An Evaluation of the 8051 Microcontroller

With the increasing availability and use of 16-bit microprocessors, the 16-bit data bus and is becoming more prevalent. However, many peripheral devices such as printers and tape/disk drives still require an 8-bit data bus for their interface. This paper will explain how an Intel 8051 microcontroller may be used to interface a 16-bit data bus to a peripheral requiring an 8-bit data bus. A FIFO is used to buffer data from a 16-bit processor so that efficient use of processing time is maintained. The 8051 is used to control the peripheral and data transfer

Capacity balancing for vanadium redox flow batteries through continuous and dynamic electrolyte overflow

The vanadium crossover through the membrane can have a significant impact on the capacity of the vanadium redox flow battery (VFB) over long-term charge–discharge cycling. The different vanadium ions move unsymmetrically through the membrane and this leads to a build-up of vanadium ions in one half-cell with a corresponding decrease in the other. In this paper, a dynamic model is developed based on different crossover mechanisms (diffusion, migration and electro osmosis) for each of the four vanadium ions, water and protons in the electrolytes. With a simple to use approach, basic mass transport theory is used to simulate the transfer of vanadium ions in the battery. The model is validated with own measurements and can therefore predict the battery capacity as a function of time. This is used to analyse the battery performance by applying an overflow from one half-cell to the other. Different constant overflow rates were analysed with regard to an impact of the performance and electrolyte stability. It was observed that a continuous overflow increases the capacity significantly but that the electrolyte stability plays an essential role using a membrane with a big vanadium crossover. Even with a good performance, a complete remixing of the tanks is necessary to prevent electrolyte precipitations. Therefore, a dynamic overflow was determined in such a way that the capacity of the battery is maximised while the electrolytes remain stable for 200 cycles

Water use of Prosopis juliflora and its impacts on catchment water budget and rural livelihoods in Afar Region, Ethiopia

CITATION: Shiferaw, H. et al. 2021. Water use of Prosopis juliflora and its impacts on catchment water budget and rural livelihoods in Afar Region, Ethiopia. Scientific Reports, 11:2688,doi:10.1038/s41598-021-81776-6.The original publication is available at https://www.nature.comDense impenetrable thickets of invasive trees and shrubs compete with other water users and thus disrupt ecosystem functioning and services. This study assessed water use by the evergreen Prosopis juliflora, one of the dominant invasive tree species in semi-arid and arid ecosystems in the tropical regions of Eastern Africa. The objectives of the study were to (1) analyze the seasonal water use patterns of P. juliflora in various locations in Afar Region, Ethiopia, (2) up-scale the water use from individual tree transpiration and stand evapotranspiration (ET) to the entire invaded area, and 3) estimate the monetary value of water lost due to the invasion. The sap flow rates of individual P. juliflora trees were measured using the heat ratio method while stand ET was quantified using the eddy covariance method. Transpiration by individual trees ranged from 1–36 L/day, with an average of 7 L of water per tree per day. The daily average transpiration of a Prosopis tree was about 3.4 (± 0.5) mm and the daily average ET of a dense Prosopis stand was about 3.7 (± 1.6) mm. Using a fractional cover map of P. juliflora (over an area of 1.18 million ha), water use of P. juliflora in Afar Region was estimated to be approximately 3.1–3.3 billion m3/yr. This volume of water would be sufficient to irrigate about 460,000 ha of cotton or 330,000 ha of sugar cane, the main crops in the area, which would generate an estimated net benefit of approximately US$320 million and US$ 470 million per growing season from cotton and sugarcane, respectively. Hence, P. juliflora invasion in the Afar Region has serious impacts on water availability and on the provision of other ecosystem services and ultimately on rural livelihoods.https://www.nature.com/articles/s41598-021-81776-6Publisher's versio

Correlation of gene expression and protein production rate - a system wide study

<p>Abstract</p> <p>Background</p> <p>Growth rate is a major determinant of intracellular function. However its effects can only be properly dissected with technically demanding chemostat cultivations in which it can be controlled. Recent work on <it>Saccharomyces cerevisiae </it>chemostat cultivations provided the first analysis on genome wide effects of growth rate. In this work we study the filamentous fungus <it>Trichoderma reesei </it>(<it>Hypocrea jecorina</it>) that is an industrial protein production host known for its exceptional protein secretion capability. Interestingly, it exhibits a low growth rate protein production phenotype.</p> <p>Results</p> <p>We have used transcriptomics and proteomics to study the effect of growth rate and cell density on protein production in chemostat cultivations of <it>T. reesei</it>. Use of chemostat allowed control of growth rate and exact estimation of the extracellular specific protein production rate (SPPR). We find that major biosynthetic activities are all negatively correlated with SPPR. We also find that expression of many genes of secreted proteins and secondary metabolism, as well as various lineage specific, mostly unknown genes are positively correlated with SPPR. Finally, we enumerate possible regulators and regulatory mechanisms, arising from the data, for this response.</p> <p>Conclusions</p> <p>Based on these results it appears that in low growth rate protein production energy is very efficiently used primarly for protein production. Also, we propose that flux through early glycolysis or the TCA cycle is a more fundamental determining factor than growth rate for low growth rate protein production and we propose a novel eukaryotic response to this i.e. the lineage specific response (LSR).</p

Modelling of redox flow battery electrode processes at a range of length scales : a review

In this article, the different approaches reported in the literature for modelling electrode processes in redox flow batteries (RFBs) are reviewed. RFB models vary widely in terms of computational complexity, research scalability and accuracy of predictions. Development of RFB models have been quite slow in the past, but in recent years researchers have reported on a range of modelling approaches for RFB system optimisation. Flow and transport processes, and their influence on electron transfer kinetics, play an important role in the performance of RFBs. Macro-scale modelling, typically based on a continuum approach for porous electrode modelling, have been used to investigate current distribution, to optimise cell design and to support techno-economic analyses. Microscale models have also been developed to investigate the transport properties within porous electrode materials. These microscale models exploit experimental tomographic techniques to characterise three-dimensional structures of different electrode materials. New insights into the effect of the electrode structure on transport processes are being provided from these new approaches. Modelling flow, transport, electrical and electrochemical processes within the electrode structure is a developing area of research, and there are significant variations in the model requirements for different redox systems, in particular for multiphase chemistries (gas–liquid, solid–liquid, etc.) and for aqueous and non-aqueous solvents. Further development is essential to better understand the kinetic and mass transport phenomena in the porous electrodes, and multiscale approaches are also needed to enable optimisation across the relevent length scales

Preparation of electrolyte for vanadium redox‐flow batteries based on vanadium pentoxide

The vanadium redox‐flow battery is a promising technology for stationary energy storage. A reduction in system costs is essential for competitiveness with other chemical energy storage systems. A large share of costs is currently attributed to the electrolyte, which can be significantly reduced by production based on vanadium pentoxide (V2O5). In this study, the dissolution kinetics of V2O5 in diluted sulfuric acid and commercial vanadium electrolyte (VE) is determined. The low solubility of V2O5 in sulfuric acid can be overcome by partially using VE with a state of charge of −50% as solvent. In this way, a complete dissolution of V2O5 is possible within ≈10 min to achieve the desired vanadium concentration of 1.6 mol L−1. Moreover, the electrochemical reduction of an electrolyte containing VO2+ coupled with the oxygen evolution reaction at the anode is investigated. For these consecutive steps, an electrical energy demand of 1.69 kWh kg−1 is required to reach a state of charge of −50%. Finally, both processes are integrated into a plant concept for continuous electrolyte production

Modellierung der Crossover-Prozesse und Entwicklung von Kapazitatsausgleichsstrategien zur Betriebsoptimierung von Vanadium-Redox-Flow-Batterien

Die Vanadium-Redox-Flow-Batterie ist ein vielversprechendes Energiespeichersystem, das eine wichtige Komponente im Rahmen der Energiewende sein kann. Im Zuge dieser nimmt die Stromproduktion aus Wind- und Solarenergie zu. Die Verfügbarkeit dieser sogenannten erneuerbaren Energien ist wetterabhängig. Hierdurch ist eine stabile und an den Stromverbrauch orientierte Versorgung, ohne eine Veränderung in der derzeitigen Stromnetzstruktur, nicht realisierbar. Die Stromerzeugung ist außerdem von der Netzkapazität abhängig. Diese kann durch einen Netzausbau vergrößert werden, um die Schwankungen abpuffern zu können, was jedoch mit hohen Kosten und einem großen Aufwand verbunden ist. Um die Aufnahmefähigkeit der Netze für erneuerbare Energien zu erhöhen, ist außerdem der Einsatz von Energiespeichern möglich. Diese sollen eine große Speicherkapazität, eine kurze Ansprechzeit und geringe Verluste in der Speicherung und Abgabe aufweisen. Durch ihren Aufbau weist die Vanadium-Redox-Flow-Batterie Vorteile als stationärer Speicher gegenüber anderen Speichertechnologien auf. So sind die Speicherkapazität und Leistung unabhängig voneinander skalierbar und es findet lediglich eine geringe Selbstentladung im Standby-Betrieb statt. Im Betrieb der Batterie kommt es jedoch durch eine Kreuzkontamination von Vanadium-Ionen durch die Membran zu Verlusten. Dieser als Crossover bezeichnete Prozess führt zur Selbstentladung der jeweils anderen Halbzelle und zur kontinuierlichen Abnahme der Batteriekapazität, was einen sinnvollen Einsatz als Energiespeicher einschränkt. Um diese Kapazitätsabnahme zu verringern, ist sowohl die Entwicklung besserer Separatoren (geringerer Widerstand, höhere Selektivität) als auch die Untersuchung der Crossover-Prozesse, was dem Fokus dieser Arbeit entspricht, erforderlich. Für die im Zuge dieser Arbeit durchgeführten Studien werden die Parameter elektrischer Widerstand und Vanadium-Diffusionskoeffizienten experimentell bestimmt und zur Entwicklung eines mathematischen Modells zur Beschreibung der Crossover-Prozesse verwendet. Um der durch den Crossover resultierenden Abnahme der Kapazität entgegenzuwirken, werden in dieser Arbeit weiterhin experimentell und mathematisch verschiedene Kapazitätsausgleichsstrategien entwickelt und analysiert. Der elektrische Widerstand unterschiedlicher Separatoren wird im Zuge dieser Arbeit unter Variation von Stromdichte und Ladungszustand untersucht. Die Messungen erfolgen in situ mit selbst hergestellten Festphasenpotentialmesssonden, mit denen mittels elektrochemischer Impedanzspektroskopie der elektrische Widerstand ermittelt wird. Die Vanadium- Diffusionskoeffizienten werden unter betriebsnahen, aber stromlosen Bedingungen für Nafion™- Membranen unterschiedlicher Dicke bestimmt. Mithilfe der ermitteltenWerte des elektrischen Widerstands und der Vanadium-Diffusionskoeffizienten wird ein mathematisches Modell für die Nafion™-Membran N117 entwickelt, das die Transportvorgänge durch die Membran beschreibt. Als Transportmechanismen wirken Diffusion, Migration und Konvektion. Messungen am eigenen Prüfstand dienen hierbei der Modellvalidierung. In das validierte Modell wird anschließend ein Elektrolytüberlauf von dem einen in den anderen Tank implementiert, um eine Methode zum Kapazitätsausgleich zu entwickeln. Eine weitere Kapazitätsausgleichsmethode wird experimentell mit dem porösen Separator FF40 von Amer-Sil untersucht. Hierbei wird durch Änderungen von Betriebsparametern der Differenzdruck am Separator verändert, sodass der Crossover beeinflusst wird. Es hat sich gezeigt, dass mit beiden Methoden die Kapazitätsabnahme der Batterie verringert und dadurch ein effizienterer Betrieb ermöglicht werden kann. Es wird außerdem deutlich, dass sich je nach Separator das Crossover-Verhalten unterscheidet und aus diesem Grund unterschiedliche Methoden zum Kapazitätsausgleich zielführend sein können.The vanadium redox flow battery is a promising energy storage system that can be an important part of the "Energiewende". As a result, electricity production from wind and solar energy is increasing. The availability of these so-called renewable energies is weather dependent. As a result, a stable supply based on electricity consumption is not feasible without a change in the grid structure. Furthermore, electricity generation is also dependent on grid capacity. This can be increased by enlarging the grid network in order to buffer the fluctuations. However, this involves high costs and a significant outlay. For increasing the grid’s capacity in order to handle renewable energies, the use of energy storage systems is a possible option. These shall have a large storage capacity, a short response time and low losses in storage and supply. Due to its setup, the vanadium redox flow battery has advantages as stationary storage system compared to other storage technologies. Thus, storage capacity and power are independently scalable and there is only a low self-discharge in standby mode. During battery operation, however, losses occur due to crossover of vanadium ions through the membrane. This process leads to self-discharge of the respectively other half cell and to a continuous decrease of the battery capacity, which limits its reasonable use as energy storage system. In order to reduce this capacity decrease, both, the development of better separators (lower resistance, higher selectivity) and the studies of crossover processes, which is the focus of this work, are necessary. In the studies of this thesis, the parameters electrical resistance and vanadium diffusion coefficients are determined experimentally and used to develop a mathematical model describing the crossover processes. In order to reduce the decrease in capacity caused by the crossover, further different capacity balancing strategies are developed and analysed experimentally and mathematically in this work. The electrical resistance of different separators is analysed in the present work under variation of current density and state of charge. The measurements are carried out in situ with self-made solid phase potential measuring probes, with which the electrical resistance is determined by electrochemical impedance spectroscopy. The vanadium diffusion coefficients are determined under operating but currentless conditions for Nafion™ membranes of different thickness. A mathematical model for the Nafion™ membrane N117, which describes the transport processes through the membrane, is developed with the determined values of the electrical resistance and the vanadium diffusion coefficients. Diffusion, migration and convection are the crossover transport mechanisms. Measurements on an own test facility are used for model validation. An electrolyte overflow from one tank to the other is then implemented in the validated model to develop a method for capacity balancing. A further capacity balancing method is being experimentally analysed with the porous separator FF40 from Amer-Sil. Here, changes in operating parameters cause a change in differential pressure at the separator, thus influencing the crossover. It has been found that both methods can reduce the capacity decrease of the battery and thus enable a more efficient operation. Furthermore, it can be seen that the cross-over behaviour differs depending on the separator and for this reason different methods of capacity balancing can be suitable