Publications

Solid oxide electrolysis cells (SOECs) have great application prospects because of their excellent performance but the long-term applications of the stacks are restricted by the structural degradation under the high-temperature conditions. Therefore an SOEC degradation model is developed and embedded in a process model of the high-temperature steam electrolysis (HTSE) system to investigate the influence of the stack degradation at the system level. The sensitivity analysis and optimization were carried out to study the influence factors of the stack degradation and system hydrogen production efficiency and search for the optimal operating conditions to improve the hydrogen production efficiency and mitigate the stack degradation. The analysis results show that the high temperature and large current density can accelerate the stack degradation but improve the hydrogen production efficiency while the high temperature gradually becomes unfavorable in the late stage. The low air-to-fuel feed ratio is beneficial to both the degradation rate and hydrogen production efficiency. The results show that the optimization method can improve the hydrogen production efficiency and inhibit the stack degradation effectively. Moreover part of the hydrogen production efficiency has to be sacrificed in order to obtain a lower stack degradation rate.

Power-to-Methane as one part of Power-to-Gas has been recognized globally as one of the key elements for the transition towards a sustainable energy system. While plants that produce methane catalytically have been in operation for a long time biological methanation has just reached industrial pilot scale and near-term commercial application. The growing importance of the biological method is reflected by an increasing number of scientific articles describing novel approaches to improve this technology. However these studies are difficult to compare because they lack a coherent nomenclature. In this article we present a comprehensive set of parameters allowing the characterization and comparison of various biological methanation processes. To identify relevant parameters needed for a proper description of this technology we summarized existing literature and defined system boundaries for Power-to-Methane process steps. On this basis we derive system parameters providing information on the methanation system its performance the biology and cost aspects. As a result three different standards are provided as a blueprint matrix for use in academia and industry applicable to both biological and catalytic methanation. Hence this review attempts to set the standards for a comprehensive description of biological and chemical methanation processes.

The share of electrical energy hailing from renewable sources in the European electricity mix is increasing. The match between renewable power supply and demand has become the greatest challenge to cope with. Gas infrastructure can accommodate large volumes of electricity converted into gas whenever this supply of renewable power is larger than the grid capacity or than the electricity demand. The Power-to-Gas (P2G) process chain could play a significant role in the future energy system. Renewable electric energy can be transformed into storable hydrogen via electrolysis and subsequent methanation. The aim of this paper is to provide an overview of the required technical adaptations of the most common devices for end users such as heating plants CHP systems home gas furnaces and cooking surfaces wherever these are fuelled with methane and hydrogen blends in variable percentages by volume. Special attention will be given to issues related to essential safety standards firstly comparing existing Italian and European regulations in this regard and secondly highlighting the potential need for legislation to regulate the suitability of hydrogen methane blends. Finally a list of foreseeable technical solutions will be provided and discussed thoroughly

Not only due to the energy crisis European policymakers are exploring options to substitute natural gas with renewable hydrogen. A condition for the application of hydrogen is a functioning transportation infrastructure. However the most efficient transport of large hydrogen quantities is still unclear and deeper analyses are missing. A promising option is converting the existing gas infrastructure. This study presents a novel approach to develop hydrogen networks by applying the Steiner tree algorithm to derive candidates and evaluate their costs. This method uses the existing grid (brownfield) and is compared to a newly built grid (Greenfield). The goal is the technical and economic evaluation and comparison of hydrogen network candidates. The methodology is applied to the German gas grid and demand and supply scenarios covering the industry heavy-duty transport power and heating sector imports and domestic production. Five brownfield candidates are compared to a greenfield candidate. The candidates differ by network length and pipeline diameters to consider the transported volume of hydrogen. The economic evaluation concludes that most brownfield candidates’ cost is significantly lower than those of the greenfield candidate. The candidates can serve as starting points for flow simulations and policymakers can estimate the cost based on the results.

With rising temperatures extreme weather events and environmental challenges there is a strong push towards decarbonization and an emphasis on renewable energy with wind energy emerging as a key player. The concept of multi-energy systems offers an innovative approach to decarbonization with the potential to produce hydrogen as one of the output streams creating another avenue for clean energy production. Hydrogen has significant potential for decarbonizing multiple sectors across buildings transport and industries. This paper explores the integration of wind energy and hydrogen production particularly in areas where clean energy solutions are crucial such as impoverished villages in Africa. It models three systems: distinct configurations of micro-multi-energy systems that generate electricity space cooling hot water and hydrogen using the thermodynamics and cost approach. System 1 combines a wind turbine a hydrogen-producing electrolyzer and a heat pump for cooling and hot water. System 2 integrates this with a biomass-fired reheat-regenerative power cycle to balance out the intermittency of wind power. System 3 incorporates hydrogen production a solid oxide fuel cell for continuous electricity production an absorption cooling system for refrigeration and a heat exchanger for hot water production. These systems are modeled with Engineering Equation Solver and analyzed based on energy and exergy efficiencies and on economic metrics like levelized cost of electricity (LCOE) cooling (LCOC) refrigeration (LCOR) and hydrogen (LCOH) under steady-state conditions. A sensitivity analysis of various parameters is presented to assess the change in performance. Systems were optimized using a multiobjective method with maximizing exergy efficiency and minimizing total product unit cost used as objective functions. The results show that System 1 achieves 79.78 % energy efficiency and 53.94 % exergy efficiency. System 2 achieves efficiencies of 55.26 % and 27.05 % respectively while System 3 attains 78.73 % and 58.51 % respectively. The levelized costs for micro-multi-energy System 1 are LCOE = 0.04993 $/kWh LCOC = 0.004722 $/kWh and LCOH = 0.03328 $/kWh. For System 2 these values are 0.03653 $/kWh 0.003743 $/kWh and 0.03328 $/kWh. In the case of System 3 they are 0.03736 $/kWh 0.004726 $/kWh and 0.03335 $/kWh and LCOR = 0.03309 $/kWh. The results show that the systems modeled here have competitive performance with existing multi-energy systems powered by other renewables. Integrating these systems will further the sustainable and net zero energy system transition especially in rural communities.

In the new scenario where the transportation sector must be decarbonized to limit global warming fuel cellpowered aerial vehicles have been selected as a strategic target application to compose part of the urban fleet to minimize road transport congestion and make goods and personal transportation fast and efficient. To address the necessity of clean and efficient urban air transport this work consists of the conceptual development of a lightweight rotary-winged transport vehicle using a hydrogen-based fuel cell propulsion system and the optimization of its energy balance. For that purpose the methods for integrating the coupled aerodynamic and propulsion system sizing and optimization was developed with the aim of designing concepts capable of carrying 0 (unmanned aerial vehicle — Design 1) and 1 (Aerotaxi — Design 2) passengers for a distance of 300 km at a cruise altitude of 500 m with a minimum climbing rate capability of 6 m s−1 at 1000 m. The results show how these designs with the desired performance specifications can be obtained with a vehicle mass ranging from 416 to 648 kg depending on the application and with specific range and endurance respectively within 46.2–47.8 km/kg and 20.4–21.3 min/kg for design 1 and 33.3–33.8 km/kg and 12.5–13.9 min/kg for design 2.

As countries seek ways to meet climate change commitments hydrogen fuel offers a low-carbon alternative for sectors where battery electrification may not be viable. Blending hydrogen with fossil fuels requires only modest technological adaptation however since combustion is retained nitrogen oxides (NOx) emissions remain a potential disbenefit. We review the potential air quality impacts arising from the use of hydrogen–diesel blends in heavy-duty diesel engines a powertrain which lends itself to hydrogen co-fuelling. Engine load is identified as a key factor influencing NOx emissions from hydrogen–diesel combustion in heavy-duty engines although variation in other experimental parameters across studies complicates this relationship. Combining results from peer-reviewed literature allows an estimation to be made of plausible NOx emissions from hydrogen–diesel combustion relative to pure-diesel combustion. At 0–30% engine load which encompasses the average load for mobile engine applications NOx emissions changes were in the range 59 to +24% for a fuel blend with 40 e% hydrogen. However at 50–100% load which approximately corresponds to stationary engine applications NOx emissions changes were in the range 28 to +107%. Exhaust gas recirculation may be able to reduce NOx emissions at very high and very low loads when hydrogen is blended with diesel and existing exhaust aftertreatment technologies are also likely to be effective. Recent commercial reporting on the development of hydrogen and hydrogen–diesel dual fuel combustion in large diesel engines are also summarised. There is currently some disconnection between manufacturer reported impacts of hydrogen-fuelling on NOx emissions (always lower emissions) and the conclusions drawn from the peer reviewed literature (frequently higher emissions).

As a clean and renewable energy source for sustainable development hydrogen energy has gained a lot of attention from the general public and researchers. Hydrogen production by electrolysis of water is the most important approach to producing hydrogen and it is also the main way to realize carbon neutrality. In this paper the main technologies of hydrogen production by electrolysis of water are discussed in detail; their characteristics advantages and disadvantages are analyzed; and the selection criteria and design criteria of catalysts are presented. The catalysts used in various hydrogen production technologies and their characteristics are emphatically expounded aiming at optimizing the existing catalyst system and developing new high-performance high-stability and low-cost catalysts. Finally the problems and solutions in the practical design of catalysts are discussed and explored.

Producing clean energy and minimising energy waste are essential to achieve the United Nations sustainable development goals such as Sustainable Development Goal 7 and 13. This research analyses the techno-economic potential of waste heat recovery from multi-MW scale green hydrogen production. A 10 MW proton exchange membrane electrolysis process is modelled with a heat recovery system coupled with an organic Rankine cycle (ORC) to drive the mechanical compression of hydrogen. The technical results demonstrate that when implementing waste heat recovery coupled with an ORC the first-law efficiency of electrolyser increases from 71.4% to 98%. The ORC can generate sufficient power to drive the hydrogen's compression from the outlet pressure at the electrolyser 30 bar up to 200 bar. An economic analysis is conducted to calculate the levelised cost of hydrogen (LCOH) of system and assess the feasibility of implementing waste heat recovery coupled with ORC. The results reveal that electricity prices dominate the LCOH. When electricity prices are low (e.g. dedicated offshore wind electricity) the LCOH is higher when implementing heat recovery. The additional capital expenditure and operating expenditure associated with the ORC increases the LCOH and these additional costs outweigh the savings generated by not purchasing electricity for compression. On the other hand heat recovery and ORC become attractive and feasible when grid electricity prices are higher.

The reduction of greenhouse gas emissions is one of the greatest global challenges through 2050. Besides greenhouse gas emissions air pollution such as nitrogen oxide and particulate matter emissions has gained increasing attention in agglomerated areas with transport vehicles being one of the main sources thereof. Alternative fuels that fulfill the greenhouse gas reduction goals also offer the possibility of solving the challenge of rising urban pollution. This work focuses on the electric drive option for heavy and light duty vehicle freight transport. In this study fuel cell-electric vehicles battery-electric vehicles and overhead catenary line trucks were investigated taking a closer look at their potential to reduce greenhouse gas emissions and air pollution and also considering the investment and operating costs of the required infrastructure. This work was conducted using a bottom-up transport model for the federal state of North Rhine-Westphalia in Germany. Two scenarios for reducing these emissions were analyzed at a spatial level. In the first of these selected federal highways with the highest traffic volume were equipped with overhead catenary lines for the operation of diesel-hybrid overhead trucks on them. For the second spatial scenario the representative urban area of the city of Cologne was investigated in terms of air pollution shifting articulated trucks to diesel-hybrid overhead trucks and rigid trucks trailer trucks and light duty vehicles to battery-electric or fuel cell-electric drives. For the economic analysis the building up of a hydrogen infrastructure in the cases of articulated trucks and all heavy duty vehicles were also taken into account. The results showed that diesel-hybrid overhead trucks are only a cost-efficient solution for highways with high traffic volume whereas battery overhead trucks have a high uncertainty in terms of costs and technical feasibility. In general the broad range of costs for battery overhead trucks makes them competitive with fuel cell-electric trucks. Articulated trucks have the highest potential to be operated as overhead trucks. However the results indicated that air pollution is only partially reduced by switching conventional articulated trucks to electric drive models. The overall results show that a comprehensive approach such as fuel cell-electric drives for all trucks would most likely be more beneficial.