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—Hydrogen can be produced through water electrolysis using photovoltaic (PV) power in a way that is both pollution-free and friendly to the environment, rendering hydrogen a clean energy source. Proton Exchange Membrane (PEM) water electrolysis is an efficient hydrogen generation process because of its compact design, fast response, high efficiency and high current density. The fast fluctuations in solar power, however, are difficult for PEM water electrolysers to control effectively. To address the problems caused by intermittent power, a system for producing hydrogen consisting of a solar panel, battery, and commercial PEM electrolyser, alongside an electrical control strategy, is proposed. The Maximum Power Point Tracking (MPPT) Perturb and Observe (P&O) technique is employed for PV systems, while a bidirectional charge controller manages the charging and discharging of the battery. A Proportional-Integral (PI) controller is also utilised for the PEM electrolyser to ensure efficient operation. This setup provides a practical solution for hydrogen production. It enhances efficiency and reduces the risk of damage to the electrolyser, thereby making the process more sustainable and reliable. The proposed approach has been validated by simulation under different conditions. A comparative analysis has also demonstrated that the proposed system can perform well despite having less PV power. When comparing systems with and without batteries for energy storage, the system with the battery for energy storage has a 10% higher energy efficiency under the same operating conditions. This suggests that adding energy storage can increase energy utilization, maintain the DC link voltage constant, and achieve stable hydrogen production. [Display omitted] • The hydrogen system incorporates a battery to reduce fluctuations in solar photovoltaic power. • The study uses a static electrical model of a commercially available proton exchange membrane electrolyser. • P&O MPPT, bidirectional charge, and PI controllers are used for optimal energy management. • Comparative analysis shows improved efficiency and hydrogen production with batteries. [ABSTRACT FROM AUTHOR]

In this work a novel mathematical programming formulation is presented for the simultaneous optimal design and operation of standalone, green hydrogen production systems. There is a pressing need to develop, test and commercialize technologies that can contribute in the medium term to our coordinated efforts to combat climate change. The system under study is inherently dynamic due to the stochastic and intermittent nature of meteorological data and there is a likelihood to overestimate its production capacity and economic performance. Failing to identify shortcoming in the design stage can result in expensive operational mistakes that will negatively affect the gathering race to build a massive new hydrogen economy. We present and demonstrate a systematic methodology that could be useful in decarbonizing our energy production systems by optimizing standalone, green hydrogen units and reducing the risk during their commercialization. • A methodology is developed to optimize standalone green hydrogen production systems • A detailed nonlinear model is proposed that captures design and operational details • A solution methodology is developed that ensures convergence [ABSTRACT FROM AUTHOR]

In 2015, the participants of the Paris Agreement collectively acknowledged the urgent need for immediate actions to decarbonize their national economies, with the aim of mitigating the adverse impacts of climate change. There is a call for policymakers to step up efforts to significantly reduce greenhouse gas (GHG) emissions in all economic sectors, with a focus on prioritizing options that can deliver substantial emission cuts. Some industry and transport subsectors present significant challenges in terms of technical and economic feasibility. Viable solutions for these sectors, known as "hard-to-abate" sectors, are limited. Green hydrogen has emerged as a promising alternative that is gaining increasing attention. It is poised to play a crucial role in transitioning towards a more sustainable future. There is a growing interest in green hydrogen among researchers, institutions, and nations, all committed to advancing its development, improving efficiency, and reducing costs. This paper explores the concept of green hydrogen, particularly its production processes that rely on renewable energy sources in Uruguay. It demonstrates the significant potential for green hydrogen production, facilitating the transition from fossil fuels to clean energy and promoting environmental sustainability through the widely accepted electrolysis process. Uruguay currently boasts a high percentage of renewable electricity generation (reaching 97 % in 2020). To support this further, there is a need to increase renewable energy capacity, which would impact the energy prices. The cost of energy accounts for more than 40 % of the levelized cost of hydrogen (LCOH) in all studied scenarios. Additionally, optimizing the costs associated with electrolysers, which can exceed 30 % of the LCOH in polymer electrolyte membrane (PEM) electrolysis, is crucial. This optimization is essential for positioning the country as a net exporter of green hydrogen. The range of LCOH values calculated in the different scenarios is between 2.11 USD/kg H2 and 4.12 USD/kg H2. According to updated specialized literature, achieving LCOH values under USD 1.4/kg H2 is essential for this goal. [ABSTRACT FROM AUTHOR]

Hydrogen provides a clean source of energy that can be produced with the aid of electrolysers. For electrolysers to operate cost-effectively and safely, it is necessary to define an appropriate maintenance strategy. Predictive maintenance is one of such strategies but often relies on data from sensors which can also become faulty, resulting in false information. Consequently, maintenance will not be performed at the right time and failure will occur. To address this problem, the artificial intelligence concept is applied to make predictions on sensor readings based on data obtained from another instrument within the process. In this study, a novel algorithm is developed using Deep Reinforcement Learning (DRL) to select the best feature(s) among measured data of the electrolyser, which can best predict the target sensor data for predictive maintenance. The features are used as input into a type of deep neural network called long short-term memory (LSTM) to make predictions. The DLR developed has been compared with those found in literatures within the scope of this study. The results have been excellent and, in fact, have produced the best scores. Specifically, its correlation coefficient with the target variable was practically total (0.99). Likewise, the root-mean-square error (RMSE) between the experimental sensor data and the predicted variable was only 0.1351. [ABSTRACT FROM AUTHOR]

The increase in industrial production and energy consumption has led to excessive exploitation of non-renewable resources, resulting in serious environmental problems such as greenhouse gas emissions. In response, there's a growing investment in renewable energies such as hydroelectric, wind, and solar power. However, these sources are unable to fully meet demand, leading to imbalances between consumption and production. An emerging solution to this challenge is green hydrogen, produced from clean sources, reducing dependence on fossil fuels and mitigating greenhouse gas emissions. The S-LCA methodology presented in the UNEP/SETAC Guidelines for the Social Life Cycle Assessment is applied to the production of green hydrogen via the electrolytic separation of water using a proton exchange electrolyser. The process involves the extraction and processing of raw materials from the electrolyser, BOP and reverse osmosis system, the manufacture of the systems and the production of green hydrogen. The data from each stage is inventoried and entered into the PSILCA v.3.1 and SHDB 2022FV5 databases, integrated into the SimaPro software version 9.3.0.2, enabling a complete analysis of the social impacts associated with the production of green hydrogen. The data was evaluated considering 4 stakeholder categories: workers, value chain actors, society and local community. The results indicate that the extraction and processing of raw materials for the electrolyser was the primary stage responsible for the social impacts in both databases. However, the electrolyser manufacturing stage was the main contributor to the indicators "weekly working hours per employee" and "union density" in the PSILCA database. Nafion® and Iridium were identified as the major contributors among components in both databases. The study highlights the significant role played by countries like China and South Africa in social impacts, particularly in the extraction and processing of raw materials. Despite this, Portugal emerged as the largest contributor to five out of fourteen indicators in the PSILCA database, while its contributions in the SHDB database were less than 7 %. Moreover, a comparison between the two databases revealed that PSILCA exhibited a greater distribution of results across various stages, components, and countries assessed, whereas SHDB showed more centralized results. The observed discrepancies between the results obtained from different databases can be attributed to three main factors: the input-output database utilized in each S-LCA tool, the assumed risk levels for each indicator, and the equivalence between indicators and subcategories. This exploratory study offers valuable insights for guiding strategic decisions regarding the social component of sustainability, providing a detailed understanding of the social impacts associated with the specific case of green hydrogen production in a planned hub in Portugal. [ABSTRACT FROM AUTHOR]

The study deals with the techno-enviro-economic aspects of hydrogen production using polymer electrolyte membrane electrolysers powered by a hybrid grid-connected tidal-wind energy system. System modelling is presented initially. The energy management strategies for hydrogen production are then analysed as rule-based approach and as optimised approach. An objective function to maximise the operating profit under optimal system operation is formulated considering the variable energy costs, capital and maintenance expenditure, and real system constraints. A comprehensive cost analysis of the system is obtained by comparing two different optimisation approaches based on fixed cost and levelised cost factors, respectively. Towards reaching this goal, the use of mixed integer genetic algorithm optimisation is investigated. The operation of electrolyser in terms of its different operating modes, namely stop, running, and stand-by is presented. The dynamic optimisation of an electrolyser capable of working at up to twice its nominal rating for a limited duration is also analysed in the study. The results of the optimisation approach are 41.5% and 47% higher than the rule-based approach in terms of the annualised profit and carbon emission savings, respectively. In addition, the recurrent switching of electrolyser unit operating modes is avoided with the optimisation approach, reducing the associated energy consumption of about 27.2 MWh annually. The proposed model can be used as a generic tool for hydrogen production analysis under different contexts and it is especially applicable in high green energy potential sites with constrained grid facilities. • Electrolyser modelling based on three different operating modes is presented. • Optimal cost analysis based on fixed and levelised cost approach is formulated. • Detailed cost data definitions for the hybrid system is presented. • Electrolyser operation with peak power operations is found to be advantageous. • Optimisation approach improves system performance compared to the rule-based approach. [ABSTRACT FROM AUTHOR]

Power generation and its storage using solar energy and hydrogen energy systems is a promising approach to overcome serious challenges associated with fossil fuel-based power plants. In this study, an exergoeconomic model is developed to analyze a direct steam solar tower-hydrogen gas turbine power plant under different operating conditions. An on-grid solar power plant integrated with a hydrogen storage system composed of an electrolyser, hydrogen gas turbine and fuel cell is considered. When solar energy is not available, electrical power is generated by the gas turbine and the fuel cell utilizing the hydrogen produced by the electrolyser. The effects of different working parameters on the cycle performance during charging and discharging processes are investigated using thermodynamic analysis. The results indicate that increasing the solar irradiation by 36%, leads to 13% increase in the exergy efficiency of the cycle. Moreover, the mass flow rate of the heat transfer fluid in solar system has a considerable effect on the exergy cost of output power. Solar tower has the highest exergy destruction and capital investment cost. The highest exergoeconomic factor for the integrated cycle is 60.94%. The steam turbine and PEM electrolyser have the highest share of exergoeconomic factor i.e., 80.4% and 50%, respectively. • An exergy-economic model is developed for a solar tower -hydrogen power plant. • A new hydrogen storage system is proposed. • The electrochemical model is validated against experimental data. • Almost 13% increase in the exergy efficiency of the cycle is achievable.. [ABSTRACT FROM AUTHOR]

The current study develops a hydrogen map concept where renewable energy sources are considered for green hydrogen production and specifically investigates the solar energy-based hydrogen production potential in Turkey. For all cities in the country, the available onshore and offshore potentials for solar energy are considered for green hydrogen production. The vacant areas are calculated after deducting the occupied areas based on the available governmental data. Abundant solar energy as a key renewable energy source is exploited by photovoltaic cells. To obtain the hydrogen generation potential, monocrystalline and polycrystalline type solar cells are considered, and the generated renewable electricity is directed to electrolysers. For this purpose, alkaline, proton exchange membrane (PEM), and solid oxide electrolysers (SOEs) are considered to obtain the green hydrogen. The total hydrogen production potential for Turkey is estimated to be between 415.48 and 427.22 Million tons (Mt) depending on the type of electrolyser. The results show that Erzurum, Konya, Sivas, and Van are found to be the highest hydrogen production potentials. The main idea is to prepare hydrogen map in detail for each city in Turkey, based on the solar energy potential. This, in turn, can be considered in the context of the current policies of the local communities and policy-makers to supply the required energy of each country. • To prepare hydrogen maps based on available solar energy potential for a country. • To assess the green hydrogen production potential of cities from their available extra electric energy. • To show the hydrogen production difference among three commercially available electrolysers. • To compare onshore and offshore hydrogen production potential of different regions of a Turkey. [ABSTRACT FROM AUTHOR]

This paper presents experimental results on the solar photovoltaic/PEM water electrolytes system performance in the Algerian Sahara regions. The first step is to present a photovoltaic module characterization under different conditions then validate the results by comparing the measured and calculated values. The main objective of this study is to develop a parametric study on the system performance (open-circuit voltage Voc, short circuit current Is, fill factor FF, maximum power Pm and the efficiency η) under hot climate conditions (Ouargla, Algeria). The ambient temperature effects and solar radiation on the solar PV performance characteristics were investigated using modeling and simulation analysis as well as experimental studies. The results show that the root mean squared error (RMSE) error of the currents and voltages and the mean bias error (MBE) are respectively 0.71%, 0.37% and 0.12%, 0.15%. The relative errors in the current and the voltage are respectively 0.83%–1.76%, and −0.58% to 0.83%. The second part provide some general characteristics concerning the indirect coupling of a lab scale proton exchange membrane (PEM) water electrolyser (HG60) powered by a set of our photovoltaic panels. Experimental results provide practical information for the modules and the electrolysis cells by the indirect coupling. The weather conditions effect on hydrogen production from the electrolyser was also investigated. The results showed a high hydrogen production of 284 L in one day for 08 h of running and the electrolyser power efficiency with solar PV system was between 18 and 40%. • PV model execution/validated by experimental tests with 0.58%,0.83% error. • Estimation of the temperature effect on the PV parameters experimentally. • Investigation PV/PEM system in indirect coupling got 284 L of H 2. • Electrolyser (PEM)/PV system performance was examined Experimental for one day. • PMU make the system run by almost constant current, which increases the stability. [ABSTRACT FROM AUTHOR]

Countries' abilities to meet their own energy needs using renewable and clean energy regardless of external sources is an important option in terms of sustainability. Moreover, very low emission systems can be developed using a combination of hydrogen energy technologies and renewable energy systems. However, renewable energy shows certain irregularities as a fact of its very nature. However, an energy source that is not affected by irregularities is quite possible using electricity produced from renewable energy in production and storage of hydrogen. At this point, the predictability of a country's energy sources is vital when investing in stable energy systems. In this study, the hydrogen production values of a PEM electrolyser (PEM-E), as supported by GaAs Photovoltaic (GaAsPV) technology, are estimated using data from a meteorological station with high solar energy potential. The observed and predicted solar radiation values constitute the main dataset. Daily radiation estimations are achieved via an Artificial Neural Network (ANN), Adaptive Network-Based Fuzzy Logic Inference System (ANFIS), Multiple Linear Regression (MLR), Empirical Angström-Prescott (EAP), and Agnostic Deep Learning (DL) models. The system, which consists of a 10 kW (68.10 m2) GaAsPV and 4688 W PEM-E, is considered for the determination of HP values. The root mean square error (RMSE) and the coefficient of determination (R2) are used as performance criteria in comparing hydrogen production based on estimated solar radiation with observed values falling on inclined surfaces. The DL model is highly compatible with the observed data and is the most successful model of those considered with a performance value of 96.26% (R2). • Hydrogen offers the promise of cleaner industry and emissions-free power. • According to the DL model, annual yields of 281.853 kg/year hydrogen can be produced. • The Deep Learning approach has been successfully applied in modeling hydrogen production. [ABSTRACT FROM AUTHOR]

This work aims at analyzing the transient behavior of a photovoltaic-Polymer Electrolyte Membrane (PV-PEM) water electrolyser system based on regional weather data. The goal of a dynamic modeling is to check how the system works against the load variations. In this study, the PV array is used for power supply then, a controller and power conditioning to provide clean energy for electrolyser. The electrolyser model is developed in MATLAB and it is used in a TRNSYS environment. The performance of a PEM electrolyser can be illustrated by the polarization curve which is voltage–load current (V–I) characteristics. Moreover, a mathematical modeling for computing dynamic voltage based on current and all operation parameters in electrolyser stacks have been developed. Then the transient behavior of the PV-PEM system is analyzed over the seasonal condition base on Vienna average weather information. [ABSTRACT FROM AUTHOR]

• Improved performance and longer service life would help the adoption of PEM electrolyzers for large-scale hydrogen production. • The Digital Twin could use real-time information from the system's sensors to optimise control and system life. • The data-driven approach improves knowledge of the plant's operating conditions by explicating latent information. Operating electrolyzers for producing green hydrogen is a critical emerging issue because of either the broader use of hydrogen for several scopes or the short life span and efficiency of these components. Digital Twin offers a new opportunity to effectively face these problems by improving online control and providing fault detection, diagnosis, and prediction services. Since the Digital Twin is, in fact, a virtual mirror of a real system continuously updated by information received from the field, it allows it to swiftly react to small signals of departure from standard or optimal conditions. Although Digital Twins are widely applied in different fields, comprehensive guidance on developing and designing a Digital Twin in the literature is still lacking. This manuscript aims to provide a comprehensive guide on how to build the Digital Twin of a PEM-Electrolyzer. In particular, the architecture of the Digital Twin is initially presented, then all its components are analyzed, showing the steps to be performed to build a Digital Twin for operating PEM-Electrolyser system. [ABSTRACT FROM AUTHOR]

Abstract Hydrogen can compensate for the intermittent nature of some renewable energy sources and encompass the options of supplying renewables to offset the use of fossil fuels. The integrating of hydrogen application into the energy system will change the current energy market. Therefore, this paper deploys the life cycle cost analysis of hydrogen production by polymer electrolyte membrane (PEM) electrolysis and applications for electricity and mobility purposes. The hydrogen production process includes electricity generated from wind turbines, PEM electrolyser, hydrogen compression, storage, and distribution by H 2 truck and tube trailer. The hydrogen application process includes PEM fuel cell stacks generating electricity, a H 2 refuelling station supplying hydrogen, and range extender fuel cell electric vehicles (RE-FCEVs). The cost analysis is conducted from a demonstration project of green hydrogen on a remote archipelago. The methodology of life cycle cost is employed to conduct the cost of hydrogen production and application. Five scenarios are developed to compare the cost of hydrogen applications with the conventional energy sources considering CO 2 emission cost. The comparisons show the cost of using hydrogen for energy purposes is still higher than the cost of using fossil fuels. The largest contributor of the cost is the electricity consumption. In the sensitivity analysis, policy supports such as feed-in tariff (FITs) could bring completive of hydrogen with fossil fuels in current energy market. Highlights • 'Green hydrogen' production cost is calculated on a remote archipelago in UK. • Hydrogen is produced by water electrolyser powered by wind energy. • Hydrogen energy applications include electricity and mobility. • The cost of hydrogen applications are compared with conventional energy supply. [ABSTRACT FROM AUTHOR]

Abstract This study aims to investigate the thermodynamic and economic aspects of a low temperature flue gas driven advanced absorption power cycle (AAPC) integrated to PEM electrolyser (PEME) for hydrogen and oxygen production. Flue gases from a small-scale coal fired power plant are utilized to energize the generator of the AAPC system. Produced power drives the PEME for primarily hydrogen generation, and oxygen as a byproduct. Use of ejector enhances the power production in the turbine favoring plant performance. The present integrated system produces daily amounts of ∼1.15 kg H 2 and ∼4.59 kg O 2 at 140 °C maximum cycle temperature with a capacity factor of 85%, 30 years of plant life and 5% annual interest rate. Cost of electricity and hydrogen are found to be 0.049 $/kWh and 2.43 $/kg, with overall energy and exergy efficiencies of 5.9% and 17.8%, respectively. The highest cost contributors are the APC turbine and the PEM electrolyser where these two accounts for almost 94% of total plant cost. Total cost of the plant is found to be ∼$61200. Cost of produced hydrogen shows promising results compared to those of electrolysis-based hydrogen production systems. Highlights • Low temperature flue gases are utilized for power generation. • LiBr based ejector absorption power cycle is used. • Power from APC is used to run PEM for hydrogen generation. • Exergoconomic assessment results show competitive hydrogen cost. [ABSTRACT FROM AUTHOR]

A three-dimensional, isothermal, multicomponent model was used for investigating the transport phenomena in a PEM electrolyser with a pin-type configuration for the bipolar plates. The need to understand the complex phenomena that take place in such electrochemical device is motivated by the requirement to improve its performance and durability. ANSYS Multiphysics 17.0 with the Fuel Cell and Electrolysis Model has been used to solve the conservation of mass, momentum, species, energy and charge equations. The 3D CFD model analysed the influence of some design and operating parameters (voltage, membrane thickness and CL active area) on the PEM electwlyser performance. An optimum membrane thickness (50 microns) was obtained in our numerical investigation and based on this result, the effect of the catalyst active area over the electrolysis performance and H2 generation rate have been taken into account. It has been shown that a higher active area of the catalyst can lead to an important increase of the electwlysis cell performance The results are discussed in the paper in terms of hydrogen generation (mass fraction contours and mass flow rate at exit) and by polarization curves. [ABSTRACT FROM AUTHOR]

Based on proton conduction of polymeric electrolyte membrane (PEM) technology, the Polymer Electrolyte Membrane Water Electrolyser (PEMWE) offers an interesting solution for efficient hydrogen production. During the electrolysis of water in PEMWE, water is split into oxygen, protons and electrons at the anode and a water-gas two-phase flow results. The aim of this study is to investigate the link between the two-phase flow at the anode side and cell performance under low-pressure conditions. We have developed a two-dimensional stationary PEMWE model that takes into account electrochemical reaction, heat transfer, mass transfer (bubble flow) and charge balance through the Membrane Electrodes Assembly (MEA). In order to take into account the changing electrical behaviour, our model combines two scales of descriptions: at microscale within anodic active layer and MEA scale. The water management at both scales is strongly linked to the Not Coalesced Bubble regime (NCB regime) or the Coalesced Bubble regime (CB regime). Therefore, water content close to active surface areas depends on two-phase flow regimes. Our simulation results demonstrate that the coalesced phenomenon is associated with improvement of mass transfer, a decrease in ohmic resistance and an enhancement of the PEMWE efficiency. At low and medium current density values, the model has been validated using two separate experiment electrolysis cells. [ABSTRACT FROM AUTHOR]

A three-dimensional, single-phase, isothermal, multicomponent model was developed for investigating the transport phenomena in a PEM electrolyser with a pin-type configuration for the bipolar plates. ANSYS Multiphysics 17.0 with the Fuel Cell and Electrolysis Model has been used to solve the conservation of mass, momentum, species and charge equations. The 3D CFD model analysed the influence of the pin type configuration and of voltage applied on the PEM electrolyser performance. The results are discussed in the paper in terms of species produced (hydrogen, oxygen) as mass fraction distributions and polarization curves. Our analysis was the first step in analysing a backup hydrogen-based power source by simulating an electrolysis cell. We intended to identify critical parameters and to give an insight into physical mechanisms that can influence a PEM electrolyser. Also, the aim of the study was to optimize some parameters in order to maximize the hydrogen production and to increase the electrolyser efficiency, as requested by the backup power system. [ABSTRACT FROM AUTHOR]

Interest in power-to-gas (P2G) as an energy storage technology is increasing, since it allows to utilise the existing natural gas infrastructure as storage medium, which reduces capital investments and facilitates its deployment. P2G systems using renewable electricity can also substitute for fossil fuels used for heating and transport. In this study, both techno-economic and life cycle assessment (LCA) are applied to determine key performance indicators for P2G systems generating hydrogen or methane (synthetic natural gas – SNG) as main products. The proposed scenarios assume that P2G systems participate in the Swiss wholesale electricity market and include several value-adding services in addition to the generation of low fossil-carbon gas. We find that none of the systems can compete economically with conventional gas production systems when only selling hydrogen and SNG. For P2G systems producing hydrogen, four other services such as heat and oxygen supply are needed to ensure the economic viability of a 1 MW P2H system. CO 2 captured from the air adds $50/MW h t of extra levelised cost to SNG compared to CO 2 supplied from biogas upgrading plants and it does not offer an economic case yet regardless of the number of services. As for environmental performance, only the input of “clean” renewable electricity to electrolysis result in environmental benefits for P2G compared to conventional gas production. In particular, more than 90% of the life cycle environmental burdens are dominated by the electricity supply to electrolysis for hydrogen production, and the source of CO 2 in case of SNG. [ABSTRACT FROM AUTHOR]

In this study an advanced integrated multigeneration energy hub is conceptualized combining solid oxide fuel cell (SOFC), molten carbonate fuel cell (MCFC), proton exchange membrane (PEM) electrolyser and methanol production unit. Using natural gas as a primary fuel input along with the renewable green excess electricity the proposed energy hub has a potential of generating electrical power, heat for district heat network, methanol for transportation use and oxygen for industry use. The thermodynamic analysis of the conceptualized multigeneration energy hub reveals that it can generate 322 kW electrical power, 766.4 kW heat, 0.024 kg/s methanol, and 0.0362 kg/s pure oxygen with 86.03% energy efficiency and 59.13% exergy efficiency. However, the economic analysis reveals that the annualized levelized cost of energy (LCOE) of the proposed energy hub is 0.06 £/kWh without having a battery storage and 0.065£/kWh with the battery storage system. The simple payback period of the proposed system is 2.16 year and 2.75 year without battery storage and with battery storage system, respectively. Two different case studies have been carried out by replacing the SOFC-MCFC combined unit with gas turbine (GT) combined with MCFC and GT combined with aqueous monoethanolamine (MEA) plant as two other alternative options for such multigeneration energy hub keeping other subunits unaltered. It has been found that the proposed system has the highest exergy efficiency, lowest levelized cost of energy (LCOE) and payback period followed by the GT-MCFC combined plant, and GT-MEA combined plant. [Display omitted] • Conceptualization of an advanced multi-generation energy hub. • Thermodynamic and economic analyses have been investigated. • Simultaneous decarbonization of transport sector and district heating network. • 90% and above CO 2 separation has been achieved. • Comparative feasibility assessments with different systems have been investigated. [ABSTRACT FROM AUTHOR]

In this work, we developed a simple and cost-effective hydrothermal route to regulate the formation of molybdenum disulfide (MoS 2 ) in different morphologies, like, nano-sheet, nano-capsule and nano-flake structure by controlling the reaction temperature and sulphur precursor employed. Such a fine tuning of different morphologies yields a leverage to obtain novel shapes with high surface area to employ them as suitable candidates for hydrogen evolution catalysts. Moreover, we report here the first time observation of MoS 2 nano-capsule formation via environmentally benign hydrothermal route and characterized them by X-ray diffraction (XRD), nitrogen adsorption and desorption by Brunaer–Emmett–Teller (BET) method, scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and X-ray photo-electron spectroscopy (XPS) techniques. MoS 2 nano-capsules exhibits superior activity towards hydrogen evolution reaction (HER) with a low over-potential of 120 mV (RHE), accompanied by large exchange current density and excellent stability in 0.5 M H 2 SO 4 solution. MoS 2 nano-capsule catalyst was coated on solid proton conducting membrane (Nafion) and IrO 2 as anode catalyst. The performance of the catalyst was evaluated in MEA mode for 200 h at 2 V without any degradation of electrocatalytic activity. [ABSTRACT FROM AUTHOR]

Fuel cells (FCs) use hydrogen as their prime fuel source, which promotes them as one of the attractive options for clean energy generators. Though they have been around for some time, their characteristics are not yet fully understood. This study offers a thorough investigation into the characteristics of proton exchange membrane (PEM) type of FCs based power system. This study first presents a concise explanation of the working principles of the PEM electrolyser and FCs supported by novel modelling using MATLAB. The simulation results are then validated by a series of experiments carried out on operational 500 mW FC followed by detailed performance parameters of such type of FCs. Parameters affect the efficiencies of each part of the system are investigated and the total system's efficiency is then calculated. The efficiency of the electrolyser and PEM FC was found to be 85 and 60%, respectively. Polarisation curve has been used in order to evaluate FC's performance. From the polarisation curve, it is noted the efficiency of the FC increases with increasing pressure and temperature. The activation losses are reduced when the temperature increased. Moreover, the mass transfer is enhanced toward reducing the PEMFC's resistance. [ABSTRACT FROM AUTHOR]

A hydrogen community energy storage (H-CES) system including a PEM electrolyser, metal hydride tank and PEMFC unit was designed, built and tested for a low carbon community. The H-CES performs end user applications including PV energy time-shift and demand load shifting. The system proved to have good flexibility and capability for mid-term and long term energy storage, with a round trip efficiency of 52%. Mid-term energy storage was demonstrated when the H-CES performed demand load shifting and hydrogen was stored for use one day later. Additionally, when PV energy time-shift was added to demand load shifting the operational hours of the electrolyser increased by 116%. Some improvements for future H-CES systems are also discussed in this study, the consideration of the optimum electronic equipment for the technology and rating being considered a key factor to maximize the discharge rating, round trip efficiency and reliability. [ABSTRACT FROM AUTHOR]

Power-to-gas (P2G) is a modular technology which offers several benefits to different types of networks and sectors while playing the role of mid-term and long-term energy storage. The core element of a P2G plant is the electrolyser which transforms low cost and/or renewable electricity into hydrogen. A thorough analysis of the implications of selecting an electrolyser technology (namely alkaline or PEM) and scale is key for understanding the performance and economic benefits of P2G plants generating hydrogen or methane. In this study, a dynamic P2G model accounting for electrolyser ageing is presented following a bottom-up approach in which the electrolyser cell is modelled by means of its polarisation curve. This model allows to determine the performance, levelised cost and value of P2G plants purchasing electricity and selling gas in the wholesale market, depending on the system configuration under the Swiss regulatory context. The results indicate that technical and economic benefits increase with the electrolyser rating but those improvements are more marked for systems on the kW scale while levelling off for the MW scale. Higher capacity factors (by approximately 11%) are needed for PEM electrolysers compared to alkaline electrolysers in order to minimise the levelised cost. [ABSTRACT FROM AUTHOR]

IrOx and Ir 0.7 Ru 0.3 Ox nanosized materials of similar crystallite size (5 nm) were prepared for application as oxygen evolution electrocatalysts in solid polymer membrane water electrolysers (PEMWEs). The physico-chemical properties of the catalysts were characterized by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray (EDX) and X-ray-Photoelectron Spectroscopy (XPS). Particular efforts were addressed to tailor the crystallographic characteristics and the surface properties. The electrochemical properties were investigated in an electrolysis cell, based on Nafion 115 and 30% Pt/C as cathode catalyst, by using linear sweep voltammetry, electrochemical impedance spectroscopy and Tafel curves. The Ir 0.7 Ru 0.3 Ox-based electrocatalyst showed a performance of 3.2 A cm −2 at 1.85 V at 90 °C which corresponds to a voltage gain of 0.1 V as compared to the IrOx catalyst at the same current density. Alternatively, an increase in current density of 0.6 A cm −2 is achieved at 90 °C and 1.85 V for the IrRuOx anode. A similar Tafel slope with a decrease of charge transfer resistance for IrRuOx compared to IrOx would indicate the same mechanism for these materials and higher intrinsic activity for the mixed oxide. [ABSTRACT FROM AUTHOR]

Pt and Ir are the most popular catalysts for electrochemical water splitting, but their low abundance on Earth's crust and high price render them unsustainable for future use. In the quest for alternative catalyst materials, a popular hydro-treating catalyst, molybdenum disulphide (MoS 2 ), has been found to be promising for hydrogen evolution reaction (HER). Two types of MoS 2 -carbon composites, (i) physical mixture of MoS 2 and carbon black (Vulcan ® ) and (ii) MoS 2 supported on reduced graphene oxide (RGO), were examined. Among the MoS 2 -based materials tested, 47 wt% MoS 2 /Vulcan ® gave the best performance in terms of current density at an encouraging level for practical application. The poor performance of bare MoS 2 was attributed to its poor electrical conductivity. No indication of performance deterioration was observed for 18 h of continuous operation at 2.0 V cell voltage with 47 wt% MoS 2 /Vulcan ® . MoS 2 /RGO hybrids showed HER activity, which was considerably higher than that of bare MoS 2 . [ABSTRACT FROM AUTHOR]

Abstract: Hydrogen as a clean energy carrier for solar energy can be produced by using photovoltaic-electrolyser (PVE) direct-coupling system that is well known as a kind of simple and low investment but unstable system for solar energy conversion. The key to improve hydrogen yield of a direct-coupling system is to keep its working points around maximum power point (MPP) of photovoltaic (PV) modules. The coupling of three different connection patterns of six PV modules with one electrolyser were investigated in summer, autumn and winter, three typical seasons in a year, to seek the optimum arrangement for higher system efficiency in Beijing (116°E, 40°N). A corresponding mathematics model of the system is applied to simulate and analyze the instantaneous efficiency of the system, which agreed well with the experimental results. The variation rate of the system instantaneous efficiency varies with the solar irradiation intensity, the ambient temperature and the resistance of the electrolyser. The working point that distinguishes the variation trends of the system efficiency is called the efficiency changing point (ECP). The author use a parameter V/V m , the ratio between the voltage of the working point to the voltage of the maximum power point, to analyze the respective ECP of each factor above. It can be concluded that the variation rate of system instantaneous efficiency changes little with the above factors when the value of V/V m of working point is smaller than that of the ECP and is sensitive to those factors when the value of V/V m is larger than that of the ECP. Following the annual historical climate data in Beijing, the result of the annual analysis is that the best scheme for the experiment system with a 1 m2 PV panel covering 1.05 m2 areas of ground can convert 78.4 kWh of solar energy to hydrogen energy in 2012. [Copyright &y& Elsevier]

Abstract: An optically transparent polymer electrolyte membrane (PEM) water electrolysis cell was studied using a high-speed camera, thermal imaging and electrochemical impedance spectroscopy to examine the relationship between flow and electrochemical performance. The flow regime spans bubble and slug flow, depending on the rate of gas formation (current density) and water feed rate. Electrochemical impedance spectroscopy (EIS) shows that there is a reduction in mass transport limitation associated with the transition to slug flow. [Copyright &y& Elsevier]

Abstract: In renewably powered remote hydrogen generation systems, on-site water production is essential so as to service electrolysis in hydrogen systems which may not have recourse to shipments of de-ionised water. Whilst the inclusion of small Reverse Osmosis (RO) units may function as a (useful) dump load, it also directly impacts the power management of remote hydrogen generation systems affecting operational characteristics. This research investigates the impact on the hydrogen generation system when simulations utilise different methods to account for solar power needed to drive the system as well as varying scales of (short-term) battery capacity. The simulations, in MATLAB/Simulink, utilise two specific methods of irradiance prediction (ASHRAE clear sky model and Neural Networks) and are benchmarked against measured irradiance data for Geraldton (Western Australia). This imposes different levels of accuracy and intermittency. Laboratory testing and device-level models help simulate the operational characteristics of a hydrogen generation system including on-site water production. Operational characteristics studied include: total energy available for PEM electrolysis, ontime of the electrolyser in steady-state, the number of start/stop cycles for the electrolyser and its duty factor (litres of hydrogen generated over the total number of start/stops). Results show that increasing systems' battery capacity only affects the operational characteristics of a PEM electrolyser up to a threshold capacity (Ah). Increasing battery capacity generally allows for more renewable energy penetration. Additionally, the hydrogen generation system behaviour is (generally) more accurately predicted, across all battery capacities, when Neural Networks are used to predict the availability of solar irradiance. The ability to predict accurate levels of solar irradiance becomes more important in winter when irradiance is at its lowest. The results also highlight the need to use highly resolved (temporal) simulations which are able to better capture device-level operational characteristics. [Copyright &y& Elsevier]

Abstract: Hydrogen fuel can be produced by using solar electric energy from photovoltaic (PV) modules for the electrolysis of water without emitting carbon dioxide or requiring fossil fuels. In this paper, an assessment of the technical potential for producing hydrogen from the PV/proton exchange membrane (PEM) electrolyser system is investigated. The present study estimates the amount of hydrogen produced by this system in six locations using hourly global solar irradiations on horizontal plane and ambient temperature. The system studied in this work is composed of 60 W PV module connected with a commercial 50 W PEM electrolyser via DC/DC converter equipped with a maximum power point tracking. The primary objective is to develop a mathematical model of hydrogen production system, including PV module and PEM electrolyser to analyze the system performance. The secondary aim is to compare the system performance in terms of hydrogen production at seven locations situated in different regions of Algeria. The amount of hydrogen produced is estimated at seven locations situated in different regions. In terms of hydrogen production, the results show that the southern region of Algeria (Adrar, Ghardaia, Bechar and Tamanrasset) is found to have the relatively highest hydrogen production. The total annual production of hydrogen is estimated to be around 20–29 m3 at these sites. The hydrogen production at various sites has been found to vary according to the solar radiation. [Copyright &y& Elsevier]

Abstract: In this study, we comprehensively analyze the probability distribution of the hydrogen production for PV assisted PEM electrolyser system. A case study is conducted using the experimental data taken from a recently installed system in Balikesir University, Turkey. A novel computational tool is developed in Matlab-Simulink for analyzing the data. The concept of probability density frequency is successfully applied in the analyses of the wind speed and the solar energy in literature. This study presents a method of applying this knowledge to solar energy assisted hydrogen production. The change in the probability distribution of the hydrogen production with the solar irradiation throughout a year is studied and illustrated. It is found that the maximum amount of hydrogen production occurs at between 600 and 650 W/m2 of solar radiation. Annual hydrogen production is determined as 2.97 kg for per m2 of PV system. Average hydrogen production efficiency of the studied PEM electrolyser is found to be 60.5% with 0.48 A/cm2 of current density. The presented results of this study are expected to be valuable for the researchers working on renewable hydrogen production systems. [Copyright &y& Elsevier]

Abstract: A complete stand-alone electrolyser system has been constructed as a transportable unit for demonstration of a sustainable energy facility based on hydrogen and a renewable energy source. The stand-alone unit is designed to support a polymer electrolyte membrane (PEM) stack operating at up to ∼4kW input power with a stack efficiency of about 80% based on HHV of hydrogen. It is self-pressurizing and intended for operation initially at a differential pressure of less than 6bar across the membrane electrode assembly with the hydrogen generation side being at a higher pressure. With a slightly smaller stack, the system has been operated at an off-site facility where it was directly coupled to a 2.4kW photovoltaic (PV) solar array. Because of its potential use in remote areas, the balance-of-plant operates entirely on 12V DC power for all monitoring, control and safety requirements. It utilises a separate high-current supply as the main electrolyser input, typically 30–40V at 100A from a renewable source such as solar PV or wind. The system has multiple levels of built-in operator and stack safety redundancy. Control and safety systems monitor all flows, levels and temperatures of significance. All fault conditions are failsafe and are duplicated, triggering latching relays which shut the system down. Process indicators monitor several key variables and allow operating limits to be easily adjusted in response to experience of system performance gained in the field. [Copyright &y& Elsevier]

Abstract: A simulation program, based on Visual Pascal, for sizing and techno-economic analysis of the performance of solar-hydrogen combined heat and power systems for remote applications is described. The accuracy of the submodels is checked by comparing the real performances of the system’s components obtained from experimental measurements with model outputs. The use of the heat generated by the PEM fuel cell, and any unused excess hydrogen, is investigated for hot water production or space heating while the solar-hydrogen system is supplying electricity. A 5kWh daily demand profile and the solar radiation profile of Melbourne have been used in a case study to investigate the typical techno-economic characteristics of the system to supply a remote household. The simulation shows that by harnessing both thermal load and excess hydrogen it is possible to increase the average yearly energy efficiency of the fuel cell in the solar-hydrogen system from just below 40% up to about 80% in both heat and power generation (based on the high heating value of hydrogen). The fuel cell in the system is conventionally sized to meet the peak of the demand profile. However, an economic optimisation analysis illustrates that installing a larger fuel cell could lead to up to a 15% reduction in the unit cost of the electricity to an average of just below 90c/kWh over the assessment period of 30years. Further, for an economically optimal size of the fuel cell, nearly a half the yearly energy demand for hot water of the remote household could be supplied by heat recovery from the fuel cell and utilising unused hydrogen in the exit stream. Such a system could then complement a conventional solar water heating system by providing the boosting energy (usually in the order of 40% of the total) normally obtained from gas or electricity. [Copyright &y& Elsevier]

Abstract: An experimental model of a photovoltaic (PV) module-proton exchange membrane (PEM) electrolyser system has been built. A model has been developed for each device separately based on the experimental results. Output current–voltage (I–V) characteristics of the PV module are modelled in respect to different irradiance and temperature conditions by experimental tests. Similarly, input I–V characteristic and hydrogen formation characteristic of the PEM electrolyser are measured and modelled. After these studies, combined PV module–PEM electrolyser system model is defined. There is a good agreement between model predictions and measurements. At 18–100% irradiance interval, operating points of PEM electrolyser on the PV module are predicted with relative errors of 0.1–0.8%. Furthermore, the study shows that these simple model system devices can easily be defined in MATLAB/Simulink and used to model similar systems of different size. [Copyright &y& Elsevier]

Abstract: This paper describes the performance of an integrated PV–wind hydrogen energy production system. The system consists of photovoltaic array, wind turbine, PEM electrolyser, battery bank, hydrogen storage tank, and an automatic control system for battery charging and discharging conditions. The system produced 130–140ml/min of hydrogen, for an average global solar radiation and wind speed ranging between 200 and 800W/m2 and 2.0 and 5.0m/s respectively. A mathematical model for each component in the system was developed and compared to the experimental results. [Copyright &y& Elsevier]

Abstract: To improve the efficiency and the safety of hydrogen electrolysis stations, some technological studies are still under investigation both on methods and materials. As methods, control, monitoring and diagnosis algorithms are relevant tools. This work focuses on the dynamical modelling and the monitoring of Proton Exchange Membrane (PEM) electrolyser. Our contribution consists of three parts: to propose a model of an analytical–dynamical PEM electrolyser, dedicated to control and monitoring; to identify the model parameters and to propose adequate monitoring tools. The proposed model is deduced from physical laws and electrochemical equations and consists of a steady-state electric model coupled with a dynamic thermal model. The estimation of the model parameters is achieved using identification and data fitting techniques based on experimental measurements. Taking into account the information given by the proposed analytical model and the experimentation data (temperature T, voltage U and current I) given by a PEM electrolyser, the model parameters are identified. After estimating the dynamical model, model-based diagnosis is used to monitor the PEM electrolyser and to ensure its safety. We illustrate how our algorithm can detect and isolate faults on actuators, on sensors or on electrolyser system. [Copyright &y& Elsevier]

Abstract: Hydrogen as an energy currency, carrier and storage medium may be a key component of the solution to problems of global warming, poor air quality and dwindling reserves of liquid hydrocarbon fuels. Hydrogen is a flexible storage medium and can be generated by the electrolysis of water. It is particularly advantageous if an electrolyser may be simply and efficiently coupled to a source of renewable electrical energy. This paper examines direct coupling of a polymer electrolyte membrane (PEM) electrolyser to a matched solar photovoltaic (PV) source for hydrogen generation and storage. Such direct coupling with minimum interfacing electronics would lead to substantial cost reduction and thereby enhance the economic viability of solar-hydrogen systems. The electrolyser is designed for fail-safe operation with multiple levels of safety and operational redundancy. A control system in the electrolyser unit provides for disconnection when required and for auto-start in the morning and auto shut-down at night, simultaneously addressing the goals of minimum energy loss and maximum safety. The PV system is a 2.4kW array (20.4m2 total area) comprising 30, 12V, 80W, Solarex polycrystalline modules in a series–parallel configuration. The integrated system has been operated for approximately 60 days over a 4-month period from September 2007 to January 2008 with many periods of unattended operation for multiple days, experiencing weather ranging from hot and sunny (above 40°C) to cool and cloudy. The principle and practicality of direct coupling of a suitably matched PV array and PEM electrolyser have been successfully demonstrated. Details of electrolyser operation coupled to a PV array along with modelling work to match current–voltage characteristics of the electrolyser and PV system are described. [Copyright &y& Elsevier]

Abstract: Renewable energy–hydrogen systems for remote applications constitute an early niche for sustainable hydrogen energy. Optimal matching between the photovoltaic (PV) system and the electrolyser is essential for maximum electrical energy transfer and hydrogen production. This paper investigates the possibility of achieving near maximum power transfer between a directly coupled PV array and a proton exchange membrane (PEM) electrolyser stack by finding an optimal configuration of series–parallel connection of both the PV panels and the PEM cells. The application of this procedure to four 75W PV modules directly coupled to five 50W PEM electrolyser stacks (250W in total) predicts an energy transfer of over 94% of the theoretical maximum. Initial experiments indicate an actual energy transfer of around 95%. Clearly, energy-efficient direct coupling is advantageous economically since the costs of an electronic coupling system (around US$) are avoided entirely. [Copyright &y& Elsevier]

Abstract: Thin films of iridium oxide deposited by reactive magnetron sputtering have been investigated as catalysts for electrochemical water splitting in a polymer electrolyte membrane (PEM) cell. The sputtered films possess excellent mechanical stability and corrosion resistance at the high anodic potentials where oxygen evolution takes place. Their catalytic activity has been assessed using the conventional electrochemical methods of cyclovoltammetry and steady state polarisation techniques. A morphology factor assessing the catalyst active surface for a series of sputtered samples with varying thickness/loading has been determined and correlated to the catalytic efficiency. It has been proven that iridium oxide is a very efficient catalyst for oxygen evolution reaction (OER). The best performance with anodic current density of 0.3Acm−2 at potential of 1.55V (versus RHE) has shown the 500nm thick film containing 0.2mgcm−2 catalyst. The results obtained have also demonstrated the advantages of the reactive magnetron sputtering as simple and reliable method for deposition of efficient and cost effective catalysts for PEM electrolysis application. [Copyright &y& Elsevier]

The potential for generating green hydrogen by electrolysis (water splitting) has resulted in a substantial amount of literature focusing on lowering the current production cost of hydrogen. A significant contributor to this high cost is the requirement for precious metals (namely Pt and Ir/Ru (oxides)) to catalyse the two main reactions involved in electrolysis: the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). Herein we overview the current literature of non-precious metal HER and OER catalysts capable of efficient water splitting within a polymer electrolyte membrane (PEM) electrolyser, recording the activity and stability of each catalyst and allowing for direct comparison to be made. Additionally, we highlight the inapplicability of catalyst stability testing in many academic studies for commercial electrolyser applications and propose a universal stability-testing regime for HER and OER catalysts that more accurately mimics the conditions within an operating electrolyser. • Stability studies of cathodic catalysts don't translate to commercial electrolysis. • Anodic catalyst stability studies are more comprehensive for electrolysis operation. • Stability of novel catalysts needs to be benchmarked against the optimal catalysts. • Combining active and stable first row transition metals shows promising catalysis. • A stability testing regime for proton exchange membrane electrolysis is proposed. [ABSTRACT FROM AUTHOR]