Description du sujet de thèse

Title: Optimization of Industrial Solar Heat Production in Fresnel Power Plants Using Direct Steam Generation (M/F)

Laboratories: CNRS PROMES - CEA L2TS
Funding: Occitanie Region - ANR (PEPR SPLEEN)
PhD Supervisor: S. RODAT (CNRS PROMES)
Co-supervisors: Q. FALCOZ (CNRS PROMES); V. VUILLERME (CEA LITEN)
Industrial Partner: F. ROGET (eLlo); F. LECAT (eLlo)

Candidate Profile:
Education: Research Master's degree or Engineering degree with research experience (e.g., M2 project in a research lab).
Discipline: Engineering Sciences.
Knowledge and Skills: Energy engineering, applied mathematics, solar technologies, thermohydraulics.
Programming: Python, Modelica
Other: Analytical thinking, good writing skills, strong English proficiency.

Introduction:

Industrial processes require heat within the 50–1500°C temperature range, and heat represents approximately 70% of industrial energy consumption. Industrial heat use is typically divided into three temperature ranges: low (below 150°C), medium (150–400°C), and high (above 400°C), each requiring different solar collector technologies. Concentrated solar power (CSP) technologies are essential for producing solar heat above 150°C. The central issue of integrating solar heat into industrial processes is addressed in the SHIP4D project (PEPR SPLEEN program).

In this PhD, CNRS PROMES and CEA LITEN, in collaboration with the eLlo direct steam generation solar power plant (located in the Pyrénées-Orientales), aim to investigate solar heat production for industrial use around 300°C. The work will rely on performance data from the eLlo thermal solar plant to validate a numerical model capable of estimating and optimizing heat production with thermal storage. A study of industrial heat needs in the Occitanie and Auvergne-Rhône-Alpes (AuRA) regions will help define how solar heat could support the decarbonization of industrial heat in these areas.

Project Positioning:
75% of the industry's energy consumption is used to produce heat for various processes (e.g., food processing, textiles). Around 50% of this demand is for heat below 400°C, which is the typical temperature range for linear CSP systems. Currently, this heat is primarily generated using fossil-fuel boilers. In this temperature range, photovoltaic solar is not relevant, as solar thermal systems offer 2 to 3 times higher conversion efficiencies, along with low-cost thermal storage. Furthermore, renewable fuel availability will be limited, making them more suitable for high-temperature applications (e.g., steel, cement). Therefore, it is highly relevant to decarbonize industrial heat using direct steam generation via solar thermal power plants—a goal aligned with Priority #2 of the European Green Deal.

Project Objectives:
The goal of the project is to promote solar heat for industry as a path toward decarbonization. To this end, PROMES, a lab specializing in concentrated solar processes, and CEA LITEN, which develops digital tools for optimal thermal system control, are partnering with the eLlo solar thermal plant, which produces steam at 286°C and 70 bars, to work on optimizing solar heat delivery for industrial processes.

Key objectives include:
A state-of-the-art review of industrial heat needs, with a focus on the Occitanie and AuRA regions.

Analysis of operational data from the eLlo plant to assess production capacities.

Development of a representative numerical model (simulator) using Modelica, limited to steam production and storage/release based on industrial process needs.

Development of a digital twin of the installation, coupling the simulator with high-level control systems.

Testing various high-level control strategies and algorithms to optimize steam production, storage management, and heat delivery, with the aim of maximizing demand coverage and solar resource utilization.

This PhD project will leverage the experience of the only commercial CSP plant with direct steam generation in France to develop a decarbonization strategy for industrial heat.

Detailed Description of the Scientific Project:
The project involves two academic partners (CNRS and CEA) and one industrial partner (eLlo).

The CNRS-PROMES lab (Processes, Materials and Solar Energy) specializes in CSP systems and possesses unique solar infrastructure (e.g., the Odeillo solar furnace, Thémis solar tower), providing key experimental and simulation expertise. Process heat is a growing area of interest for the lab.

The CEA L2TS lab (Thermodynamic and Solar Technologies Lab) leads the CEA-Liten roadmap on “solar heat for industry and territories.” It has advanced CSP prototypes (e.g., two linear Fresnel plants at the Cadarache site) and expertise in the design and optimal control of mid-temperature industrial heat systems.

The eLlo solar plant is the only commercial CSP plant in France. Located in Llo (Cerdagne, Occitanie), it is a linear Fresnel plant delivering 10MWe with 4 hours of full-capacity thermal storage. Commissioned in 2019, its 5-year performance was positively presented at the SolarPACES 2024 conference in Rome. It is also the only known plant worldwide using pressurized water tanks for thermal storage, employing water as the sole working fluid for heat transfer, storage (saturated liquid), and turbine operation (saturated steam), making it environmentally friendly compared to typical oil-based plants and well-suited for industrial steam needs.

This PhD builds upon a dynamic and fruitful collaboration between eLlo and PROMES. The research will focus on four main actions:
1. Literature Review:
The PhD will begin with a review of industrial heat needs and available sustainable heat supply options. A regional analysis will identify the heat demand in Occitanie and AuRA and the key industries to target based on thermal requirements.
2. Analysis of eLlo Plant Data:
In collaboration with eLlo, the PhD student will assess the heat production capacity of the existing 30 MWth installation. Though the plant produces 10MWe, the project will focus on its steam supply capabilities (286°C, 70 bars), and its 4-hour thermal storage enabling production beyond sunlight hours—a key advantage for process heat. This data will inform the validation of numerical models and assessment of solar heat delivery potential.
3. Development of Simulator and Digital Twin:
A numerical model (simulator) of the plant will be developed in Modelica, focusing on steam production and thermal storage/release (excluding the power block). The model will integrate optical, thermal, and hydraulic subsystems, along with low-level controllers, to accurately represent plant behavior. CEA's co-simulation platform will be used to build the digital twin, linking the simulator with high-level control strategies.
4. System Optimization:
The digital twin will be used to optimize plant and storage operation and maximize output. This will be done for both the eLlo plant and a representative industrial process to assess the broader potential of CSP for decarbonization in Occitanie and AuRA. The concept of hybrid heat supply (e.g., solar + gas) will be explored to ensure reliable year-round delivery. Avoided CO₂ emissions will be quantified by comparing conventional (gas-fired) and hybrid (e.g., solar-gas) scenarios.

Outreach and Scientific Goals:
This PhD will contribute to promoting and gradually introducing solar thermal energy to the industrial sector. It will also have a strong outreach component, promoting the little-known but mature CSP technology, which is expanding across Europe and beyond. CSP offers stable energy costs, energy independence, and compatibility with circular economy principles, thanks to its reliance on simple, locally manufactured, and recyclable materials.

Expected Outcomes:
At least 2 publications in international journals (e.g., Energy, Applied Energy, Energy Conversion and Management).
Participation in 2 national and/or international conferences (e.g., SolarPACES, JNES, SFT).
Participation in public scientific outreach events.

Contexte de travail

The PhD will take place at the PROMES-CNRS laboratory, located at the Odeillo solar furnace site. The numerical developments will require occasional travel to the INES site (Le Bourget du Lac, Savoie) to collaborate with the CEA Liten teams.

Le poste se situe dans un secteur relevant de la protection du potentiel scientifique et technique (PPST), et nécessite donc, conformément à la réglementation, que votre arrivée soit autorisée par l'autorité compétente du MESR.