1,721,108 research outputs found
Data repository for ‘Predicting battery end of life from solar off-grid system field data using machine learning’
No full textThis dataset was generated by 1027 lead-acid batteries from BBOXX Ltd., each with nominal voltage 12 V (internally comprising 6 cells in series), nominal capacity 20 Ah, and attached to a 50 Wp photovoltaic panel. These systems are used for lighting, phone charging and small appliances, and are located across sub-Saharan Africa. Each battery was in use for 400-760 days. A full explanation is given in the associated paper which may be found at https://arxiv.org/abs/2107.13856
Oxford Battery Degradation Dataset 1
No full textLithium-ion (Li-ion) batteries are the most popular energy storage technology in consumer electronics and electric vehicles and are increasingly applied in stationary storage systems. Yet, concerns about safety and reliability remain major obstacles, which must be addressed in order to improve the acceptance of this technology. The gradual degradation of Li-ion cells over time lies at the heart of this problem. Time, usage and environmental conditions lead to performance deterioration and cell failures, which, in rare cases, can be catastrophic due to fires or explosions. The physical and chemical mechanisms responsible for degradation are numerous, complex and interdependent. Our understanding of degradation and failure of Li-ion cells is still very limited and more limited yet are reliable and practical methods for the detection and prediction of these phenomena.
This dataset contains the results of long term cycling of 8 lithium-ion cells in our lab in Oxford. The full details are given in the readme.txt file
Locating large-scale energy storage: spillover effects, carbon emissions, and balancing costs across Italy
No full textReaching net zero requires substantial large-scale energy storage systems (LESS) deployment. This strategy poses key challenges, including understanding how different LESS technologies compare in terms of both economic benefits and environmental impact, as well as analysing the complex interactions within and between markets when storage is deployed. To help shed light on these aspects, we investigate how LESS location, rated power, duration, and technology can affect welfare and carbon emissions in the Italian electricity system by modelling the day-ahead and the ancillary services markets. We considered lithium-ion batteries, pumped-storage hydro, and vanadium redox flow batteries. The results show that deploying LESS is always beneficial in the day-ahead market, but ancillary services costs can increase due to spillover effects because these markets run sequentially. Lithium-ion is the technology that yields the best social welfare increase. Location, rated power, and duration significantly impact carbon emissions, with changes ranging from −260 kgCO2 to 190 kgCO2 per MWh traded. These results suggest that LESS can help increase welfare and induce unintended consequences, such as spillovers across markets with a mixed effect on emissions
Data repository for 'Understanding long-term energy use in off-grid solar home systems in sub-Saharan Africa'
No full textThis dataset contains hourly load demand time-series from 1,000 off-grid solar home systems deployed across sub-Saharan Africa. These systems typically power lighting, phone charging, fans, radios, and small televisions. Each column represents one household, with hourly consumption values (Wh) recorded for 391–1232 days. Further details are provided in the associated preprint: https://arxiv.org/abs/2502.1463
Data repository for 'Multiscale coupling of surface temperature with solid diffusion in large lithium-ion pouch cells'
No full textPlease see the file readme.tx
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Improved Analytical Model of an Outer Rotor Surface Permanent Magnet Machine for Efficiency Calculation with Thermal Effect
Full text linkIn this paper, an improved analytical model accounting for thermal effects in the electromagnetic field solution as well as efficiency map calculation of an outer rotor surface permanent magnet (SPM) machine is described. The study refers in particular to an in-wheel motor designed for automotive electric powertrain. This high torque and low speed application pushes the electric machine close to its thermal boundary, which necessitates estimates of winding and magnet temperatures to update the winding resistance and magnet remanence in the efficiency calculation. An electromagnetic model based on conformal mapping is used to compute the field solution in the air gap. The slotted air-gap geometry is mapped to a simpler slotless shape, where the field solution can be obtained by solving Laplace's equation for scalar potential. The canonical slottless domain solution is mapped back to the original domain and verified with finite element model (FEM) results. Closed form solutions of core loss and magnet loss are derived from the air-gap field solution. The copper loss is calculated by considering the proximity loss and skin effects. In order to estimate the winding and magnet temperatures, a thermal model is built using a lumped parameter thermal network with an improved discretization approach. The model has been validated experimentally using the end-winding and coolant temperatures. The energy consumption calculation with the New European Driving Cycle (NEDC) is performed and the benefit of having the thermal model is quantified in terms of percentage difference in the calculated energy consumptions
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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