Energy Systems and Processes: STEP

Scientific guidelines

The overall objective of this theme is to understand and master the physics of innovative processes designed for integration into sustainable buildings. To this end, the studies conducted within the STEP theme aim to model their behavior, evaluate their efficiency under controlled and in situ conditions, and optimize their operating parameters according to environmental conditions and needs.

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

One of the key challenges is to design systems with the lowest possible environmental impact, by implementing robust processes with minimal energy costs or, in the case of oxidation processes for example, by designing processes that are acceptable in terms of by-products or reaction intermediates. Beyond the process itself, integration into the building and its environment remains a scientific challenge (linked to the SITE theme), particularly when it comes to studying the transfer of pollutants between the outside and inside (buildings), to assess the ratio between health benefits and energy costs of purification systems, or to study the solar thermal energy conversion chain, at the level of each component (collector, storage, diffuser, sorption heat pump, etc.) and at the level of their coupling.

The methods used in this area are, on the one hand, experiments under controlled conditions and in situ 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 (cooling, heating, work, thermal energy storage, or hybrid operation), using a multi-scale approach. Numerical and thermodynamic modeling will be carried out at three process scales: characterization of local hydrodynamic, mass, thermal, and thermochemical phenomena in falling films during sorption; their efficient implementation in sorption exchangers; and the integration of these components into innovative processes. One challenge that will be addressed for the integration of these machines into solar buildings is variable-speed modeling at these different scales. At the film scale, the challenge is to understand the couplings between transfers and hydrodynamic instabilities by developing simple and robust mathematical models that enable detailed analysis of the phenomena and statistically resolved 3D simulations at the scale of an exchanger element. At the exchanger scale, robust and experimentally validated design laws must be obtained.

A second objective isto optimize solar production and sensible or latent storage. The development of solar energy in NZEB (Nearly Zero Energy Buildings) requires maximizing both solar production (heat and electricity) and storage efficiency in relation to the intermittency of the resource and user needs. The associated scientific issues relate, on the one hand, to 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 study under controlled conditions (PIV, artificial lighting). On the other hand, it involves characterizing and optimizing the performance of the components and systems developed. Modeling focuses on coupled phenomena (complete system), and prototype testing can be carried out under controlled or real conditions.

A third objective is to contribute to the development of methods and tools for evaluating and predicting the performance of absorbents for treating micropollutants and for energy storage. The modeling work undertaken in recent years will be extended to sensitivity studies and the use of dimensional analyses. These studies should enable us to justify the choice of the most suitable models. All of these tools can be studied for our boundary conditions, 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 continuing our collaboration with the L2ST (Laboratory of Solar and Thermodynamic Systems) at CEA-INES, as well as with laboratories at HES-SO in Switzerland (Lesbat, LTE, etc.). We are also actively involved in the Transinter GDR. 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 objective of "high-performance adsorbents," 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 laboratories (test benches for dynamic characterization of adsorbents, thermogravimetric analysis) are being put to good use in numerous research projects (ANR, Carnot project, etc.). A special effort is planned to consolidate the devices used to measure micropollutants.

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

Finally, an ANR project (WINFIL) is being launched to address the issue of jointly controlling indoor air quality, comfort, and energy consumption in residential and commercial buildings. This project, conducted in partnership with LaSiE, aims to develop and characterize the performance of a new generation of parietal-dynamic windows equipped with an electrostatic particle filtration module.

Examples of ongoing projects: the ANTEA project or the CONICS project!