Electrolysis System Research Articles

Techno-economic analysis of solar powered green hydrogen system based on multi-objective optimization of economics and productivity

Green hydrogen, hydrogen produced from renewable sources, is emerging as clean energy carrier to combat climate change. In particular, on-site hydrogen production by solar power has the advantage of being simple to install with fewer regional limits. Cost and productivity of solar-based hydrogen, however, can be difficult to estimate and balance as the production is intermittent and unpredictable due to the volatility of renewable energy source. In this study, a multi-objective optimization-based framework for solar powered green hydrogen is presented for optimal system design that balances between economic cost and productivity. A system-wide model is developed that uses meteorological data to estimate how much solar power would be generated and how much hydrogen would be produced as a result. Then, using the model, a framework is suggested for calculating and simultaneously optimizing the amount of hydrogen produced and levelized cost of hydrogen (LCOH). The United States, China, Australia and Korea, all the major countries with interest in solar-based green hydrogen, are assessed using the framework. As a result, it is shown that an optimal system size exists for each different objective, and that a significant improvement in LCOH can be accomplished by enhancing the components’ cost and performance. More importantly, it is revealed that, for all the nations, the optimal electrolyser size to minimize LCOH is roughly 60% of the solar power capacity, and installing batteries is ineffective for boosting the economic viability, but can improve hydrogen production by utilizing unused electricity during peak period. Tradeoffs between economic viability and productivity vary depending on the size of the water electrolysis system and whether or not batteries are installed. An optimization study is carried out with an objective function combining the system’s economic viability and productivity, where key design variables such as the size and number of each unit system are determined. The results show that the consideration of multiple objective functions requires a trade-off and the multi-objective optimization framework allows for a customized design by simultaneously considering the hydrogen demand and economic viability with varying bias of preference.

On the hazards of proton exchange membrane (PEM) water electrolysis systems using system theoretic process analysis (STPA)

Green hydrogen energy is environmentally sustainable and critical to achieving a carbon-neutral society. Among several water electrolysis technologies, the proton exchange membrane water electrolysis (PEMWE) system, when integrated with renewable energy sources (RES), is seen as a promising green hydrogen production method. PEMWE is especially preferred for high-pressure operation, which decreases the energy usage and cost associated with hydrogen compression. However, it also poses significant operational risks, such as component reliability under dynamic operation, potential hydrogen leakage due to overpressure or component failure, possible hydrogen-oxygen mixtures in the system, and other unanticipated operational challenges. To fully understand the PEMWE system’s operational risk and facilitate risk management, this study conducts a systematic risk analysis using the System Theoretic Process Analysis (STPA) method, involving component failure, system design, human and organizational factors. Combined with the automated and dynamic nature of the system, salient issues during the dynamic operation of the PEMWE system, such as control reliability, component communication reliability and thermal runaway risk, are identified semi-quantitatively. This research is expected to provide a case for STPA research in the highly automated and socio-technical process industry. The findings are expected to offer valuable insights into the safety and reliability of the PEMWE system, providing engineers with technical guidelines for safer system designs, operations, and risk engineering applications, while delivering systematic strategies for risk management. Consequently, a more reliable PEMWE system could lead to the efficient utilization of fluctuating RES.

Modified carbon paste electrode with choline proline in enhancing the performance of water electrolysis system for hydrogen production

Hydrogen has been under the light to be one of the future energy prospects to replace the non-renewable energy sources such as fossil fuels and natural gas. The drawbacks of the conventional methods in hydrogen production are the large emission of greenhouse gases (GHGs) associated with the process that required a highly cost CO2 sequestration method to reduce substantially the emission. Therefore, this study focusses on the hydrogen production rate as well as power consumption per hydrogen produced through water splitting process. This study also emphasizes the utilization of carbon paste electrode (CPE) as the electrode in the water electrolysis system with the modification of CPE by the addition of amino acid-based ionic liquid (AAIL). Prior to the modification of CPE, choline proline [Ch][Pro] has been determined as the most suitable modifier for CPE through chemical quantum approach via Conductor-like Screening Model for Realistic Solvents. As the modification of CPE, the best optimum composition of paraffin oil to [Ch][Pro] was 90 vol% of paraffin oil to 10 vol% of [Ch][Pro] which can produce the maximum hydrogen production of 18.2 mL/h with the power consumption of 249.3 kWh/kg H2 as compared to CPE without IL modification with merely 8.0 mL/h of hydrogen production and power consumption of 378.1 kWh/kg H2.

Electro-catalytic adsorption mechanism of acetonitrile in water using a ME-ACFs system

Acetonitrile wastewater is difficult to treat due to its high salinity and toxicity to microorganisms. In this paper, a micro electro-activated carbon fiber coupled system (ME-ACF) was established to treat simulated acetonitrile wastewater. In the 200 ml system, the concentration of acetonitrile adsorbed by ACF was 91.3 mg/L, while that of acetonitrile adsorbed by ME-ACF was 150.6 mg/L, and the removal efficiency was increased by 65 % in comparison. The activated carbon fibers before and after the reaction were subjected to a series of characterization, and it was found that the SABET decreased from 1393.48 m2/g to 1114.93 m2/g and 900.23 m2/g, respectively, but the oxygen on the surface of the activated carbon fibers was increased, and the effect of the micro electrolytic system on the activated carbon fibers was then analyzed. The possible reasons for the formation of acetic acid contained in the products were also discussed using DFT simulations. The removal mechanism of acetonitrile by ME-ACF was considered to be electrically enhanced adsorption and electro-catalytic hydrolysis.

A hBN/B-Si-Al-O-glass composite coating growth on SiCp/Al composite using one-step PEO with nanoparticle addition for outstanding electrical insulation performance

A comprehensive study of the formation of electrical insulation coatings on SiCp/Al composite using plasma electrolytic oxidation (PEO) in an electrolytic system with hBN nanoparticles has been carried out. A complete coating can be formed under a high positive voltage (550–600 V) in a short period of time (3 min), and the coating is mainly composed of the hBN crystal phase as well as some amorphous phases. The high temperature of the local plasma in the PEO process impels these amorphous phases to form an amorphous B-Si-Al-O glass phase. As the treatment time goes on, the cross-sectional porosity of the coating first decreases rapidly and then increases slowly. This is attributed to the fact that the nanoparticles continuously deposit and sinter to repair the larger pores during the coating growth process, hence reducing porosity. Within 6 min, the coating thickness rapidly increases to 133.3 μm, showing excellent electrical insulation performance (with a breakdown voltage of 1460 ± 28 V, volume resistance of 5.52 ± 0.26 G·Ω, electrical resistivity of 4.18 × 1010 Ω∙cm) and high optical band gap value (above 5 eV), which is suitable for electronic packaging or dielectric materials.

시뮬레이션 기반 PEM 수전해 시스템 고장 진단 모델 개발

시뮬레이션 기반 PEM 수전해 시스템 고장 진단 모델 개발

Green hydrogen production and utilization in a novel SOFC/GT-based zero-carbon cogeneration system: A thermodynamic evaluation

Owing to the rise in global energy demand and environmental issues caused by energy supply and distribution, the attempt to design and develop novel eco-friendly and efficient cogeneration energy systems is one of the current research focuses. In this regard, this study presents a novel zero-carbon cogeneration energy system based on a pressurized solid oxide fuel cell-gas turbine (SOFC/GT) with a carbon capture and storage (CCS) process. The designed system accomplishes the joint production of energy (electricity, cooling, and heating) and matter (hydrogen, oxygen, condensate water recovery, and carbon dioxide). The proposed system also includes an advanced alkaline electrolyzer (AAE) system, an organic Rankine cycle, a LiBr-H2O absorption refrigeration cycle, and an LNG regasification cycle. A combination of a solar concentrated photovoltaic/thermal (CPV/T) system and wind turbines feed the AAE system, resulting in green hydrogen production. According to the simulation results, the suggested system under the design conditions generates power, cooling, and domestic hot water with 315 kW, 137.5 kW, and 1.012 kg/s, respectively. Also, this system can capture and store carbon dioxide, recover condensate water, and supply natural gas to the pipeline with values of 74.88 kg/h, 137.9 kg/h, and 624.24 kg/h, respectively. The results from thermodynamic analysis indicate that the CPV/T system has the highest contribution to the exergy destruction rate, and the presented cogeneration system operates with energy and exergy efficiency of 58.09% and 38.58%, respectively. Furthermore, a comprehensive parametric study has been conducted on the developed system in which the impact of important parameters, such as SOFC operating temperature, current density, solar radiation, air velocity, etc., on the output parameters of the system has been examined.

Stability Issues in Electrochemical CO2 Reduction: Recent Advances in Fundamental Understanding and Design Strategies.

Electrochemical CO2 reduction reaction (CO2 RR) offers a promising approach to close the anthropogenic carbon cycle and store intermittent renewable energy in fuels or chemicals. On the path to commercializing this technology, achieving the long-term operation stability is a central requirement but still confronts challenges. This motivates to organize the present review to systematically discuss the stability issue of CO2 RR. This review starts from the fundamental understanding on the destabilization mechanisms of CO2 RR, with focus on the degradation of electrocatalyst and change of reaction microenvironment during continuous electrolysis. Subsequently, recent efforts on catalyst design to stabilize the active sites are summarized, where increasing atomic binding strength to resist surface reconstruction is highlighted. Next, the optimization of electrolysis system to enhance the operation stability by maintaining reaction microenvironment especially mitigating flooding and carbonate problems is demonstrated. The manipulation on operation conditions also enables to prolong CO2 RR lifespan through recovering catalytically active sites and mass transport process. This review finally ends up by indicating the challenges and future opportunities.

Simultaneous phosphorus precipitation and sludge thickening by electrolysis with an anode covered by bivalve shells

A wastewater treatment plant with a large inflow of phosphorus (P) is a potential P source that can act as an alternative to phosphate rocks and a renewable source of P. During electrolysis with inert electrodes, hydroxide ions generated from the cathode cause calcium phosphate (CaP) precipitation, and oxygen and hydrogen generated from the electrodes cause thickening of the sludge by electroflotation in sludge treatment streams. However, these two effects have not been achieved simultaneously because the precipitation of CaP requires much more time than that required for thickening by electroflotation. In this study, an electrolysis system that used an anode covered with bivalve shells was used. Batch experiments were conducted and the results demonstrated that covering the anode with shells resulted in their dissolution and that the calcium ions provided by this process considerably enhanced P removal in the form of CaP, thereby shortening the time required for CaP precipitation. In continuous experiments with excess sludge, electrolysis with shells accomplished sludge thickening by electroflotation (the thickened sludge had 5.5 times the total solids in the original excess sludge) and low relative phosphate-P concentrations (0.0545–0.0812) in the effluent compared to the influent. This effect is attributed to CaP precipitation. Additional mixing of the CaP precipitates in the effluent enhanced their settleability. The results demonstrate that electrolysis using an anode covered with bivalve shells simultaneously achieved CaP precipitation and sludge thickening.

Optimization of alkaline electrolyzer operation in renewable energy power systems: A universal modeling approach for enhanced hydrogen production efficiency and cost-effectiveness

This study presents a comprehensive analysis of an Alkaline Water Electrolysis System (AWES) for hydrogen production, focusing on thermal balance, operating conditions, efficiency, and lifecycle cost. A thermal balance model was developed and further refined using machine learning techniques based on experimental data, to accurately calculate electrolysis power, cooling requirements, and temperature maintenance, enabling cost-effective operation. This study provides insights for optimizing AWES performance and economic feasibility in hydrogen production. Selecting appropriate operating conditions considering current density, inlet temperature, and electricity price is crucial. Implementing these optimizations improves energy efficiency, reduces lifecycle hydrogen production costs, and enables integration with renewable energy systems.

Enabling LVRT Compliance of Electrolyzer Systems Using Energy Storage Technologies

This paper presents a comprehensive techno-economic analysis of different energy storage systems (ESSs) in providing low-voltage ride-through (LVRT) support for power electronics-based electrolyzer systems. A framework for analyzing the performance of a grid-integrated electrolyzer-ESS system is developed, taking into account realistic scenarios and accurate models. The system components consist of a 500 kW alkaline electrolyzer module integrated with a medium-voltage grid and three different commercially available ESSs based on Li-ion battery, Li-ion capacitor, and supercapacitor technology, respectively. The performance of these ESSs is extensively studied for three LVRT profiles, with a primary focus on the upcoming Danish grid code. In order to perform simulation studies, the system is implemented on the MATLAB®/Simulink®-PLECS® platform. The results demonstrate that all three energy storage technologies are capable of supporting the electrolyzer systems during low-voltage abnormalities in the distribution grid. The study also reveals that the supercapacitor-based technology seems to be more appropriate, from a techno-economic perspective, for fault ride-through (FRT) compliance.

Demonstration and scale‐up of high‐temperature electrolysis systems

AbstractHigh‐temperature electrolysis (HTE) is a key to link the electricity sector with other industries and to evolve the electricity transition into a full energy transition. After years of development, HTE is now on the threshold to reach market readiness. The present work shows the latest achievements of Sunfire's development based on the results of the project GrInHy2.0 demonstrating hydrogen production (solid oxide electrolysis cell [SOEC]) in an industrial environment and the project SynLink demonstrating co‐electrolysis (Co‐SOEC) for renewable synthesis gas production. The GrInHy2.0 system is a 720 kWAC electrolyzer operating in the iron‐and‐steel works Salzgitter (Germany). It is now in operation for approx. 14,500 h and achieved a mean degradation rate below 23 mOhm cm2 kh−1 and an electrical efficiency of up to 84%LHV. It also proved that HTE now reached industrial‐relevant availability of over 90%. While the HTE system in Salzgitter consists of eight modules, a single module was tested in co‐electrolysis mode within the project SynLink. It demonstrated synthesis gas generation via Co‐SOEC with a flexible H2/CO ratio between 1 and 4. The work provides insight into how HTE will play a major role in the near future to efficiently produce renewable feedstock for an economy with a drastically reduced carbon footprint.

Bifunctional Al-Doped Cobalt Ferrocyanide Nanocube Array for Energy-Saving Hydrogen Production via Urea Electrolysis.

The very slow anodic oxygen evolution reaction (OER) greatly limits the development of large-scale hydrogen production via water electrolysis. By replacing OER with an easier urea oxidation reaction (UOR), developing an HER/UOR coupling electrolysis system for hydrogen production could save a significant amount of energy and money. An Al-doped cobalt ferrocyanide (Al-Co2Fe(CN)6) nanocube array was in situ grown on nickel foam (Al-Co2Fe(CN)6/NF). Due to the unique nanocube array structure and regulated electronic structure of Al-Co2Fe(CN)6, the as-prepared Al-Co2Fe(CN)6/NF electrode exhibited outstanding catalytic activities and long-term stability to both UOR and HER. The Al-Co2Fe(CN)6/NF electrode needed potentials of 0.169 V and 1.118 V (vs. a reversible hydrogen electrode) to drive 10 mA cm-2 for HER and UOR, respectively, in alkaline conditions. Applying the Al-Co2Fe(CN)6/NF to a whole-urea electrolysis system, 10 mA cm-2 was achieved at a cell voltage of 1.357 V, which saved 11.2% electricity energy compared to that of traditional water splitting. Density functional theory calculations demonstrated that the boosted UOR activity comes from Co sites with Al-doped electronic environments. This promoted and balanced the adsorption/desorption of the main intermediates in the UOR process. This work indicates that Co-based materials as efficient catalysts have great prospects for application in urea electrolysis systems and are expected to achieve low-cost and energy-saving H2 production.

Enhanced recovery of high purity Cu powder from reclaimed copper smelting fly ash by NH3·H2O–NH4Cl slurry electrolysis system

Reclaimed copper smelting fly ash (RCA) is a residue produced during the smelting process of waste miscellaneous copper, containing heavy metals such as Cu, Zn, and Cd. In this study, a slurry electrolysis system was used to recover Cu from RCA. The results showed that the recovery efficiency, current efficiency, and purity of Cu on cathode were 97.11 %, 91.22 %, and 98.47 %, respectively, when the concentration of NH3·H2O was 2 mol/L, the concentration of NH4Cl was 1 mol/L, the concentration of CuSO4·5H2O was 20 g/L, the solid-liquid ratio was 50 g/L, the electric current density was 30 mA/cm2 and the reaction time was 2 h. The content of Zn in the RCA decreased from 144.54 mg/g to 23.7 mg/g and Cd from 0.72 mg/g to 0.005 mg/g after slurry electrolysis, and other heavy metals in the RCA also decreased. The potential difference that occurs between the two poles under the NH3·H2O slurry electrolysis system promotes the leaching of Cu from the RCA, while the leached Cu2+ combines with NH4+ to form the Cu–NH3 complex (Cu(NH3)42+, Cu(NH3)2+), thus increasing the current efficiency and promoting the cathodic copper deposition. The high-purity Cu obtained at the cathode belongs to the face-centered cubic structure (111), (200) and (220) of the Cu crystalline surface. This study provides a new method for the resourceful recovery of copper from RCA.

Time-averaged wind power data hides variability critical to renewables integration

Most publicly available wind data are aggregated to a temporal resolution of 30 or 60 min. This is adequate for some purposes, such as large-scale wind integration studies. However, the consequent loss of high-frequency power fluctuations from the data can significantly impact analysis on local and regional scales. The importance of this missing variability to the accurate assessment of renewables integration is increasingly being recognised as wind power is considered for energy autarky and local energy systems. Here, we investigate the statistics of the lost variability using two high-temporal-resolution datasets from France and the US. In particular, we focus on the likelihood that minimum and maximum thresholds are exceeded and illustrate the importance of sub-half-hourly variability for assessing sector-coupling applications, such as wind farm – electrolyser systems. We find that using half-hourly averaged turbine data can underestimate the occurrence of zero power by a factor of two. This matters if a wind turbine is coupled to an electrolyser, either directly or with only short-duration storage, because of dynamic operating constraints. The lower output limit means that half-hourly wind output could overestimate the hydrogen production and energy storage capabilities of alkaline electrolysers by up to 70 %.

Influence of the Geometry of the Oxygen Removal Chamber on the Oxygen Concentration in a PEM Water Electrolysis System

In this paper, we investigate the optimization of an oxygen removal system for water electrolysis plants because high oxygen concentrations can be dangerous and compromise the quality of the hydrogen produced. The design of an oxygen removal system was investigated using numerical analysis. The results showed that the diameter of the chamber had a significant effect on the oxygen removal efficiency, and a diameter twice the size of the gas inlet was found to be optimal. The porosity of the catalyst layer also played a crucial role in the efficiency, with a lower porosity resulting in higher removal rates. Additionally, the optimal chamber length was found to be 76.8 D to achieve an oxygen mole fraction of 2.4 ppm after the chamber, which satisfied the safety criterion of 4.0 ppm. These results can aid in the design of oxygen removal systems for water electrolysis plants, providing a more efficient and safer operation.

Solar photovoltaic–thermal hydrogen production system based on full-spectrum utilization

Full-spectrum high-temperature water electrolysis enables efficient conversion from solar to hydrogen. However, the supply of electric and thermal energy derived from solar energy does not match the demand for electric and thermal energy in high-temperature water electrolysis, resulting in significant energy losses within the system. In this study, a solar photovoltaic-thermal hydrogen production system based on full-spectrum utilization is proposed. The concentrated sunlight is divided into two parts based on wavelength. Longer-wavelength sunlight is directed to the reactor, where it is converted into thermal energy to directly supply the endothermic water electrolysis reaction. Shorter-wavelength sunlight is directed to photovoltaic cells to generate electrical power for the reaction. To achieve a match between the supply and demand of electric and thermal energy, system parameters are optimized for the proposed system. The results demonstrate that the mismatch losses of the proposed system are reduced by 42.8 percentage points compared to a conventional photovoltaic water electrolysis system. The proposed system achieves a solar-to-hydrogen efficiency of 39.0% under optimum conditions with a cutoff wavelength of 1000 nm, surpassing that of photovoltaic water electrolysis and water-splitting thermochemical cycle systems by 19.0 and 21.6 percentage points, respectively. Based on the proposed method, the solar-to-hydrogen efficiency can be improved.

Integration of waste heat recovered from water electrolysis to desalinate feedwater with membrane distillation

The production of green hydrogen from water electrolysis results in hot water which must be cooled using a heat exchanger to avoid process inefficiencies. Concomitantly there exists a demand for purified water to ensure the electrolysers operate successfully. Thus, the hypothesis was that if the waste heat was used to desalinate feedwater using membrane distillation (MD), then the process may be improved. Therefore, a thermally integrated electrolyser and MD system was designed, constructed, and operated. The MD unit successfully employed waste heat from water electrolysis to provide high quality water (conductivity of 2.8 μS/cm) extracted from brine solutions (up to 70,000 mg/L) for use in the water electrolysis process. Indeed, at the maximum rate of hydrogen production the amount of desalinated water produced was 20 % more than the amount of water consumed by the electrolysis unit. The water flux in the MD system was 5 L per square meter per hour (LMH) and the process water recovery was 0.1 %. This study validated previous models relating to the potential benefit of integrating MD to remove excess heat producer during electrolysis processes. Future research should focus on determining if the replacement of the existing heat exchanger in the electrolysis system with a membrane distillation heat exchanger provides operational and economic benefits.

Hybrid Acid/Base Electrolytic Cell for Hydrogen Generation and Methanol Conversion Implemented by Bifunctional Ni/MoN Nanorod Electrocatalyst.

Combining the methanol oxidation reaction (MOR) and hydrogen evolution reaction (HER) within an integrated electrolytic system may offer the advantages of enhanced kinetics of the anode, reduced energy consumption, and the production of high-purity hydrogen. Herein, it is reported the construction of Ni─MoN nanorod arrays supported on a nickel foam substrate (Ni─MoN/NF) as a bifunctional electrocatalyst for electrocatalytic hydrogen production and selective methanol oxidation to formate. Remarkably, The optimal Ni─MoN/NF catalyst displays exceptional HER performance with an overpotential of only 49mV to attain 10mAcm-2 in acid, and exhibits a high activity for MOR to achieve 100mAcm-2 at 1.48V in alkali. A hybrid acid/base electrolytic cell with Ni─MoN/NF electrode as anode and cathode is further developed for an integrated HER-MOR cell, which only requires a voltage of 0.56V at 10mAcm-2 , significantly lower than that of the HER-OER system (0.70V). The density functional theory studies reveal that the incorporation of Ni effectively modulates the electronic structure of MoN, thereby resulting in enhanced catalytic activity. The unique combination of high electrocatalytic activity and excellent stability make the Ni─MoN/NF catalyst a promising candidate for practical applications in electrocatalytic hydrogen production and methanol oxidation.

Improved hydrogen production efficiency of a Photovoltaic-Electrolysis system with P&O Algorithm: A case study

In this study, a mathematical model of PV panel coupled electrolyzer system model is developed in MATLAB/Simulink environment to optimize the hydrogen production. A maximum power point tracking (MPPT) algorithm is applied to make more effective use of photovoltaic power for hydrogen production. It is found that the DC/DC buck converter with MPPT control can better adapt to PV and electrolysis. What’s more, the system is used for a 0.5 MW photovoltaic array and it could produce 2 × 107 L of hydrogen in a month.