The aim of this work is to analyse the price of renewable hydrogen production in a stand-alone photovoltaic plant. The energy studied herein is generated in a photovoltaic plant. Two dependent ...parameters that directly affect the price of hydrogen are analysed in detail: the price of the electricity needed to carry out its production process, and the utilisation rate of the connected electrolyser. To this end, a photovoltaic plant is dimensioned with the help of the PVsyst simulator, by means of which the hourly generation curves are obtained. A variable power electrolyser is employed to study its performance according to these photovoltaic production curves. Furthermore, the system is studied by introducing batteries capable of storing the energy left over during the day and of supplying the electrolyser when the photovoltaic power is insufficient. The selling prices calculated in the various scenarios in terms of efficiency and electricity cost are calculated. The significance of a combined analysis of these two parameters and their real impact on the final price of hydrogen is also analysed. This article aims to analyse the price of green hydrogen produced through an isolated photovoltaic system. When the hourly production is evaluated, differences are found with respect to global production that justify the importance of the variables analysed herein, which could not be determined in any other way. The behaviour of isolated production and its effects are discussed.
•It is technically and economically feasible to produce hydrogen via solar energy.•The intermittent nature of the solar source penalises hydrogen production.•Hydrogen price depends on electricity and utilisation factor of the electrolyser.•Batteries improve overall performance but penalize the system's economic balance.
Over the last twenty years, there has been a resurgent research interest in direct borohydride fuel cells (DBFCs) highlighting the fundamental aspects that need to be addressed to achieve their ...optimal performance. The main problem is the hydrolysis of borohydride ions, which generates hydrogen, decreases the energy efficiency and reduces the power density. The electrons released during borohydride oxidation, the cell potential difference and the power output are strongly influenced by the choice of anode and cathode, including three-dimensional and nanostructured electrodes, the electrolyte composition and the operating conditions. Extensive investigations on various anodic electrocatalysts and their effect on the oxidation and hydrolysis have been quantified as well as the cathode catalyst and its influence on the overall fuel cell performance. Computational methods such as ab-initio and physical modelling could play prominent roles in the design and fundamental characterisation of DBFCs but are currently underused and only small number of studies in well-defined materials such as Pt (111) or Au (111) exist. Cell design and configuration have also been considered but the basic requirement to engineer a selective catalyst able to suppress the hydrogen evolution and the elucidation of the mechanism of borohydride ion oxidation, remain.
► We review aspects of the borohydride fuel cell that have not been revised previously. ► Aspects of the borohydride hydrolysis, modelling, simulation and recycling are discussed. ► Future trends and recommendations to improve the technology are suggested
Iron-based aqueous batteries, such as the iron-air and nickel-iron chemistries, are limited by passivation and hydrogen evolution at the iron anode, especially at high current densities. In this ...paper, strategies to minimise these issues are investigated with iron electrodes composed of 20–50 nm Fe2O3 nanoparticles produced by the Adams and Oxalate methods. The strategies include ball milling the Fe2O3 with Ketjenblack carbon to improve conductivity, addition of bismuth sulphide to the electrode and 1-octanethiol to the electrolyte, and addition of potassium carbonate as a pore-forming agent. The ratio of Fe/C in the electrode and the 1-octanethiol additive have the greatest impact on the electrode capacity. The Fe/C ratio should be below 2.0 to ensure conductivity of the discharged electrode. The presence of 1-octanethiol can protect the electrodes from passivation during discharge; at very high 2C discharge rates adding 1-octanethiol increases the electrode specific capacity from 17 to 171 mAh/gFe. The synthesis method and use of pore former do not have a significant effect on the capacity. In all electrodes, the Fe2O3 nanoparticles are in the same crystalline phase after cycling and do not undergo significant crystal growth and passivation, demonstrating the stability and suitability of these materials for iron-based batteries.
3D image of experimental configuration (iron electrode versus a nickel counter electrode), with SEM image of electrode surface, and polarisation curves showing the discharge potential of the electrode in 6 mol dm−3 electrolyte with and without the presence of 0.1 mol dm−3 1-octanethiol additive. Display omitted
•Effect of Fe/C ratio, synthesis method, and additives on Fe2O3 electrodes.•The best ratio was Fe/C = 2.0, allowing a compact, dense electrode.•Synthesis methods gave capacities >900 mAhg−1Fe higher than previously reported.•Electrodes showed none of the structural changes caused by passivation.•1-octanethiol additive increased the capacity more than tenfold at the 2C rate.
Although interest in redox flow batteries (RFBs) for energy storage has grown over the last few years, implementation of RFB technology has been slow and challenging. Recent developments in ...3D-printing of materials enable a transforming technology for fast, reproducible and documented cell manufacture. This technology can give an improved engineering approach to cell design and fabrication, needed to fulfil requirements for lower cost, longer lifetime hardware capable of efficient reliable performance. It can also be used to implement a flexible design methodology to suit various scales of operation, usually important during RFB development. In the case of electrolyte flow features, these needs are especially well met by fast prototyping strategies. This paper demonstrates the importance of 3D-printing for the realization of a hybrid zinc-cerium RFB laboratory cell. The design and fabrication process is described and the benefits offered by 3D-printing are considered. Finally, further opportunities offered by this approach to RFB manufacture and research are highlighted.
In a 100% renewable energy scenario, power generation fluctuates, requiring management and control of this generation. Storage is presented as a solution to regulate production discontinuity. In ...particular, seasonal storage can compensate for long-term fluctuations and serve as a necessary complement to short-term storage management. Due to the potential role of hydrogen in the decarbonization of energy production systems, this research attempts to analyse the levelized cost of storage (LCOS) of this energy carrier as a solution to long-term electricity requirements. The research focuses on the analysis of the total Power-to-Power (P2P) process cost, all factors affecting the input of electricity up to the output of electricity after the conversion of the hydrogen are considered. A transformation of the surplus electricity to hydrogen through a PEM electrolyzer is proposed in this paper. This hydrogen would be stored seasonally in salt caverns. Finally, a gas-to-energy transformation using gas turbines or fuel cells is contemplated. The analysis presents highly competitive results in terms of cost, demonstrating the system's competitiveness and potential: the turbine powered by 100% hydrogen solution appears to be more cost effective than the fuel cell solution: 0.207€/kWh and 0.284€/kWh respectively. Hydrogen storage presents itself as the most cost-effective long-term alternative in the near future, even better than pumped hydro, compressed air or batteries.
•LCOS: Levelized Costs of Storage for a large-scale and long-term system.•The use of hydrogen as an energy carrier to store electrical energy from renewable sources at large scale.•Long-term storage of hydrogen in salt caverns.•Transformation of stored hydrogen into electricity through turbine and fuel cells.
The present study evaluated the effects of web‐based training on Spanish pre‐service and in‐service teacher knowledge and implicit beliefs on learning to write. A sample of pre‐service teachers and ...in‐service teachers from Mexico, Guatemala, Ecuador, Colombia, and Spain participated in the online course. Findings suggest that teachers may improve their knowledge of transcription skills (i.e., handwriting/typing, spelling), text production, and strategies for composing as necessary components of quality writing instruction. Effects were also found on the teachers' implicit beliefs. Finally, both pre‐service and in‐service teachers positively rated the online course received.
Lay Description
What is currently known about the subject
Teaching children how to write demands a high degree of specialization.
The benefits of web‐based training to professional development have been well‐documented in the literature.
Preparing of pre‐service and in‐service teachers through an online context is limited in the field of writing.
Teachers' knowledge, satisfaction, and beliefs have been commonly used as outcome measures to define high‐quality e‐learning instruction.
What this paper adds
A Spanish web‐based training was developed to improve professional development in writing instruction.
The Trazo web‐based training changed teacher's beliefs about learning to write.
Teachers learned more about the essential component of the writing process.
Teachers' rating of the training and support website was highly positive.
Implications for practitioners
Web‐based training allows teachers to learn at their own pace.
Teachers can improve their knowledge from virtually at any geographic location with an Internet connection.
The Trazo web‐based training offers research‐based knowledge to Spanish‐speaking teachers.
Abstract Aim This work describes the human papillomavirus (HPV) prevalence and the HPV type distribution in a large series of vaginal intraepithelial neoplasia (VAIN) grades 2/3 and vaginal cancer ...worldwide. Methods We analysed 189 VAIN 2/3 and 408 invasive vaginal cancer cases collected from 31 countries from 1986 to 2011. After histopathological evaluation of sectioned formalin-fixed paraffin-embedded samples, HPV DNA detection and typing was performed using the SPF-10/DNA enzyme immunoassay (DEIA)/LiPA25 system (version 1). A subset of 146 vaginal cancers was tested for p16INK4a expression, a cellular surrogate marker for HPV transformation. Prevalence ratios were estimated using multivariate Poisson regression with robust variance. Results HPV DNA was detected in 74% (95% confidence interval (CI): 70–78%) of invasive cancers and in 96% (95% CI: 92–98%) of VAIN 2/3. Among cancers, the highest detection rates were observed in warty-basaloid subtype of squamous cell carcinomas, and in younger ages. Concerning the type-specific distribution, HPV16 was the most frequently type detected in both precancerous and cancerous lesions (59%). p16INK4a overexpression was found in 87% of HPV DNA positive vaginal cancer cases. Conclusions HPV was identified in a large proportion of invasive vaginal cancers and in almost all VAIN 2/3. HPV16 was the most common type detected. A large impact in the reduction of the burden of vaginal neoplastic lesions is expected among vaccinated cohorts.
This study aimed to explore the utility of a math curriculum‐based measurement (M‐CBM) to identify Spanish‐speaking students at risk of math failure in third grade. The M‐CBM includes a set of number ...sense based single and composite screening for third graders. The study's sample included 236 Spanish third‐graders from the Canary Islands tested in the fall, winter, and spring. Reliability and validity of all measures were explored, finding adequate indexes. Receiver operating characteristics (ROC) and Hierarchical linear modeling analyses were conducted for both single and composite measures. All the measures revealed an area under the ROC curve values at or above 0.84, the composite measures ranging from 0.86 to 0.94. When comparing the single and composite measures, the latter revealed a higher classification accuracy for identifying students at risk in third grade than quantity discrimination, missing number, and multi‐digit computation measures, but not for single‐digit computation and place value measures. Finally, significant differences were found between at‐risk and non‐risk students learning growth throughout the school year.
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