Publications

Fuel cell electric vehicles are a promising solution for reducing the environmental impacts of the automotive sector; however there are still some key points to address in finding the most efficient and less impactful implementation of this technology. In this work three electrical architectures of fuel cell electric vehicles were modeled and compared in terms of the environmental impacts of their manufacturing and use phases. The three architectures differ in terms of the number and position of the DC/DC converters connecting the battery and the fuel cell to the electric motor. The life cycle assessment methodology was employed to compute and compare the impacts of the three vehicles. A model of the production of the main components of vehicles and fuel cell stacks as well as of the production of hydrogen fuel was constructed and the impacts were calculated using the program SimaPro. Eleven impact categories were considered when adopting the ReCiPe 2016 midpoint method and the EF (adapted) method was exploited for a final comparison. The results highlighted the importance of the converters and their influence on fuel consumption which was identified as the main factor in the comparison of the environmental impacts of the vehicle.

To achieve carbon neutrality in Japan by 2050 renewable energy needs to be used as the main energy source. Based on the constraints of various renewable energies the importance of hydrogen cannot be ignored. This study aimed to investigate the diffusion of hydrogen demand technologies in various sectors and used projections and assumptions to investigate the hydrogen supply side. By performing simulations with the E3ME-FTT model and comparing various policy scenarios with the reference scenario the economic and environmental impacts of the policy scenarios for hydrogen diffusion were analyzed. Moreover the impact of realizing carbon neutrality by 2050 on the Japanese economy was evaluated. Our results revealed that large-scale decarbonization via hydrogen diffusion is possible (90% decrease of CO2 emissions in 2050 compared to the reference) without the loss of economic activity. Additionally investments in new hydrogen-based and other low-carbon technologies in the power sector freight road transport and iron and steel industry can improve the gross domestic product (1.6% increase in 2050 compared to the reference) as they invoke economic activity and require additional employment (0.6% increase in 2050 compared to the reference). Most of the employment gains are related to decarbonizing the power sector and scaling up the hydrogen supply sector while a lot of job losses can be expected in the mining and fossil fuel industries.

The transition to a decarbonized gas network requires the adaptation of existing infrastructure to accommodate hydrogen and hydrogen-enriched natural gas. This study presents the development of calibration facilities at NEL VSL and DNV for evaluating the performance of flow meters under hydrogen conditions. Nine flow meters were tested covering applications from household consumption to distribution networks. Results demonstrated that rotary displacement meters and diaphragm meters are typically suitable for hydrogen and hydrogenenriched natural gas domestic and commercial consumers use. Tests results for an orifice meter confirmed that a discharge coefficient calibrated with nitrogen can be reliably used for hydrogen by matching Reynolds numbers. Thermal mass flow meters when not configured for the specific test gas exhibited significant errors emphasizing the necessity of gas-specific calibration and configuration. Turbine meters showed predictable error trends influenced by Reynolds number and bearing friction with natural gas calibration providing reliable hydrogen and hydrogen-enriched natural gas performance in the Reynolds domain. It was confirmed that ultrasonic meter performance varies by manufacturers with some meter models requiring a correction for gas composition bias when used in hydrogen enriched natural gas applications. These findings provide critical experimental data to guide future hydrogen metering standards and infrastructure adaptations supporting the European Union’s goal of integrating hydrogen into the gas network.

In the maritime domain hydrogen fuel cell propulsion and autonomous vessels are two important issues that are yet to be implemented together because of a few challenges. It is obvious that there are several individual safety studies on Maritime Autonomous Surface Ships and hydrogen storage as well as fuel cells based on various risk assessment tools but the combined safety studies that include hydrogen fuel cells on autonomous vessels with recent risk analysis methods are extremely limited. This research chooses the “System-Theoretic Process Analysis” (STPA) method which is a recent method for potential risk identification and mitigation. Both hydrogen and autonomous vessels are analyzed and assessed together with the STPA method. Results are not speculative but rather flexible compared to conventional systems. The study finds a total of 44 unsafe control actions (UCAs) evolved from human and central control unit controllers through STPA. Further the loss scenarios (LS) are identified that lead to those UCAs so that loss scenarios can be assessed and UCAs can be mitigated for safe operation. The objective of this study is to ensure adequate safety for hydrogen fuel cell propulsion on autonomous vessels.

In this work the Design and Operation of Integrated Technologies (DO-IT) framework is developed a comprehensive tool to support short- and long-term technology investment and operation decisions for integrated energy generation conversion and storage technologies in buildings. The novelty of this framework lies in two key aspects: firstly it integrates essential open-source modelling tools covering energy end uses in buildings technology performance and cost and energy system design optimisation into a unified and easily-reproducible framework. Secondly it introduces a novel optimisation tool with a concise and generic mathematical formulation capable of modelling multi-energy vector systems capturing interdependencies between different energy vectors and technologies. The model formulation which captures both short- and long-term energy storage facilitates the identification of smart design and operation strategies with low computational cost. Different building energy demand and price scenarios are investigated and the economic and energy benefits of using a holistic multi-energy-vector approach are quantified. Technology combinations under consideration include: (i) a photovoltaic-electric heat pump-battery system (ii) a photovoltaic-electric heat pump-battery-hot water cylinder system (iii) a photovoltaic-electrolyser‑hydrogen storage-fuel cell system and (iv) a system with all above technology options. Using a university building as a case study it is shown that the smart integration of electricity heating cooling and hydrogen generation and storage technologies results in a total system cost which is >25% lower than the scenario of only importing grid electricity and using a fuel oil boiler. The battery mitigates intra-day fluctuations in electricity demand and the hot-water cylinder allows for efficiently managing heat demand with a small heat pump. In order to avoid PV curtailment excess PV-generated electricity can also be stored in the form of green hydrogen providing a long-term energy storage solution spanning days weeks or even seasons. Results are useful for end-users investment decision makers and energy policy makers when selecting building-integrated low-carbon technologies and relevant policies.

There are a large number of applications in which hydrogen internal combustion engines represent a sensible alternative to battery electric propulsion systems and to fuel cell electric propulsion systems. The main advantages of combustion engines are their high degree of robustness and low manufacturing costs. No critical raw materials are required for production and there are highly developed production plants worldwide. A CO2-free operation is possible when using hydrogen as a fuel. The formation of nitrogen oxides during hydrogen combustion in the engine can be effectively mitigated by a lean-burn combustion process. However achieving low NOx raw emissions conflicts with achieving high power yields. In this work a series industrial diesel engine was converted for hydrogen operation and comprehensive engine tests were carried out. Various measures to improve the trade-off between NOx emissions and performance were investigated and evaluated. The rated power output and the maximum torque of the series diesel engine could be exceeded while maintaining an indicated specific NOx emission of 1 g/kWh along the entire full load curve. In the low-end-torque range however the gap to the full load curve of the series diesel engine could not be fully closed with the hardware used.

Hydrogen produced from electrolysis is an attractive carbon-free fuel and feedstock but potential benefits depend on the carbon intensity of electricity production. This study uses technoeconomic modeling to analyze the benefits of producing zero-carbon hydrogen through dynamically operated polymer electrolyte membrane electrolyzers connected to photovoltaic and wind variable renewable energy (VRE) sources. Dynamic operation is considered for current densities between 0 and 6 A cm2 and compared to a constant current density of 2 A cm2 for different combinations of VRE to electrolysis (VRE:E) capacity ratios and compositions of photovoltaic and wind energy in four locations across the United States. For optimal VRE:E and wind:photovoltaic capacity ratios dynamic operation is found to reduce the levelized cost of hydrogen by 5%–9% while increasing hydrogen production by 134%–173% and decreasing excess electrical power by 82%–95%. The framework herein may be used to determine the optimal VRE:E capacity and VRE mix for dynamically operated green hydrogen systems.

Currently meeting the global energy demand is largely dependent on fossil fuels such as natural gas coal and oil. Fossil fuels represent a danger to the Earth’s environment and its biological systems. The utilisation of these fuels results in a rise in atmospheric CO2 levels which in turn triggers global warming and adverse changes in the climate. Furthermore these represent finite energy resources that will eventually deplete. There is a pressing need to identify and harness renewable energy sources as a replacement for fossil fuels in the near future. This shift is expected to have a minimal environmental impact and would contribute to ensuring energy security. Hydrogen is considered a highly desirable fuel option with the potential to substitute depleting hydrocarbon resources. This concise review explores diverse methods of renewable hydrogen production with a primary focus on solar wind geothermal and mainly water-splitting techniques such as electrolysis thermolysis photolysis and biomass-related processes. It addresses their limitations and key challenges hampering the global hydrogen economy’s growth including clean value chain creation storage transportation production costs standards and investment risks. The study concludes with research recommendations to enhance production efficiencies and policy suggestions for governments to mitigate investment risks while scaling up the hydrogen economy.

The increase in the overall global temperature and its subsequent impact on extreme weather events are the most critical consequences of human activity. In this scenario transportation plays a significant role in greenhouse gas (GHG) emissions which are the main drivers of climate change. The decline of non-renewable energy sources coupled with the aim of reducing GHG emissions from fossil fuels has forced a shift towards a net-zero emissions economy. As an example of this transition the European Union has set 2050 as the target for achieving carbon neutrality. Hydrogen (H2 ) is gaining increasing relevance as one of the most promising carbon-free energy vectors. If produced from renewable sources it facilitates the integration of various alternative energy sources for achieving a carbon-neutral economy. Recently interest in its application to the transportation sector has grown including different power plant concepts such as fuel cells or internal combustion engines. Despite exhibiting significant drawbacks such as low density combustion instabilities and incompatibilities with certain materials hydrogen is destined to become one of the future fuels. In this publication experimental activities are reported that were conducted on a sparkignition engine fueled with hydrogen at different operating points. The primary objective of this research is to gain a better understanding of the thermodynamic processes that control combustion and their effects on engine performance and pollutant emissions. The results show the emission levels performance and combustion characteristics under different conditions of dilution load and injection strategy and timing.

In this work the performance of anion exchange membrane (AEM) electrolysis is evaluated. A parametric study is conducted focusing on the effects of various operating parameters on the AEM efficiency. The following parameters—potassium hydroxide (KOH electrolyte concentration (0.5–2.0 M) electrolyte flow rate (1–9 mL/min) and operating temperature (30–60 ◦C)—were varied to understand their relationship to AEM performance. The performance of the electrolysis unit is measured by its hydrogen production and energy efficiency using the AEM electrolysis unit. Based on the findings the operating parameters greatly influence the performance of AEM electrolysis. The highest hydrogen production was achieved with the operational parameters of 2.0 M electrolyte concentration 60 ◦C operating temperature and 9 mL/min electrolyte flow at 2.38 V applied voltage. Hydrogen production of 61.13 mL/min was achieved with an energy consumption of 48.25 kW·h/kg and an energy efficiency of 69.64%.