- Home
- A-Z Publications
- Publications
Publications
The Influence of Hydrogen Sulfide Contaminations on Hydrogen Production in Chemical Looping Processes
Aug 2021
Publication
Chemical looping with iron-based oxygen carriers enables the production of hydrogen from various fossil and biogenic primary energy sources. In applications with real producer gases such as biogas or gasified biomass hydrogen sulfide represents one of the most challenging contaminants. The impact of H2S on the reactivity of a Fe2O3/Al2O3 oxygen carrier material in chemical looping hydrogen production was investigated in the present work. First potential sulfur deactivation mechanisms are discussed in detail on the basis of thermodynamic data. Afterwards an experimental study in a fixed-bed reactor system gave experimental evidence on the fate of sulfur in chemical looping hydrogen systems. The chemisorption of hydrogen sulfide (H2S) was identified as the main cause for the accumulative adsorption of H2S in the reduction phase and was confirmed by ex-situ ICP-EOS analysis. In the subsequent steam oxidation step significant quantities of H2S were released resulting in an undesirable contamination of the hydrogen product gas. The reason was found as weakened sulfur bonds through increasing reactor temperatures caused by the exothermic oxidation reactions. In additional air oxidation steps no further contaminants as sulfur dioxide were identified. A profound interpretation was achieved through the fulfillment of the overall sulfur mass balance within a mean deviation of 3.7%. Quantitative investigations showed that the hydrogen consumption decreased by 12% throughout the reduction phase in the event of 100 ppm H2S in the feed gas
The Challenges of Integrating the Principles of Green Chemistry and Green Engineering to Heterogeneous Photocatalysis to Treat Water and Produce Green H2
Jan 2023
Publication
Nowadays heterogeneous photocatalysis for water treatment and hydrogen production are topics gaining interest for scientists and developers from different areas such as environmental technology and material science. Most of the efforts and resources are devoted to the development of new photocatalyst materials while the modeling and development of reaction systems allowing for upscaling the process to pilot or industrial scale are scarce. In this work we present what is known on the upscaling of heterogeneous photocatalysis to purify water and to produce green H2. The types of reactors successfully used in water treatment plants are presented as study cases. The challenges of upscaling the photocatalysis process to produce green H2 are explored from the perspectives of (a) the adaptation of photoreactors (b) the competitiveness of the process and (c) safety. Throughout the text Green Chemistry and Engineering Principles are described and discussed on how they are currently being applied to the heterogeneous photocatalysis process along with the challenges that are ahead. Lastly the role of automation and high-throughput methods in the upscaling following the Green Principles is discussed.
Energy Saving in Public Transport Using Renewable Energy
Jan 2017
Publication
Hydrogen produced by renewable sources represents an interesting way to reduce the energetic dependence on fossil fuels in the transportation sector. This paper shows a feasibility study for the production storage and distribution of hydrogen in the western Sicilian context using three different renewable sources: wind biomass and sea wave. The objective of this study is the evaluation of the hydrogen demand needed to replace all diesel supplied buses with electrical buses equipped with fuel cells. An economic analysis is presented with the evaluation of the avoidable greenhouse gas emissions. Four different scenarios correlate the hydrogen demand for urban transport to the renewable energy resources present in the territories and to the modern technologies available for the production of hydrogen. The study focuses on the possibility of tapping into the potential of renewable energies (wind biomass and sea wave) for the production of hydrogen by electrolysis. The use of hydrogen would reduce significantly the emissions of particulate and greenhouse gases in the urban districts under analysis.
Fuel Flexibility of Solid Oxide Fuel Cells
Aug 2021
Publication
One of the major advantages of SOFCs is their high fuel flexibility. Next to natural gas and hydrogen which are today’s most common fuels for SOFC-systems and cell-/stack-testing respectively various other fuels are applicable as well. In the literature a number of promising results show that available fuels as propane butane ammonia gasoline diesel etc. can be applied. Here the performance of an anode supported cell operated in specialized single cell test benches with different gaseous and liquid fuels and reformates thereof is presented. Fuels as ammonia dissolved urea (AddBlueTM) methane/steam and ethanol/water mixtures can directly be fed to the cell whereas propane and diesel require external reforming. It is shown that in case of a stable fuel supply the cell performance with such fuels is similar to that of appropriate mixtures of H2 N2 CO CO2 and steam if the impact of endothermic reforming or decomposition reactions is considered. Even though a stable fuel cell operation with such fuels is possible in a single cell test bench it should be pointed out that an appropriate fuel processing will be mandatory on the system level.
Energy-Economic Assessment of Islanded Microgrid with Wind Turbine, Photovoltaic Field, Wood Gasifier, Battery, and Hydrogen Energy Storage
Sep 2022
Publication
Island energy systems are becoming an important part of energy transformation due to the growing needs for the penetration of renewable energy. Among the possible systems a combination of different energy generation technologies is a viable option for local users as long as energy storage is implemented. The presented paper describes an energy-economic assessment of an island system with a photovoltaic field small wind turbine wood chip gasifier battery and hydrogen circuit with electrolyzer and fuel cell. The system is designed to satisfy the electrical energy demand of a tourist facility in two European localizations. The operation of the system is developed and dynamically simulated in the Transient System Simulation (TRNSYS) environment taking into account realistic user demand. The results show that in Gdansk Poland it is possible to satisfy 99% of user demand with renewable energy sources with excess energy equal to 31% while in Agkistro Greece a similar result is possible with 43% of excess energy. Despite the high initial costs it is possible to obtain Simple Pay Back periods of 12.5 and 22.5 years for Gdansk and Agkistro respectively. This result points out that under a high share of renewables in the energy demand of the user the profitability of the system is highly affected by the local cost of energy vectors. The achieved results show that the system is robust in providing energy to the users and that future development may lead to an operation based fully on renewables.
A Review of The Methanol Economy: The Fuel Cell Route
Jan 2020
Publication
This review presents methanol as a potential renewable alternative to fossil fuels in the fight against climate change. It explores the renewable ways of obtaining methanol and its use in efficient energy systems for a net zero-emission carbon cycle with a special focus on fuel cells. It investigates the different parts of the carbon cycle from a methanol and fuel cell perspective. In recent years the potential for a methanol economy has been shown and there has been significant technological advancement of its renewable production and utilization. Even though its full adoption will require further development it can be produced from renewable electricity and biomass or CO2 capture and can be used in several industrial sectors which make it an excellent liquid electrofuel for the transition to a sustainable economy. By converting CO2 into liquid fuels the harmful effects of CO2 emissions from existing industries that still rely on fossil fuels are reduced. The methanol can then be used both in the energy sector and the chemical industry and become an all-around substitute for petroleum. The scope of this review is to put together the different aspects of methanol as an energy carrier of the future with particular focus on its renewable production and its use in high-temperature polymer electrolyte fuel cells (HT-PEMFCs) via methanol steam reforming.
Comparative Life Cycle Assessment of Sustainable Energy Carriers Including Production, Storage, Overseas Transport and Utilization
Aug 2020
Publication
Countries are under increasing pressure to reduce greenhouse gas emissions as an act upon the Paris Agreement. The essential emission reductions can be achieved by environmentally friendly solutions in particular the introduction of low carbon or carbon-free fuels. This study presents a comparative life cycle assessment of various energy carriers namely; liquefied natural gas methanol dimethyl ether liquid hydrogen and liquid ammonia that are produced from natural gas or renewables to investigate greenhouse gas emissions generated from the complete life cycle of energy carriers accounting for the leaks as well as boil-off gas occurring during storage and transportation. The entire fuel life cycle is considered consisting of production storage transportation via an ocean tanker to different distances and finally utilization in an internal combustion engine of a road vehicle. The results show that using natural gas as a feedstock total greenhouse gas emissions during production ocean transportation (over 20000 nmi) by a heavy fuel oil-fueled ocean tanker and utilization in an internal combustion engine are 73.96 95.73 93.76 50.83 and 100.54 g CO2 eq. MJ1 for liquified natural gas methanol dimethyl ether liquid hydrogen and liquid ammonia respectively. Liquid hydrogen produced from solar electrolysis is the cleanest energy carrier (42.50 g CO2 eq. MJ1 fuel). Moreover when liquid ammonia is produced via photovoltaic-based electrolysis (60.76 g CO2 eq. MJ1 fuel) it becomes cleaner than liquified natural gas. Although producing methanol and dimethyl ether from biomass results in a large reduction in total greenhouse gas emissions compared to conventional methanol and dimethyl ether production with a value of 73.96 g CO2 eq. per MJ liquified natural gas still represents a cleaner option than methanol and dimethyl ether considering the full life cycle.
Research on the Hydrogen Consumption of Fuel Cell Electric Vehicles Based on the Flowmeter and Short-cut Method
Sep 2022
Publication
Energy consumption is essential for evaluating the competitiveness of fuel cell electric vehicles. A critical step in energy consumption measurement is measuring hydrogen consumption including the mass method the P/T method and the flowmeter method. The flowmeter method has always been a research focus because of its simple operation low cost and solid real-time performance. Current research has shown the accuracy of the flowmeter method under specific conditions. However many factors in the real scenario will influence the test result such as unintended vibration environment temperature and onboard hydrogen capacity calibration. On the other hand the short-cut method is also researched to replace the run-out method to improve test efficiency. To evaluate whether the flowmeter method basing on the short-cut method can genuinely reflect the hydrogen consumption of an actual vehicle we research and test for New European Driving Cycle (NEDC) and China Light-Duty Vehicle Test Cycle (CLTC) using the same vehicle. The results show that the short-cut method can save at least 50% of the test time compared with the run-out method. The error of the short-cut method based on the flowmeter for the NEDC working condition is less than 0.1% and for the CLTC working conditions is 8.12%. After adding a throttle valve and a 4L buffer tank the error is reduced to 4.76% from 8.12%. The test results show that hydrogen consumption measurement based on the flowmeter and short-cut method should adopt corresponding solutions according to the scenarios.
Air Mass Flow and Pressure Optimisation of a PEM Fuel Cell Range Extender System
Aug 2022
Publication
In order to eliminate the local CO2 emissions from vehicles and to combat the associated climate change the classic internal combustion engine can be replaced by an electric motor. The two most advantageous variants for the necessary electrical energy storage in the vehicle are currently the purely electrochemical storage in batteries and the chemical storage in hydrogen with subsequent conversion into electrical energy by means of a fuel cell stack. The two variants can also be combined in a battery electric vehicle with a fuel cell range extender so that the vehicle can be refuelled either purely electrically or using hydrogen. The air compressor a key component of a PEM fuel cell system can be operated at different air excess and pressure ratios which influence the stack as well as the system efficiency. To asses the steady state behaviour of a PEM fuel cell range extender system a system test bench utilising a commercially available 30 kW stack (96 cells 409 cm2 cell area) was developed. The influences of the operating parameters (air excess ratio 1.3 to 1.7 stack temperature 20 °C–60 °C air compressor pressure ratio up to 1.67 load point 122 mA/cm2 to 978 mA/cm2) on the fuel cell stack voltage level (constant ambient relative humidity of 45%) and the corresponding system efficiency were measured by utilising current voltage mass flow temperature and pressure sensors. A fuel cell stack model was presented which correlates closely with the experimental data (0.861% relative error). The air supply components were modelled utilising a surface fit. Subsequently the system efficiency of the validated model was optimised by varying the air mass flow and air pressure. It is shown that higher air pressures and lower air excess ratios increase the system efficiency at high loads. The maximum achieved system efficiency is 55.21% at the lowest continuous load point and 43.74% at the highest continuous load point. Future work can utilise the test bench or the validated model for component design studies to further improve the system efficiency.
Cost Assessment of Alternative Fuels for Maritime Transportation in Ireland
Aug 2022
Publication
In this study we investigated the cost-effectiveness of four alternatives: Liquified Natural Gas (LNG) methanol green hydrogen and green ammonia for the case of top 20 most frequently calling ships to Irish ports in 2019 through the Net Present Value (NPV) methodology incorporating the benefits incurred through saved external carbon tax and conventional fuel costs. LNG had the highest NPV (€6166 million) followed by methanol (€1705 million) and green hydrogen (€319 million). Green ammonia utilisation (as a hydrogen carrier) looks inviable due to higher operational costs resulting from its excessive consumption (i.e. losses) during the cracking and purifying processes and its lower net calorific value. Green hydrogen remains the best option to meet future decarbonisation targets although a further reduction in its current fuel price (by 60%) or a significant increment in the proposed carbon tax rate (by 275%) will be required to improve its cost-competitiveness over LNG and methanol.
A Bird’s-Eye View on Polymer-Based Hydrogen Carriers for Mobile Applications
Oct 2022
Publication
Globally reducing CO2 emissions is an urgent priority. The hydrogen economy is a system that offers long-term solutions for a secure energy future and the CO2 crisis. From hydrogen production to consumption storing systems are the foundation of a viable hydrogen economy. Each step has been the topic of intense research for decades; however the development of a viable safe and efficient strategy for the storage of hydrogen remains the most challenging one. Storing hydrogen in polymer-based carriers can realize a more compact and much safer approach that does not require high pressure and cryogenic temperature with the potential to reach the targets determined by the United States Department of Energy. This review highlights an outline of the major polymeric material groups that are capable of storing and releasing hydrogen reversibly. According to the hydrogen storage results there is no optimal hydrogen storage system for all stationary and automotive applications so far. Additionally a comparison is made between different polymeric carriers and relevant solid-state hydrogen carriers to better understand the amount of hydrogen that can be stored and released realistically.
The Effect of Hydrogen Addition on the Pollutant Emissions of a Marine Internal Combustion Engine Genset
Sep 2022
Publication
Hydrogen as a maritime fuel is one of the solutions that will assist the shipping sector in addressing the challenges regarding decarbonization taking into consideration the targets set for 2030 and 2050. The extensive utilization of hydrogen requires massive production of green hydrogen and the development of proper infrastructure to support a sustainable supply chain. An alternative solution is based on the on-board production of hydrogen where production units are installed on-board the vessel. Along these lines the HYMAR project aims to test the utilization of a hydrogen production unit for on-board use. The article deals with the use of hydrogen as a fuel for internal combustion engines taking into consideration reports from literature and the preliminary results of the HYMAR project focusing on the environmental impact and the reduction in emissions. Experimental investigation on a marine auxiliary engine for power generation under the HYMAR project leads to promising results regarding the environmental footprint of the internal combustion engine when hydrogen is added in the fuel mix with increasing percentages.
An Overview of Water Electrolysis Technologies for Green Hydrogen Production
Oct 2022
Publication
Decarbonizing the planet is one of the major goals that countries around the world have set for 2050 to mitigate the effects of climate change. To achieve these goals green hydrogen that can be produced from the electrolysis of water is an important key solution to tackle global decarbonization. Consequently in recent years there is an increase in interest towards green hydrogen production through the electrolysis process for large-scale implementation of renewable energy based power plants and other industrial and transportation applications. The main objective of this study was to provide a comprehensive review of various green hydrogen production technologies especially on water electrolysis. In this review various water electrolysis technologies and their techno-commercial prospects including hydrogen production cost along with recent developments in electrode materials and their challenges were summarized. Further some of the most successful results also were described. Moreover this review aims to identify the gaps in water electrolysis research and development towards the techno-commercial perspective. In addition some of the commercial electrolyzer performances and their limitations also were described along with possible solutions for cost-effective hydrogen production Finally we outlined our ideas and possible solutions for driving cost-effective green hydrogen production for commercial applications. This information will provide future research directions and a road map for the development/implementation of commercially viable green hydrogen projects.
Alternative Vehicular Fuels for Environmental Decarbonization: A Critical Review of Challenges in Using Electricity, Hydrogen, and Biofuels as a Sustainable Vehicular Fuel
Jan 2023
Publication
Using vehicles powered by alternative fuels such as electricity hydrogen and biofuels have been envisioned as the ideal way to curb noxious vehicular emissions. However the availability of resources for the sustainable use of these alternative fuels the possible risks and their fate at the end of their life are frequently questioned necessitating a detailed assessment of factors influencing the use of all three alternative fuels for vehicular use. Though the vehicles powered by batteries and fuel cells are “locally” zero-emission vehicles (ZEVs) they have resource scarcity infrastructure limitations and are relatively expensive thus restricting their market penetration and consumer acceptance. Biofuels though can be used in the existing vehicles procuring the required amounts of feedstock and mitigating food-versus-fuel issues is still a challenge. Overcoming these challenges is a crucial and critical step for the sustained use of these alternative fuels as primary vehicular fuels. To accomplish this all these challenges need to be categorized and a comparative analysis among them is necessary to address them. This work can therefore serve as a ready reference for researchers and policy makers to take appropriate and informed decisions for long-term action to achieve the goals of the Paris agreement to reduce global temperature.
UK Hydrogen Strategy
Aug 2021
Publication
The UK’s first-ever Hydrogen Strategy drives forward the commitments laid out in the Prime Minister’s ambitious 10 Point Plan for a green industrial revolution by setting the foundation for how the UK government will work with industry to meet its ambition for 5GW of low carbon hydrogen production capacity by 2030 – the equivalent of replacing natural gas in powering around 3 million UK homes each year as well as powering transport and businesses particularly heavy industry.<br/>A booming UK-wide hydrogen economy could be worth £900 million and create over 9000 high-quality jobs by 2030 potentially rising to 100000 jobs and worth up to £13 billion by 2050. By 2030 hydrogen could play an important role in decarbonising polluting energy-intensive industries like chemicals oil refineries power and heavy transport like shipping HGV lorries and trains by helping these sectors move away from fossil fuels. Low-carbon hydrogen provides opportunities for UK companies and workers across our industrial heartlands.<br/>With government analysis suggesting that 20-35% of the UK’s energy consumption by 2050 could be hydrogen-based this new energy source could be critical to meet our targets of net zero emissions by 2050 and cutting emissions by 78% by 2035 – a view shared by the UK’s independent Climate Change Committee. In the UK a low-carbon hydrogen economy could deliver emissions savings equivalent to the carbon captured by 700 million trees by 2032 and is a key pillar of capitalising on cleaner energy sources as the UK moves away from fossil fuels.
Levelized Cost of Hydrogen for Refueling Stations with Solar PV and Wind in Sweden: On-grid or Off-grid?
Dec 2021
Publication
The European Union expects that hydrogen will play a vital role in future energy systems. Fuel cell electric vehicles currently present a key development path for electrification of the transport sector which requires infrastructure investments of hydrogen refueling stations preferably powered by renewables such as solar and wind energy. The economic feasibility of refueling stations depends on geographical locations. This study introduces a model to identify the key cost components of renewable hydrogen for refueling stations and simulates the performance using solar radiation wind speed and electricity price data in a selection of Swedish cities. The study demonstrates the importance of integrating the electricity grid in green hydrogen production. Wind speed is crucial in reducing the cost whereas solar radiation has less influence. In addition a combination of solar and wind brings better performance in an off-grid scenario. The most encouraging finding is the cost of 35e72 SEK/kg (3.5e7.2 V/kg) which is competitive with reported costs in other EUcountries especially since this cost excludes any government support scheme. The study provides a reference for investors and policy makers foreseeing the industrial landscape for hydrogen energy development.
The Role of Hydrogen in a Greenhouse Gas-neutral Energy Supply System in Germany
Sep 2022
Publication
Hydrogen is widely considered to play a pivotal role in successfully transforming the German energy system but the German government’s current “National Hydrogen Strategy” does not specify how hydrogen utilization production storage or distribution will be implemented. Addressing key uncertainties for the German energy system’s path to greenhouse gas-neutrality this paper examines hydrogen in different scenarios. This analysis aims to support the concretization of the German hydrogen strategy. Applying a European energy supply model with strong interactions between the conversion sector and the hydrogen system the analysis focuses on the requirements for geological hydrogen storages and their utilization over the course of a year the positioning of electrolyzers within Germany and the contributions of hydrogen transport networks to balancing supply and demand. Regarding seasonal hydrogen storages the results show that hydrogen storage facilities in the range of 42 TWhH2 to 104 TWhH2 are beneficial to shift high electricity generation volumes from onshore wind in spring and fall to winter periods with lower renewable supply and increased electricity and heat demands. In 2050 the scenario results show electrolyzer capacities between 41 GWel and 75 GWel in Germany. Electrolyzer sites were found to follow the low-cost renewable energy potential and are concentrated on the North Sea and Baltic Sea coasts with their high wind yields. With respect to a hydrogen transport infrastructure there were two robust findings: One a domestic German hydrogen transport network connecting electrolytic hydrogen production sites in northern Germany with hydrogen demand hubs in western and southern Germany is economically efficient. Two connecting Germany to a European hydrogen transport network with interconnection capacities between 18 GWH2 and 58 GWH2 is cost-efficient to meet Germany’s substantial hydrogen demand.
The Significance of Formal & Legal Factors in Selecting a Location for a Hydrogen Buffer to Stabilize the Operation of Power Distribution Networks
Oct 2022
Publication
This article presents the conceptual assumptions for the process of identifying and evaluating the formal & legal factors that impact the choice of a hydrogen buffer location to stabilize the operation of power distribution networks. The assumption for the research process was establishing a methodological framework for an in-depth analysis of legislative acts (the EU legislation and the national law) to enable identification of synthetic groups of formal & legal factors to be further analyzed using the DEMATEL method. As a result the cause-and-effect relations between the variables were examined and an in-depth analysis was carried out to investigate the level of impact of the formal & legal factors on the functioning and location of a hydrogen energy buffer.
Combined Effects of Stress and Temperature on Hydrogen Diffusion in Non-hydride Forming Alloys Applied in Gas Turbines
Jul 2022
Publication
Hydrogen plays a vital role in the utilisation of renewable energy but ingress and diffusion of hydrogen in a gas turbine can induce hydrogen embrittlement on its metallic components. This paper aims to investigate the hydrogen transport in a non-hydride forming alloy such as Alloy 690 used in gas turbines inspired by service conditions of turbine blades i.e. under the combined effects of stress and temperature. An appropriate hydrogen transport equation is formulated accounting for both stress and temperature distributions of the domain in the non-hydride forming alloy. Finite element (FE) analyses are performed to predict steady-state hydrogen distribution in lattice sites and dislocation traps of a double notched specimen under constant tensile load and various temperature fields. Results demonstrate that the lattice hydrogen concentration is very sensitive to the temperature gradients whilst the stress concentration only slightly increases local lattice hydrogen concentration. The combined effects of stress and temperature result in the highest concentration of the dislocation trapped hydrogen in low-temperature regions although the plastic strain is only at a moderate level. Our results suggest that temperature gradients and stress concentrations in turbine blades due to cooling channels and holes make the relatively low-temperature regions susceptible to hydrogen embrittlement.
Hydrogen Blending in Gas Pipeline Networks—A Review
May 2022
Publication
Replacing fossil fuels with non-carbon fuels is an important step towards reaching the ultimate goal of carbon neutrality. Instead of moving directly from the current natural gas energy systems to pure hydrogen an incremental blending of hydrogen with natural gas could provide a seamless transition and minimize disruptions in power and heating source distribution to the public. Academic institutions industry and governments globally are supporting research development and deployment of hydrogen blending projects such as HyDeploy GRHYD THyGA HyBlend and others which are all seeking to develop efficient pathways to meet the carbon reduction goal in coming decades. There is an understanding that successful commercialization of hydrogen blending requires both scientific advances and favorable techno-economic analysis. Ongoing studies are focused on understanding how the properties of methane-hydrogen mixtures such as density viscosity phase interactions and energy densities impact large-scale transportation via pipeline networks and enduse applications such as in modified engines oven burners boilers stoves and fuel cells. The advantages of hydrogen as a non-carbon energy carrier need to be balanced with safety concerns of blended gas during transport such as overpressure and leakage in pipelines. While studies on the short-term hydrogen embrittlement effect have shown essentially no degradation in the metal tensile strength of pipelines the long-term hydrogen embrittlement effect on pipelines is still the focus of research in other studies. Furthermore pressure reduction is one of the drawbacks that hydrogen blending brings to the cost dynamics of blended gas transport. Hence techno-economic models are also being developed to understand the energy transportation efficiency and to estimate the true cost of delivery of hydrogen blended natural gas as we move to decarbonize our energy systems. This review captures key large-scale efforts around the world that are designed to increase the confidence for a global transition to methane-hydrogen gas blends as a precursor to the adoption of a hydrogen economy by 2050.
No more items...