Energy and Process Systems: STEP

Scientific orientations

The overall objective of this theme is to understand and master the physics of innovative processes dedicated to integration within sustainable buildings. To achieve this, studies carried out within the STEP theme aim to model their behavior, assess their efficiencies under controlled and in situ conditions, and optimize their operating parameters according to environmental conditions and requirements.

The processes concerned are absorption and adsorption energy processes for the valorization of low-temperature renewable or recovered heat, coupled heat and mass exchangers (falling-film exchangers), storage systems using sensible (water, soil), latent and sorption heat, solar thermal collectors, solar chimneys, hybrid collectors, solar trees, energy transformation and conversion processes in buildings, air treatment processes (adsorption, electrofiltration, ionization).

A particular challenge is to design systems with the lowest possible environmental impact, by implementing robust processes with minimized energy costs, or for oxidation processes, for example, by designing acceptable processes in terms of by-products or reaction intermediates. Beyond the process itself, integration into the building and its environment remains a scientific challenge (in connection with the SITE theme), in particular to study the transfer of pollutants from outside to inside (buildings), to assess the ratio between health benefits and energy costs of purification systems, or to study the solar thermal energy transformation chain, at the scale of each component (collector, storage, diffuser, sorption heat pump, etc.) and at the scale of their coupling.

The methods used in this theme are, on the one hand, experiments under controlled and in situ conditions and, on the other hand, phenomenological modeling, thermodynamic analyses, asymptotic methods and optimization (thermodynamic approach, genetic algorithm, etc.).

Specific scientific objectives

One of the objectives is to improve the performance of trithermal absorption machines, used in different operating modes (production of cold, heat, work, thermal energy storage, or hybrid operation), using a multi-scale approach. Numerical and thermodynamic modeling will be carried out at all three process scales: characterization of local hydrodynamic, mass, thermal and thermochemical phenomena in sorption falling films; their efficient implementation in sorption exchangers; integration of these components in innovative processes. One issue that will be addressed for the integration of these machines in solar buildings is variable-regime modeling at these different scales. At the film scale, the challenge is to understand the couplings between transfers and hydrodynamic instabilities, by developing simple, robust mathematical models enabling fine analysis of the phenomena and statistically resolved 3D simulations at the scale of an exchanger element. At exchanger scale, robust and experimentally validated sizing laws need to be obtained.

A second objective is tooptimize solar production and sensitive or latent storage. The development of solar energy in NZEB (Nearly Zero Energy Buildings) type buildings requires maximizing both solar production (heat and electricity) and storage efficiency in relation to the intermittence of the resource and the needs of users. The associated scientific issues involve the study of mass/heat transfer and photo-conversion phenomena. The methodologies developed are based on dimensional analysis, modeling of isolated phenomena (CFD, radiation, phase change) and experimental studies under controlled conditions (PIV, artificial lighting). On the other hand, the aim is to characterize and optimize the performance of the components and systems developed. Modeling covers coupled phenomena (complete systems), and prototype testing can be carried out under controlled or real-life conditions.

A third objective is to contribute to the development of methods and tools for evaluating and predicting the performance of sorbents for the treatment of micropollutants and for energy storage. The modeling work undertaken in recent years will be extended to include sensitivity studies and the use of dimensional analyses. These studies should make it possible to justify the choice of the most appropriate models. All these tools can be studied for our limit cases, i.e. for low adsorbate concentrations and/or very strong competition between compounds (water-pollutant).

Theme leaders

• Michel ONDARTS
  
• Anne-Laure PERRIER
  

Projects and collaborations

In connection with the "absorption machines" objective, we are maintaining our collaboration with the L2ST laboratory (Laboratoire des Systèmes Solaire et Thermodynamique) at CEA-INES, as well as with HES-SO laboratories in Switzerland (Lesbat, LTE...). We are also actively involved in the GDR Transinter research group. A platform for characterizing falling-film heat and mass exchangers under controlled conditions is currently being finalized and should be fully operational by 2021-2025.

With regard to the "high-performance adsorbents" objective, existing collaborations with laboratories specializing in the synthesis and characterization of adsorbent materials (LCME USMB, IS2M UHA, LMI UCBL, LMCPA UPHF, IPRA UPPA) and the experimental resources developed within the laboratory (test benches for dynamic characterization of adsorbents, thermogravimetric analysis) are being put to good use in numerous research projects (ANR, Carnot project, etc.). A particular effort is envisaged to consolidate systems for measuring micropollutants.

With regard to storage using phase-change materials, existing collaborations with academic laboratories (LaTEP and LGcGe) and other partners (CEA, DATE, SMCI) will be continued. Actions will be launched on the combined issues of solar drying and PVT hybrid collectors.

Finally, an ANR project (WINFIL) is getting underway to address the issue of joint control of indoor air quality, comfort and energy consumption in residential and tertiary buildings. This project, conducted in partnership with LaSiE, aims to develop and characterize the performance of a new-generation parieto-dynamic window equipped with an electrostatic particle filtration module.

Examples of current projects include ANTEA and CONICS!