Netherlands

A reversible solid oxide cell (rSOC) reactor can operate efficiently in both electrolysis mode and in fuel cell mode. The bidirectional operability enables rSOC reactors to play a central role as an efficient energy conversion system for energy storage and sector coupling for a renewable energy driven society. A combined system for electrolysis and fuel cell operation can result in complex system configurations that should be able to switch between the two modes as quickly as possible. This can lead to temperature profiles within the reactor that can potentially lead to the failure of the reactor and eventually the system. Hence the behavior of the reactor during the mode switch should be analyzed and optimal transition strategies should be taken into account during the process system design stage. In this paper a one dimensional transient reversible solid oxide cell model was built and experimentally validated using a commercially available reactor. A simple hydrogen based system model was built employing the validated reactor model to study reactor behavior during the mode switch. The simple design leads to a system efficiency of 49% in fuel cell operation and 87% in electrolysis operation where the electrolysis process is slightly endothermic. Three transient operation strategies were studied. It is shown that the voltage response to transient operation is very fast provided the reactant flows are changed equally fast. A possible solution to ensure a safe mode switch by controlling the reactant inlet temperatures is presented. By keeping the rate of change of reactant inlet temperatures five to ten times slower than the mode switch a safe transition can be ensured.

In this work a novel reactor concept referred to as Membrane-Assisted Chemical Looping Reforming (MA-CLR) has been demonstrated at lab scale under different operating conditions for a total working time of about 100 h. This reactor combines the advantages of Chemical Looping such as CO₂ capture and good thermal integration with membrane technology for a better process integration and direct product separation in a single unit which in its turn leads to increased efficiencies and important benefits compared to conventional technologies for H₂ production. The effect of different operating conditions (i.e. temperature steam-to-carbon ratio or oxygen feed in the reactor) has been evaluated in a continuous chemical looping reactor and methane conversions above 90% have been measured with (ultra-pure) hydrogen recovery from the membranes. For all the cases a maximum recovery factor of around 30% has been measured which could be increased by operating the concept at higher pressures and with more membranes. The optimum conditions have been found at temperatures around 600°C for a steam-to-carbon ratio of 3 and diluted air in the air reactor (5% O₂). The complete demonstration has been carried out feeding up to 1 L/min of CH4 (corresponding to 0.6 kW of thermal input) while up to 1.15 L/min of H2 was recovered. Simultaneously a phenomenological model has been developed and validated with the experimental results. In general good agreement is observed with overall deviations below 10% in terms of methane conversion H₂ recovery and separation factor. The model allows better understanding of the behavior of the MA-CLR concept and the optimization and design of scaled-up versions of the concept.

The envisioned role of hydrogen in the energy transition – or the concept of a hydrogen economy – has varied through the years. In the past hydrogen was mainly considered a clean fuel for cars and/or electricity production; but the current renewed interest stems from the versatility of hydrogen in aiding the transition to CO2 neutrality where the capability to tackle emissions from distributed applications and complex industrial processes is of paramount importance. However the hydrogen economy will not materialise without strong political support and robust infrastructure design. Hydrogen deployment needs to address multiple barriers at once including technology development for hydrogen production and conversion infrastructure co-creation policy market design and business model development. In light of these challenges we have brought together a group of hydrogen researchers who study the multiple interconnected disciplines to offer a perspective on what is needed to deploy the hydrogen economy as part of the drive towards net-zero-CO2 societies. We do this by analysing (i) hydrogen end-use technologies and applications (ii) hydrogen production methods (iii) hydrogen transport and storage networks (iv) legal and regulatory aspects and (v) business models. For each of these we provide key take home messages ranging from the current status to the outlook and needs for further research. Overall we provide the reader with a thorough understanding of the elements in the hydrogen economy state of play and gaps to be filled.

A larger adoption of hydrogen fuel-cell electric vehicles (FCEVs) is typically included in the strategies to decarbonize the transportation sector. This inclusion is supported by life-cycle assessments (LCAs) which show the potential greenhouse gas (GHG) emission benefit of replacing internal combustion engine vehicles with their fuel cell counterpart. However the literature review performed in this study shows that the effects of durability and performance losses of fuel cells on the life-cycle environmental impact of the vehicle have rarely been assessed. Most of the LCAs assume a constant fuel consumption (ranging from 0.58 to 1.15 kgH2/100 km) for the vehicles throughout their service life which ranges in the assessments from 120000 to 225000 km. In this study the effect of performance losses on the life-cycle GHG emissions of the vehicles was assessed based on laboratory experiments. Losses have the effect of increasing the life-cycle GHG emissions of the vehicle up to 13%. Moreover this study attempted for the first time to investigate via laboratory analyses the GHG implications of replacing the hydrophobic polymer for the gas diffusion medium (GDM) of fuel cells to increase their durability. LCA showed that when the service life of the vehicle was fixed at 150000 km the GHG emission savings of using an FC with lower performance losses (i.e. FC coated with fluorinated ethylene propylene (FEP) instead of polytetrafluoroethylene (PTFE)) are negligible compared to the overall life-cycle impact of the vehicle. Both the GDM coating and the amount of hydrogen saved account for less than 2% of the GHG emissions arising during vehicle operation. On the other hand when the service life of the vehicle depends on the operability of the fuel cell the global warming potential per driven km of the FEP-based FCEV reduces by 7 to 32%. The range of results depends on several variables such as the GHG emissions from hydrogen production and the initial fuel consumption of the vehicle. Higher GHG savings are expected from an FC vehicle with high consumption of hydrogen produced with fossil fuels. Based on the results we recommend the inclusion of fuel-cell durability in future LCAs of FCEVs. We also advocate for more research on the real-life performance of fuel cells employing alternative materials.

The North Sea Offshore Grid concept has been envisioned as a promising alternative to: 1) ease the integration of offshore wind and onshore energy systems and 2) increase the cross-border capacity between the North Sea region countries at low cost. In this paper we explore the techno-economic benefits of the North Sea Offshore Grid using two case studies: a power-based offshore grid where only investments in power assets are allowed (i.e. offshore wind HVDC/HVAC interconnectors); and a power-and-hydrogen offshore grid where investments in offshore hydrogen assets are also permitted (i.e. offshore electrolysers new hydrogen pipelines and retrofitted natural gas pipelines). In this paper we present a novel methodology in which extensive offshore spatial data is analysed to define meaningful regions via data clustering. These regions are incorporated to the Integrated Energy System Analysis for the North Sea region (IESA-NS) model. In this optimization model the scenarios are run without any specific technology ban and under open optimization. The scenario results show that the deployment of an offshore grid provides relevant cost savings ranging from 1% to 4.1% of relative cost decrease (2.3 bn € to 8.7 bn €) in the power-based and ranging from 2.8% to 7% of relative cost decrease (6 bn € to 14.9 bn €) in the power-and-hydrogen based. In the most extreme scenario an offshore grid permits to integrate 283 GW of HVDC connected offshore wind and 196 GW of HVDC meshed interconnectors. Even in the most conservative scenario the offshore grid integrates 59 GW of HVDC connected offshore wind capacity and 92 GW of HVDC meshed interconnectors. When allowed the deployment of offshore electrolysis is considerable ranging from 61 GW to 96 GW with capacity factors of around 30%.

This paper aims to holistically study hydrogen production options essential for a sustainable and carbon-free future. This study also outlines the benefits and challenges of hydrogen production methods to provide sustainable alternatives to fossil fuels by meeting the global energy demand and net-zero targets. In this study sixteen hydrogen production methods are selected for sustainability investigation based on seven different criteria. The criteria selected in the comparative evaluation cover various dimensions of hydrogen production in terms of economic technical environmental and thermodynamic aspects for better sustainability. The current study results show that steam methane reforming with carbon capture could provide sustainable hydrogen in the near future while the other technologies’ maturity levels increase and the costs decrease. In the medium- and long-terms photonic and thermal-based hydrogen production methods can be the key to sustainable hydrogen production.

The intermittent nature of renewable energy resources such as wind and solar causes the energy supply to be less predictable leading to possible mismatches in the power network. To this end hydrogen production and storage can provide a solution by increasing flexibility within the system. Stored hydrogen as compressed gas can either be converted back to electricity or it can be used as feed-stock for industry heating for built environment and as fuel for vehicles. This research is the first to examine optimal strategies for operating integrated energy systems consisting of renewable energy production and hydrogen storage with direct gas-based use-cases for hydrogen. Using Markov decision process theory we construct optimal policies for day-to-day decisions on how much energy to store as hydrogen or buy from or sell to the electricity market and on how much hydrogen to sell for use as gas. We pay special emphasis to practical settings such as contractually binding power purchase agreements varying electricity prices different distribution channels green hydrogen offtake agreements and hydrogen market price uncertainties. Extensive experiments and analysis are performed in the context of Northern Netherlands where Europe’s first Hydrogen Valley is being formed. Results show that gains in operational revenues of up to 51% are possible by introducing hydrogen storage units and competitive hydrogen market-prices. This amounts to a e126000 increase in revenues per turbine per year for a 4.5 MW wind turbine. Moreover our results indicate that hydrogen offtake agreements will be crucial in keeping the energy transition on track.

The publication gives an overview of the production costs of synthetic methane in a Power-to-Gas process. The production costs depend in particularly on the electricity price and the full load hours of the plant sub-systems electrolysis and methanation. The full-load hours of electrolysis are given by the electricity supply concept. In order to increase the full-load hours of methanation the size of the intermediate hydrogen storage tank and the size of the methanation are optimised on the basis of the availability of hydrogen. The calculation of the production costs for synthetic methane are done with economics for 2030 and 2050 and the expenditures are calculated for one year of operation. The sources of volume of purchased electricity are the short-term market long-term contracts direct-coupled renewable energy sources or seasonal use of surpluses. Gas sales are either traded on the short-term market or guaranteed by long-term contracts. The calculations show that an intermediate storage tank for hydrogen adjustment of the methanation size and operating electrolysis and methanation separately increase the workload of the sub-system methanation. The gas production costs can be significantly reduced. With the future expected development of capital expenditures operational expenditure electricity prices gas costs and efficiencies an economic production of synthetic natural gas for the years 2030 especially for 2050 is feasible. The results show that Power-to-Gas is an option for long-term large-scale seasonal storage of renewable energy. Especially the cases with high operating hours for the sub-system methanation and low electricity prices show gas production costs below the expected market prices for synthetic gas and biogas.

Bi-directional solid oxide cell systems (Bi-SOC) are being increasingly considered as an electrical energy storage method and consequently as a means to boost the penetration of renewable energy (RE) and to improve the grid flexibility by power-to-gas electrochemical conversion. A major advantage of these systems is that the same SOC stack operates as both energy storage device (SOEC) and energy producing device (SOFC) based on the energy demand and production. SOEC and SOFC systems are now well-optimised as individual systems; this work studies the effect of using the bi-directionality of the SOC at a system level. Since the system performance is highly dependent on the cell-stack operating conditions this study improves the stack parameters for both operation modes. Moreover the year-round cumulative exergy method (CE) is introduced in the solid oxide cell (SOC) context for estimating the system exergy efficiencies. This method is an attempt to obtain more insightful exergy assessments since it takes into account the operational hours of the SOC system in both modes. The CE method therefore helps to predict more accurately the most efficient configuration and operating parameters based on the power production and consumption curves in a year. Variation of operating conditions configurations and SOC parameters show a variation of Bi-SOC system year-round cumulative exergy efficiency from 33% to 73%. The obtained thermodynamic performance shows that the Bi-SOC when feasible can prove to be a highly efficient flexible power plant as well as an energy storage system.

Public acceptability of low-carbon energy projects is often measured with one-off polls. This implies that opinion-shifts over time are not always taken into consideration by decision makers relying on these polls. Observations have given the impression that public acceptability of energy projects increases after implementation. However this positive shift over time has not yet been systematically studied and is not yet understood very well. This paper aims to fill this gap. Based on two psychological mechanisms loss aversion and cognitive dissonance reduction we hypothesize that specifically people who live in proximity of a risky low-carbon technology—a hydrogen fuel station (HFS) in this case—evaluate this technology as more positive after its implementation than before. We conducted a survey among Dutch citizen living nearby a HFS and indeed found a positive shift in the overall evaluation of HFS after implementation. We also found that the benefits weighed stronger and the risks weaker after the implementation. This shift did not occur for citizens living further away from the HFS. The perceived risks and benefits did not significantly change after implementation neither for citizens living in proximity nor for citizens living further away. The societal implications of the findings are discussed.