Renewable Electricity Sources Research Articles

Performance evaluation of off-grid solar systems for critical medical instruments in remote regions

In areas with limited access to electricity or during power outages, ensuring continuous and reliable use of grid-powered electrical instruments is challenging, especially in remote emergency centers. A stable source of electricity is crucial to prevent disruptions in power supply, as they can lead to severe medical complications, jeopardize patient well-being, and even result in fatal incidents. To address this issue, integrating renewable electricity sources such as off-grid solar systems into existing power supply infrastructure can be a viable solution. Recent studies suggest that off-grid solar systems can be reliable and sustainable options for powering medical facilities, particularly in areas lacking uninterrupted grid connectivity. Therefore, this research aims to evaluate the feasibility, benefits, and challenges of integrating off-grid power to support critical medical instruments. Based on an extensive literature review, interviews with experts, and surveys among relevant users, this study finds that the system has the capability to maintain a consistent, dependable power supply, even during adverse weather conditions. Cost and feasibility are highlighted as paramount considerations, based on surveys and focus group results. The study concludes that off-grid solar systems offer an economical, low-maintenance, and environmentally sustainable alternative for remote medical facilities. Finally, this study proposes recommendations to optimize critical device performance during power outages and improve overall system functionality and efficiency.

Life cycle assessment of synthetic natural gas production from captured cement’s CO2 and green H2

Research on the environmental benefits of carbon capture and utilization (CCU) in cement production so far, has predominantly emphasized energy efficiency enhancements and CO2 emission reductions at a CCU product level, neglecting broader environmental consequences for the sector. This research broadens this perspective by providing an extensive life cycle assessment (LCA) of a circular Portland cement (CPC) model. Synthesized methane is used as input fuel through green hydrogen and calcium-looping (CaL) post-combustion captured CO2 from cement flue gas. Comparative analysis with ordinary Portland cement (OPC) reveals significant reductions in climate change and fossil resource use environmental impact categories. However, trade-offs are evident in acidification, water use, and minerals and metals resource consumption. The electrolysis system is a critical contributor due to the high electricity demand for hydrogen production, and its environmental impact depends largely on the renewable electricity source. The wind-based electrolysis model yields the most favourable results, followed by mixed (50% solar – 50% wind) and solar scenarios. These findings offer valuable insights for the cement industry, supporting stakeholders decision making on the adoption of sustainable circular production methods.

Renewable hydrogen production through electrolysis: An analysis of the cost gap for its economic competitiveness in Italy

With global policies targeting greenhouse gas emission reduction, renewable hydrogen produced by water electrolysis powered with renewable electricity appears a promising alternative to fossil fuels. However, still high capital costs, reliance on intermittent renewable electricity sources, and high electricity cost hinder the economic viability of electrolyzers. This work develops a comprehensive analysis for assessing the need of an incentive to make renewable hydrogen economically viable, identifying different archetypes of electrolysis plant representative of a wide range of applications. A techno-economic optimization model is set up that minimize the average hydrogen production cost and compute the cost gap that makes hydrogen economically competitive with the fossil alternative, defining the optimal size and operation of the plant components while satisfying the hydrogen demand. The model is applied to the Italian case study. Sensitivity analyses investigate the impact of economy of scales, renewable electricity availability and introduction of the emission trading system. Cost gaps ranging between 8.1 €/kg and 29.9 €/kg highlights the need of an incentive to allow the deployment of this technology, thus meeting the hydrogen penetration targets.

Green Hydrogen Production at the Gigawatt Scale in Portugal: A Technical and Economic Evaluation

The European Union has committed to achieving carbon neutrality by 2050 and green hydrogen has been chosen as a priority vector for reaching that goal. Accordingly, Portugal has drafted a National Hydrogen Strategy laying out the various steps for the development of a green hydrogen economy. One element of this strategy is the development of a gigawatt-scale hydrogen production facility powered by dedicated renewable electricity sources. This work presents an analysis of the technical and economic feasibility of a facility consisting of a gigawatt-scale polymer electrolyte membrane electrolyser powered by solar photovoltaic and wind electricity, using the energy analysis model EnergyPLAN. Different capacities and modes of operation of the electrolyser are considered, including the complementary use of grid electricity as well as different combinations of renewable power, resulting in a total of 72 different configurations. An economic analysis is conducted addressing the related annualised capital expenditures, maintenance, and variable costs, to allow for the determination of the levelised cost of hydrogen for the different configurations. This analysis shows the conditions required for maximising annual hydrogen production at the lowest levelised cost of hydrogen. The best options consist of an electrolyser powered by a combination of solar photovoltaic and wind, with limited exchanges with the electricity grid, and a levelised cost of hydrogen in the range 3.13–3.48 EUR/kg.

Cross-border electricity transfers in the case of differentiated renewable energy sources: A simulation analysis for Germany and Spain

Renewable electricity plays an increasingly important role in the effort to reduce CO2 emissions in the electricity sector. One of the major challenges that must be addressed is the fluctuating supply of renewable electricity. We explore the impact of cross-border electricity transfers on both the security of electricity supply and renewable electricity expansion. We focus on Spain and Germany due to the relative abundance of their country-specific renewable electricity sources (solar for Spain and wind for Germany). We develop an electricity market model that allows for cross-border electricity transfers by connecting country-specific electricity markets. We apply six policy scenarios aiming towards securing the electricity supply and renewable electricity expansion. Our simulation results show that cross-border electricity transfers postpone supply shortages in both countries. These shortages occur as a result of an increasing amount of low-marginal-cost renewable electricity, which, in turn, leads to a decrease in the electricity price, so that power plants cannot operate profitably. However, the postponement of these supply shortages is primarily achieved through an excess supply of German conventional power plants that are utilised to meet excess demand in Spain. Although this serves to reduce required government subsidies, it also leads to an increase in CO2 emissions.

Visualizing the Maximum Energy Zone of Wind Turbines Operating at Time-Varying Wind Speeds

Wind turbines are one of the leading renewable sources of electricity. They are located in areas where the energy potential of the wind is high and more or less permanent. Their efficient operation depends on certain technical characteristics of the entire wind system (wind turbines, generator, automation system, regulation, and control). This paper analyses experimental data from wind turbines, WT, in the Dobrogea area: wind speed, v, velocity, n, and power, PEG, at the electric generator, EG. These are used to identify the local maxima of wind turbine power at different wind speeds. Based on this, a mathematical model for wind turbines and the power losses caused by inefficient control are determined. The mathematical model is used to visualize the maximum energy zones. At the end of this study, an algorithm is given that allows for the visualization of the optimal energy zone. The algorithm resulting from the analyzed case studies can be implemented by the control system in order to maximize the produced electricity with any variation in wind speed.

Experimental demonstration of a dispatchable power-to-power high temperature latent heat storage system

The development of electricity storage solutions is crucial to support the integration of variable renewable electricity sources in electricity systems. This study experimentally characterizes a state-of-the-art full-scale electrical thermal energy storage (ETES) system in outdoor conditions. The system integrates a 600 kWhth high-temperature latent heat storage module and a 13 kWe Stirling engine. The heat storage module uses an 88Al12Si metallic alloy as the phase change material to store electricity converted to thermal energy by a resistive heater in charging mode. The Stirling engine uses hydrogen as the working fluid for re-electrification (discharging). The system uses liquid sodium as the heat transfer fluid between the latent heat storage module and both the charging (electrical heater) and discharging (engine) sub-systems. Over the characterization period, the ETES prototype produced stable electricity at an average rate of 10.5 ± 1 kW for 13 consecutive hours daily with overall and power block first-law efficiencies of 23 % and 25 %, respectively. The effective storage utilization ratio varied between 0.58 and 0.94 depending on the discharge parameters. The response time was <5 s for output power regulation. The results highlight the potential of this latent heat thermal energy storage system to satisfy long-duration electricity storage applications and therefore contribute to the stabilization of electricity grids.

What is the environmental impact of a blood transfusion? A life cycle assessment of transfusion services across England.

Healthcare activities significantly contribute to greenhouse gas (GHG) emissions. Blood transfusions require complex, interlinked processes to collect, manufacture, and supply. Their contribution to healthcare emissions and avenues for mitigation is unknown. We performed a life cycle assessment (LCA) for red blood cell (RBC) transfusions across England where 1.36 million units are transfused annually. We defined the process flow with seven categories: donation, transportation, manufacturing, testing, stockholding, hospital transfusion, and disposal. We used direct measurements, manufacturer data, bioengineering databases, and surveys to assess electrical power usage, embodied carbon in disposable materials and reagents, and direct emissions through transportation, refrigerant leakage, and disposal. The central estimate of carbon footprint per unit of RBC transfused was 7.56 kg CO2 equivalent (CO2eq). The largest contribution was from transportation (2.8 kg CO2eq, 36% of total). The second largest was from hospital transfusion processes (1.9 kg CO2eq, 26%), driven mostly by refrigeration. The third largest was donation (1.3 kg CO2eq, 17%) due to the plastic blood packs. Total emissions from RBC transfusion are ~10.3 million kg CO2eq/year. This is the first study to estimate GHG emissions attributable to RBC transfusion, quantifying the contributions of each stage of the process. Primary areas for mitigation may include electric vehicles for the blood service fleet, improving the energy efficiency of refrigeration, using renewable sources of electricity, changing the plastic of blood packs, and using methods of disposal other than incineration.

The visual effect of wind turbines on property values is small and diminishing in space and time

Renewable power generation is the key to decarbonizing the electricity system. Wind power is the fastest-growing renewable source of electricity in the United States. However, expanding wind capacity often faces local opposition, partly due to a perceived visual disamenity from large wind turbines. Here, we provide a US-wide assessment of the externality costs of wind power generation through the visibility impact on property values. To this end, we create a database on wind turbine visibility, combining information on the site and height of each utility-scale turbine having fed power into the U.S. grid, with a high-resolution elevation map to account for the underlying topography of the landscape. Building on hedonic valuation theory, we statistically estimate the impact of wind turbine visibility on home values, informed by data from the majority of home sales in the United States since 1997. We find that on average, wind turbine visibility negatively affects home values in an economically and statistically significant way in close proximity ([Formula: see text]5 miles/8 km). However, the effect diminishes over time and in distance and is indistinguishable from zero for larger distances and toward the end of our sample.

Solar thermal vs. PV with a heat pump: A comparison of different charging technologies for seasonal storage systems in district heating networks

The majority of district heating networks (DHNs) in Germany and other European countries are still supplied by fossil fuels. While several possible technical solutions exist to decarbonize DHNs, the problem is the availability of solar energy – thermal and electric – or other renewable electric sources during winter. A solution is to shift the available energy from the summer to the winter by using seasonal thermal energy storage systems. Especially pit thermal energy storage systems (PTES) have shown an economic advantage compared to other storage types. Therefore, we would like further to investigate the design of PTES under different techno-economic conditions.In this study, different charging options for the PTES were examined. Solar thermal energy was compared to photovoltaic (PV), supplying an air-source heat pump (ASHP). We developed an open-source Python package based on mixed-integer linear programming, minimizing the total system cost, i.e., the annuity, including opex and capex. The tool selects, operates, and designs energy converters and storages. Furthermore, it optimizes the network’s storage capacity during the operation. The optimization takes the characteristics of an existing DHN as input and designs the supply systems across different locations (LOCs). The model separates the hydraulic and thermal calculation and builds up a multi-stage process to consider temperatures inside the network and the PTES.The tool was applied to a DHN in Eastern Germany. The results show a low sensitivity to the electricity price in all concepts. Operating the PTES at low temperatures negatively affects the heat capacity, and therefore, it is best suited for high-temperature networks. The concept of PV with an ASHP is better suited for densely populated regions. However, both concepts have a total system cost above 20ct/kWh for an area price of over 120€/m2. For an electricity price of ca. 19ct/kWh, the total system cost is below 17ct/kWh for both concepts.

Designing and Modelling of Wind Turbine Simulation Using MATLAB / SIMULINK

Abstract: The renewable energy, Malaysia hopes to lessen its reliance on oil and gas. Wind energy is one of the more promising renewable sources of electricity. Malaysia is situated in an area with low wind speeds, with an annual mean wind speed of 1.2- 4.1 m/s, close to the equator. The northeast monsoon and the southwest monsoon are the two monsoonseasons that Malaysia experiences. While wind speeds during the northeast monsoon can approach 15 m/s, they can only reach 7 m/s during the southwest monsoon season. The potential for wind energy in Sarawak, Malaysia, has only receiveda limited amount of research and study. In this article, MATLAB/SIMULINK will be used for modelling and simulation of numerous wind energy conversion systems (WESC) utilizing different generators operating under the same conditionsin order to analysis the generators' efficiency. Although ultimately all of them are equally efficient, PMSG has shown tobe more efficient than SCIG and DFIG at lower wind speeds. SCIG, DFIG, and PMSG efficiency are, respectively, 66.25%, 69.38%, and 71.88% at the rated wind speed.

Critical mineral demands may limit scaling of green hydrogen production

Hydrogen (H2) is widely viewed as critical to the decarbonization of industry and transportation. Water electrolysis powered by renewable electricity, commonly referred to as green H2, can be used to generate H2 with low carbon dioxide emissions. Herein, we analyze the critical mineral and energy demands associated with green H2 production under three different hypothetical future demand scenarios, ranging from 100–1,000 Mtpa H2. For each scenario, we calculate the critical mineral demands required to build water electrolyzers (i.e., electrodes and electrolyte) and to build dedicated or additional renewable electricity sources (i.e., wind and solar) to power the electrolyzers. Our analysis shows that scaling electrolyzer and renewable energy technologies that use platinum group metals and rare earth elements will likely face supply constraints. Specifically, larger quantities of lanthanum, yttrium, or iridium will be needed to increase electrolyzer capacity and even more neodymium, silicon, zinc, molybdenum, aluminum, and copper will be needed to build dedicated renewable electricity sources. We find that scaling green H2 production to meet projected net-zero targets will require ∼24,000 TWh of dedicated renewable energy generation, which is roughly the total amount of solar and wind projected to be on the grid in 2050 according to some energy transition models. In summary, critical mineral constraints may hinder the scaling of green H2 to meet global net-zero emissions targets, motivating the need for the research and development of alternative, low-emission methods of generating H2.

Switched Z-Source Boost Converter in Hybrid Renewable Energy System for Grid-Tied Applications

The world's focus is shifting toward Renewable Energy Sources (RES) as a result of the sharp rise in energy demand and the depletion of conventional energy sources. Distributed generation (DG) units developed on RES are easily and reliably integrated into grid due to microgrid technology. Inverters are typically used to integrate DGs into microgrid. At present, the fastestgrowing renewable sources of electricity in the world is photovoltaic (PV) and wind energy conversion system (WECS), which evolved in response to growing environmental concerns about the risks of climate change connected with power generation. Recent technological developments have made it a top priority for researchers to find ways to enhance the efficiency of hybrid systems and the power converter stage. In order to achieve transmission losses and ensure energy savings, a new 13-bus system is developed in this work for regulating the output voltage in distribution networks. Switched Z-source Boost converter along with Proportional Integral (PI) controller is employed to boost the voltage obtained from PV system. A battery converter along with a bi-directional battery is connected to the DC link, to store energy generated by Hybrid Renewable Energy System (HRES) in excess amount. The obtained DC link voltage is transferred to three-phase voltage source inverter (VSI) for the conversion of DC to AC voltage. Effective harmonic reduction is attained with the aid of LC filter coupled to Three phase grid, and the PI controller associated to the grid supports in achieving effective grid synchronization. The proposed research is validated using MATLAB Simulink by considering the 13-bus system and an efficiency of 96.8 % is obtained with 0.93% Total Harmonic Distortion (THD).

Investigating the Role of Byproduct Oxygen in UK-Based Future Scenario Models for Green Hydrogen Electrolysis

Water electrolysis for hydrogen production with renewable electricity is regularly studied as an option for decarbonised future energy scenarios. The inclusion of byproduct electrolytic oxygen capture and sale is of interest for parallel decarbonisation efforts elsewhere in the industry and could contribute to reducing green hydrogen costs. A deterministic hydrogen electrolysis system model is constructed to compare oxygen inclusion/exclusion scenarios. This uses wind and solar-PV electricity generation timeseries, a power-dependent electrolysis model to determine the energy efficiency of gas yield, and power allocation for gas post-processing energy within each hourly timestep. This maintains a fully renewable (and therefore low/zero carbon) electricity source for electrolysis and gas post-processing. The model is validated (excluding oxygen) against an existing low-cost GW-scale solar-hydrogen production scenario and an existing hydrogen production costs study with offshore wind generation at the multi-MW scale. For both comparisons, oxygen inclusion is then evaluated to demonstrate both the benefits and drawbacks of capture and utilisation, for different scenario conditions, and high parameter sensitivity can be seen regarding the price of renewable electricity. This work subsequently proposes that the option for the potential utilisation of byproduct oxygen should be included in future research to exemplify otherwise missed benefits.

Renewable energy electric sources as a support for multilevel cellular communication networks in various environment conditions – case study

Renewable energy electric sources as a support for multilevel cellular communication networks in various environment conditions – case study

Electrocatalysts for High Temperature (100-200 ºC) and Pressure (45 bar) Alkaline Electrolysis

Electrolytic hydrogen production is key in transitioning to a sustainable energy system, as it enables the production of sustainable fuels and chemicals from renewable electricity sources and a means to address their intermittent nature at the same time. Amongst the main electrolysis technologies, Alkaline Electrolysis (AE) is the most suitable for the hundreds of GW capacity that is required, as it relies only on abundant, low-cost materials, and has a proven record of reliability and scalability. However, AE suffers from poor efficiency and productivity. Increasing operating temperature and pressure offers a means to overcome this limitation [1, 2]. Nevertheless, electrodes with good long-term stability in the hot corrosive alkaline environment are required. Here, we report the performance of Co3O4 and NiMoOx coated nickel foam (NF) electrodes for the anode and cathode, respectively. The electrodes are tested from room temperature to 150 ºC at 45 bar pressure in 45 wt.% KOH. The Co3O4 coated NF (Co3O4/NF) anode performance is compared to that of commercial pristine NF and Inconel coated NF (Inconel/NF) electrodes. At room temperature the Inconel/NF electrode outperforms both the pristine NF as well as the Co3O4/NF electrodes. At 150 ºC and 45 bar pressure, the Co3O4/NF and Inconel/NF electrode perform quite similar. During the 108 h long-term stability test at 150 ºC and 45 bar, the Co3O4/NF electrode remains stable requiring an overpotential of ~185 mV at 500 mA.cm-2, whereas the overpotential of the Inconel/NF electrode increased from 178 mV to 209 mV after 84 h of operation at the same conditions. The structural and chemical evolution of these electrodes was explored by post-mortem scanning electron microscopy (SEM) in comparison to the fresh electrodes. The NiMoOx coated NF (NiMoOx/NF) cathode showed a low and stable overpotential (~130 mV) at the same conditions, similar to a precious metal coated nickel perforated plate electrode (~125 mV). References C. Chatzichristodoulou, F. Allebrod, and M. B. Mogensen, J. Electrochem. Soc., 163, F3036–F3040 (2016).F. Allebrod, C. Chatzichristodoulou, and M. B. Mogensen, J. Power Sources, 229, 22–31 (2013).

A Two-Dimensional Transport Model of Bipolar Membrane Electrodialysis for the Electro-Regeneration of Carbon Capture Solvents

Bipolar membrane electrodialysis (BPMED) is a promising technology that uses an electric field to split water into H+ and OH- ions. A repeating stack of cation selective, anion selective, and bipolar membranes are placed between two electrodes, creating a repeating pattern of acid, base, and diluting flow chambers. A major application of BPMED is the electrochemical solvent regeneration of capture solutions used in CO2 point source (PS) or direct air capture (DAC). Protons generated using BPMED can be used to shift the acid-base equilibria back to CO2, providing a more sustainable alternative to traditional thermal regeneration methods when integrated with renewable electricity sources. This method combines electrosynthesis and separation, producing a pure stream of CO2 for sequestration and a concentrated base stream.Despite its potential, current limitations to BPMED implementation for this application stem from a large power consumption and high membrane costs. In addition, gas bubbles in solution can cause high electrical resistances, and experimental studies of this phenomenon are challenging due to the small scale on which it occurs. To address these challenges, we present a two-dimensional model of BPMED for CO2 capture solvent recovery. This model depicts a single repeating cell triplet and was constructed using COMSOL Multiphysics version 6.1. The Navier-Stokes equations were implemented to compute a convection field, and the ionic species concentration was found by solving the Nernst-Planck equation. A source term in the concentration partial differential equations was implemented to account for ionic speciation and water splitting reactions, captured through kinetic rate expressions.Experimental validation was conducted on a PC Cell BED 1-4 recirculating batch system with a stack of seven cell pairs of PC acid 60 (anion selective), PC SK (cation selective), and PC Bip (bipolar) membranes. Good agreement between the model and experimental results across a range of conditions and variables demonstrates accuracy and robustness. The calculated pH and concentration profiles revealed that the majority of the speciation reaction takes place inside, or directly adjacent to, the bipolar membrane, including bubble nucleation. Bubbles form inside membrane pores and displace the electrolyte, greatly increasing the electrical resistance of the membrane, particularly when membrane porosity is low. However, the reaction plane location where bubbles are generated can be manipulated by increasing the channel width or reducing the applied voltage.Future research will focus on expanding to multiphase CFD simulations to investigate the effect on flow. Our two-dimensional model provides valuable insights into the complex and multifaceted nature of BPMED, offering a powerful tool for investigating small-scale processes and advancing the use of BPMED for CO2 capture solvent recovery. Figure 1

In Situ Transmission Electron Microscopy and Soft X-Ray Spectro-Microscopy to Understand Electrochemical Processes

Electrochemical CO2 conversion offers a route to use renewable sources of electricity to convert CO2 into valuable carbon-based fuels and chemicals, including carbon monoxide, ethanol and ethylene. For electrochemical CO2 conversion technologies to become a viable component of future sustainable energy infrastructures, improved performance materials (catalysts, electrodes, membrane electrode assemblies) are needed to achieve high conversion rates, selectivity and single-pass utilization of CO2. This talk will focus on the development of techniques to characterize the properties of electrochemical CO2 conversion materials under reaction conditions. These in-situ methods are producing results which will guide the design of next generation materials and reactors. The talk will focus primarily on in situ transmission electron microscopy (TEM) and related spectroscopic techniques (energy dispersive X-ray analysis and selected area electron diffraction), along with synchrotron-based methods including in-situ soft X-ray scanning transmission X-ray microscopy (STXM).

A Novel Circuit-Based Model of Electrodialysis Avoiding the Use of Empirical Parameters

Electrodialysis (ED) is an emerging membrane-based electroseparation technology for desalination, water treatment, and ionic pollutant removal. Compared to conventional separation methods such as reverse osmosis, ED offers several advantages including lower energy consumption, higher selectivity, and lower fouling propensity. Further, coupling ED with renewable electricity sources enables it to be far more sustainable than competing technologies (reverse osmosis and evaporation) across a wide range of scales. However, the design and operation of ED systems are still challenging due to the complex interactions between the membrane, the electrolytes, and the applied electric field. To address this issue, advanced process models are required to provide accurate predictions of ED performance and to guide system optimisation. Existing ED models tend to be highly dependent on empirical parameters and thus are only applicable to a narrow range of process conditions and require several data sets to validate. Therefore, in this work we aimed to develop a glabal model of ED without reliance on experimental training data.Herein, we present a novel circuit-based model for ED. The model considers the membrane stack as a series of resistors, where the membranes and electrolytes are represented as separate resistive elements. Crucially, the membrane resistance is calculated directly from the electrostatic interaction between ions and fixed charge groups, rather than from manufacturer data or empirical sub-model. This allows for consideration of the ion identity and electrolyte concentration when determining the membrane resistance. Ohm's law is used to relate the applied voltage and stack electrical resistance to a current density, which is then converted to a flux using Faraday's law and current efficiency model. Historically, current efficiencies are calculated from transport numbers provided from membrane manufactures and assumed constant. A novel model for the current efficiency has been developed by us in which the current efficiency is a function of the trans-membrane concentration difference. A space-wise material balance is employed to determine the concentration profile along the stack, while a time-wise material balance tracks the changes in reservoir concentration for recirculating batch experiments.To validate the model, desalination experiments were conducted on a PC BED 1-4 recirculating batch system and compared the model predictions with experimental data. The model demonstrated excellent matching on a range of variables across a range of conditions, including current density, current efficiency, and ion concentration.The proposed model has various applications in ED process modelling, optimisation, and economic analysis. It can be used to evaluate the impact of different design parameters such as membrane thickness, membrane charge density, and flow rate on system performance as well as to optimise these.In summary, the circuit-based model presented in this work offers a robust and versatile tool for ED process simulation and optimisation, which can be used for effective and efficiency desalination and water treatment. Two major advancements presented include models for the membrane electrical resistance and current efficiency, which have historically been considered constant. Figure 1

Characterizing Reversible and Irreversible Degradation Effects of PEM Water Electrolyzer Stacks

Polymer electrolyte membrane water electrolyzers (PEMEL) have been identified as a key component in a decarbonized large-scale energy system, as they can produce high-purity hydrogen from renewable electricity sources for the chemical industry or energy storage. However, the long-term durability and performance of PEM electrolyzers remain a major challenge, with degradation being a critical factor that limits their lifespan and efficiency. Recent studies have focused on developing accelerated stress test (AST) protocols for PEM electrolyzers to better understand the conditions and mechanisms that lead to degradation.1, 2 Especially the reversible rise in cell potential, which in the literature is often regarded as apparent or reversible degradation, must be further investigated to find mitigation strategies for operation.3, 4 We present our research on the development of two testing protocols (static, dynamic) characterizing reversible and irreversible degradation effects for PEMEL stacks in different operation modes. Our aim is to gain a better understanding of the variance of these phenomena in general and the recovery of reversible effects across PEMEL stacks. The measurements are carried out on a commercialized Greenlight E400 test bench equipped with a 7kW 8 cell PEMEL stack (Hydrogen Innovation GmbH). The potential of all cells will be monitored during testing. The measurements include repeated electrochemical characterization protocols measuring i/E-curves, HFR and impedance spectroscopy (EIS) of the PEMEL stack and if possible, every single cell. These protocols include the introduction of low potential regeneration phases before every characterization during the test protocol to distinguish between reversible effects and the irreversible cell degradation. This was seen to be effective for potential recovery by Suermann et al. 2019 for single PEMEL cells.4 The results consist of a description of the two testing procedures and the used equipment. Due to the duration of each test protocol (3000 h) only results of the static test protocol can be presented.The contribution of the presented research is threefold. Firstly, we break down the degradation across a whole stack. Giving valuable insights regarding the distribution of cell efficiency and degradation effects. Secondly, the presented test protocols characterize and account for the reversible rise in cell/stack potential. Thirdly, the characterization of the recovery time of the cell potential across the stack will have implications for the operation of stacks to mitigate or recover these performance losses. We address both static and dynamic operation modes aiming to simulate the application of PEMEL stacks for a constant production of hydrogen used in downstream processes and the volatile operation due to a direct coupling with renewable energy sources.This publication is to be seen as presentation of first results in our ongoing research to find test protocols for short stack systems to develop operation strategies, which can be applied to large scale electrolyzer systems. Furthermore, we try to deepen the understanding of the reversible cell potential rise as well as standardize the general testing of PEMEL stacks.This work is funded by the Federal Ministry of Education and Research (BMBF) in the project “hyBit” under the grant 03SF0687E. The authors declare that the opinions expressed in this submission are their own and are based on a thorough review of existing scientific literature. Sources 1. G. Tsotridis and A. Pilenga, EU harmonized protocols for testing of low temperature water electrolysis, Publications Office of the European Union, Luxembourg (2021). 2. A. Voronova, H.-J. Kim, J. H. Jang, H.-Y. Park and B. Seo, International Journal of Energy Research, 46 (2022) 11867. 3. C. Rakousky, U. Reimer, K. Wippermann, S. Kuhri, M. Carmo, W. Lueke and D. Stolten, Journal of Power Sources, 342 (2017) 38. 4. M. Suermann, B. Bensmann and R. Hanke-Rauschenbach, Journal of The Electrochemical Society, 166 (2019) F645-F652.