Scientific direction Development of key enabling technologies
Transfer of knowledge to industry

PhD : selection by topics

MILP models for optimal management of hybrid CSP plants

Département Thermique Biomasse et Hydrogène (LITEN)

Laboratoire Systèmes Solaires Haute Température

01-12-2019

SL-DRT-19-0769

valery.vuillerme@cea.fr

The hybridisation of CSP plants with "conventional" plants (existing or not) has many advantages, but in return brings more complexity in the control of the system and the steering strategy. At present, we do not find in the study literature dealing with this issue and highlighting the principles of predictive management of hybrid CSP plants. The planned work will allow the development of dynamic models of CSP plants by taking advantage of the special possibilities offered by the Cathare code in co-simulation environment (PEGASE). This environment will address the advanced control-command aspects of hybrid CSP systems (biomass, geothermal, incineration, coal, nuclear, H2 ...), and we will implement examples to demonstrate the contribution of predictive management to such systems constrained by variations in demand (market) and resource. For validation purposes, certain internal and external experimental means will be used, such as the prototypes of the solar zone at Cadarache for elements relating to CSP / storage pairs, or infrastructures made available under the SFERA III project to which participates the CEA. Ultimately, the numerical demonstrator developed will highlight the hybrid CSP systems of major interest at national, European and international level.

Numerical and experimental studies of a combined cooling and power cycle

Département Thermique Biomasse et Hydrogène (LITEN)

Laboratoire Systèmes Solaires Haute Température

01-10-2019

SL-DRT-19-0770

haitrieu.phan@cea.fr

The TRICYCLE project aims to study and develop a thermodynamic heat recovery cycle for the combined production of cold and low power electricity (5 kW of cold, 1 kW of electricity). The target temperature range is sufficiently low (80 to 160 °C) to target industrial heat recovery applications, but also heat networks and non-concentrated solar thermal energy. In the previous work, the thermodynamic modeling of the cycle was carried out and allowed the definition of an parallel architecture: the refrigerant vapor at the output of the generator can be used to feed the expander(production of electricity) and/or the condensation-expansion-evaporation part (production of cold). This is a unique cycle and not a juxtaposition of two machines (cold + generator), which makes it a particularly innovative system. The objective in 2019 of the project is to achieve an operational prototype of this combined cycle by integrating an expander to the existing absorption-chiller available in our laboratory. This thesis is the next steps of the project in order to: ? Conduct the experimental measurements of the TRICYCLE machine using an adapted instrumentation in order to better understand its behavior (static and dynamic) ? Conduct numerical simulations of the machine (under DYMOLA / MODELICA) and validate the models by comparison to the measurements ? Simulate the coupling of this machine with add-ons (heat storage and / or electrical storage) in a system (application: heat network, automobile, etc.).

Investigation of a dielectric fluid flow boilng in a vertical mini-channel: application to battery thermal management

Département Thermique Biomasse et Hydrogène (LITEN)

Laboratoire Echangeurs et Réacteurs

01-10-2019

SL-DRT-19-0782

pierre.coste@cea.fr

The battery packs power used in electric vehicles is more and more demanding. A battery pack is made of a large number of cells. It is then a major challenge to demonstrate that a thermal runaway coming from a single cell will not propagate through the entire battery pack, leading to a catastrophic fire. An efficient temperature control is needed for the cells. A dielectric liquid flow is an innovative solution for the battery thermal management which has been recently studied with non-boiling oils. The present PHD objective is to introduce boiling dielectric fluids which would make it possible to reach higher cooling rates thanks to the latent heat. The decisive advantage of a boiling flow is the heat transfer increase with a passive triggering between the saturation temperature and the dry-out temperature. At higher temperature, the dry-out could contribute to isolate the healthy cells from the accidental one. The objective is to explore the various single and two-phase flow configurations in different geometries. The work will be both experimental (on a test section at the scale of the channel between two cells) and theoretical (for the interpretation and the application of the experimental results).

Experimental and Theoretical Study of the Scaling Limits of GaN Power Electronics Devices for High Efficiency Converters

Département Composants Silicium (LETI)

Laboratoire Composants Electroniques pour l'Energie

01-09-2019

SL-DRT-19-0783

julien.buckley@cea.fr

Background: High Electron Mobility Transistors (HEMT) using a heterostructure built on gallium nitride (GaN) are highly promising in the field of power electronics. GaN is a wide bandgap semiconductor that can withstand high electric fields while allowing low conduction losses due to the high mobility of the carriers in the 2 Dimensional Electron Gas (2DEG) at the heterostructure interface. Proposed work: The study will focus on the identification of the size limitations of current devices by using the electrical characterization results of componants with multiple geometries, already fabricated at CEA. Finite element simulations (with SYNOPSYS software) will be performed in order to interpret the electrical results and test multiple hypotheses regarding their physical operation. Expected results: The advances achieved regarding the understanding of the devices will be used in order to identify improvements of the architecture studied by simulation. An electrical evaluation of the proposed solutions will be performed after fabrication of the new components in collaboration with the device integration and process development teams.

Innovating programming schemes and designs to solve RRAM variability

Département Composants Silicium (LETI)

Laboratoire de Composants Mémoires

01-10-2019

SL-DRT-19-0789

gabriel.molas@cea.fr

RRAM Resistive memories, which are based on the formation of a conductive filament in a resistive layer, are one of the most serious candidate to replace standard Flash memories. They are envisaged for embedded applications, but also for the new opportunities they offer (storage class memories, Internet of Things?). RRAM maturity keeps growing, and 1st products start appearing on the market. However, available densities are still small (kb-Mb), due to variability issue. Indeed, RRAM filament formation mechanisms are stochastic, leading to an overlap between the memory states. This is particularly critical when a high number of memory cells is involved. In summary, RRAM variability is today the main roadblock to be solved before this technology could widely enter the market. In order to solve variability, new memory stacks were proposed. However, solutions at the circuit level should be added. In particular, smart programming schemes or specific operating circuits were developed to improve memory reliability. In this PhD, we propose to investigate new circuit solutions and to implement them on new designs to reduce RRAM variability and improve memory performances.

Wet Electrostatic Precipitation to reduce urban air pollution

Département Microtechnologies pour la Biologie et la Santé (LETI)

Laboratoire Biologie et Architecture Microfluidiques

01-10-2019

SL-DRT-19-0793

jean-maxime.roux@cea.fr

Air pollution, especially urban air pollution, is a public health problem leading in France to nearly 50 000 deaths per year. In 2018 the World Health Organization reported that toxic levels of pollution leads annually to the early death of about 7 million people. The PhD subject deals with the design of a new urban clean-up system based on wet electrostatic precipitation. Air purifiers based on this principle are usually intended for an industrial use. The PhD will focus on a multiphysical numerical simulation of such a device, but adapted to an urban deployment, starting with the central and difficult problem posed by the stability of an air/water interface in an intense electric field. While being based on this simulation, the final challenge is to develop a numerical optimization of the system aiming at a significant reduction of its size and an appropriate integration of the toxic gas / airborne particles sensors developed at CEA GRENOBLE/Leti/DTBS. Experimental studies carried out at CEA will be guided by the obtained numerical results which will in return be validated.

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