Thermodynamics, energetic and reactive systems
Scientific policy, aims
The team TES (Thermodynamics, Energetics and reactive Systems) develops applications dealing with :
- High density storage of thermal energy, without losses (lien vers ESSI à venir),
- Heat transformation , i.e. cold production (Climsol) and/or heat production including heat upgrading ,
- Transportation of thermal energy over long distances (Valotherm)
- Energy conversion from heat (especially solar energy) to power or electricity.
The simulation and optimization of distribution networks, particularly electricity network.
Thermochemical converters are the key points of our research development. They combine two or more univariant reaction between a gas and a condensed phase (liquid or porous solid). Moreover, we recently patented a new kind of energy converters : the thermo-hydraulic converters that involve motor or receiver cycles, at a maximal efficiency.
The optimization of theses processes (combining highly endo or exothermal steps in a dynamic working) and of the related materials and reactive fluids requires experimental researches and modeling at four scales, strongly connected :
- the reactive solid (for thermochemical processes): we measure and analyze the thermodynamic data and equilibrium of their reaction with various gases (H2O, NH3, CO2). These equilibria must fit to the operating condition of the application, i.e. the heat source and heat sink temperatures. The reactive pair selection has to take into account environmental criteria (toxicity, GWP…) , cost, availability of the solid, life cycle analysis…
- the reactive porous composite, made of a solid reactant and an inert binder (Fig.1) : we characterize, model and try to control heat and mass transfers parameters according to the implementation of the solid reactant in the composite. The challenge differs depending on the application and its main limitation: for applications targeting high power output, the main limitation is usually due to the conductive heat transfer in the porous reactive media (the binder is then expanded natural graphite) ; for storage applications, the limitation is more linked to mass transfer in these high density materials (thus, the binder will be a dispersant in order to allow a sufficient porosity).
- the solid / gas reactor: we investigate the optimal integration of gas diffusers and heat exchangers in the reactive composite, and the effect of non-equilibrium thermodynamic constraints (P,T) on the kinetics of the reactor transformation. For example, we develop a constructal approach to optimize transfer networks that minimize the destruction of exergy. This new approach has been extended to the coupling of heat and mass transfer in porous reactive material, and recently to the coupling between radiative and conductive heat transfer and chemical reactions for applications in thermochemistry using concentrated solar flux (H2 production, storage).
the process (thermochemical or thermo-hydraulic transformer) that combines one or more components (reactors, condenser, evaporator, ... depending on the applications listed above): through a thermodynamic analysis, we develop new concepts of processes, and the dynamic simulations of these non-stationary systems . These simulations allow to optimize these processes according to various criteria such as : COP, energy density, specific power (per mass or volume), complexity,... These criteria are weighted according to the application of the process.