Power electronics (PE) is the key technology to control the flow of electrical energy from the source to the load. New developments in PE allow the increase of the total power density of the conversion systems through the advances in: semiconductor technology (wide band-gap semiconductor), packaging materials, system integration and design reliability. However, this also increases the electric field, thus stressing electrically more and more the insulating materials. Field reinforcements in insulating polymers can reach critical values, resulting in space-charge build-up, partial discharge activity, treeing or even breakdown of the solid materials. We propose a new approach to deal with field reinforcements in the polymeric dielectric materials. Appropriate dielectric properties across the dielectric will be simulated and tailored. First by elementary, then by complex structures, such as power modules; the developed materials will be processed and then characterized to determine their performance as insulators. The overall proposed strategy for material development could have an impact on the conception and use of insulators in electrical engineering (particularly in PE), since it could also be used to control other physical properties on the composites.

The FASTER-3D project proposes a breakthrough approach to address the reliability issues of standard packaging materials (encapsulation, substrate, interconnect, thermal interface material) in 3D electronic modules by replacing all of them by tailored functionalized polymer-based composites with advanced dielectric, thermal conductive, electrical conductive and thermo-mechanical properties. It is expected that the proposed multifunctional materials will allow a large reduction of the physical constraints (electrical, thermal, mechanical) into 3D integrated modules involving new wide bandgap power devices thanks to tailored stress relaxation. An efficient reduction of all the constraints with the proposed materials should have a major impact on the overall performances and reliability of the next generation of 3D power modules. Consequently, this project strongly supports the development of more efficient power electronic systems to help electrical energy saving during its conversion and distribution.

The main objective of the present project is to control the formation of space charge in insulating synthetic materials for HVDC applications, focussing on polyethylene and its interfaces in HVDC systems. The specific aim would be to avoid/decrease space charge formation by tailoring interfaces in such a way to introduce “blocking layers” for charge injection. The project is a fundamental research oriented to many potential applications in technologies. The interface properties at the contact between HV parts and polymeric insulation are not described properly in the literature. The project aims at evaluating a scenario in which the surface states of the dielectric play a crucial role in controlling charge injection. The basic idea is to tailor the interface with deep trapping centres by using chemical/plasma processes. It is proposed that by doping the interface with entities having electron stabilizing properties the injected charge would be deeply trapped and would radiate an electric field that would oppose to the injecting field, thereby decreasing the injection. Moreover, being deeply trapped, the charges would not be available for charge transport and would not give any contribution to bulk space charge. The interface would therefore act as a smart assembly, counteracting the phenomenon that creates a threat. Two strategies will be used to tailor the interface properties: one is chemical (area of expertise of the Chinese partner, the State Key Laboratory of Electrical Insulation and Power Equipment at Xi’an Jiaotong University of China –SKLEIPE–), the other is by plasma processing (area of expertise of the French partner, Laboratoire Plasma et Conversion d'Energie, Toulouse, France –LAPLACE–). The first method ends with the existence of a gradient of polar species in a modified-layer. The second one allows to functionalize the surface by oxygen (or nitrogen) atoms, or to deposit a silver nano-grains containing dielectric layer with electron stabilizing properties (non percolating nano-clusters). The injection ability of the tailored interfaces will be evaluated relatively to model interfaces using up-to-date pulsed electro-acoustic methods for space charge measurement with a high temporal resolution (< sec). The scientific complementarities between the two teams, the strategic importance of the research in a context of increasing energy demand, the number of HVDC components and technologies that can be addressed and the blooming of HVDC technologies provide a formidable framework for this project.

Because of their large coverage and cooling effect of the Earth system, boundary-layer clouds are key elements of the climate system. They modulate the water and energy cycles of the atmosphere and strongly impact surface temperatures at various scales. These clouds are often much smaller than a grid cell of global weather forecast and climate models and must thus be “parameterized” through a set of approximate equations that aims at representing the collective behaviour of an ensemble of clouds and their impact on the large-scale model variables. The approximate nature of parameterizations and the diversity of approaches for the choices of associated free parameters through tuning are responsible for important biases in global models. Moreover, the spread of the boundary-layer cloud radiative effects dominates the spread of climate change projections for global warming, in response to a given perturbation of greenhouse gases. The main objective of HIGH-TUNE is to improve the representation of boundary-layer clouds focusing on the boundary-layer dynamics and cloud-radiation interaction. Important progresses have been made in the last decades in boundary-layer cloud parameterizations, based on the comparison of single-column versions of the global models (SCM) with explicit 3D high-resolution Large-Eddy Simulations (LES) of the same scene of boundary layer clouds. To go one step further, we will build on this approach based on SCM/LES comparison, thanks to two important methodological breakthroughs that benefited from recent advances in other scientific disciplines: i/ estimation of the radiative effect of clouds from LES results using efficient Monte-Carlo algorithms will be used as a reference for parameterization evaluation and tuning; and ii/ state-of-the-art statistical tools for automatic tuning will be adapted to the SCM/LES comparison. Combining automatic tuning tools and full radiative computations will allow us: 1/ to address the energetic tuning of climate models on process-based studies and propose parameter ranges for the final global tuning and 2/ to progress in the representation of clouds themselves and in the understanding of how they depend on boundary-layer dynamics and radiative approximations. To reach these objectives, the consortium gathers applied mathematicians, radiative transfer experts, climate and atmosphere modelling experts, which guarantees a real and significant outcome of the project in state-of-the-art global weather forecast and climate models. Beyond the range of acceptable parameters values, the automatic tuning with radiative metrics will provide a more comprehensive documentation and understanding of the parameterization behaviour in several cloud regimes. It will be used to revisit several aspects of cloud parameterizations and consider new developments as: (i) adding the representation of dry air intrusion (key process in the transport of water vapour) (ii) improving the representation of the subgrid horizontal and vertical heterogeneities of clouds, the overlap assumption for cloudy grids as well as the solar zenith angle dependency at high latitudes and (iii) refining the assumptions made on cloud optical properties and microphysics. The improved and tuned parameterizations will be systematically tested in full 3D configuration and compared with satellite and in-situ observations. The main outcomes of the project will be: 1/ the first demonstration of a tuning strategy at the process scale, with in particular, the use of cloud radiative effects as a central metrics; 2/ the availability of an efficient code for computing radiation on 3D cloud scenes from LES; 3/ improved representation of boundary layer clouds for global weather forecast and climate models, through improved parameterizations and better tuning of free parameters.

Since some years energy efficiency in datacenters is improving but the amount of electricity needed for operating those for hosting Cloud services is growing with the sizes of the infrastructure and the user demands. With renewable energies and the usage of direct current in datacenters, we believe that we can cope with this problem. On the one hand several efforts have been conducted at the computing level in datacenters (for service placement and scheduling) and, on the other hand, for energy provisioning partly with renewable energies, but without much interaction between these two efforts. DATAZERO will give consistent solutions for high availability of IT (Information Technologies) services, avoiding unnecessary redundancies, under the constraints of intermittent nature of electrical and services flows. We noticed that, despite a true interest towards pragmatic and market-based solutions, comprehensive studies are missing to cope with the robustness of a cloud infrastructure in the conditions of datacenters powered by renewable energy. The question we address in DATAZERO is: How to manage the electricity and the service flows in order to deliver services to customers in a robust and efficient manner within datacenters operated with several energy sources? Any solution for electricity and IT management must maintain the health state of the infrastructure in nominal conditions. IT services must be resilient to electrical problems and their operation must be assured. The methodology we propose is: 1. using the characterization of power sources, we will optimize the decision process managing how to balance electricity production and storage among potential power sources (multisource), how to optimize the electricity flow in the system, in order to ensure a given level of constrained energy demand. 2. using the characterization of hosted services in the cloud, we will optimize the decision process solving how to balance the service execution among the computers, how to schedule and place hosted services in the system, in order to ensure resilience in a dynamic and prone-to-failure power distribution system. 3. using the two preceding decision processes, we will introduce a negotiation loop able to match the constraints coming from both sides (adapting energy production depending on the computing demand and adapting computing service level depending on the energy offer) and optimize the renewable energy utilization. While the computer level and the energy level can be treated separately, we believe there is a need to formulate a global optimization problem mixing constraints, scheduling and requests from both sides. IT tasks dispatching should take into account the source capacities and, depending on the foreseen workflow, the different energy sources should be used at their optimal functioning. At energy level, hybridization of different sources (or several sources with lower power than the maximum requested) is challenging in the architecture design (dimensioning, type of suitable sources…) and global management of energy flow transiting between sources is of paramount importance. The main targets are middle-size datacenters where IT load can be managed either through Virtualization or Cloud orchestrator (up to 1000 m2 and 1 MW) commonly seen in enterprise and public institutions. The main outcomes are the optimization of datacenters powered partially with renewable sources and the production of a simulation toolkit. When developed this simulation toolkit will allow for testing, tuning and comparing several mixes of renewable sources, electrical and computer equipment, and scheduling policies. It will provide recommendations on the IT and electrical redundancies in hybrid architectures for reaching a given level of performance. DATAZERO brings together an interdisciplinary team (academic and industry, from both IT and electrical engineering) to find suitable solutions in a cooperative way.