s episode Alicia Chris and Patrick are chatting with Vonjy Rakajoba UK Managing Director at Robert Bosch. The Bosch Group is a leading global supplier of technology and services and employs roughly 402600 associates worldwide. Its operations are divided into four business sectors: Mobility Solutions Industrial Technology Consumer Goods and Energy and Building Technology. Bosch believes that hydrogen has a bright future as an energy carrier and is making considerable upfront investments in this area. From 2021 to 2024 the company plans to invest around 600 million euros in mobile fuel-cell applications and a further 400 million euros in stationary ones for the generation of electricity and heat. Vonjy is here with us to discuss more about what Bosch’s expansion into the hydrogen energy sector will look like and how the company expects the market to grow moving forward.

The podcast can be found on their website.

The increasing urgency with which climate change must be addressed has led to an unprecedented level of interest in hydrogen as a clean energy carrier. Much of the analysis of hydrogen until this point has focused predominantly on hydrogen production. This paper aims to address this by developing a flexible techno-economic analysis (TEA) tool that can be used to evaluate the potential of future scenarios where hydrogen is produced stored and distributed within a region. The tool takes a full year of hourly data for renewables availability and dispatch down (the sum of curtailment and constraint) wholesale electricity market prices and hydrogen demand as well as other user-defined inputs and sizes electrolyser capacity in order to minimise cost. The model is applied to a number of case studies on the island of Ireland which includes Ireland and Northern Ireland. For the scenarios analysed the overall LCOH ranges from V2.75e3.95/kgH2. Higher costs for scenarios without access to geological storage indicate the importance of cost-effective storage to allow flexible hydrogen production to reduce electricity costs whilst consistently meeting a set demand.

The world-wide sustainability implications of transport technologies remain unclear because their assessment often relies on metrics that are hard to interpret from a global perspective. To contribute to filling this gap here we apply the concept of planetary boundaries (PBs) i.e. a set of biophysical limits critical for operating the planet safely to address the optimal design of sustainable fuel supply chains (SCs) focusing on hydrogen for vehicle use. By incorporating PBs into a mixed-integer linear programming model (MILP) we identify SC configurations that satisfy a given transport demand while minimising the PBs transgression level i.e. while reducing the risk of surpassing the ecological capacity of the Earth. On applying this methodology to the UK we find that the current fossil-based sector is unsustainable as it transgresses the energy imbalance CO2 concentration and ocean acidification PBs heavily i.e. five to 55-fold depending on the downscale principle. The move to hydrogen would help to reduce current transgression levels substantially i.e. reductions of 9–86% depending on the case. However it would be insufficient to operate entirely within all the PBs concurrently. The minimum impact SCs would produce hydrogen via water electrolysis powered by wind and nuclear energy and store it in compressed form followed by distribution via rail which would require as much as 37 TWh of electricity per year. Our work unfolds new avenues for the incorporation of PBs in the assessment and optimisation of energy systems to arrive at sustainable solutions that are entirely consistent with the carrying capacity of the planet.

The energy transition to wind and solar opens up opportunities for green hydrogen as wind and solar generation tend to bring electricity prices down to very low levels. We evaluate whether green hydrogen can integrate well with wind and solar PVs to improve the South Australian electricity grid. Green hydrogen can use membrane electrolysis plants during periods of surplus renewable energy. This hydrogen can then be electrified or used in industry. The green hydrogen system was analysed to understand the financial viability and technical impact of integrating green hydrogen. We also used system engineering techniques to understand the system holistically including the technical social environmental and economic impacts. The results show opportunities for the system to provide seasonal storage grid firming and reliability services. Financially it would need changes to electricity rules to be viable so at present it would not be viable without subsidy.

: In the last decade with the increased concerns about the global environment attempts have been made to promote the replacement of fossil fuels with sustainable sources. For transport which accounts for around a quarter of total greenhouse gas emissions meeting climate neutrality goals will require replacing existing fleets with electric or hydrogen-propelled vehicles. However the lack of adequate decision support approach makes the introduction of new propulsion technologies in the transportation sector a complex strategic decision problem where distorted non-optimal decisions may easily result in long-term negative effects on the performance of logistic operators. This research addresses the problem of transport fleet renewal by proposing a multi-criteria decision-making approach and takes into account the multiple propulsion technologies currently available and the objectives of the EU Green Deal as well as the inherent scenario uncertainty. The proposed approach based on the TOPSIS model involves a novel decision framework referred to as a generalized life cycle evaluation of the environmental and cost objectives which is necessary when comparing green and traditional propulsion systems in a long-term perspective to avoid distorted decisions. Since the objective of the study is to provide a practical methodology to support strategic decisions the framework proposed has been validated against a practical case referred to the strategic fleet renewal decision process. The results obtained demonstrate how the decision maker’s perception of the technological evolution of the propulsion technologies influences the decision process thus leading to different optimal choices.

Airlines are faced with the challenge of reducing their environmental footprint in an effort to push for climate-neutral initiatives that comply with international regulations. In the past the aviation industry has followed the approach of incremental improvement of fuel efficiency while simultaneously experiencing significant growth in annual air traffic. With the increase in air traffic negating any reduction in Greenhouse Gas (GHG) emissions more disruptive technologies such as hydrogen-based onboard power generation are required to reduce the environmental impact of airline operations. However despite initial euphoria and first conceptual studies for hydrogen-powered aircraft several decades ago there still has been no mass adoption to this day. Besides the challenges of a suitable ground infrastructure this can partly be attributed to uncertainties with the associated maintenance requirements and the expected operating costs to demonstrate the economic viability of this technology. With this study we address this knowledge gap by estimating changes towards scheduled maintenance activities for an airborne hydrogen storage and distribution system. In particular we develop a detailed system design for a hydrogen-powered fuel-cell-based auxiliary power generation and perform a comparative analysis with an Airbus A320 legacy system. That analysis allows us to (a) identify changes for the expected maintenance effort to enhance subsequent techno-economic assessments (b) identify implications of specific design assumptions with corresponding maintenance activities while ensuring regulatory compliance and (c) describe the impact on the resulting task execution. The thoroughly examined interactions between system design and subsequent maintenance requirements of this study can support practitioners in the development of prospective hydrogen-powered aircraft. In particular it allows the inclusion of maintenance implications in early design stages of corresponding system architectures. Furthermore since the presented methodology is transferable to different design solutions it provides a blueprint for alternative operating concepts such as the complete substitution of kerosene by hydrogen to power the main engines.

Hydrogen (H2) is expected to be a key instrument to meet the European Union (EU) Green Deal main objective: i.e. climate neutrality by 2050. Renewable hydrogen deployment is expected to significantly reduce EU greenhouse gas (GHG) emissions by displacing carbon-intensive sources of energy. However concerns have been raised recently regarding the potential global warming impact caused by hydrogen emissions. Although hydrogen is neither intentionally emitted to the atmosphere when used nor a direct greenhouse gas hydrogen losses affect atmospheric chemistry indirectly contributing to global warming. To better understand the potential environmental impact of a hydrogen economy and to assess the need for action in this respect the Clean Hydrogen Joint Undertaking and the U.S. Department of Energy jointly organised with the support of the European Commission Hydrogen Europe Hydrogen Europe Research the Hydrogen Council and the International Partnership for Hydrogen and Fuel Cells in the Economy a 2-day expert workshop. Experts agreed that a low-carbon and in particular a renewable hydrogen economy would significantly reduce the global warming impact compared to a fossil fuel economy. However hydrogen losses to the atmosphere will impact the lifetime of other greenhouse gases namely methane ozone and water vapour indirectly contributing to the increase of the Earth’s temperature in the near-term. To minimise the climate impact of a hydrogen economy losses should therefore be minimised prevented and monitored. Unfortunately current loss rates along the hydrogen supply chain are not well constrained and are currently estimated to go from few percents for compressed hydrogen (1-4%) up to 10-20% for liquefied hydrogen. Both the global warming impact of hydrogen emissions and the leakage rates from a developed hydrogen economy are subject to a high level of uncertainty. It is therefore of paramount importance to invest in developing the ability to accurately quantify hydrogen emissions as well as engage in more research on hydrogen leakage prevention and monitoring systems. More data from the hydrogen industry and improved observational capacity are needed to improve the accuracy of the global hydrogen budget. Finally it is recommended to always report the amount and location of hydrogen emissions when environmental assessments are performed. There is a range of emission metrics and time scales that are designed to evaluate the climate impacts of short-lived GHG emissions compared to CO2 (i.e. CO2 equivalents). The metric choice must depend on the specific policy goal as they can provide very different perspectives on the relative importance of H2 emissions on the climate depending on the time horizon of concern. These differences need to be viewed in the context of the specific policy objectives.

Motor vehicles are the backbone of global transport. In recent years due to the rising costs of fossil fuels and increasing concerns about their negative impact on the natural environment the development of low-emission power supply systems for vehicles has been observed. In order to create a stable and safe global transport system an important issue seems to be the diversification of propulsion systems for vehicles which can be achieved through the simultaneous development of conventional internal combustion vehicles electric vehicles (both battery and fuel cell powered) as well as combustion hydrogen-powered vehicles. This publication presents an overview of commercial vehicles (available on the market) powered by internal combustion hydrogen engines. The work focuses on presenting the development of technology from the point of view of introducing ready-made hydrogen-powered vehicles to the market or technical solutions enabling the use of hydrogen mixtures in internal combustion engines. The study covers the history of the technology dedicated hydrogen and bi-fuel vehicles and vehicles with an engine powered by a mixture of conventional fuels and hydrogen. It presents basic technology parameters and solutions introduced by leading vehicle manufacturers in the vehicle market.