Publications

Hypothesis: Hydrogen geo-storage is considered as an option for large scale hydrogen storage in a full-scale hydrogen economy. Among different types of subsurface formations coal seams look to be one of the best suitable options as coal’s micro/nano pore structure can adsorb a huge amount of gas (e.g. hydrogen) which can be withdrawn again once needed. However literature lacks fundamental data regarding H2 diffusion in coal. Experiments: In this study we measured H2 adsorption rate in an Australian anthracite coal sample at isothermal conditions for four different temperatures (20 C 30 C 45 C and 60 C) at equilibrium pressure 13 bar and calculated H2 diffusion coefficient (DH2 ) at each temperature. CO2 adsorption rates were measured for the same sample at similar temperatures and equilibrium pressure for comparison. Findings: Results show that H2 adsorption rate and consequently DH2 increases by temperature. DH2 values are one order of magnitude larger than the equivalent DCO2 values for the whole studied temperature range 20–60 C. DH2 / DCO2 also shows an increasing trend versus temperature. CO2 adsorption capacity at equilibrium pressure is about 5 times higher than that of H2 in all studied temperatures. Both H2 and CO2 adsorption capacities at equilibrium pressure slightly decrease as temperature rises.

This study compares the cost of several low-greenhouse gas (GHG) or GHG-neutral residential heating technologies in the year 2050: (1) hydrogen boilers (2) hydrogen fuel cells with an auxiliary hydrogen boiler for cold spells (3) air-source heat pumps using renewable electricity and (4) heat pumps with an auxiliary hydrogen boiler for cold spells. The assessment includes low-carbon hydrogen from steam-methane reforming (SMR) using natural gas combined with carbon capture and storage (CCS) or SMR + CCS and zero-carbon hydrogen produced from renewable electricity using electrolysis.

The analysis finds that air-source heat pumps are the most cost-effective residential heating technology in 2050 and are at least 50% lower cost than the hydrogen-only technologies. In a sensitivity analysis we find that even if natural gas costs were 50% lower or renewable electricity prices were 50% higher in 2050 compared to our central assumptions heat pumps would still be more cost-effective than hydrogen boilers or fuel cells. Renewable electrolysis hydrogen can be cost-competitive with SMR + CCS hydrogen in 2050 although electrolysis hydrogen is not produced at scale today. At the same time energy efficiency measures to reduce heat demand would be a more cost-effective strategy for achieving GHG reductions than any of the low-GHG heating pathways we assess in this study.

The analysis shows that all pathways using renewable electricity have a near-zero GHG intensity while SMR + CCS hydrogen could reduce GHG emissions by 69%–93% compared to natural gas if improvements are made in the future to reduce the GHG intensity of this pathway. Quantifying the GHG impact and cost effectiveness of various heating pathways is relevant for European policymakers facing decisions on how to both decarbonize buildings and alleviate energy poverty in line with commitments made in the Renovation Wave Initiative.

The document can be downloaded from the ICCT website

The paper presents and discusses results of mechanical spectroscopy (MS) tests carried out on a Cr martensitic steel. The study regards the following topics: (i) embrittlement induced by Cr segregation; (ii) interaction of hydrogen with C–Cr associates; (iii) nucleation of Cr carbides. The MS technique permitted characterising of the specific role played by point defects in the investigated phenomena: (i) Cr segregation depends on C–Cr associates distribution in as-quenched material in particular a slow cooling rate (~150 K/min) from austenitic field involves an unstable distribution which leads to Cr concentration fluctuations after tempering at 973 K; (ii) hydrogen interacts with C–Cr associates and the phenomenon hinders hydrogen attack (HA) because hydrogen atoms bound by C–Cr associates are not able to diffuse towards grain boundaries and dislocation where CH4 bubbles may nucleate grow and merge to form the typical HA cracks; (iii) C–Cr associates take part in the nucleation mechanism of Cr7C3 carbides and specifically these carbides form by the aggregation of C–Cr associates with 1 Cr atom.

A pseudo-homogeneous model for the methanol steam reforming process was developed based on reaction kinetics over a CuO/ZnO/Al2O3 catalyst and non-adiabatic heat and mass transfer performances in a co-current packed-bed reactor. A Thiele modulus method and an intraparticle distribution method were applied for predicting the effectiveness factors for main reactions and providing insights into the diffusion-reaction process in a cylindrical catalyst pellet. The results of both methods are validated and show good agreements with the experimental data but the intraparticle distribution method provides better predictions. Results indicate that increases in catalyst size and bulk fluid temperature amplify the impact of intraparticle diffusion limitations showing a decrease in effectiveness factors. To satisfy the requirements of a high temperature polymer electrolyte membrane fuel cell stack the optimized operating conditions which bring the methanol and CO concentrations to less than 1% vol in the reformate stream are determined based on the simulation results.

Hydrogen as an energy carrier is understood as a system capable of storing energy for a later use in a controlled manner. Surplus electricity from renewable energy serves for green hydrogen generation via electrolysis. Once produced the hydrogen is stored for later consumption. This paper describes the Spanish Case Study of the HyUnder project which aims to evaluate the potential of underground hydrogen storage for large-scale energy storage along Europe analysing besides the Spanish Case France Germany the Netherlands Romania and the United Kingdom. This case study has considered for the assessment the competitiveness of hydrogen storage against other large scale energy storage concepts the geological potential for hydrogen storage in the region how to embed the hydrogen energy storage in the energy market and the possible business cases in four different applications: transport Power to Gas re-electrification and industry taking into account all the economic aspects such us the electrolyser OPEX and CAPEX or the cavern electricity and water costs. It is shown that the Spanish geology can provide four technical options for hydrogen underground storage. Results have shown the interest of the technology in short – medium term especially linked to certain conditions of high intermittent renewable energy penetration in the Spanish power grid that result in surplus or residual electricity. Hydrogen storage is interesting because it can integrate renewable energy systems in other sectors which do not have overcapacity and a high use of fossil fuels as the natural gas sector and the transport sector. Moreover all the economic issues have been analysed for two different horizons 2025 and 2050; concluding that the average price of electricity is the main cost. From the financial results transport application represents a business case which although in order has enough values of hydrogen demand to be stored combination of different applications must be needed in order to make sense to the development of the cavern.

Although proton exchange membrane fuel cell (PEMFC) systems are expected to have lower environmental impacts in the operational phase compared to conventional energy conversion systems there are still certain economic operational and environmental setbacks. Durability under a wide range of operating conditions presents a challenge because degradation processes affect the PEMFC efficiency. Typically life cycle assessment (LCA) of PEMFC systems do not include performance degradation. Thus a novel semi-empirical PEMFC model is developed which includes degradation effects caused by different operational regimes (dynamic and steady-state). The model is integrated into LCA through life cycle inventory (LCI) to achieve a more realistic and accurate evaluation of environmental impacts. Verification of the model clearly showed that the use of existing LCI models underestimates the environmental impacts. This is especially evident when green hydrogen is used in PEMFC operational phase where manufacturing phase and maintenance (stack replacements) become more influential. Input parameters of the model can be modified to reflect technological improvements (e.g. platinum loading or durability) and evaluate the effects of future scenarios.

In this study electrochemical measurements immersion tests and slow strain rate tensile (SSRT) tests were applied to investigate the electrochemical and stress corrosion cracking (SCC) behavior of X70 steel in simulated seawater with the interference of different alternating current (AC) densities. The results indicate that AC significantly strengthens the cathodic reaction especially the oxygen reduction reaction. Simultaneously hydrogen evolution reaction occurs when the limiting diffusion current density of oxygen reaches and thus icorr sharply increases with the increase in AC density. Additionally when AC is imposed the X70 steel exhibits higher SCC susceptibility in the simulated seawater and the susceptibility increases with the increasing AC density. The SCC mechanism is controlled by both anodic dissolution (AD) and hydrogen embrittlement (HE) with the interference of AC.

An engineering tool is presented to predict steady state two-phase choked flow through a discharge line with variable cross section with account of friction and without wall heat transfer. The tool is able to predict the distribution of all relevant physical quantities along the discharge line. Choked flow is calculated using the possible-impossible flow algorithm implemented in a way to account for possible density discontinuities along the line. Physical properties are calculated using the Helmholtz Free Energy formulation. The tool is verified against previous experiments with water and evaluated against previous experiments with cryogenic two-phase hydrogen.

The present work aims to identify critical materials in water electrolysers with potential future supply constraints. The expected rise in demand for green hydrogen as well as the respective implications on material availability are assessed by conducting a case study for Germany. Furthermore the recycling of end‐of‐life (EoL) electrolysers is evaluated concerning its potential in ensuring the sustainable supply of the considered materials. As critical materials bear the risk of raising production costs of electrolysers substantially this article examines the readiness of this technology for industrialisation from a material perspective. Except for titanium the indicators for each assessed material are scored with a moderate to high (platinum) or mostly high (iridium scandium and yttrium) supply risk. Hence the availability of these materials bears the risk of hampering the scale‐up of electrolysis capacity. Although conventional recycling pathways for platinum iridium and titanium already exist secondary material from EoL electrolysers will not reduce the dependence on primary resources significantly within the period under consideration—from 2020 until 2050. Notably the materials identified as critical are used in PEM and high temperature electrolysis whereas materials in alkaline electrolysis are not exposed to significant supply risks.

The main aim of this paper is to characterize the concept of a novel energy storage system based on compressed CO2 storage installation that uses an infrastructure of depleted coal mines to provide required volume of tanks and additionally hydrogen generators and a methanation installation to generate synthetic natural gas that can be used within the system or taken out of it e.g. to a gas grid. A detailed mathematical model of the proposed solution was built using own codes and Aspen Plus software. Thermodynamic evaluation aiming at determining parameters composition and streams in all the most important nodes of the system for the nominal point and when changing a defined decision variable δ (in the range from 0.1 to 0.9) was made. The evaluation was made based on the storage efficiency volume of the tanks and flows of energy within the system. The storage efficiency in the nominal point reached 45.08% but was changing in the range from 35.06% (for δ = 0.1) to 63.93% (for δ = 0.9). For the nominal value of δ equal to 0.5 volume of the low-pressure tank (LPT) was equal to 132869 m3 while of the high pressure tank (HPT) to 1219 m3 . When changing δ these volumes were changing from 101900 m3 to 190878 m3 (for LPT) and from 935 to 1751 m3 (for HPT) respectively. Detailed results are presented in the paper and indicate high storage potential of the proposed solution in regions with underground mine infrastructure.