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Article | Energies


Published on 15 December 2023

Objectives: At I-Tésé, one of our missions is to devleop a proprietary toolkit of numerical models, data and information sets, and analysis methods. These tools are fundamental to the research we conduct for the CEA and partners.

Numerical models  

Numerical models capable of supporting systemic analysis are vital to our work at I-Tésé. We are active users and developers of analysis and modeling software, utilizing the CEA's proprietary data to build and test scenarios for customers within and outside the organization. By providing factual estimates of the value the technologies being developed can capture or create, we also support the CEA's technology development roadmaps.


We mainly rely on three tools: TIMES, for multi-energy-vector, multi-use-use-case scenarios; OPERA, which does the same thing, but through system dynamics and with a focus on the French market; and Antares-Simulator, which simulates electricity grids on an hour-by-hour basis. 

TIMES: Energy system optimization modeling

TIMES (for “The Integrated MARKAL-EFOM System") is a technical and economic modeling tool developed by the Energy Technology System Analysis Program (ETSAP) of the International Energy Agency (IEA). It is based on a bottom-up approach to energy systems modelling. The software, which has modules for primary resources, conversion, transportation and distribution, storage, and end users, generates a relatively accurate and detailed technological representation of integrated energy markets. 

This type of approach to integrated energy systems modeling is vital to : 

  • Understanding the full technical and economic complexity of proposed energy-industry strategies (like for the nuclear industry) and deploying new energy technologies.
  • Ensuring that the technical and economic data produced by CEA research and the CEA's associated expertise utilizing this data are made available, regardless of the type of energy.
  • Identifying the endogenous mechanisms that impact energy market dynamics and the energy cost-price systems associated with each energy technology for different time-slice resolutions.
  • Producing quantitative assessments of the impacts of actual and alternative strategies (new technical requirements or limitations, different regulatory scenarios, additional investment, etc.).


We use the Veda modelling environment and GAMS mathematical modeling software. Models are generally on an annual time scale. However, seasonal, monthly, weekly, and even day-to-night time scales can also be integrated

 Contact : Oualid Gharbi 

OPERA: Scenario simulator for the French market

OPERA (Outil de Prospective EneRgétique de l'Alliance Nationale de Coordination de la Recherche pour l'Energiewas developed in 2017 to produce energy transition scenarios for France up to a 2050 time horizon with the support of experts from the Alliance's member research organizations. The software is a simulator and integrator (on an annual basis), representing the energy system through a series of sector-specific demand modules (for buildings, transportation, industry, agriculture, and data centers) and supply modules (for electricity, heat networks, and gas grids). Hydrogen, biomass (biomass available for energy production in France), and nuclear power are also covered by specific modules. 

In 2020-21, I-Tésé developed a Vensim-compatible (a system dynamics simulator) version of OPERA so that changes to the energy system model could be made more easily and the impact of different parameters on GHG emissions simulated rapidly. The goal was to provide insights to inform national policy.

Contact : Anne Baschwitz

Antares-Simulator: Electricity grid modeling

RTE originally developed Antares-Simulator for France's grid. Antares-Simulator is an open-source linear integer optimization tool that optimizes system operation only; energy generation assets and end-user demand are inputs. The software can be used to simulate electricity grid transmission and distribution (T&D) from the regional to national and cross-border scales. 

Antares-Simulator is also a useful toolkit for much more than T&D simulations. The grid can be described in more or less detail (spatially and in terms of technology), and with a few adjustments, multi-vector (gas, heat, hydrogen) energy systems can also be simulated. 

- Analysis of the energy transition in France and the impacts on nuclear assets.

As the installed base of intermittent renewable energy generation assets grows, demand on nuclear power plants is changing. This new demand profile has implications for the reactors themselves (i.e., the power ramp rate) and on asset management (shutdowns for refueling and maintenance). A changing energy mix will also come with economic impacts that also need to be analyzed. A third-year PhD student is using Antares-Simulator to study nuclear flexibility against the backdrop of the energy transition. (Lien vers la thèse ou la page) 

- Analysis of historical time series

Antares-Simulator studies require a large number of inputs, including time series for intermittent ENR production (annual with hourly steps). Analyzing time series in terms of statistical distributions helps limit the amount of historical data required and improves the results. 

- Effect of climate change 

Climate change can be factored in via time series for intermittent renewable energies and variations in demand.

 Contact : Sophie Gabriel


Access to relevant datasets and organized, shared market, regulatory, and tech intelligence to support our numerical models is vital to creating a systemic representation of our energy system, to building scenarios, and to advancing energy roadmaps.


I-Tésé is leading this multidisciplinary project with fellow CEA institutes ISEC, IRESNE, ISAS and LITEN .

 Contact : Elvire Leblanc 


The development of new methods is one of the pillars of I-Tésé's roadmap. Our strategy is not to develop generic methods, but to capitalize on the specific methods developed for different projects with our partners (companies, academic research labs, RTOs).


I-Tésé specialists oversee these efforts for the different types of tools we develop and use.

Specialist multicriteria analysis : Guillaume Boissonnet

Specialist systems dynamics : Anne Baschwitz