Continuous Hydrogen Production Research Articles

Iron (Magnetite) Nanoparticle-Assisted Dark Fermentation Process for Continuous Hydrogen Production from Rice Straw Hydrolysate

The use of metal nanoparticles (NPs) to enhance hydrogen production in dark fermentation (DF) has become a pioneering field of interest. In particular, iron-based nanoparticles (FeNPs) play a pivotal role in enhancing the activity of metalloenzymes and optimizing feedstock utilization, resulting in improved hydrogen production. This study investigated the effect of FeNPs (magnetite) supplementation at three different concentrations of 50, 100, and 200 ppm in a continuous dark fermenter for the production of hydrogen from rice straw acid hydrolysate. The highest hydrogen production rate of 2.6 ± 0.3 NL H2/L-d was achieved with the addition of 100 ppm of nanoparticles, representing a 53% increase compared to the condition without FeNPs addition. This improvement was driven by a microbial community in which Clostridium was the major dominant genus. In addition, increasing the nanoparticle concentration to 100 ppm resulted in an increase in butyrate concentration to 2.0 ± 0.1 g/L, which is 43% higher than the butyrate concentration without FeNPs. However, when the NP concentration was increased to 200 ppm, the hydrogen production rate decreased to 1.6 ± 0.2 NL H2/L-d. This study can serve as a guideline for future research aimed at evaluating the effects of FeNPs in continuous dark fermentation systems. This work highlights the potential benefits and challenges associated with the use of FeNPs, paving the way for future studies to optimize their application and improve the efficiency of dark fermentation processes.

Periodic polarity reversal triggered sequential electrochemical redox of blue TiO2 nanotube arrays for efficient removal of antibiotics and inorganic nitrogen from actual mariculture wastewater

Using blue TiO2 nanotube arrays (Ti/BTNAs) as both anode and cathode, a novel bipolar system that is suitable for operating in periodic polarity reversal (PR) and flow-through mode was established, aiming to effectively remove antibiotics and inorganic nitrogen from actual mariculture wastewater. Under optimal conditions of 4.0 mA/cm2 current density, 3.0 mL/min water flow rate and 2.0 cycles/h polarity reversal frequency, the PR-induced synergistic effect endows Ti/BTNAs abundant oxygen vacancies (20.53 %), high activity and extended service lifetime (5.25 years), realizing continuous production of surface-adsorbed active hydrogen (Hads∗) at cathode and reactive chlorine species (Cl, ClO, Cl2−, ClO−) over anode through Cl− reacting with reactive oxygen species (HO, SO4−, O2−) and ∼0.7 kWh/gTOC energy consumption. Bipolar system can also flexibly regulate denitrification mechanism through the PR-triggered sequential electrochemical redox of Ti/BTNAs in water flow direction, achieving minimum energy consumption of ∼43.4 ± 3.2 kWh/kg(NH4+-N) and 33.7 ± 2.3 % current efficiency. Berberine antibiotic degradation pathway was suggested by DFT calculations and LC-MS/MS analyses. This study provides a long-acting and low-consuming strategy for comprehensive treating mariculture wastewater.

Adaptive Active Site Turning for Superior OER and UOR on Ir‐Ni3N Catalyst

AbstractRenewable energy‐based electrocatalytic oxidation for hydrogen production in complex reaction environments such as industrial wastewater and human urine demands high‐performing catalysts to conduct switchable urea oxidation reactions (UOR) and traditional oxygen evolution reactions (OER). Here, a novel bifunctional nanosheet electrocatalyst is reported, Ir‐Ni3N, which exhibits excellent electrocatalytic activity for both OER and UOR under alkaline conditions. Specifically, the overpotentials at 100 mA cm−2 for OER and UOR are 1.59 and 1.37 V vs. reversible hydrogen electrode (RHE) respectively, which are superior to most of the recently reported nickel‐based catalysts. Accordingly, a comprehensive mechanism for competitive catalytic activities of Ni and Ir sites in Ir‐Ni3N and the switch between OER and UOR that guarantees consistent hydrogen production is proposed. This study provides a feasible strategy for continuous hydrogen production aided by reagent‐adaptive electrocatalysts in urea‐containing wastewater.

Investigation into the electrolysis performance of a novel directly solar irradiated solid oxide electrolysis cell

Current coupling methods linking solar energy to solid oxide electrolysis cell (SOEC) mostly involve indirect coupling, with limited studies exploring direct coupling. This study is the first to evaluate a novel directly solar irradiated solid oxide electrolysis cell, anticipating a reduction in polarization loss incurred during the electrolysis process and improving the electrochemical performance of the system through direct solar irradiation. Additionally, it aims to reduce electric energy consumption required to maintain the high-temperature environment for the reaction and enhance the energy conversion efficiency of the electrolysis system, presenting a unique coupling technology. Hence, this paper proposes and develops the inaugural solar SOEC system, directly harnessing sunlight on the SOEC electrode surface, achieving stable and continuous hydrogen production through experimental methods. Experimental results demonstrate that direct solar irradiation increases the SOEC system’s heating rate by 12 times compared to electric heating, with a notably swifter response time. Under identical electrolysis voltages, the system exhibits significantly higher efficiency under direct solar irradiation than under electric heating. Moreover, for equivalent hydrogen production, the total energy input from solar energy is lower than that from electric heating, saving about 76 % of energy. Under specific conditions—solar radiation power of 123.2 W, electrolysis temperature of 655 °C, cathode-side gas input maintaining a water-hydrogen molar ratio of 8:2, and an electrolysis voltage of 1.5 V—the SOEC system sustains a nearly constant current density of about 359 mA/cm2 for 3 h. Comparative experiments conducted under identical working conditions, both in solar and electrically heated environments, reveal that the electrochemical impedance spectroscopy indicates inhibited mass transfer processes during electrolysis under direct solar irradiation. Consequently, the electrochemical performance of the SOEC system operating under direct solar irradiation was lower than that under electrically heated environments, across varying electrolysis temperatures and water contents. This study uncovers the pivotal influence of direct solar irradiation on concentration losses during the electrolysis process. The corresponding concentration losses can be subsequently mitigated by optimizing the reactor structure of the solar SOEC system.

Visible light driven ZnFe2O4 for the degradation of oxytetracycline in the presence of HSO5− at semi-pilot scale and additional H2 production

This study investigated the synthesis of visible light driven ZnFe2O4 for photocatalytic degradation of oxytetracycline (OTC) in a continuous flow reactor and production of hydrogen (H2). OTC is widely used as a medication and found to create severe health and environmental issues. The use of advanced characterization techniques proved successful formation of ZnFe2O4 which was found to be reusable, stable, highly crystalline, and nano-sized. The prepared ZnFe2O4 caused 60% removal of OTC and removal efficiency of the latter was promoted to 85% by adding HSO5– with ZnFe2O4 at 240 min employing reactor flow rate of 0.1 L/min and concentrations of ZnFe2O4, OTC, and HSO5– as 1.0 g/L, 20 mg/L, and 100 mg/L, respectively. The addition of HSO5– was found to give hydroxyl radical (•OH) and sulfate radical (SO4•−) and the latter caused degradation of OTC into degradation products. The removal of OTC was promoted by factors facilitating the rate of formation of •OH and SO4•−. The ZnFe2O4 proved effective in photocatalytic H2 production and showed H2 production rate of 23.4 μmol h−1 g−1. The results suggest that ZnFe2O4 could be used as an economically viable technology for emerging pollutants degradation and green energy production.

Nanoporous Silica Lattice Coated with LiCl@PHEA for Continuous Water Harvesting from Atmospheric Humidity

AbstractRecently, atmospheric water harvesting (AWH) based on hygroscopic salt on an inorganic or organic carrier has attracted great attention because of its significant potential applications in the environment. The major technical challenges for practical applications are how to prevent the leakage of hygroscopic salt while achieving a high capacity for sorption of atmospheric water and a high sorption rate. Additionally, techniques for converting sorbed water (in the form of a lithium chloride (LiCl) solution) into clean water need to be developed. Here, a novel method for continuous atmospheric water harvesting, leveraging LiCl@PHEA hydrogels is introduced. Synthesized via one‐step UV polymerization in saturated LiCl solutions, these hydrogels exhibit remarkable air distension ability (>60 times), achieving high water sorption efficiency (11.18 gg−1 at 90% relative humidity in 30 min) with over 90 wt.% salt content and no leakage. This water collection system integrates a porous evaporator and a 3D‐printed silica substrate, ensuring an extraordinarily high evaporation rate (>11 kgm−2 h−1 under sunlight) and efficient water transmission. A prototype based on this achieves a record‐breaking collection rate of over 5 kgm−2 h−1, enabling large‐scale efficient atmospheric water harvesting. Additionally, continuous hydrogen production through electrolysis using the collected water (< 5 ppm of salts) is demonstrated.

Hierarchical multiphase heterointerfaces Ni2P–CoP/MoO2 catalyst for efficient and stable hydrogen evolution reaction over the entire pH range

The development of pH-versatile, high-performing, and durable catalysts for hydrogen evolution reaction (HER) is crucial to satisfy the complex environment of water electrolysis industry. Herein, we present the synthesis of a hierarchical multiphase heterointerfaces Ni2P–CoP/MoO2 nanocatalyst with exceptionally high HER activity in the entire pH range through a facile three-step process involved hydrothermal, electrodeposition, and in situ phosphating treatment. Experiments and characterization revealed the strong electronic interactions among the phases of Ni2P, CoP, and MoO2, which endowed the Ni2P–CoP/MoO2 with high hydrogen evolution activity in different pH ranges. Meanwhile, the layered structure of our as-prepared catalyst makes the massive exposure of active sites. As a result, the Ni2P–CoP/MoO2 catalyst shows remarkable performance, requiring mere overpotentials of 33, 41, and 23 mV to drive 10 mA cm−2 in 1 M KOH, 1 M phosphate buffer solution, 0.5 M H2SO4, respectively. Moreover, the catalyst exhibits excellent stability in the chronopotentialmetry test under different pH electrolyte. Impressively, the Ni2P–CoP/MoO2 catalyst coupled with Ni–Fe LDH to form an overall water splitting system only require 1.50 V to drive 10 mA cm−2. Furthermore, this system actuated by wind and solar energy can stably undergo a continuous production of hydrogen and oxygen.

Optimization of Renewable Energy Hydrogen Production Systems Using Volatility Improved Multi-Objective Particle Swarm Algorithm

Optimizing the energy structure to effectively enhance the integration level of renewable energy is an important pathway for achieving dual carbon goals. This study utilizes an improved multi-objective particle swarm optimization algorithm based on load fluctuation rates to optimize the architecture and unit capacity of hydrogen production systems. It investigates the optimal configuration methods for the architectural model of new energy hydrogen production systems in Xining City, Qinghai Province, as well as the internal storage battery, ALK hydrogen production equipment, and PEM hydrogen production equipment, aiming at various scenarios of power sources such as wind, solar, wind–solar complementary, and wind–solar–storage complementary, as well as intermittent hydrogen production scenarios such as hydrogen stations, hydrogen metallurgy, and continuous hydrogen production scenarios such as hydrogen methanol production. The results indicate that the fluctuation of hydrogen load scenarios has a significant impact on the installed capacity and initial investment of the system. Compared with the single-channel photovoltaic hydrogen production scheme, the dual-channel hydrogen production scheme still reduces equipment capacity by 6.04% and initial investment by 6.16% in the chemical hydrogen scenario with the least load fluctuation.

Magnesium implantation as a continuous hydrogen production generator for the treatment of myocardial infarction in rats

Molecular hydrogen is an emerging broad-spectrum antioxidant molecule that can be used to treat myocardial infarction (MI). However, with hydrogen inhalation, the concentration that can be reached within target organs is low and the duration of action is short, which makes it difficult to achieve high dose targeted delivery of hydrogen to the heart, seriously limiting the therapeutic potential of hydrogen for MI. As a result of reactions with the internal environment of the body, subcutaneous implantation of magnesium slices leads to continuous endogenous hydrogen production, leading to a higher hydrogen concentration and a longer duration of action in target organs. In this study, we propose magnesium implant-based hydrogen therapy for MI. After subcutaneous implantation of magnesium slices in the dorsum of rats, we measured hydrogen production and efficiency, and evaluated the safety of this approach. Compared with hydrogen inhalation, it significantly improved cardiac function in rats with MI. Magnesium implantation also cleared free radicals that were released as a result of mitochondrial dysfunction, as well as suppressing cardiomyocyte apoptosis.

Enhancing bioelectrochemical hydrogen production from industrial wastewater using Ni-foam cathodes in a microbial electrolysis cell pilot plant

Microbial electrolysis cells (MECs) have garnered significant attention as a promising solution for industrial wastewater treatment, enabling the simultaneous degradation of organic compounds and biohydrogen production. Developing efficient and cost-effective cathodes to drive the hydrogen evolution reaction is central to the success of MECs as a sustainable technology. While numerous lab-scale experiments have been conducted to investigate different cathode materials, the transition to pilot-scale applications remains limited, leaving the actual performance of these scaled-up cathodes largely unknown. In this study, nickel-foam and stainless-steel wool cathodes were employed as catalysts to critically assess hydrogen production in a 150 L MEC pilot plant treating sugar-based industrial wastewater. Continuous hydrogen production was achieved in the reactor for more than 80 days, with a maximum COD removal efficiency of 40 %. Nickel-foam cathodes significantly enhanced hydrogen production and energy efficiency at non-limiting substrate concentration, yielding the maximum hydrogen production ever reported at pilot-scale (19.07 ± 0.46 L H2 m−2 d−1 and 0.21 ± 0.01 m3 m−3 d−1). This is a 3.0-fold improve in hydrogen production compared to the previous stainless-steel wool cathode. On the other hand, the higher price of Ni-foam compared to stainless-steel should also be considered, which may constrain its use in real applications. By carefully analysing the energy balance of the system, this study demonstrates that MECs have the potential to be net energy producers, in addition to effectively oxidize organic matter in wastewater. While higher applied potentials led to increased energy requirements, they also resulted in enhanced hydrogen production. For our system, a conservative applied potential range from 0.9 to 1.0 V was found to be optimal. Finally, the microbial community established on the anode was found to be a syntrophic consortium of exoelectrogenic and fermentative bacteria, predominantly Geobacter and Bacteroides, which appeared to be well-suited to transform complex organic matter into hydrogen.

Pilot composite tubular bioreactor for outdoor photo-fermentation hydrogen production: From batch to continuous operation

A novel 70 L composite tubular photo-bioreactor was constructed, and its photo-fermentation hydrogen production characteristics of batch and continuous modes were investigated with glucose as the substrate in an outdoor environment. In the batch fermentation stage, the hydrogen production rate peaked at 37.6 mL H2/(L·h) accompanied by a high hydrogen yield of 7 mol H2/mol glucose. The daytime light conversion efficiency is 4 %, with 37 % of light energy from the sun. An optimal hydraulic retention time of 5 d was identified during continuous photo-fermentation. Under this condition, the stability of the cell concentration is maintained and more electrons can be driven to the hydrogen generation pathway while attaining a hydrogen production rate of 20.7 ± 0.9 mL H2/(L·h). The changes of biomass, volatile fatty acids concentration and ion concentration during fermentation were analyzed. Continuous hydrogen production by composite tubular photo-bioreactor offers new ideas for the large-scale deployment of photobiological hydrogen production.

Specific Organic Loading Rate Control for Improving Fermentative Hydrogen Production

Inhibiting homoacetogens is one of the main challenges in fermentative hydrogen production because these hydrogen consumers have similar growth features to hydrogen producers. Homoacetogens have been related to the excessive accumulation of biomass in fermentative reactors. Therefore, a suitable food/microorganism ratio has the potential to minimize the homoacetogenic activity. In this work, the specific organic loading rate (SOLR) was controlled in two fermentative fixed-bed up-flow reactors through scheduled biomass discharges. Reactors were differentiated by the bed arrangement, namely, packed and structured conformation. The SOLR decay along the time in both reactors was previously simulated according to the literature data. The volume and volatile suspended solids (VSS) concentration of discharges was estimated from the first discharge, and then additional discharges were planned. Biomass discharges removed 21% of the total biomass produced in the reactors, maintaining SOLR values of 3.0 ± 0.4 and 3.9 ± 0.5 g sucrose g−1 VSS d−1 in the packed-bed and structured-bed reactors, respectively. Such a control of the SOLR enabled continuous and stable hydrogen production at 2.2 ± 0.2 L H2 L−1 d−1 in the packed-bed reactor and 1.0 ± 0.3 L H2 L−1 d−1 in the structured-bed one. Controlling biomass was demonstrated to be a suitable strategy for keeping the continuous hydrogen production, although the fermentative activity was impaired in the structured-bed reactor. The homoacetogenic was partially inhibited, accounting for no more than 30% of the total acetic acid produced in the reactor. Overall, the high amount of attached biomass in the packed-bed reactor provided more robustness to the system, offsetting the periodic suspended biomass losses via the planned discharges. Better characterizing both the VSS composition (aiming to differentiate cells from polymeric substances) and the bed hydrodynamics could be useful to optimize the online SOLR control.

Numerical assessment and optimization of photovoltaic-based hydrogen-oxygen Co-production energy system: A machine learning and multi-objective strategy

Green hydrogen production technology based on photovoltaic (PV), battery energy storage system (BESS) and proton exchange membrane (PEM) water electrolysis plays a crucial part in the transition process of energy to zero carbon technology. But few studies have focused on achieving all-day continuous hydrogen production, which is the key to large-scale hydrogen utilization. In this study, we developed an off-grid PV-BESS-PEM system for hydrogen and oxygen production. Firstly, the PV, BESS and PEM water electrolysis components were modeled and model validation was performed. Secondly, an energy management strategy (EMS) is proposed to achieve the goal of continuous and stable hydrogen production. Then, a surrogate model between design variables and optimization objectives is established based on machine learning methods, and a multi-objective optimization algorithm is used to drive the optimization process. Finally, a case study of the PV-BESS-PEM system is presented based on solar irradiation data in Lhasa, where there is sufficient solar resources and oxygen demand. The results demonstrate that the EMS can satisfy the purpose of all-day continuous and stable hydrogen production. The number of cells in the electrolyzer and the water temperature have a significant effect on the hydrogen production and the electrolysis efficiency. And the optimal system has increased the hydrogen production by 16.80 % and the electrolysis efficiency of PEM by 12.08 %, respectively. Herein, the methodological framework is expected to provide theoretical guidance for large-scale water electrolysis hydrogen production applications based on solar energy.

Round-the-Clock and Continuous Generation of Hydrogen and Oxygen

The main methods of industrial hydrogen production are: steam restructuring of methane and natural gas; coal gasification; biotechnology; water electrolysis. The most efficient method for producing pure hydrogen and oxygen is to produce pure hydrogen and oxygen in a photoelectrochemical cell. A photoelectrochemical cell produces hydrogen and oxygen directly from solar energy. In a photoelectrochemical cell, a combined anode, made from silicon semiconductor and metal mesh with large cells, submerged in water electrolyte solution, agitated by four photons of light, forms an oxygen molecule, which in the form of a gas bubble lifts from the surface of anode to the free surface of the water electrolyte solution. Two hydrogen cations, formed because of the dissociation of water, reaching the cathode, form a gaseous hydrogen molecule, which, turn into an electrolysis bubble, lifts from surface of cathode to the free surface of the water electrolyte solution. The article presents a new method for round-the-clock and continuous generation of hydrogen and oxygen, using a developed photoelectrolyzer-generator, taking a horizontally located combine anode, made from silicon semiconductor and metal mesh with large cells and burnt graphite cathode (electrolysis base) at the bottom of the photoelectrolyzer-generator; a membrane from fire hose material, located between electrodes; device, regulating the gap between the electrodes. Round-the-clock and continuous production of hydrogen and oxygen in the photoelectrolyzer-generator is ensured by using lamp, including LED with a daylight battery charger as a useful electrical load, which brightens the combined anode, made from silicon semiconductor and metal mesh with large cells at night until the morning and by continuously filling the photoelectrolyzer-generator with water.

A stable flow hydrogen production of sodium borohydride hydrolysis using millimeter-scale Ru/Al2O3 spheres as catalyst

In this study, we investigated the performance of continuous flow hydrogen production from NaBH4 hydrolysis by loading Ru onto millimeter-scale Al2O3 spheres (0.5–1 mm in diameter) (Ru/m-Al2O3) using a simple impregnation method. The results from transmission electron microscopy (TEM) and N2 adsorption and desorption revealed that Ru particles, with an average size of 2.73 nm, were evenly distributed on the Al2O3 spheres, and the catalysts exhibited a typical mesoporous structure. The study investigated the impact of Ru loading, catalyst quantity, catalyst reduction temperature, hydrogen production temperature, feeding rate, and concentrations of NaBH4 and NaOH on the rate of hydrogen production (HPR). The evaluation of hydrogen production revealed that the top-performing Ru/m-Al2O3 catalyst achieved a HPR of 22.44 L min–1 gRu–1 at 30 °C, with an apparent activation energy (Ea) of 33.98 kJ mol–1. The catalyst could continuously produce hydrogen for 1700 min with a 20 % decrease in activity. The characterization results before and after hydrogen production revealed that Ru/m-Al2O3 exhibited excellent structural stability after a prolonged period of hydrogen production, with no apparent changes in its morphology, crystal structure, Ru particle size, and pore structure. In addition, the X-ray diffraction (XRD), inductively coupled plasma optical emission spectrometry (ICP-OES), and hydrogen production performance results showed that the flow system could effectively prevent the aggregation of NaBO2 on the catalyst's surface, thereby significantly improving the hydrogen production activity.

P-Ni co-doped Mo2C embedded in carbon-fiber paper as a highly efficient electrocatalyst for hydrogen evolution in alkaline media

The development of noble-metal-free electrocatalysts with high electrocatalytic performance and stability by adopting a scalable route is key to solving the energy crisis. We report a PNi co-doped Mo2C-based electrocatalyst with high hydrogen evolution reaction (HER) catalytic activity prepared by a molten-salt method. Using phosphating times of 2 h and 4 h yielded P-Ni-Mo2C-2h and P-Ni-Mo2C-4h, respectively, both of which exhibited nanoflower-like structures that provided abundant active sites for the reaction. P-Ni-Mo2C-2h possessed good electrocatalytic properties with a low overpotential of only 140.5 mV at j = 10 mA cm−2 and a small Tafel slope of 50.7 mV dec−1 in an alkaline environment. P-Ni-Mo2C-2h exhibited excellent stability after 20 h of continuous hydrogen production. The use of an excessively long phosphating time caused a narrow down of spaces formed by nanoflakes, thereby reducing the HER performance of the electrocatalyst. The results of this study provide guidelines for the preparation of high-efficiency PNi co-doped electrocatalysts.

Dynamic Modeling of a Solar-To-Hydrogen Flexible High Temperature Steam Electrolysis Plant

Sustainble hydrogen production for use as a renewable combustible fuel and clean chemical feedstock is an important objective as the world moves towards a renewable energy future. High temperature steam electrolysis is a promising hydrogen production technology due to its reduced electric input that is offset by heat input into steam generation and steam superheating. An option to provide this heat is to use concentrating solar thermal technology that can sustainably provide heat input while renewable electricity is used for the electrolysis reaction. In this work, a solar-to-hydrogen high temperature steam electrolysis plant is designed and dynamically modeled, showing continuous hydrogen production by utilizing supplemental heating and efficient recuperative heating from the electrolysis product streams. Through this design, over 90% of the required heat input for the process can by met by a combination of solar and recuperative heat. Additionally, the plant can flexibility operate by ramping down hydrogen production and through flexible heat integration, which intelligently integrates solar heat based on solar conditions. Smooth operation with flexible hydrogen production is demonstrated which decreases electrical input during on-peak grid times and also decreases the total supplemental heat load over the course of a day from 26.1% to 24.5%. In addition, by using flexible heat integration, the plant can increase its solar heat usage by 4.1% relative to a base case. Both options for flexibility show efficient use of solar thermal energy to sustainably and continuously produce hydrogen.

Simultaneous and Continuous Production of Carbon Nanotubes and Hydrogen by Catalytic CH4 Decomposition in a Pressurized Fluidized-Bed Reactor

Simultaneous and Continuous Production of Carbon Nanotubes and Hydrogen by Catalytic CH₄ Decomposition in a Pressurized Fluidized-Bed Reactor

Experimental investigation on parameter optimization of liquid spectral beam splitter for continuous photocatalytic hydrogen production accompanied with photovoltaic power generation under solar full spectrum

Effective utilization of solar energy is of great significance for a sustainable future. Herein, we report a cascade system for hydrogen-electricity co-production (PH-PV) utilizing solar full spectrum. The output performance of the system can be precisely adjusted by controlling certain parameters of liquid spectral beam splitter (LSBS) which contains TiO2 nanoparticle suspension simultaneously generating hydrogen via a photocatalytic reaction process. Typically, the thickness of LSBS, the loading amount of TiO2, the flowrate of suspension and the light intensity have been investigated in detail. It is found that LSBS is necessary in our system as it could ensure the safe operation of PV while the light intensities larger than 8 suns. With the decrease of the thickness or loading amount of photocatalyst, more electricity could be produced by PV module but less hydrogen from PH module. Further increase of above two parameters simultaneously could lead to aggregation and settlement of particle suspension in LSBS, which is detrimental to the optical absorbance of the system. Besides, changing the flowrate will diversify the surface features of particles by shear-induced effect. At optimal flowrate, the particles in LSBS could exhibit oscillation characteristics under synergistic effect of shear force and gravity, which would lead to excellent light absorption and transmittance. Furthermore, an obvious gain for both hydrogen and electricity output and system efficiency could be obtained through increasing light intensity appropriately. Finally, the improved merit function (MF) was employed to evaluate the performance of hybrid system and more obvious effect of flowrate on MF value than other parameters was found. The optimal MF value of 3.07 was reached when flowrate was 60 mL/min. Our work is expected to provide important guidance for the optimization of PH-PV cascade system driven by outdoor direct solar energy.

Optimizing solar energy coupled with energy storage for uninterrupted PEM electrolytic hydrogen production.

A Photovoltaic (PV) system integrated with Proton Exchange Membrane (PEM) water electrolysis offers an avenue for enhancing solar energy utilization and generating environmentally friendly hydrogen. Nevertheless, there has been limited focus on developing systems that can consistently produce hydrogen throughout the entire day, a critical aspect for the future widespread adoption of hydrogen. In this study, we established a PV-Battery-PEM electrolysis system for hydrogen generation. To achieve the objective of continuous hydrogen production, enhance energy efficiency, and minimize wasted sunlight, we introduced an energy management strategy (EMS). At the outset, we developed separate components, such as the PV system, the battery, and the PEM for hydrogen production, employing the Matlab/Simulink platform. Following this, we integrated these components into the comprehensive PV-Battery-PEM electrolysis system for hydrogen generation and confirmed the efficiency of the EMS through validation. Our analysis included an evaluation of energy efficiency under various operational scenarios, comparing systems with and without energy storage via batteries. The outcomes clearly indicate that the suggested EMS effectively achieves continuous hydrogen production throughout the entire day. Furthermore, when compared to systems without energy storage, systems equipped with energy storage batteries exhibit an energy efficiency improvement of 1.3 to 6.5% higher efficiency of hydrogen under similar operating conditions. This finding underscores the value of incorporating energy storage, as it enhances overall energy utilization and reduces the wastage of sunlight.