Thèse Intégration des Limites Planétaires dans l'Optimisation des Systèmes Énergétiques une Approche Fondée sur l'Analyse du Cycle de Vie Appliquée aux Matériaux Critiques H/F Doctorat.Gouv.Fr

Cette thèse vise à développer un cadre intégré combinant analyse du cycle de vie (ACV), limites planétaires et optimisation des systèmes énergétiques afin d'identifier des trajectoires de transition économiquement et technologiquement réalisables tout en respectant des limites environnementales définies.

Le premier axe de recherche portera sur la traduction des limites planétaires définies à l'échelle globale en contraintes environnementales pertinentes aux échelles nationale et régionale. Ces contraintes seront directement intégrées dans un modèle d'optimisation afin d'influencer les choix technologiques et la conception du système énergétique.

Le deuxième axe concernera la cohérence entre les données d'ACV et les modèles d'optimisation des systèmes énergétiques. Une couche de traduction entre bases de données ACV et modèles énergétiques sera développée afin de traiter notamment les hypothèses d'allocation, de substitution, d'expansion des frontières du système, les bouquets électriques marginaux et les crédits liés aux coproduits. Cette méthodologie sera validée sur un cas d'étude existant portant sur le système énergétique et la chaîne d'approvisionnement en hydrogène développée au LGC.

Le troisième axe portera sur les matériaux critiques nécessaires aux technologies bas-carbone, notamment le lithium, le cobalt, le nickel, le cuivre et les terres rares. En collaboration avec le groupe VUB-EVERGi, des contraintes relatives aux ressources minérales et métalliques seront traduites en contraintes de flux de matières directement intégrables dans le modèle d'optimisation. L'analyse portera notamment sur les batteries, les éoliennes, les systèmes photovoltaïques, les électrolyseurs, les véhicules électriques et les infrastructures électriques.

La méthodologie combinera ACV, évaluation des limites planétaires, optimisation mathématique, principalement par programmation linéaire en nombres entiers mixtes (MILP), modélisation des flux de matières et analyses de scénarios et de sensibilité. L'application portera initialement sur le système énergétique français, avec une analyse nationale et, lorsque cela sera pertinent, régionale.

La thèse permettra ainsi de comparer des trajectoires de transition contraintes principalement par les émissions de gaz à effet de serre à des trajectoires intégrant un ensemble élargi de limites environnementales et de contraintes liées aux ressources. Elle contribuera au développement de méthodes d'évaluation de la durabilité environnementale absolue appliquées aux systèmes énergétiques et fournira des outils d'aide à la décision pour analyser les compromis entre performance économique, réduction des émissions, impacts environnementaux et utilisation des ressources. The transition towards a low-carbon energy system requires the rapid deployment of renewable energy generation, energy storage and transport, renewable molecules, and the associated infrastructures. However, reducing greenhouse-gas emissions does not necessarily guarantee overall environmental sustainability. These technologies also require land, water and mineral resources and generate environmental pressures throughout their life cycles. These challenges extend beyond the energy sector and are increasingly relevant to strategic technology-intensive sectors such as advanced mobility, aeronautics and space, which also face growing dependencies on critical materials and increasing pressure to reduce their environmental footprint.
Life Cycle Assessment (LCA) provides a comprehensive framework for quantifying these environmental pressures, while the Planetary Boundaries (PB) framework defines limits within which human activities can remain in a safe operating space.
Recent studies have demonstrated the feasibility of integrating planetary-boundary indicators and LCA into energy-system models (ESM) for planning and design optimization. However, this emerging research field still raises important questions regarding the regionalization of environmental limits, the consistency of LCA data with endogenous technology choices, and the role of material-resource constraints in future energy transitions.
This PhD will address these challenges by developing an integrated planetary-boundary-constrained energy-system modelling framework, with particular attention to regional environmental limits, LCA-optimization consistency and critical materials.
The main objective is to develop an integrated LCA-Planetary Boundaries-Energy System Optimization framework capable of identifying energy-transition pathways that are economically and technologically feasible while remaining within defined environmental limits.
The research will address three interconnected challenges.
1. From global planetary boundaries to regional energy systems
Planetary boundaries are defined at the Earth-system scale, whereas energy systems are planned at national or regional scales.
The PhD will investigate how global environmental limits can be translated into meaningful regional environmental budgets, and how alternative regionalization principles affect the resulting energy-transition pathways.
These environmental budgets will be introduced directly into a mathematical optimization model, so that environmental limits influence technology selection and system design rather than being assessed only after the optimization.

2. From LCA data to consistent environmental constraints
LCA databases provide detailed environmental information for energy technologies and material supply chains. However, their allocation, substitution and system-expansion assumptions may not always be consistent with the endogenous technology choices made by an energy-system optimization model.
For example, an LCA database may represent a predefined electricity mix or a by-product credit according to a specific system model, while the optimization model may determine a different marginal technology or substitution pathway. Combining these two approaches without reconciliation can lead to inconsistent environmental accounting, double counting or credits that do not correspond to the substitutions represented by the optimization.
This issue becomes particularly important when LCA results are used to define planetary-boundary constraints, since inconsistencies in environmental accounting can affect both the estimated environmental pressures and the resulting optimized system configuration.
The PhD will therefore develop an intermediate translation layer between LCA databases and energy-system models. This layer will:
- reconcile allocation, substitution and system-expansion assumptions with the endogenous substitution logic of the optimization model;
- address representative cases such as marginal electricity mixes, co-products and by-product credits, technology substitution and material supply chains;
- formalize a reusable ESM-oriented database architecture, rather than a case-specific implementation;
- be validated using an existing hydrogen energy-system case study developed at LGC;
- quantify how conventional and reconciled LCA-ESM coupling affect environmental impacts, planetary-boundary constraints and optimized technology choices.
This approach will ensure that environmental constraints and LCA information are consistently integrated into the energy-system optimization framework.
3. Critical materials as a potential constraint on the energy transition
The integrated framework will be applied to critical materials required by low-carbon technologies, including lithium, cobalt, nickel, copper and rare-earth elements, depending on their relevance to the selected energy-transition pathways. The objective is to investigate whether material-resource constraints could become a limiting factor in the deployment of future energy technologies, including the electrification of transport, which concentrates much of the projected demand for lithium, cobalt, nickel and copper.
In collaboration with the VUB-EVERGi research group, the PhD will investigate how emerging planetary-boundary approaches for mineral and metal resources can be translated into material-flow constraints that can be directly incorporated into energy-system optimization.
The research will consider transition pathways involving technologies such as batteries, wind turbines, photovoltaic systems, electrolysers, electric vehicles and their charging infrastructure, and electricity infrastructure, and will compare conventional low-carbon pathways with pathways subject to critical-material constraints.
Key questions will include:
- Which critical materials are most likely to constrain future energy transitions ?
- How do material constraints modify the optimal technology mix and infrastructure choices?
- Which technology options become less attractive when material-resource limits are considered?
- To what extent can recycling, material efficiency, technology substitution or changes in technology deploymentalleviate these constraints?
- How sensitive are the results to alternative assumptions regarding material availability and the allocation of resource boundaries?
The application will initially focus on the French energy system, with national and, where relevant, NUTS2 regional analyses to capture spatial differences in energy demand, technology deployment and resource requirements.
The final objective is to quantify how moving from a conventional GHG-constrained energy transition towards a multi-boundary and material-constrained transition changes technology deployment, infrastructure choices and overall environmental performance.
The research will combine several complementary approaches:
- Life Cycle Assessment, to quantify environmental impacts and material requirements associated with energy technologies and their supply chains;
- Planetary-boundary assessment, to define environmental limits and translate them into national or regional environmental budgets;
- Mathematical optimization, primarily Mixed-Integer Linear Programming (MILP), to identify optimal technology deployment and operation under multiple competing objectives and constraints;
- Material-flow modelling, to quantify critical-material requirements associated with alternative energy-transition pathways, including those of low-carbon and transport-electrification technologies. This component will be led by VUB-EVERGi, which contributes the material-flow and resource-sustainability expertise of the consortium;
- Scenario and sensitivity analysis, to assess the robustness of the results under alternative technological, environmental and resource assumptions.
These approaches will be integrated into a planetary-boundary-constrained energy-system model, developed within an existing MILP modelling framework at LGC. Environmental limits may be formulated as hard constraints and, where relevant, incorporated through multi-objective or epsilon-constraint formulations.
The framework will first be developed and validated on an existing French/regional energy-system case, providing a benchmark against conventional GHG-constrained optimization. The methodology will then be extended to the critical-material application in collaboration with VUB.
The overall approach will allow the candidate to explore how economic objectives, technology choices, life-cycle environmental impacts and resource constraints interact within a single energy-system optimization framework.