Production & Supply Chain

Green hydrogen production is essential to meeting the conference of the parties’ (COP) decarbonization goals; however this method of producing hydrogen is not as cost-effective as hydrogen production from fossil fuels. This study analyses an off-grid photovoltaic energy system designed to feed a proton-exchange membrane water electrolyzer for hydrogen production to evaluate the optimal electrolyzer size. The system has been analyzed in Baghdad the capital of Iraq using experimental meteorological data. The 12 kWp photovoltaic array is positioned at the optimal annual tilt angle for the selected site. The temperature effect on photovoltaic modules is taken into consideration. Several electrolyzers with capacities in the range of 2–14 kW were investigated to assess the efficiency and effectiveness of the system. The simulation process was conducted using MATLAB and considering the project life span from 2021 to 2035. The results indicate that various potentially cost-competitive alternatives exist for systems with market combinations resembling renewable hydrogen wholesale. It has been found that the annual energy generated by the analyzed photovoltaic system is 18892 kWh at 4313 operating hours and the obtained hydrogen production cost ranges from USD 5.39/kg to USD 3.23/kg. The optimal electrolyzer capacity matches a 12 kWp PV system equal to 8 kW producing 37.5 kg/year/kWp of hydrogen for USD 3.23/kg.

The analysis here presented investigates the influence of electrical load on the operational performances of a plant for hydrogen production from solar energy and its conversion in electricity via a fuel cell. The plant is an actual one currently under construction in Reggio Calabria (Italy) at the site of the Mediterranean university campus; it is composed of a Renewable Energy Source (RES) section (photovoltaic panels) a hydrogen production section and a fuel cell power section feeding the electrical energy demand of the load. Two different load configurations have been analysed and simulations have been carried out through HomerTM simulation code. Results allow interesting conclusions regarding the plant operation to be drawn. The study could have a remarkable role in supporting further research activities aimed at the assessment of the optimal configuration of this type of pioneering plants designed for feeding electrical loads possibly in a self-sufficient way.

Porous cotton stalk activated carbons (CSAC) were prepared by phosphoric acid activation of cotton stalks in a fluidized bed. The CSAC-supported Co–B and Co–Ce–B catalysts were prepared by the impregnation-chemical reduction method. The samples were characterized by the nitrogen adsorption XRD FTIR and TEM measurements. The effects of the sodium borohydride (NaBH₄) and sodium hydroxide (NaOH) concentrations reaction temperature and recyclability on the rate of NaBH4 hydrolysis over the CSAC-supported Co–Ce–B catalysts were systematically investigated. The results showed that the agglomeration of the Co–Ce–B nanoclusters on the CSAC support surface was significantly reduced with the introduction of cerium. The CSAC-supported Co–Ce–B catalyst exhibited superior catalytic activity and the average hydrogen generation rate was 16.42 L min⁻¹ g⁻¹ Co at 25°C which is higher than the most reported cobalt-based catalysts. The catalytic hydrolysis of NaBH₄ was zero order with respect to the NaBH4 concentration and the hydrogen generation rate decreased with the increase in the NaOH concentration. The activation energy of the hydrogen generation reaction on the prepared catalyst was estimated to be 48.22 kJ mol⁻¹. A kinetic rate equation was also proposed.

This work reports a detailed chemical looping investigation of strontium ferrite (SrFeO_3−δ) a material with the perovskite structure type able to donate oxygen and stay in a nonstoichiometric form over a broad range of oxygen partial pressures starting at temperatures as low as 250°C (reduction in CO measured in TGA). SrFeO_3−δ is an economically attractive simple but remarkably stable material that can withstand repeated phase transitions during redox cycling. Mechanical mixing and calcination of iron oxide and strontium carbonate was evaluated as an effective way to obtain pure SrFeO_3−δ. In–situ XRD was performed to analyse structure transformations during reduction and reoxidation. Our work reports that much deeper reduction from SrFeO_3−δ to SrO and Fe is reversible and results in oxygen release at a chemical potential suitable for hydrogen production. Thermogravimetric experiments with different gas compositions were applied to characterize the material and evaluate its available oxygen capacity. In both TGA and in-situ XRD experiments the material was reduced below δ=0.5 followed by reoxidation either with CO₂ or air to study phase segregation and reversibility of crystal structure transitions. As revealed by in-situ XRD even deeply reduced material regenerates at 900°C to SrFeO_3−δ with a cubic structure. To investigate the catalytic behaviour of SrFeO_3−δ in methane combustion experiments were performed in a fluidized bed rig. These showed SrFeO_3−δ donates O₂ into the gas phase but also assists with CH4 combustion by supplying lattice oxygen. To test the material for combustion and hydrogen production long cycling experiments in a fluidized bed rig were also performed. SrFeO3−δ showed stability over 30 redox cycles both in experiments with a 2-step oxidation performed in CO₂ followed by air as well as a single step oxidation in CO₂ alone. Finally the influence of CO/CO₂ mixtures on material performance was tested; a fast and deep reduction in elevated pCO₂ makes the material susceptible to carbonation but the process can be reversed by increasing the temperature or lowering pCO₂.

This review gives a worldwide overview on Power-to-Gas projects producing hydrogen or renewable substitute natural gas focusing projects in central Europe. It deepens and completes the content of previous reviews by including hitherto unreviewed projects and by combining project names with details such as plant location. It is based on data from 153 completed recent and planned projects since 1988 which were evaluated with regards to plant allocation installed power development plant size shares and amounts of hydrogen or substitute natural gas producing examinations and product utilization phases. Cost development for electrolysis and carbon dioxide methanation was analyzed and a projection until 2030 is given with an outlook to 2050.<br/>The results show substantial cost reductions for electrolysis as well as for methanation during the recent years and a further price decline to less than 500 euro per kilowatt electric power input for both technologies until 2050 is estimated if cost projection follows the current trend. Most of the projects examined are located in Germany Denmark the United States of America and Canada. Following an exponential global trend to increase installed power today's Power-to-Gas applications are operated at about 39 megawatt. Hydrogen and substitute natural gas were investigated on equal terms concerning the number of projects.

There can be observed global interest in waste pyrolysis technology due to low costs and availability of raw materials. At the same time there is a literature gap in forecasting environmental effects of thermal waste treatment installations. In the article was modelled the chemical composition of pyrolysis gas with main focus on the problem in terms of environmental hazards. Not only RDF fuel was analysed but also selected waste fractions included in its composition. This approach provided comprehensive knowledge about the chemical composition of gaseous pyrolysis products which is important from the point of view of the heterogeneity of RDF fuel. The main goal of this article was to focus on the utilitarian aspect of the obtained calculation results. Final results can be the basis for estimating ecological effects both for existing and newly designed installations.

Pyrolysis process was modelled using Ansys Chemkin-Pro software. The investigation of the process were carried out for five different temperatures (700 750 800 850 and 900 °C). As an output the mole fraction of H2 H₂O CH₄ C₂H₂C₂H₄ C₃H₆ C₃H₈ CO CO₂ HCl and H₂S were presented. Additionally the reaction pathways for selected material were presented.

Based on obtained results it was established that the residence time did not influenced on the concentration of products contrary to temperature. The chemical composition of pyrolytic gas is closely related to wastes origin. The application of Chemkin-Pro allowed the calculation of formation for each products at different temperatures and formulation of hypotheses on the reaction pathways involved during pyrolysis process. Further based on the obtained results confirmed the possibilities of using pyrolysis gas from RDF as a substitute for natural gas in energy consumption sectors. Optimization of the process can be conducted with low financial outlays and reliable results by using calculation tools. Moreover it can be predicted negative impact of obtained products on the future installation.

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.

CeO2- ZrO2- and La2O3-supported Rh-Pt catalysts were tested to assess their ability to catalyze the steam reforming of ethanol (SRE) for H2 production. SRE activity tests were performed using EtOH:H2O:N2 (molar ratio 1:3:51) at a gaseous space velocity of 70600 h−1 between 400 and 700 °C at atmospheric pressure. The SRE stability of the catalysts was tested at 700 °C for 27 h time on stream under the same conditions. RhPt/CeO2 which showed the best performance in the stability test also produced the highest H2 yield above 600 °C followed by RhPt/La2O3 and RhPt/ZrO2. The fresh and aged catalysts were characterized by TEM XPS and TGA. The higher H2 selectivity of RhPt/CeO2 was ascribed to the formation of small (~5 nm) and stable particles probably consistent of Rh-Pt alloys with a Pt surface enrichment. Both metals were oxidized and acted as an almost constant active phase during the stability test owing to strong metal-support interactions as well as the superior oxygen mobility of the support. The TGA results confirmed the absence of carbonaceous residues in all the aged catalysts.

The current status of a project is described which aims to demonstrate the technical and economic feasibility of converting the vast wind energy available over the globe’s oceans and lakes into storable energy. To this end autonomous high-performance sailing ships are equipped with hydrokinetic turbines whose output is stored either in electric batteries or is fed into electrolysers to produce hydrogen which then is compressed and stored in tanks. In the present paper the previous analytical studies which showed the potential of this “energy ship concept” are summarized and progress on its hardware demonstration is reported involving the conversion of a model sailboat to autonomous operation. The paper concludes with a discussion of the potential of this concept to achieve the IPCC-mandated requirement of reducing the global CO₂ emissions by about 45% by 2030 reaching net zero by 2050.

The direct hydrogenation of CO₂ to dimethyl ether (DME) is a promising technology for CO₂ valorisation. In this work a 1D phenomenological reactor model is developed to evaluate and optimize the performance of a membrane reactor for this conversion otherwise limited by thermodynamic equilibrium and temperature gradients. The co-current circulation of a sweep gas stream through the permeation zone promotes both water and heat removal from the reaction zone thus increasing overall DME yield (from 44% to 64%). The membrane properties in terms of water permeability (i.e. 4·10⁻⁷ mol·Pa⁻¹m−2s⁻¹) and selectivity (i.e. 50 towards H₂ 30 towards CO₂ and CO 10 towards methanol) for optimal reactor performance have been determined considering for the first time non-ideal separation and non-isothermal operation. Thus this work sheds light into suitable membrane materials for this applications. Then the non-isothermal performance of the membrane reactor was analysed as a function of the process parameters (i.e. the sweep gas to feed flow ratio the gradient of total pressure across the membrane the inlet temperature to the reaction and permeation zone and the feed composition). Owing to its ability to remove 96% of the water produced in this reaction the proposed membrane reactor outperforms a conventional packed bed for the same application (i.e. with 36% and 46% improvement in CO₂ conversion and DME yield respectively). The results of this work demonstrate the potential of the membrane reactor to make the CO₂ conversion to DME a feasible process.