Linear Degradation Rate Research Articles

Experimental and numerical approach for the evaluation of PV-system performance on energy and environmental behavior of nearly zero energy buildings: Case study in Mediterranean climate

Nowadays, the performance of photovoltaic (PV) systems has strategic role for satisfying the standard of net or nearly zero energy building with in-situ production. In this frame, the novelty of the paper is the proposal of a combined experimental and numerical approach for evaluating the mismatch between PV production and consumptions during design, operational and future performance under expected emissions scenarios. First of all, it proposes a comparison of production estimation by means of several tools for the evaluation of the energy balance in the design phase; then the expected and real behavior is compared with also the evaluation of the performance ratio (PR) evolution as function of cell temperature. Finally, a sensitivity analysis is proposed in the short and medium scenarios by varying the size of installed system and considering the degradation rate under future weather conditions. The approach is applied to a case study in a typical Mediterranean climate, starting from the monitoring data available for the building energy request and the renewable production (2016–2022). The results of the case study indicate that the PR greatly influences the performance, mainly under expected climate changes, since the operational emissions could increase of more than 15 % compared to actual performance also if the zero energy balance is satisfied. Furthermore, through a sensitivity analysis on the PV-system size, the study demonstrates that with a maximum linear degradation rate of 1.51 %/year, the building could be configured as nearly zero energy in the medium term (20 years) also with lower peak power. The analysis also suggests that the maximization of installed power is a prerequisite to follow the implementation of positive energy goal because, under all considered climatic evolutions it can balance the penalties both due to technical aspects that to modification of consumption and production profiles.

A polynomial of degree five representing the selling price of an inventory of deteriorating items with a linear degradation rate, constant holding cost, and demand-dependent selling price

The study suggests a deterministic inventory model as opposed to a probabilistic one. With just odd powers considered, the model's demand rate is a degree five polynomial of the selling price. The keeping expense is assumed to stay constant. Time has an impact on how quickly things degrade. The backlog and shortages are both acceptable. The inventory model used a single article inventory. It is assumed that there is no lead time. In this study, the differential equation's solution was used to determine the best values. The model is numerically validated, and in a maple application, convexity is displayed as a two-dimensional graph.

Storage Stability of 6FDA-DMB Polyamic Acid Solution Detected by Gel Permeation Chromatography Coupled with Multiple Detectors

Polyamic acid (PAA) is the precursor of polyimide (PI), and its solution's properties have a direct influence on the final performances of PI resins, films, or fibers. The viscosity loss of a PAA solution over time is notorious. A stability evaluation and revelation of the degradation mechanism of PAA in a solution based on variations of molecular parameters other than viscosity with storage time is necessary. In this study, a PAA solution was prepared through the polycondensation of 4,4'-(hexafluoroisopropene) diphthalic anhydride (6FDA) and 4,4'-diamino-2,2'-dimethylbiphenyl (DMB) in DMAc. The stability of a PAA solution stored at different temperatures (-18, -12, 4, and 25 °C) and different concentrations (12 wt% and 0.15 wt%) was systematically investigated by measuring the molecular parameters, including Mw, Mn, Mw/Mn, Rg, and [η], using gel permeation chromatography coupled with multiple detectors (GPC-RI-MALLS-VIS) in a mobile phase 0.02 M LiBr/0.20 M HAc/DMF. The stability of PAA in a concentrated solution decreased, as shown by the reduction ratio of Mw from 0%, 7.2%, and 34.7% to 83.8% and that of Mn from 0%, 4.7%, and 30.0% to 82.4% with an increase of temperature from -18, -12, and 4 to 25 °C, respectively, after storage for 139 days. The hydrolysis of PAA in a concentrated solution was accelerated at high temperatures. Notably, at 25 °C, the diluted solution was much less stable than the concentrated one and exhibited an almost linear degradation rate within 10 h. The Mw and Mn decreased rapidly by 52.8% and 48.7%, respectively, within 10 h. Such faster degradation was caused by a greater water ratio and less entanglement of chains in the diluted solution. The degradation of (6FDA-DMB) PAA in this study did not follow the chain length equilibration mechanism reported in literature, given that both Mw and Mn declined simultaneously during storage.

Enhanced proton conductivity and CO2-tolerance of intermediate-temperature protonic ceramic fuel cell with lanthanum tungstate-based composite cathode

Despite the low activation energy for proton diffusion under protonic ceramic fuel cell (PCFC) operation, the high-performance PCFC is still limited by the low proton conductivity of most cathode materials. A decrease in cathode acidity can enhance proton affinity; however, the severe CO2-tolerance associated with the doping of alkaline earth metals in perovskite oxides is also a challenge. Herein, a proton conducting oxide La5.5W0.45Mo0.4Nb0.15O11.25-δ (LWMN), which possesses excellent chemical stability under a CO2-containing atmosphere, is composited with Sr2Sc0.1Nb0.1Co1.5Fe0.3O6-δ (SSNCF) as the PCFC cathode. A 3 wt% alkali earth ion-free oxide LWMN composite in the cathode material can strengthen proton diffusion while weakening CO2 adsorption. Thus, in wet air containing CO2, the symmetrical cell based on the 3 wt% LWMN-SSNCF achieved a linear degradation rate of ASRs of 1.33 × 10−3 Ω cm2 min−1 for the first 3 h, which was lower than the 2.15 × 10−3 Ω cm2 min−1 achieved by the symmetrical cell based on the single-phase SSNCF cathode. Furthermore, the PCFC based on the composite cathode shows an improved performance of 1.114 W cm−2 at 650 °C due to its superior proton conduction. This strategy endowed the cathode with superior proton diffusion as well as low CO2 adsorption.

Profitability of Solar Photovoltaic Projects: A Sensitivity Analysis of Performance Loss Curves and Operation and Maintenance Expenses

Literature highlights the fact that degradation curves are frequently not linear. This technical knowledge is, however, neglected by developers, which continues to use simplified linear degradation rates to assess the profitability of solar photovoltaic (PV) projects. Herein, the unleveraged equity interest return rate (IRR) of utility‐scale (50 MWp in size) PV projects deployed in different parts of Europe is computed and a sensitivity analysis of how the profitability of the plant is impacted when nonlinear degradation curves are used is carried out. In general, a 2‐step performance loss curve leads to the highest project‐IRRs at equal total loss, whereas the lowest IRRs are achieved if module degradation is undergoing a negative logarithmic or exponential curve. Further, the sensitivity of profitability to the different degradation trajectories increases at higher latitudes for which the absolute project‐IRR is lower. Then, a similar analysis is performed mimicking situations that would lead to a significant revamping of the PV plant after 10 years of operation. This allows us to identify thresholds for overall module degradation that would justify this kind of intervention. Finally, the impact that loss rates and combined operation–maintenance and insurance costs have on the project IRR is highlighted.

Underestimated permafrost degradation: Improving the TTOP model based on soil thermal conductivity

Under the continuing influence of global warming, resolving the inconsistency of permafrost degradation rates and quantifying the spatial distribution characteristics are critical for high-altitude water cycle processes. The dynamics of permafrost degradation are mainly manifested in soil temperature, which can be measured with high accuracy and high temporal resolution. This study considered the influence of soil thermal conductivity (K) by periodic land surface temperature (LST), improved the static output of the temperature at the top of permafrost (TTOP) model, and verified the reliability of the TTOP model improvement by the Kappa coefficient. The results showed that from 2000 to 2020, the extent of dynamically simulated permafrost was 5.42 × 105 km2 less than that of static simulated permafrost, and the linear degradation rate doubled. The degraded permafrost showed an increasing degradation from southeast to northwest. Among them, the degradation in the Nujiang River and the Changjiang River north of the Nyainqentanglha Mountain has exacerbated the permafrost degradation in the hinterland of the Qiangtang Plateau. Based on the AWI-CM-1-1-MR LST from CMIP6, SSP126 to SSP585 dynamic simulation results of permafrost indicate that the extent will decrease by 11.35 % by 2100. Overall, the extent and rate of permafrost degradation, considering high spatiotemporal resolution, were twice as fast as expected. Our results will inform policymakers with a more accurate spatiotemporal distribution of frozen soil types in high-altitude regions and characteristics of permafrost degradation within the watershed.

Long term operational performance and experimental on-field degradation measurement of 10 MW PV plant in remote location in India

The paper presents extensive monitoring, detailed long term operational performance and on-field degradation measurement of utility scale grid connected 10 MW solar photovoltaic (PV) plant in real operating conditions. Different performance indices are evaluated incorporating IEC standard 61724 guidelines based on actual plant monitoring data (incident solar irradiation, ambient and module temperature and generated electrical energy) from January 2016 to December 2020 (period of five years). The annual average reference, array and final yield, performance ratio, capacity utilization factor, array capture and system losses, PV array and system efficiency of the plant were found to be 6–6.7 h/day, 4.83–5.1 h/day, 4.69–4.86 h/day, 72–74%, 19–20%, 1.02–1.33 h/day, 0.15–0.156 h/day, 12% and 11% respectively. Degradation of fielded modules is assessed by visual inspection and I-V curve tracing. Correlation of I-V characterization with electrical parameters of visually degraded installed PV modules is also presented. The calculated linear degradation rates varied from 0.97 to 1.52%/year in modules with considerable bird dropping, 1.33 to 1.61%/year in modules with light EVA discoloration, 1.6 to 1.86%/year in modules with glass breakage, 2.31 to 3.94%/year in modules with glass breakage and dark EVA discoloration, and 2.97 to 5.8%/year in modules with glass breakage and cell cracks. The annual linear degradation rates were found to be in the range of 0.9 to 1.1%/year for normal fielded modules with no visible degradation and 0.97 to 2.9%/year for visually degraded modules with mean and median values of 1.8%/year and 1.6%/year with six years operational period. The levelized cost of electricity, simple and discounted payback period and return on investment were found to be 4.05 Rs, 5.5 years, 11 years and 62.22% respectively. Annual CO2 savings of the plant is around 16,000 tons and CO2 emission reduction potential of installed pc-Si technology is found to be 1.6 tons/kWp.

Computational modeling of mRNA degradation dynamics using deep neural networks.

messenger RNA (mRNA) degradation plays critical roles in post-transcriptional gene regulation. A major component of mRNA degradation is determined by 3'-UTR elements. Hence, researchers are interested in studying mRNA dynamics as a function of 3'-UTR elements. A recent study measured the mRNA degradation dynamics of tens of thousands of 3'-UTR sequences using a massively parallel reporter assay. However, the computational approach used to model mRNA degradation was based on a simplifying assumption of a linear degradation rate. Consequently, the underlying mechanism of 3'-UTR elements is still not fully understood. Here, we developed deep neural networks to predict mRNA degradation dynamics and interpreted the networks to identify regulatory elements in the 3'-UTR and their positional effect. Given an input of a 110 nt-long 3'-UTR sequence and an initial mRNA level, the model predicts mRNA levels of eight consecutive time points. Our deep neural networks significantly improved prediction performance of mRNA degradation dynamics compared with extant methods for the task. Moreover, we demonstrated that models predicting the dynamics of two identical 3'-UTR sequences, differing by their poly(A) tail, performed better than single-task models. On the interpretability front, by using Integrated Gradients, our convolutional neural networks (CNNs) models identified known and novel cis-regulatory sequence elements of mRNA degradation. By applying a novel systematic evaluation of model interpretability, we demonstrated that the recurrent neural network models are inferior to the CNN models in terms of interpretability and that random initialization ensemble improves both prediction and interoperability performance. Moreover, using a mutagenesis analysis, we newly discovered the positional effect of various 3'-UTR elements. All the code developed through this study is available at github.com/OrensteinLab/DeepUTR/. Supplementary data are available at Bioinformatics online.

A quick evaluation method for the lifetime of the fuel cell MEA with the particle filter algorithm

ABSTRACT The proton exchange membrane fuel cell (PEMFC) has bright prospects in energy applications, but its durability and cost still affect its commercialization. In this work, a group of membrane electrode assemblies (MEAs) were tested to study the quick evaluating method for predicting their lifetimes. MEA1 was tested under the real constant load till the end of its lifetime and MEA2 was tested with a quick evaluating method. The data were treated with the particle filter algorithm to eliminate the influence of all kinds of errors, including the system error and random error. Based on this, the lifetime prediction model was developed. For a degradation rate of 10% of the initial working voltage, the lifetime of MEA1 was 6140 h; that of MEA2 was 3575 h if predicted with the test data directly, and 6776 h if the data was treated with the particle filter algorithm. The relative errors for both cases were about 41.8% and 10.3%, respectively, when compared with the lifetime of MEA1; indicating that the prediction accuracy was greatly improved. Furthermore, it was found that the voltage degradation rate was nonlinear when the whole lifetime of the MEA was considered, and the degradation rate increased significantly near the end period. In the quick evaluating method employed in most studies, the lifetime prediction model uses a linear degradation rate, which tends to cause errors; therefore, further research is needed.

Zirconia‐dispersed polyethylene glycol composites with a low temperature‐degradation rate

AbstractThe effect of tetragonal‐zirconia nanoparticle inclusion on the temperature‐dependent storage modulus, or the temperature‐degradation rate, of polyethylene glycol (PEG)‐based composites was investigated using shear‐mode dynamic mechanical analysis (DMA) at temperatures ranging from room temperature up to 75°C. We carried out further investigations in the rubbery area in terms of the characteristic of the degradation rate with temperature and compared it with silica‐quartz‐filled PEG composites, which exhibited a potential as phase‐change materials (PCMs). The investigation began by plotting the shear storage modulus (G′) of the composites and observing the slopes of the curves in the range of the rubbery area, which were assumed to follow a straight‐line equation. Then, we completed the investigation by developing and introducing a temperature‐dependent storage modulus model in the rubbery area for describing the storage modulus of such filler‐dispersed PEG/inorganic composites, to yield the degradation rates of the composites. The new model includes parameters k1 and C that are associated with the degradation rate and the amount of a filler, respectively. The model shows a satisfactory agreement with the experimental data of G′ in the rubbery area, being parameter k1 is associated with a linear degradation rate.

Spectral Aerosol Optical Depth Retrievals by Ground-Based Fourier Transform Infrared Spectrometry

Aerosol Optical Depth (AOD) and the Ångström Exponent (AE) have been calculated in the near infrared (NIR) and short-wave infrared (SWIR) spectral regions over a period of one year (May 2019–May 2020) at the high-mountain Izaña Observatory (IZO) from Fourier Transform Infrared (FTIR) solar spectra. The high-resolution FTIR measurements were carried out coincidentally with Cimel CE318-T photometric observations in the framework of the Aerosol Robotic Network (AERONET). A spectral FTIR AOD was generated using two different approaches: by means of the selection of seven narrow FTIR micro-windows (centred at 1020.90, 1238.25, 1558.25, 1636.00, 2133.40, 2192.00, and 2314.20 nm) with negligible atmospheric gaseous absorption, and by using the CE318-AERONET’s response function in the near-coincident bands (1020 nm and 1640 nm) to degrade the high-resolution FTIR spectra. The FTIR system was absolutely calibrated by means of a continuous Langley–Plot analysis over the 1-year period. An important temporal drift of the calibration constant was observed as a result of the environmental exposure of the FTIR’s external optical mirrors (linear degradation rate up to 1.75% month−1). The cross-validation of AERONET-FTIR databases documents an excellent agreement between both AOD products, with mean AOD differences below 0.004 and root-mean-squared errors below 0.006. A rather similar agreement was also found between AERONET and FTIR convolved bands, corroborating the suitability of low-resolution sunphotometers to retrieve high-quality AOD data in the NIR and SWIR domains. In addition, these results demonstrate that the methodology developed here is suitable to be applied to other FTIR spectrometers, such as portable and low-resolution FTIR instruments with a potentially higher spatial coverage. The spectral AOD dependence for the seven FTIR micro-windows have been also examined, observing a spectrally flat AOD behaviour for mineral dust particles (the typical atmospheric aerosols presented at IZO). A mean AE value of 0.53 ± 0.08 for pure mineral dust in the 1020–2314 nm spectral range was retrieved in this paper. A subsequent cross-validation with the MOPSMAP (Modeled optical properties of ensembles of aerosol particles) package has ensured the reliability of the FTIR dataset, with AE values between 0.36 to 0.60 for a typical mineral dust content at IZO of 100 cm−3 and water-soluble particle (WASO) content ranging from 600 to 6000 cm−3. The new database generated in this study is believed to be the first long-term time series (1-year) of aerosol properties generated consistently in the NIR and SWIR ranges from ground-based FTIR spectrometry. As a consequence, the results presented here provide a very promising tool for the validation and subsequent improvement of satellite aerosol products as well as enhance the sensitivity to large particles of the existing databases, required to improve the estimation of the aerosols’ radiative effect on climate.

Photovoltaic cleaning frequency optimization under different degradation rate patterns

Dust accumulation significantly affects the performance of photovoltaic modules and its impact can be mitigated by various cleaning methods. Optimizing the cleaning frequency is essential to minimize the soiling losses and, at the same time, the costs. However, the effectiveness of cleaning lowers with time because of the reduced energy yield due to degradation. Additionally, economic factors such as the escalation in electricity price and inflation can compound or counterbalance the effect of degradation on the soiling mitigation profits. The present study analyzes the impact of degradation, escalation in electricity price and inflation on the revenues and costs of cleanings and proposes a methodology to maximize the profits of soiling mitigation of any system. The energy performance and soiling losses of a 1 MW system installed in southern Spain were analyzed and integrated with theoretical linear and nonlinear degradation rate patterns. The Levelized Cost of Energy and Net Present Value were used as criteria to identify the optimum cleaning strategies. The results showed that the two metrics convey distinct cleaning recommendations, as they are influenced by different factors. For the given site, despite the degradation effects, the optimum cleaning frequency is found to increase with time of operation.

The Relationship between Entropy and the Reliability Function in Application of Physical and Statistical Approach to Nanosystems

The paper considers application of the physical and statistical approach to the issue of nanosystems reliability. A general method of solving the main equation in this approach is suggested and the solution in quadratures is obtained in one-dimensional stationary case. It is used to study the behaviour of entropy and the reliability function under certain assumptions. The cases of constant, linear, and quadratic degradation rates are analysed. In the first two cases the results correspond to physical intuition while in the last case (quadratic rate) the formal solution demonstrates counterintuitive behaviour. Numerical correlations between the distribution entropy dynamics and the reliability function are given.

Biocatalytic Degradation Efficiency of Postconsumer Polyethylene Terephthalate Packaging Determined by Their Polymer Microstructures.

Polyethylene terephthalate (PET) is the most important mass‐produced thermoplastic polyester used as a packaging material. Recently, thermophilic polyester hydrolases such as TfCut2 from Thermobifida fusca have emerged as promising biocatalysts for an eco‐friendly PET recycling process. In this study, postconsumer PET food packaging containers are treated with TfCut2 and show weight losses of more than 50% after 96 h of incubation at 70 °C. Differential scanning calorimetry analysis indicates that the high linear degradation rates observed in the first 72 h of incubation is due to the high hydrolysis susceptibility of the mobile amorphous fraction (MAF) of PET. The physical aging process of PET occurring at 70 °C is shown to gradually convert MAF to polymer microstructures with limited accessibility to enzymatic hydrolysis. Analysis of the chain‐length distribution of degraded PET by nuclear magnetic resonance spectroscopy reveals that MAF is rapidly hydrolyzed via a combinatorial exo‐ and endo‐type degradation mechanism whereas the remaining PET microstructures are slowly degraded only by endo‐type chain scission causing no detectable weight loss. Hence, efficient thermostable biocatalysts are required to overcome the competitive physical aging process for the complete degradation of postconsumer PET materials close to the glass transition temperature of PET.

Impacts of Current Rates on the Degradation Behaviors of Lithium-Ion Batteries under Over-Discharge Conditions

With the popularity of lithium-ion batteries, especially the widespread use of battery packs, the phenomenon of over-discharge may be common. To gain a better insight into over-discharge behavior, an experimental study is carried out in the present work to investigate the impact of current rate, i.e. cycle rate, charge rate and discharge rate on the degradation behavior of a lithium-ion battery under over-discharge condition. It is found that battery capacity experiences obvious degradation during over-discharge cycling, while the current rate is shown to have little impact on the degraded capacity within a unit cycle. Therefore, nearly all the over-discharged batteries present a linear degradation rate as the over-discharge cycling proceeds, 0.05%/cycle. The impact of current rate on the degradation is revealed by influencing the cycle time, whereby a high current rate usually brings about a shorter cycle time and further accelerates the degradation. Among, the cycle rate is exhibited to have the largest impact on the degradation of the over-discharged battery, followed by the discharge rate and charge rate. Moreover, the degradation behaviors of these batteries are demonstrated through the evolution of battery surface temperature, charge/discharge voltage and internal resistance.

A Comparative Investigation on Outdoor and Laboratory Test of the Degradation Rates for Different Types of Photovoltaic Modules with Different Exposure Periods

Understanding field failure and degradation modes in solar photovoltaic (PV) modules is very important for various reasons especially for this widely used technology. The University of Applied Sciences Ostwestfalen-Lippe in Höxter owns photovoltaic-modules of different cell types, sizes and operation periods in German weather conditions. This paper presents a detailed degradation investigation and performance parameters analysis for chosen samples of polycrystalline, monocrystalline and thin film modules in the laboratory and outdoor test conditions after 10 years of exposure. The obtained measurements were standardized and then compared with the warranted values of the manufacturer’s datasheets for each module type. The real outdoor measurements for the larger units show that the maximum power Pmax after 10 years of exposure for polycrystalline, monocrystalline and amorphous thin film modules had declined by: 8.47%, 37.67%, and 19.05% respectively, which translates to an annual linear degradation rates of 0.652%, 3.67%, and 1.465% for each type respectively. While the maximum power output of the smaller units had declined by 19.05%, 19.36%, and 21.75% for polycrystalline, monocrystalline and amorphous thin film modules respectively, which also translated to annual linear degradation rates of 1.48%, 1.67%, and 0.6% for each type respectively. On the other hand, the laboratory tests for these modules show that there is a clear variation with the obtained outdoor results, where the Pmax for the same larger units had declined by 39.6%, 57.4%, and 82.5% for polycrystalline, monocrystalline and thin film modules respectively, While the Pmax output of smaller units had declined by 51.2%, 39.38%, and 9.39% for polycrystalline, monocrystalline and thin film modules respectively, The comparison of the efficiency and fill factor parameters for the obtained results with the manufacturer’s data shows that the outdoor measurements introduce close results than the laboratory results. The discoloration of the encapsulant is the most frequently occurring visually observable defects on the modules.

Ageing and degradation in solar photovoltaic modules installed in northern Ghana

Understanding field failure and degradation modes in solar photovoltaic (PV) modules is important for various actors along the value chain. This paper presents results from field studies on performance degradation in twenty-two mono-crystalline silicon modules exposed for 16 years in three communities in the northern part of Ghana, prior to electricity grid extension. The results show, that, maximum power of the modules (Pmax) had declined by 18.2–38.8% (median – 24.6%) over the period, which translates to an annual linear degradation rate of 1.54%. The losses in module power output are dominated by losses in short-circuit current (Isc) and fill factor (FF), which are 0.75%/year and 0.54%/year respectively (median values). Discolouration of the encapsulant and degradation of the junction-box adhesive were the most frequently occurring visually observable defects on the modules.

Optimization of ESC Performance for Co-Electrolysis Operation

Production of synthetic hydrocarbon fuels from co-electrolysis of steam/CO2 mixtures using renewable energy has been already presented as a promising solution to diminish problems from energy and environmental point of view. The possibility to recycle CO2 into chemicals and value-added fuels helps to reduce the accumulation of atmospheric CO2 and realize the carbon neutral cycling of fuels. The solid oxide cells have great potential within this field and can been used for converting of steam/CO2 mixtures to the syngas for following Fischer-Tropsch conversion by excessive electricity at high temperatures above 750°C. It presents an opportunity for recycling of CO2 into a useful liquid fuel. While the co-electrolysis is more complicated than steam electrolysis, the electrochemical performance electrolyte supported cell with G3 electrodes were investigated over a wide range of operating conditions (SOEC as well as SOFC), varying the ratio of H2O/H2 and CO2/CO, the operating temperature (750–850°C) and current. Comparable activity for operation in the SOEC and SOFC modes was observed and electrodes exhibited similar polarization losses during operation in steam electrolysis and steam/CO2 co-electrolysis. During electrolysis and co-electrolysis operation anomalous increase of polarization resistance during first 50 h on both sides has been observed. The raise of polarization resistance was reversible and diminished after switching to SOFC operation mode. Operating temperature variation during co-electrolysis helped to get insight into relationship between observed performance and electrodes microstructure. Additional experiments and electrochemical testing combined with detailed microstructural analysis have been carried out to better understand the observed phenomena. Obtained performance for single cell has been reproduced also on stack level. To improve electrochemical performance the additional modification of both electrodes, especially of their microstructure, is done. Durability of solid oxide electrolyte supported electrolysis cells (standard G3 and modified) tested at different current densities (from -300 mA/cm2 up to -500 mA/cm2) for high temperature steam or steam/CO2 electrolysis is investigated under stack relevant operating conditions (up to 5,000 h) and showed power degradation rate of ca. 1%/1,000 h for steam electrolysis. The changes in polarization resistance of single cells under different operating conditions as well as during durability tests are performed and discussed on basis of analysis of impedance spectra. Microstructure observations at the interfaces in both electrodes were carried out after long-term tests to understand the reasons for degradation. The cell with optimized fuel and air electrodes was successfully tested for ~2400 hours at 803°C under co-electrolysis conditions (H2/CO2/H2O/CO mixture as fuel, j = -400 mA/cm2). The calculated linear power degradation rate over all durability test (~2400 h) is about 0.4%/1,000 h. Further development of ESC for co-electrolysis and its verification in stack is topic of ongoing activities. Fig. 1 Power density vs. time for long-term test with modified G3 cell based on 165µm 10Sc1CeSZ electrolyte at 803°C in air : (H2/CO2/H2O/CO) mixture (j = - 400 mA/cm2). As reference point the power density in SOFC mode (air : H2/H2O) mixture (j = 300 mA/cm2) is also represented. Figure 1

Optimization of ESC Performance for Co-Electrolysis Operation

Production of synthetic hydrocarbon fuels from co-electrolysis of steam/CO2 mixtures using renewable energy has been already presented as a promising solution to diminish environmental problems. The possibility to recycle CO2 into chemicals and value-added fuels helps to reduce the accumulation of atmospheric CO2 and realize the carbon neutral cycling of fuels. While the co-electrolysis is more complicated than steam electrolysis, the electrochemical performance of electrolyte supported cell with LSMM’/ScSZ and Ni/GDC electrodes were investigated over a wide range of operating conditions (SOEC as well as SOFC), varying the ratio of H2O:H2 and CO2:CO, the operating temperature (750–850°C) and current. The modified G3´´ cell with optimized fuel and air electrodes was successfully tested for ~2400 hours at 803°C under co-electrolysis conditions (H2/H2O/CO2/CO mixture as fuel, j = -400 mA/cm2). The calculated linear power degradation rate over all durability test (~2400 h) is about 0.4%/1,000 h.

Mechanical, structural and dissolution properties of heat treated thin-film phosphate based glasses

Here we show the deposition of 2.7μm thick phosphate based glass films produced by magnetron sputtering, followed by post heat treatments at 500°C. Variations in degradation properties pre and post heat treatment were attributed to the formation of Hematite crystals within a glass matrix, iron oxidation and the depletion of hydrophilic P-O-P bonds within the surface layer. As deposited and heat treated coatings showed interfacial tensile adhesion in excess of 73.6MPa; which surpassed ISO and FDA requirements for HA coatings. Scratch testing of coatings on polished substrates revealed brittle failure mechanisms, amplified due to heat treatment and interfacial failure occurring from 2.3 to 5.0N. Coatings that were deposited onto sandblasted substrates to mimic commercial implant surfaces, did not suffer from tensile cracking or trackside delamination showing substantial interfacial improvements to between 8.6 and 11.3N. An exponential dissolution rate was observed from 0 to 2h for as deposited coatings, which was eliminated via heat treatment. From 2 to 24h ion release rates ordered P>Na>Mg>Ca>Fe whilst all coatings exhibited linear degradation rates, which reduced by factors of 2.4–3.0 following heat treatments.