Deep Convolutional Variational Autoencoder as a 2D-Visualization Tool for Partial Discharge Source Classification in Hydrogenerators

International audienceHydrogenerators are strategic assets for power utilities. Their reliability and availability can lead to significant benefits. For decades, monitoring and diagnosis of hydrogenerators have been at the core of maintenance strategies. A significant part of generator diagnosis relies on Partial Discharge (PD) measurements, because the main cause of hydrogenerator breakdown comes from failure of its high voltage stator, which is a major component of hydrogenerators. A study of all stator failure mechanisms reveals that more than 85 % of them involve the presence of PD activity. PD signal can be detected from the lead of the hydrogenerator while it is running, thus allowing for on-line diagnosis. Hydro-Québec has been collecting more than 33 000 unlabeled PD measurement files over the last decades. Up to now, this diagnostic technique has been quantified based on global PD amplitudes and integrated PD energy irrespective of the source of the PD signal. Several PD sources exist and they all have different relative risk, but in order to recognize the nature of the PD, or its source, the judgement of experts is required. In this paper, we propose a new method based on visual data analysis to build a PD source classifier with a minimum of labeled data. A convolutional variational autoencoder has been used to help experts to visually select the best training data set in order to improve the performances of the PD source classifier

Reducing greenhouse gas emissions in agriculture without compromising food security?

To keep global warming possibly below 1.5◦C and mitigate adverse effects of climate change, agriculture, like all other sectors, will have to contribute to efforts in achieving net negative emissions by the end of the century. Cost-efficient distribution of mitigation across regions and economic sectors is typically calculated using a global uniform carbon price in climate stabilization scenarios. However, in reality such a carbon price would substantially affect food availability. Here, we assess the implications of climate change mitigation in the land use sector for agricultural production and food security using an integrated partial equilibrium modelling framework and explore ways of relaxing the competition between mitigation in agriculture and food availability. Using a scenario that limits global warming cost-efficiently across sectors to 1.5◦C, results indicate global food calorie losses ranging from 110–285 kcal per capita per day in 2050 depending on the applied demand elasticities. This could translate into a rise in undernourishment of 80–300 million people in 2050. Less ambitious greenhouse gas (GHG) mitigation in the land use sector reduces the associated food security impact significantly, however the 1.5◦C target would not be achieved without additional reductions outside the land use sector. Efficiency of GHG mitigation will also depend on the level of participation globally. Our results show that if non-Annex-I countries decide not to contribute to mitigation action while other parties pursue their mitigation efforts to reach the global climate target, food security impacts in these non-Annex-I countries will be higher than if they participate in a global agreement, as inefficient mitigation increases agricultural production costs and therefore food prices. Land-rich countries with a high proportion of emissions from land use change, such as Brazil, could reduce emissions with only a marginal effect on food availability. In contrast, agricultural mitigation in high population (density) countries, such as China and India, would lead to substantial food calorie loss without a major contribution to global GHG mitigation. Increasing soil carbon sequestration on agricultural land would allow reducing the implied calorie loss by 65% when sticking to the initially estimated land use mitigation requirements, thereby limiting the impact on undernourishment to 20–75 million people, and storing significant amounts of carbon in soils

REMIND2.1: transformation and innovation dynamics of the energy-economic system within climate and sustainability limits

This paper presents the new and now open-source version 2.1 of the REgional Model of INvestments and Development (REMIND). REMIND, as an integrated assessment model (IAM), provides an integrated view of the global energy–economy–emissions system and explores self-consistent transformation pathways. It describes a broad range of possible futures and their relation to technical and socio-economic developments as well as policy choices. REMIND is a multiregional model incorporating the economy and a detailed representation of the energy sector implemented in the General Algebraic Modeling System (GAMS). It uses non-linear optimization to derive welfare-optimal regional transformation pathways of the energy-economic system subject to climate and sustainability constraints for the time horizon from 2005 to 2100. The resulting solution corresponds to the decentralized market outcome under the assumptions of perfect foresight of agents and internalization of external effects. REMIND enables the analyses of technology options and policy approaches for climate change mitigation with particular strength in representing the scale-up of new technologies, including renewables and their integration in power markets. The REMIND code is organized into modules that gather code relevant for specific topics. Interaction between different modules is made explicit via clearly defined sets of input and output variables. Each module can be represented by different realizations, enabling flexible configuration and extension. The spatial resolution of REMIND is flexible and depends on the resolution of the input data. Thus, the framework can be used for a variety of applications in a customized form, balancing requirements for detail and overall runtime and complexity

Floating macro litter in European rivers - top items

The JRC exploratory project RIMMEL provides information about litter, mainly plastic waste, entering the European Seas through river systems. RIMMEL has collected data on riverine floating macro litter inputs to the sea. Data acquisition was based on the Riverine Litter Observation Network (RiLON) activities, which collected data from rivers in the European marine basins over a period of one year (September 2016 – September 2017). Data was collected by visual observations and documented with the JRC Floating Litter Monitoring Application for mobile devices, allowing a harmonized reporting, compatible with the MSFD Master List of Categories for Litter Items. This report includes the Top Items lists of riverine floating macro litter, based on the total amount of litter items identified during RiLON activities and ranked by abundance. Top Items lists have been elaborated considering the whole database for the European Seas and further detailed for each individual European regional sea: Baltic Sea, Black Sea, Mediterranean Sea and North-East Atlantic. The North-East Atlantic and the Mediterranean Sea regions showed similar litter categories in their Top 20 Items. These two regions provided most of the available data, influencing the general Top Items list. In the Black Sea and Baltic Sea regions, where data availability was limited, the Top Items lists showed more differences among the different regions. Overall, the general Top Items list for the European Seas showed a predominance of plastic item categories (artificial polymer materials). As a whole, plastic items made up to 80.8% of all objects, with plastic and polystyrene fragments comprising 45% of the identified items in the database. Additionally, Single Use Plastics such as bottles, cover/packaging and bags were also ranked among the most frequently found floating litter. The similarities in the Top 10 and Top 20 items for the different regions, and the appearance of Single Use Plastics scoring high in the ranking, support the need for common actions against plastic pollution at EU level.JRC.D.2-Water and Marine Resource

Search for gravitational-lensing signatures in the full third observing run of the LIGO-Virgo network

Gravitational lensing by massive objects along the line of sight to the source causes distortions of gravitational wave-signals; such distortions may reveal information about fundamental physics, cosmology and astrophysics. In this work, we have extended the search for lensing signatures to all binary black hole events from the third observing run of the LIGO--Virgo network. We search for repeated signals from strong lensing by 1) performing targeted searches for subthreshold signals, 2) calculating the degree of overlap amongst the intrinsic parameters and sky location of pairs of signals, 3) comparing the similarities of the spectrograms amongst pairs of signals, and 4) performing dual-signal Bayesian analysis that takes into account selection effects and astrophysical knowledge. We also search for distortions to the gravitational waveform caused by 1) frequency-independent phase shifts in strongly lensed images, and 2) frequency-dependent modulation of the amplitude and phase due to point masses. None of these searches yields significant evidence for lensing. Finally, we use the non-detection of gravitational-wave lensing to constrain the lensing rate based on the latest merger-rate estimates and the fraction of dark matter composed of compact objects

Search for eccentric black hole coalescences during the third observing run of LIGO and Virgo

Despite the growing number of confident binary black hole coalescences observed through gravitational waves so far, the astrophysical origin of these binaries remains uncertain. Orbital eccentricity is one of the clearest tracers of binary formation channels. Identifying binary eccentricity, however, remains challenging due to the limited availability of gravitational waveforms that include effects of eccentricity. Here, we present observational results for a waveform-independent search sensitive to eccentric black hole coalescences, covering the third observing run (O3) of the LIGO and Virgo detectors. We identified no new high-significance candidates beyond those that were already identified with searches focusing on quasi-circular binaries. We determine the sensitivity of our search to high-mass (total mass M>70 M⊙) binaries covering eccentricities up to 0.3 at 15 Hz orbital frequency, and use this to compare model predictions to search results. Assuming all detections are indeed quasi-circular, for our fiducial population model, we place an upper limit for the merger rate density of high-mass binaries with eccentricities 0<e≤0.3 at 0.33 Gpc−3 yr−1 at 90\% confidence level

Ultralight vector dark matter search using data from the KAGRA O3GK run

Among the various candidates for dark matter (DM), ultralight vector DM can be probed by laser interferometric gravitational wave detectors through the measurement of oscillating length changes in the arm cavities. In this context, KAGRA has a unique feature due to differing compositions of its mirrors, enhancing the signal of vector DM in the length change in the auxiliary channels. Here we present the result of a search for U(1)B−L gauge boson DM using the KAGRA data from auxiliary length channels during the first joint observation run together with GEO600. By applying our search pipeline, which takes into account the stochastic nature of ultralight DM, upper bounds on the coupling strength between the U(1)B−L gauge boson and ordinary matter are obtained for a range of DM masses. While our constraints are less stringent than those derived from previous experiments, this study demonstrates the applicability of our method to the lower-mass vector DM search, which is made difficult in this measurement by the short observation time compared to the auto-correlation time scale of DM

Klimapolitik auf der Seite der Energienachfrage: Die Rolle des Gebäudesektors

In 2015, the international community committed to limiting global warming well below 2°C. Since 2015, however, and before the coronavirus pandemic stroke, GHG emissions have continued on their growing track and the achievement of ambitious climate targets has become even more arduous. In order to rein in global warming well below 2°C, energy systems must reach net-zero emissions by mid-century. The energy supply, in particular the electricity sector, offers a great potential for reducing emissions. But in the absence of large transformations on the energy demand side, achieving the Paris Agreement’s target would necessitate an extensive recourse to debated negative emission technologies. The interest in demand-side solutions has therefore risen over the last few years. Today, buildings account for 28% of CO2 emissions in the energy system. This sector is therefore an essential building block of any successful mitigation strategy. The aim of this thesis is to investigate the contribution of buildings to limit climate change. The widespread view on the role of buildings is that there is a large and cost-effective potential for energy demand reductions, and that this potential remains unexploited due to some barriers, which policies should remove. This thesis relies on energy modeling to shed a new light on that widespread view. It uses the strengths of both an energy simulation model and of an integrated assessment model representing the energy, economy and climate systems. In order to assess the role of buildings in climate policies, the thesis addresses the following complementary questions: How will buildings energy consumption evolve in the future? What is the technological and behavioral potential for demand reductions? What are optimal climate change mitigation pathways for the buildings sector in the context of the overall energy system, and when the energy efficiency gap is taken into account? This thesis shows that the landscape of buildings energy demand will undergo major changes in the 21st century: while cooking and other heating purposes account for the bulk of the demand today; space cooling, appliances and lighting will represent the lion’s share tomorrow. Similarly, despite its current weight in demand, traditional biomass will gradually leave the stage. Against this background, radical changes in technologies and behaviors could lead to a halving of energy demand. The decarbonization of the sector however does not only pass through energy demand reductions. In the scenarios presented in this thesis, most of the decarbonization is attributed to the decline in the emissions per unit of energy consumed—a topic under-represented in the literature dealing with buildings energy demand. In light of the thesis’ results, and supported by the literature, we challenge the widespread view on the role of buildings in climate change mitigation. Indeed, the widespread narrative focuses mostly on energy demand reductions and does not embrace the strategy consisting in decreasing the amount of emissions per unit of energy — in particular via electrification and fuel switching. This strategy accounts however for a substantial part of the sector’s decarbonization. We therefore propose an alternative narrative: Two complementary and interacting strategies can lead to a deep decarbonization of buildings energy demand: reducing energy demand and decreasing the carbon content of energy demand through energy supply decarbonization and fuel switching. Virtually all energy services in buildings could be provided by carbon-free energy carriers. However market incentives as well as barriers do not allow for a widespread uptake of clean energy carriers and efficient technologies. Policies should remove barriers to the uptake of efficient and low-carbon technologies, and design markets to give the right incentives in favor of these options.Im Jahr 2015 hat sich die internationale Gemeinschaft verpflichtet, die globale Erwärmung deutlich unter 2°C zu begrenzen. Seit 2015 und vor der Corona-Krise sind die Treibhausgasemissionen jedoch weiter gestiegen und derWeg zu ehrgeizigen Klimazielen ist noch beschwerlicher geworden. Um die globale Erwärmung deutlich unter 2°C einzudämmen, müssen die Energiesysteme bis Mitte des Jahrhunderts Netto-Null-Emissionen erreichen. Die Energieversorgung, insbesondere der Elektrizitätssektor, bietet ein großes Potenzial für Emissionsreduktionen. Ohne große Veränderungen auf der Seite der Energienachfrage, würde es einen umfangreichen Rückgriff auf die umstrittenen Technologien zur CO2-Entnahme erfordern, um das Ziel des Pariser Abkommens zu erreichen. Das Interesse an Lösungen auf der Seite der Nachfrage ist daher in den letzten Jahren gestiegen. Heute sind Gebäude für 28% der gesamten Emissionen im Energiesystem verantwortlich. Dieser Sektor ist daher ein wesentlicher Baustein jedes erfolgreichen Klimaschutzes. Das Ziel dieser Dissertation besteht darin, den Beitrag zu untersuchen, den Gebäude zur Begrenzung des Klimawandels leisten könnten. Die weit verbreitete Sichtweise zur Rolle von Gebäuden beim Klimaschutz lässt sich wie folgt zusammenfassen: Es gibt ein großes und kostenwirksames Potenzial für die Verringerung der Energienachfrage, und dieses Potenzial bleibt aufgrund einiger Hindernisse ungenutzt. Die Politik sollte diese Hindernisse beseitigen. Diese Dissertation beruht auf Energie- und Integrated Assessment Modellen, um ein neues Licht auf diese verbreitete Sicht zu werfen. Um die Rolle von Gebäuden in der Klimapolitik zu bewerten, befasst sich die Arbeit mit den folgenden ergänzenden Fragen: Wie wird sich der Energiebedarf im 21. Jahrhundert entwickeln? Was ist das technologische und verhaltensbedingte Potenzial für die Reduzierung des Energiebedarfs in Gebäuden? Was sind optimale Wege zur Eindämmung des Klimawandels für den Gebäudesektor im Kontext des Gesamtenergiesystems, und wenn die Energieeffizienzlücke berücksichtigt wird? Diese Dissertation zeigt, dass sich die Energienachfragelandschaft der Gebäude im 21. Jahrhundert stark verändern wird: Während heute Kochen und andere Heizbedarfe den Großteil der Nachfrage ausmachen, werden zukünftig Raumkühlung, Geräte und Beleuchtung den Löwenanteil des Bedarfs ausmachen. In ähnlicher Weise wird die traditionelle Biomasse trotz ihres derzeitigen Gewichts bei der Nachfrage allmählich die Bühne verlassen. Vor diesem Hintergrund könnten radikale Veränderungen der Technologien und Verhaltensweisen zu einer Halbierung des Energiebedarfs führen. Die Dekarbonisierung des Sektors geht jedoch nicht nur über die Reduzierung der Energienachfrage. Die in dieser Dissertation vorgestellten Szenarien zeigen, dass der größte Teil der Dekarbonisierung darauf zurückzuführen ist, dass weniger Kohlenstoff pro Einheit verbrauchter Energie emittiert wird — ein Thema, das in der Fachliteratur zur Energienachfrage im Gebäudesektor unterrepräsentiert ist. Anhand der in dieser Arbeit vorgestellten Ergebnisse und unterstützt durch die Literatur stellen wir die konventionelle Sichtweise in Frage. Tatsächlich konzentriert sich die verbreitete Erzählung auf die Reduzierung der Energienachfrage und geht nicht auf die Strategie ein, die darin besteht, den Kohlenstoffgehalt der Energie zu verringern, insbesondere durch Brennstoffwechsel. Diese Strategie macht jedoch einen wesentlichen Teil der Dekarbonisierung des Sektors aus. Wir schlagen daher eine alternative Erzählung vor: Zwei komplementäre und interagierende Strategien können zu einer tiefgreifenden Dekarbonisierung des Energiebedarfs von Gebäuden führen: die Verringerung des Energiebedarfs an sich und die Verringerung des Kohlenstoffgehalts des Energiebedarfs. Praktisch alle Energiedienstleistungen in Gebäuden könnten durch kohlenstofffreie Energieträger bereitgestellt werden. Die Marktanreize und -barrieren erlauben jedoch keine breite Nutzung von Energieeffizienz und kohlenstofffreien Energieträgern. Die Politik sollte Hindernisse für die Einführung effizienter und kohlenstoffarmer Technologien beseitigen und Märkte so gestalten, dass die richtigen Anreize für diese Technologien gegeben werden

Chronique bibliographique : Les publications récentes (1987-1989) sur la Préhistoire et l'Archéologie historique de la Normandie

Jigan Claude, Chancerel Antoine, Levesque Jean-Marie. Chronique bibliographique : Les publications récentes (1987-1989) sur la Préhistoire et l'Archéologie historique de la Normandie. In: Revue archéologique de l'ouest, tome 7, 1990. pp. 137-143