Resource and energy management of synfuels production with hydrogen and oxygen requirements from electrolysis

The Resource and Energy Management System (REM) is an integrated self-sufficient system for the efficient and clean recovery of synthetic crudes at high yields from a variety of heavy hydrocarbon deposits. The system integrates the following: heavy oil/tar sand bitumen/shale oil/coal recovery; upgrading by “hydrogen addition”; residual oil/coal gasification; and combined cycle electricity generation for water electrolysis.Recovered heavy hydrocarbons are upgraded by “hydrogen addition”. Hydrogen is available, in the REM system, from electrolysis, from gasifying the waste carbonaceous residues from upgrading and from gasifying coal. Gasification is efficiently carried out with oxygen, available from electrolysis. Gasifier synthesis gases are also used in a combined-cycle power system to generate power. Power, produced economically by this means, is used to electrolyse water which is the source of hydrogen for upgrading and of oxygen for gasification.Favourable technical and economic circumstances now prevail for the commercialization of large-scale electrolytic units in the synfuels industry according to a technical and economic analysis.The Government of Canada and the Province of Alberta through the Alberta Oil Sands Technology and Research Authority and Norcen Energy Resources Limited are jointly funding a feasibility study of the REM system, as applied to small-scale hydrogen addition synfuels plants on the Canadian tar sands and heavy oil deposits. Canadian Patent 1065780 and U.S. Patent 4 160 479 have been issued with patents pending in Venezuela and Mexico covering the REM system.     

PEM electrolysis for production of hydrogen from renewable energy sources

PEM electrolysis is a viable alternative for generation of hydrogen from renewable energy sources. Several possible applications are discussed, including grid independent and grid assisted hydrogen generation, use of an electrolyzer for peak shaving, and integrated systems both grid connected and grid independent where electrolytically generated hydrogen is stored and then via fuel cell converted back to electricity when needed. Specific issues regarding the use of PEM electrolyzer in the renewable energy systems are addressed, such as sizing of electrolyzer, intermittent operation, output pressure, oxygen generation, water consumption and efficiency.     

Feasibility of hydrogen production from coal electrolysis at intermediate temperatures

Hydrogen production via coal electrolysis was evaluated at intermediate temperatures (40–108 °C). A coal electrolytic cell (CEC) was designed and constructed to carry out galvanostatic experiments with concentrated electrolyte (4 M H₂SO₄). Operating temperatures above 100 °C were found to significantly improve the kinetics of electro-oxidation of coal, coal conversion, and CO₂/coal Faradaic efficiency. CO₂/coal Faradaic efficiencies and coal conversions of up to 57.29 and 3.21%, respectively, were observed at 108 °C.     

Pure hydrogen production by PEM electrolysis for hydrogen energy

Last years hydrogen as energy carrier becomes one of the best solutions of energy and ecological problems. Intensive development of fuel cells, especially based on proton exchange membrane (PEM), where pure hydrogen is needed, stimulates electrolyzers development for the future application in hydrogen energy and technology. From point of view of the authors PEM electrolysis is very perspective for this goal. Advantages and possible fields of applications of this type of electrolyzers in comparison with another one are reviewed. Some results achieved up to now in PEM electrolysis, including last achievement of the authors, are summarized.     

Chlorine-free alkaline seawater electrolysis for hydrogen production

A new process for chlorine-free seawater electrolysis is proposed in this study. The first step of the process is separation of Mg²⁺ and Ca²⁺ ions from seawater by nanofiltration. Next, the NF permeate is dosed into the electrochemical system. There it is completely split into hydrogen and oxygen gases and NaCl precipitate. The electrochemical system comprises an electrochemical cell operated at elevated temperatures (e.g. ≥ 50 °C) and a settling tank filled with aqueous NaOH solution (20–40 %wt) that operates at lower temperatures (e.g. 20–30 °C). High concentration of hydroxide ions in the electrolyzed solution prevents anodic chlorine evolution, while the accumulated NaCl precipitates in the settling tank. Batch electrolysis tests, performed in NaCl-saturated NaOH solutions, showed absolutely no chlorine formation on Ni200 and Ti/IrO₂RuO₂TiO₂ anodes at [NaOH] > 100 g/kgH₂O. Three long-term operations (9, 12 and 30 days) of the electrochemical system showed no Cl₂ or chlorate (ClO₃^?) production on both electrodes operated at current densities of 93–467 mA/cm². The Ni200 anode was corroded in the continuous operation that resulted in formation of nickel oxide on the anode surface. On the other hand, the system was successfully operated at 467 mA/cm² with Ti/IrO₂RuO₂TiO₂ electrodes in NaCl-saturated solution of NaOH (30 %wt) for 12 days. During this period no formation of Cl₂ and ClO₃^? has been observed and precipitation of NaCl occurred only in the settling tank. The performance of the system was stable during the operation as indicated by the insignificant fluctuations in the applied cell potentials and measured constant concentrations of NaOH_(aq) and NaCl_(aq) in the electrolyte solution. During 12 days of operation at ≈ 470 mA/cm² about 1.2 m³ of H₂ and ≈150 g of solid NaCl were produced in the system. Electrical energy demand of the electrolysis cell was 5.6–6.7 kWh/m³H₂ for the current density range of 187–467 mA/cm².     

Solar hydrogen production via alkaline water electrolysis

Electricity generation via direct conversion of solar energy with zero carbon dioxide emission is essential from the aspect of energy supply security as well as from the aspect of environmental protection. Therefore, this paper presents a system for hydrogen production via water electrolysis using a 960 Wp solar power plant. The results obtained from the monitoring of photovoltaic modules mounted in pairs on a fixed, a single-axis and a dual-axis solar tracker were examined to determine if there is a possibility to couple them with an electrolyzer. Energy performance of each photovoltaic system was recorded and analyzed during a period of one year, and the data were monitored on an online software service. Estimated parameters, such as monthly solar irradiance, solar electricity production, optimal angle, monthly ambient temperature, and capacity factor were compared to the observed data. In order to get energy efficiency as high as possible, a novel alkaline electrolyzer of bipolar design was constructed. Its design and operating UI characteristic are described. The operating UI characteristics of photovoltaic modules were tuned to the electrolyzer operating UI characteristic to maximize production. The calculated hydrogen rate of production was 1.138 g per hour. During the study the system produced 1.234 MWh of energy, with calculated of 1.31 MWh , which could power 122 houses, and has offset 906 kg of carbon or an equivalent of 23 trees.     

A comparative assessment on hydrogen production from low- and high-temperature electrolysis

In this work a comparative analysis between low- and high-temperature electrolysis for hydrogen generation is assessed. A hydrogen production system based on Solid Oxide Electrolysis Cells (SOEC) is designed and modeled and compared to the performance of a more mature system based on PEM technology. The SOEC system mainly consists of an SOEC stack, a heat recovery system and a hydrogen compression section. Experimental data measured in steam electrolysis tests performed on single solid oxide cells were utilized into the model to characterize the stack performance. The model carries out a thermodynamic analysis in order to calculate the energy efficiency and the exergetic consumption of the system; these performances are subsequently compared with those of a low-temperature hydrogen generation system evaluated from experimental data measured in test sessions performed on a complete BoP integrating a pressurized Proton Exchange Membrane (PEM) electrolyser. The comparison is carried out with the two electrolysis systems generating hydrogen at the same production rate and pressure. The results of this study show that the modeled SOEC hydrogen generation system can compete with the PEM electrolyser, achieving better performance than the low-temperature system at hydrogen production rate higher than 18.3 g h⁻¹ (corresponding to 0.25 A cm⁻²) and showing an energy efficiency up to 14% higher than the PEM system at 1 A cm⁻².     

UV enhanced denitrification using chlorine from seawater electrolysis for hydrogen production

Seawater electrolysis is an attractive way to generate hydrogen energy. However, to commercialize this technology, it has been focused on developing chlorine-less oxygen generating electrodes for decades. Here, different from common ideas of minimizing chlorine formation at the anode, we aimed at reusing the waste chlorine from seawater electrolysis to mitigate nitrogen oxide (NOx) emissions. NOx removal performance of electrolyzed seawater containing chlorine was investigated under 254 nm ultraviolet (UV) irradiation in a semi-continuous bubbling reactor. Comparative parametric experiments were conducted for each factor with and without UV irradiation. Significant contributions of UV irradiation on denitrification performance of chlorine were observed under all investigated conditions. A ten-folder improvement in denitrification efficiency by the UV irradiated electrolyzed seawater was achieved under optimal conditions. Possible free radicals’ reaction mechanisms were discussed preliminarily. Results reveal that UV irradiated electrolyzed seawater is a promising way to reuse electrolyzed chlorine and mitigate acid gas emissions.     

Review of hydrogen production with photovoltaic electrolysis systems

Of vital importance for the increasing share of nonfossil primary energy in energy supply systems is the development and economic availability of a new chemical energy carrier, which offers large-scale and long-term storage of thermal and electrical energy, the main products of nonfossil primary energy conversion. The potential of H₂ for the extensive utilization of solar energy is of particular importance. Characteristics and performance of H₂ production by means of photovoltaic solar energy conversion and water electrolysis are studied and discussed. Experimental results of a small system consisting of a polycrystalline solar cell generator, water electrolysis and power conditioning are compared with calculated results of a system simulation model. The stationary and dynamic behaviour of system and components and the efficiency and performance of power conditioning are investigated. For an optimized and reliable operation of photovoltaic electrolyzer systems, the behaviour of electrolysis at part-load and overload, the start-up and shut-down behaviour, corrosion and degradation effects are important aspects. The status and further improvements of advanced electrolysis are discussed, as well as results of system analysis studies for future large-scale solar H₂ production.     

Development and operation of alternative oxygen electrode materials for hydrogen production by high temperature steam electrolysis

High temperature steam electrolysis (HTSE) is one of the most promising ways for hydrogen mass production. To make this technology suitable from an economical point of view, each component of the system has to be optimized, from the balance of plant to the single solid oxide electrolysis cell. At this level, the optimization of the oxygen electrode is of particular interest since it contributes to a large extent to the cell polarization resistance. The present paper is focused on alternative oxygen electrode materials with improved performances compared to the usual ones mainly based on perovskite structure. Two nickelates, with compositions La₂NiO_4+δ and Nd₂NiO_4+δ are investigated and evaluated in HTSE operation at the button cell level. The performances of the Ln₂NiO_4+δ - containing cells (Ln = La, Nd) is improved compared to a cell containing the classical Sr-doped LaMnO₃ (LSM) perovskite oxygen electrode showing that nickelates are promising candidates for HTSE oxygen electrodes, especially for operation below 800 °C. Indeed, current densities determined at 1.3 V are 1.1 times larger for the La₂NiO_4+δ - containing cell and 1.6 times larger for the Nd₂NiO_4+δ one compared to the LSM - containing cell at 850 °C, whereas at 750 °C they are 1.8 and 4.4 times larger, respectively. Thanks to the use of a reference electrode, by coupling impedance spectroscopy and polarization measurements, the overpotential of each working electrode is deconvoluted from the complete cell voltage under HTSE operating conditions.     

Forecasting hydrogen production potential in islamabad from solar energy using water electrolysis

The focus of this study is the use of Machine Learning methods to forecast Solar Hydrogen production potential for the Islamabad region of Pakistan. For this purpose, we chose a Photovoltaic-Electrolytic (PV-E) system to forecast electricity and, hence, hydrogen production. The weather data used for forecasting and simulation were recorded with precise meteorological instruments stationed in Islamabad, over the course of 13 and a half months. Out of the three tested algorithms, Prophet performs the best with Mean Absolute Percentage Error of 3.7%, forecasting a daily average Hydrogen production of 93.3 × 10³ kg/Km². Although, the forecast in this study is made for the month of August and September, during which the local season moves towards winter, this study demonstrates solar hydrogen production, as a green energy source, has a tremendous potential in this region.     

Enhanced oxygen evolution reaction kinetics through biochar-based nickel-iron phosphides nanocages in water electrolysis for hydrogen production

Highly-efficient and stable non-noble metal electrocatalysts for overcoming the sluggish kinetics of oxygen evolution reaction (OER) is urgent for water electrolysis. Biomass-derived biochar has been considered as promising carbon material because of its advantages such as low-cost, renewable, simple preparation, rich structure, and easy to obtain heteroatom by in-situ doping. Herein, Ni₂P–Fe₂P bimetallic phosphide spherical nanocages encapsulated in N/P-doped pine needles biochar is prepared via a simple two-step pyrolysis method. Benefiting from the maximum synergistic effects of bimetallic phosphide and biochar, high conductivity of biochar encapsulation, highly exposed active sites of Ni₂P–Fe₂P spherical nanocages, rapid mass transfer in porous channels with large specific surface area, and the promotion in adsorption of reaction intermediates by high-level heteroatom doping, the (Ni_0.75Fe_0.25)₂P@NP/C demonstrates excellent OER activity with an overpotential of 250 mV and a Tafel slope of 48 mV/dec at 10 mA/cm² in 1 M KOH. Also it exhibits a long-term durability in 10 h electrolysis and its activity even improves during the electrocatalytic process. The present work provides a favorable strategy for the inexpensive synthesis of biochar-based transition metal electrocatalysts toward OER, and improves the water electrolysis for hydrogen production.     

Analysis of copper chlorine electrolysis for large-scale hydrogen production

Nuclear hydrogen production is experiencing an unprecedented momentum worldwide, in response to the increasing demand for clean large-scale hydrogen production in line with the outcomes of the UN Conference of the Parties (COP26). A seamless integration of several innovative nuclear designs including Small Modular Reactors with steam Rankine cycle and the cogeneration of Hydrogen using thermochemical water-splitting cycles (e.g., the Cu–Cl cycle) is possible for a complete solution of hydrogen, oxygen, and electric power generation. In this paper, a process and flow sheet for large-scale hydrogen production by CuCl electrolysis at 50 tonnes per day is proposed and analyzed. The scaled-up process and flow sheet is based on lab-scale experience with 50 l/h hydrogen generation. Pressurized Cu–Cl electrolysis and basic electrolysis are reported to support the scaling up parameters, assumptions, and considerations. Based on determined sizing parameters and energy analysis, the Cu–Cl cycle consumes substantially less primary energy (thermal) than water electrolysis, which makes it a serious competitor, despite its obvious higher investment cost in the hardware.     

A new analysis of two phase flow on hydrogen production from water electrolysis

It is clear that the entire world have to research, develop, demonstrate and plan for alternative energy systems for shorter term and also longer term. As a clean energy carrier, hydrogen has become increasingly important. It owes its prestige to the increase within the energy costs as a result of the equivocalness in the future availability. Two phase flow and hydrogen gas flow dynamics effect on performance of water electrolysis. Hydrogen bubbles are recognized to influence energy and mass transfer in gas-evolving electrodes. The movement of hydrogen bubbles on the electrodes in alkaline electrolysis is known to affect the reaction efficiency. Within the scope of this research, a physical modeling for the alkaline electrolysis is determined and the studies about the two-phase flow model are carried out for this model. Internal and external forces acting on the resulting bubbles are also determined. In this research, the analytical solution of two-phase flow analysis of hydrogen in the electrolysis is analyzed.     

Modeling to get hydrogen and oxygen by solar water electrolysis

On the basis of experimental investigations carried out in natural conditions this article gives: one of the possible schemes of mathematical model of solar electrolysis plant for the production of hydrogen and oxygen from water under pressure; the block-scheme of solar electrolysis plant; the software that is prepared in the Fortran algorithmic language for practical application in a computer; and also the results of calculation in a computer at the plant-operating regime under pressures P=0.1 and 0.4 MPa.     

Achieving high-efficiency hydrogen production using planar solid-oxide electrolysis stacks

Steam electrolysis in solid oxide electrolysis cells (SOECs) is considered as an effective method to achieve high-efficiency hydrogen production. In the present investigation, samples of 1-cell, 2-cell and 30-cell SOEC stacks were tested under electrolysis of steam to give a practical evaluation of the SOEC system efficiency of hydrogen production. The samples were tested at 800 °C under various operating conditions up to 500 h without significant degradation, and obtained steam conversion rates of 12.4%, 23% and 82.2% for the 1-cell, 2-cell and 30-cell stacks, respectively. System efficiencies of hydrogen production were calculated for the samples based on their real performance. A maximum efficiency value of 52.7% was achieved in the 30-cell stack.     

High hydrogen production from glycerol or glucose by electrohydrogenesis using microbial electrolysis cells

The use of glycerol for hydrogen gas production was examined via electrohydrogenesis using microbial electrolysis cells (MECs). A hydrogen yield of 3.9 mol-H₂/mol was obtained using glycerol, which is higher than that possible by fermentation, at relatively high rates of 2.0 ± 0.4 m³/m³ d (E_ap = 0.9 V). Under the same conditions, hydrogen was produced from glucose at a yield of 7.2 mol-H₂/mol and a rate of 1.9 ± 0.3 m³/m³ d. Glycerol was completely removed within 6 h, with 56% of the electrons in intermediates (primarily 1,3-propanediol), with the balance converted to current, intracellular storage products or biomass. Glucose was removed within 5 h, but intermediates (mainly propionate) accounted for only 19% of the electrons. Hydrogen was also produced using the glycerol byproduct of biodiesel fuel production at a rate of 0.41 ± 0.1 m³/m³ d. These results demonstrate that electrohydrogenesis is an effective method for producing hydrogen from either pure glycerol or glycerol byproducts of biodiesel fuel production.     

Biochar sacrificial anode assisted water electrolysis for hydrogen production

Carbon-assisted water electrolysis uses carbon oxidation reaction replacing oxygen evolution reaction to decrease the anode potential and the energy consumption for water electrolysis hydrogen production. However, the mass transfer between carbon particle-electrolyte-anode limits its energy saving effect. Based on the principle of self-corrosion/oxidation of carbon-based electrode materials, the biochar sacrificial anode was proposed and investigated to solve the mass transfer issue in carbon slurry assisted water electrolysis for hydrogen production. Results showed that the activity and stability of sacrificial anode could be improved simultaneously in high concentration alkaline electrolyte using pinewood char as active substance, graphite as conductive agent and coal liquefying residue as binder. The biochar anode produced less oxygen than Pt anode, and the anode potential of biochar was 60–76% of that Pt anode. The application of biochar as sacrificial anode offers an industrial clean, scalable and sustainable idea to obtain green hydrogen.     

Nanocarbon boosts energy-efficient hydrogen production in carbon-assisted water electrolysis

To improve upon our previously reported slow hydrogen evolution rate R_H at the energy-efficient lower voltages in CAWE (carbon-assisted water electrolysis) at room temperature, new results using different carbons and catalysts to improve R_H are reported here. Compared to earlier results with carbon GX203, about a ten-fold increase in R_H is reported using high surface area carbon BP2000 at the operating voltage E^o = 1.12 V. With added FeSO₄ catalyst, E^o is lowered to 0.72 V without lowering R_H, representing about 30% decrease in the energy barrier of the process. For comparison, in water electrolysis without carbon, measurable R_H is observed only for E^o ≥ 2 V. This large improvement in R_H at the energy efficient E^o = 0.72 V is suggested to result from nanoscale particle size of carbon BP2000 as well as from electrons provided by the catalyst through the reaction Fe²⁺ ? Fe³⁺ + e⁻. By measuring the amounts of H₂ evolved at the cathode and CO₂ evolved at the anode using gas chromatography, the mechanism for CAWE is established to be the reaction: C (s) + 2H₂O (?) → CO₂ (g) + 2H₂ (g). The reaction slows down with time as carbon is depleted by oxidation.