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A Study of Rock Breakage Under Extreme Submerged Confining Pressure: Can DTH Hammer Drilling Deliver
No full textInternational audienceDrilling costs are a major barrier to developing deep geothermal energy, particularly in hard granite formations. As part of the EU H2020 ORCHYD project, we are developing an innovative technology that combines percussion drilling with high-pressure water jetting to enhance performance in hard crystalline rocks. Laboratory tests show a fourfold increase in efficiency over conventional methods. This study investigates the impact of realistic operational conditions-characterised by high in situ confining stress and hydrostatic pressure-on the performance of this drilling technique. Key variables influencing the performance of the mud hammer were examined. Experimentally, drilling tests were conducted using a laboratory setup that simulates rock fracture mechanisms under confining pressures up to 30 MPa, reflecting semi-realistic downhole conditions. Numerically, a hybrid finite-discrete element method (FDEM) was employed to model the interactions between the bit insert and rock under confining pressures up to 130 MPa and mud pressures up to 50 MPa, representing extended real-world deep drilling conditions. The results show that rock breakage is 2-3 times more challenging under higher confinement than lower confinement. The effects of impact energy and weight on bit were also studied. This improvement is due to two factors: a global stress release at the bottom hole, increasing crater depth by up to three times, and a local effect at the insert impact point, where crater depth matches the groove depth. These insights guide optimisation of bit design and drilling strategies-where full-scale trials are costly/impractical-de-risking deep geothermal operations, reducing costs, and improving economic viability. Highlights• High confining pressures significantly reduce the crater volume during rock drilling, especially above 100 MPa.• Grooving around the impact point helps release stress, leading to more efficient rock fragmentation.• Increased initial impact energy enhances overall rock fragmentation, but does not increase crater depth significantly.• Numerical modelling extends experimental insights to deeper geothermal reservoirs, predicting drilling performance at high pressures.</div
Évaluation de la durabilité environnementale absolue des bâtiments tenant compte de la production d’électricité renouvelable
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Dynamic heat balance modeling of industrial bioleaching plant: Influence of both environment and operating conditions and heat management improvement
No full textInternational audienceA heat balance model was developed for bioleaching processes in stirred tank reactors, based on mechanistic and semi-empirical models to describe the contribution of each heat transfer phenomena. It was validated based on the cooling power required for two industrial case studies at typical bioleaching temperature of 40 °C and sulfide concentrations of 0.80 and 0.52 %. It was then tested on various scenarios. At high sulfide concentration, heat transfer from pulp addition and aeration was more significant than environmental transfers. This was validated using environmental ranges of values (temperature, wind speed, relative humidity, cloud cover) from either subarctic or equatorial climates. In the case of Finland, 12 % more power was predicted in summer than in winter. Regarding the number of primary tanks, one tank may be removed on the KCC-cascade system to save investments, by accepting a 4 % reduction in conversion rate. Finally, heat loss due to environmental conditions increased as the pyrite concentration decreased, passing from only 12 % with a concentration of 80 to 53 % with a concentration of 10 %. Control of the feeding pulp temperature could reduce the use of heat exchangers, and even eliminate them at low sulfide concentration
France’s 2050 energy pathways: Evaluating environmental impacts through the lens of Decent Living Standards
No full textInternational audienceThe French agency for ecological transition envisages four prospective scenarios aiming to achieve carbonneutrality by 2050. In this context, ambitious strategies are established to decarbonize the natural gas network byincreasing biomethane production from anaerobic digestion, pyrogasification, and power-to-methane. This workexplores the implications of this shift on France's absolute environmental sustainability performance, evaluatingthe impact of this transition on achieving decent living standards within the safe operating space assigned toFrance.Projected supply and demand scenarios of methane were used to create a tailor-made version of the ecoinventdatabase for 2020, 2030, and 2050 using the premise python package. Modeled supply chains fully capture thelife-cycle environmental impacts of the gas network under different technological choices and advancements.Changes encompass increasing the proportion of biomethane, alongside considering energy efficiencyenhancements, such as the reduction of methane leaks in the anaerobic digestion. French markets were combinedwith various integrated assessment models to consider future changes in natural gas imports.Life-cycle environmental impacts of decent living standards accomplishment were quantified from 2020 to 2050,considering proposed transition scenarios. Decent living standards cover housing, nutrition, hygiene, shelter,clothing, mobility, collective services, communication, and education. The different scenarios quantify theremaining safe operating space to be shared among other human activities in France while achieving decent livingstandards until 2050.This work provides a comprehensive life-cycle assessment model of the current and future gas network, allowingusers to directly implement it as background life-cycle inventory. Our findings underscore the importance ofconsidering technological advances when assessing provisioning systems, such as energy, while addressinghuman needs to assign carrying capacities
La contractualisation financière entre l’État et les collectivités locales : la controverse des deux dépenses publique
No full textInternational audienceFollowing the scholarship on austeritarian public finances, this article focuses on one of the latest instruments governing fiscal and financial relations between the State and local authorities in France, called the “Cahors contracts”. This tool, introduced in 2017 (and then suspended at the start of the pandemic in 2020), aims to limit the growth of operating expenditures through a contract signed between the State and some local authorities. While tracing the conception of this instrument within the central government and its negotiation with—and contestation by—local government associations, the article produces two main findings. First, it highlights the concrete ways in which a budget consolidation order is implemented and maintained across different levels of government, from the European Union to local authorities and central administrations. Second, it underlines how the controversies surrounding the instrument—its binding and a-territorial nature, the type of targeted expenditures—stem from the gap between two different conventions of public spending, opposing the State as guarantor of the consolidation order and local authoritiesDans la lignée des travaux sur l'austérité dans les finances publiques, cet article porte sur l'un des derniers instruments organisant les relations fiscalo-financières entre l'État et les collectivités locales en France : la contractualisation financière. Ce dispositif introduit en 2017 (puis suspendu au début de la pandémie en 2020) vise à limiter la progression des dépenses de fonctionnement par un contrat signé entre l'État et certaines collectivités. En retraçant l'élaboration de cet instrument au sein de l'État central et dans ses relations avec les associations de collectivités locales, l'article produit deux résultats principaux. Il contribue d'abord à mettre en évidence les modalités concrètes par lesquelles un ordre de consolidation budgétaire se déploie et se maintient entre différentes échelles d'action publique, de l'Union Européenne aux collectivités en passant par les administrations centrales. Il montre ensuite que les controverses autour du caractère contraignant et a-territorialisé de cet instrument et de la nature des dépenses contractualisées résultent du décalage entre deux conventions différentes de la dépense publique, opposant l'État garant de l'ordre de consolidation et les collectivités locales
Deep tech entrepreneurship – a viable response to today’s grand challenges?
No full textLSE Business ReviewThe rise of “deep tech” in recent years has captured the attention of investors, policymakers and innovators alike. But what’s beyond the hype? At its core, deep tech is grounded in cutting-edge scientific discovery and technological complexity, with far-reaching consequences for industry, society and the global economy
Repenser la transmission des savoirs situés dans un monde en transitions
No full textInternational audienceDans un contexte marqué par des transformations démographiques, digitales et technologiques permanentes, la transmission des savoirs situés représente un enjeu stratégique majeur pour les entreprises. Cette recherche propose une approche renouvelée de la transmission à travers trois points fondamentaux : sortir d’une logique duale formé-formateur pour penser l’écosystème des parties prenantes actrices des savoirs ; partir des enjeux pour comprendre les formes de transmission à modifier ou créer ; et enfin, reconnaître les savoirs comme étant incarnés et contextualisés (portés par des individus, façonnés par leurs expériences et/ou leur place dans l’organisation…)
Implementation and short-term outcomes of minimally invasive liver surgery in France
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Effects of Stress Extrapolation and Dilatancy on Salt Cavern Design: An Application to Underground Hydrogen Storage
No full textInternational audienceAbstract The long-term behavior of rock salt is commonly predicted using creep laws fitted on laboratory data at medium-high deviatoric stresses ( ≥ 5 MPa), which do not fully capture the relevant stress range for underground applications. Indeed, it is a common practice in numerical modeling to extrapolate high-stress experimental data to estimate material behavior at lower stress levels. Additionally, the analysis of the simulation results is often combined with specific design criteria, with particular focus on dilatancy. While some dilatancy criteria are embedded at the constitutive level, others are used only during post-processing, or are of empirical nature. This study simulates hydrogen storage in salt caverns using two in-house finite element codes and the RTL constitutive model. This model accounts for deviatoric and volumetric viscoplastic strains, incorporates dilatancy at the constitutive level and has been calibrated with recent multi-stage confined creep tests over a differential stress range of 0.5–20 MPa and temperatures of 20–50 ∘ C. The results of the thermomechanical simulations show that extrapolating high-stress data to low-stress regimes can lead to significant underestimations of cavern volume loss and to misrepresentation of stress and strain magnitudes and profiles. Likewise, incorporating dilatancy at the constitutive level offers more accurate predictions of the onset and extent of dilatancy zones. Such zones stabilize over time, remaining smaller than the region influenced by very low deviatoric stresses. As emphasized in this study, accurate assessments of stability require that laboratory experiments and the calibration of constitutive models be conducted as much as possible within the ranges of stress, temperature, strain and strain rates relevant for the underground application
