Scientific direction Development of key enabling technologies
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PhD : selection by topics

Technological challenges >> Solar energy for energy transition
7 proposition(s).

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Model of energy losses due to fouling of bifacial PV modules and the reduction in induced albedo.

Département des Technologies Solaires (LITEN)

Laboratoire Systèmes PV

01-10-2020

SL-DRT-20-0303

eric.pilat@cea.fr

Solar energy for energy transition (.pdf)

The generation of energy from solar technologies becomes more and more important and consequently the serious consideration of a problem, the soiling Today, the unit of measurement is no longer the Giga Wh but the Tera Wh and, therefore, the smallest percentage of losses can generate a considerable economic deficit. In order to reduce the cost of the energy produced (LCOE), the players are looking to locate their installations in the sunniest, arid and unfortunately often very dusty regions. Finally, a promising new technology of PV cells, capable of capturing photons on both sides, has recently emerged and requires a fundamental review of the soiling approach, taking particular account of variations in soil albedo. The context of the study is favorable, because motivated by an increasing number of patents and articles, strong pressure on the cost of cleaning and water consumption, new applications such as agro-PV particularly sensitive. The main objective of the doctoral student is to develop algorithms for calculating the impact of soiling from the characteristics of the PV fields, data measured on the systems and taking into account the influencing environmental parameters. He identifies the best measurement methods and instruments to quantify the level of soiling. The scientific difficulty lies in the diversity of the materials concerned and the challenge consists in apprehending and reproducing multiple physico-chemical phenomena involved in the process of accumulation of soiling.

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Ageing study of perovskites?based solar cells in space environments: absorber degradation mechanism and devices optimization

Département des Technologies Solaires (LITEN)

Laboratoire Photovoltaïque à Concentration

01-10-2020

SL-DRT-20-0800

romain.cariou@cea.fr

Solar energy for energy transition (.pdf)

Over the last decades, the development of photovoltaic cells alternative to crystalline silicon ones has progressed following two paths: inorganic-based thin films (e.g. CdTe, CIGS) and organic ones. Until very recently, there was no semiconducting materials that could both be processed at low temperature via wet process and provide sufficient efficiencies to compete with silicon-based technologies. Yet, in 2012, several works showed that lead-based metal halide perovskite (ABX3, CH3NH3PbI3) could fulfil all these requirements1. Since then, such materials and devices have attracted a considerable amount of research and power conversion efficiency has been skyrocking2. Record performance over 25% in single junction configuration are now achieved and steady progress has been made to increase the process stability & up-scalabilty3. In addition, given their excellent absorbing properties, perovskite solar cells are very thin by nature (< 1 µm of photoactive material) and can thus show a high specific power (e.g. beyond 20 W/g)4. This would for instance represent more than one order of magnitude increase over that of thin film silicon cells or flexible single-junction GaAs cells. Recent studies have shown the excellent resilience of this type of PV material against some charged particles flux representative of space environment5. With their high specific power and radiation hardness potential, combined with the low cost manufacturing processes, perovskites cells can be game changing for space PV applications where bulky and expensive III-V triple-junction have been the standard for the last ~ 20 years. To this end, understanding degradation mechanisms triggered by space conditions ? charged particles, deep UV photons and temperature cycles ? is of paramount importance to identify materials & device architecture that provide high end-of-life performance. The main goals of this PhD will then be to: - Understand the degradation mechanism of perovskite materials & associated devices under space environment - Tune perovskite compositions to optimize their behavior (efficiency & stability) under such conditions - Develop specific devices (e.g. materials & architectures) to maintain high power density until their end-of-life. To reach this goal, this PhD work will go through defined steps: bibliography review, solar cells fabrication and characterization, material/device ageing in space conditions and characterization of final properties. These steps can be applied recursively. This experimental PhD work will be conducted on CEA-INES (Le Bourget du Lac, FR) and ONERA (Toulouse, FR) facilities. References: 1 M.M. Lee et al., Science 338, 643 (2012). 2 M.A. Green et al., Prog. Photovolt. Res. Appl. 28, 3 (2020). 3 A. Extance, Nature 570, 429 (2019). 4 M. Kaltenbrunner et al., Nat. Mater. 14, 1032 (2015). 5 F. Lang et al., Adv. Mater. 28, 8726 (2016).

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Dynamic simulation and control of Continious solar fuel gazeification process

Département Thermique Biomasse et Hydrogène (LITEN)

Laboratoire des Systèmes Solaires et Thermodynamiques

01-10-2020

SL-DRT-20-0989

nathalie.dupassieux@cea.fr

Solar energy for energy transition (.pdf)

The topic of this thesis studies deals with the valorisation of solar energy as a storable and/or transportable energy vector. For this purpose, the so-called solar thermochemical processes, combining thermal solar technologies and thermochemical conversions of renewable or waste carbonaceous materials have been selected. The reactor studied previously implements endothermic reactions. Those reactions carry out under solar thermal input, generate gaseous products in which solar energy is stored in chemical form. For the scale-up of the SOLAR-FUEL reactors studied in previous work (theses, Carnot and European projects), a major obstacle to industrial deployment remains : the variability of the solar resource does not allow continuous operation. The objective of the research project is to propose a hybrid process (carbon/solar resource) able of continuously produce a renewable solar fuel. The research work will be based both on dynamic simulation and on experimental validation, in order to ensure optimal control of the process according to the available solar resource. The energy and environmental balance will also be studied in order to compare this solar energy storage pathway with other technologies.

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Modelling, Characterization and optimizations of electronic transport at the passivating contact PV cells interfaces

Département des Technologies Solaires (LITEN)

Laboratoire HETerojonction

01-10-2020

SL-DRT-20-1015

wilfried.favre@cea.fr

Solar energy for energy transition (.pdf)

Resistive losses reduction and engineering in PV cells are becoming a major topic for further efficiency increase. The main actors are focused to identify and quantify the different sources of losses at the various interfaces of the passivating contact PV devices. For this purpose there is a need to consider both test structures representative of the final PV cell (similar process) and operando conditions (light and temperature close to outdoor environment), while present methodologies are far away from these requirements (different fabrication process and dark conditions). The work will be divided into two main parts: (i) Participate to the development and validation of a new setup dedicated to characterization of PV cells contact resistance in operando conditions and (ii) evaluate physical models for the interfacial electronic transport using 2D/3D simulation tools together with advanced characterization techniques (EBIC, EPR). The samples will be produced in the CEA PV cells pilot lines at INES campus (24.63% record efficiency demonstrated) and the knowledge produced will allow further single junction and tandem device optmizations.

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Interaction mechanisms of hydrogen with defects of silicon bulk and at the interfaces of passivated contacts in PV cells

Département des Technologies Solaires (LITEN)

Laboratoire HoMoJonction

01-10-2020

SL-DRT-20-1018

raphael.cabal@cea.fr

Solar energy for energy transition (.pdf)

Although fluctuating, the photovoltaic market is still dominated by silicon technologies occupying ~94%. The most promising homo-junction cell architectures systematically integrate a so-called "passivated" contact through a stack of polycrystalline silicon on tunnel oxide. The hydrogenation of such structures makes it possible to achieve very efficient yields >25%. However, the introduction of hydrogen can also lead to layer delamination or resistive losses through accumulation effects at the interfaces, significantly degrading the efficiency of the final device. To avoid its effects and develop this type of structure with associated yields, it is essential to understand the interactions of hydrogen involved and to understand its role in passivation phenomena. However, hydrogen is an extremely difficult element to characterize by its very nature. Its characterization therefore represents a real challenge, to which are added the difficulties related to the textured surface state of solar silicon and the configuration of poly-Si/Si/SiOx/Si interfaces. To meet this challenge, the work proposed here will be to implement and correlate characterization techniques, allowing both to locate and quantify hydrogen in the volume of silicon and at the interfaces of passivated contact structures. The implementation of a characterization methodology will lead to the main objective of the thesis, which is to propose mechanisms of hydrogen interaction with defects and its role in the quality of passivated contacts. This will open up opportunities for the development and optimization of passivated contact structures. This study will benefit from the infrastructure for the realization of samples from CEA-LITEN in INES and the means of characterization of the nano-characterization platform with its expert environment.

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Improvement and understanding of the performance of silicon cell-based solar generators in harsh environments

Département des Technologies Solaires (LITEN)

Laboratoire Photovoltaïque à Concentration

01-09-2020

SL-DRT-20-1061

philippe.voarino@cea.fr

Solar energy for energy transition (.pdf)

The thesis will be carried out at the interface of several laboratories of the Department of Solar Technologies (DTS) of the CEA located in Le Bourget du Lac on the campus of the National Institute for Solar Energy (INES). The objective of this thesis is to improve the resistance to environmental conditions (radiation, e/H+, UV, thermal cycling) of space solar generators based on silicon solar cells, and to better understand the degradation mechanisms of cells/materials associated. By finely controlling the manufacturing of cells (doping, impurity, architecture, etc.) and modules (materials, thickness, architecture, optical trapping, etc.), it is possible to improve the performance of silicon modules at the end of their lifetime while maintaining a competitive price (?/W), 1 to 3 orders of magnitude lower than space III-V modules.

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High efficiency photovoltaic modules developement for building applications

Département des Technologies Solaires (LITEN)

Laboratoire Modules Photovoltaïques Silicium

01-10-2020

SL-DRT-20-1116

bertrand.chambion@cea.fr

Solar energy for energy transition (.pdf)

Performance of photovoltaic (PV) modules has not stopped to evolve in recent years to reach higher values at 20%. This is possible by a significant effort focussed on the architecture solar cells through gains in light absorption and better collection of photo-generated charges. In contrast, the module packaging and module structure remain similar as previous module structure. On one hand, these modules have been developed in order to work in a standard outdoor PV farm configuration. On the other hand, optimization and development are carried out under standard conditions where the temperature is set at 25 ° C. For Building Integrated (BIPV) applications, it can dramatically decrease their performance. This is related to the urban environment and local microclimate conditions (temperature, surrounding diffuse radiation), orientation and the tilt of the components. In addition, non-optimized integration conditions has a direct consequence and could increase the module temperature, making the thermal dependence on yield (estimated at -0.4% per degree) much more sensitive than in standard application. In addition, BIPV poses other issues related to the architectural aspects of the building: The quality of materials and their colours must match the environment, especially for old buildings. The purpose of this thesis project is to develop integrated PV modules prototypes, optimized for BIPV application, in accordance to the following steps: - State of the art on BIPV applications, materials, light management, thermal and thermomechanical modelling tools - Multi-scale modelling (cell, module, building, town) to understand the PV system thermal behaviour and performances consequences. - PV modules prototypes definition and realization on CEA INES Lab. - Outdoor ageing test and performances monitoring, comparison to standard PV solutions

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