Energy Systems and Processes: STEP

Scientific orientations

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

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

One of the challenges particularly addressed is to design systems with the least possible environmental impact, by implementing robust processes whose energy costs are minimised, or for 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 (in connection with the SITE theme), in particular to study the transfer of pollutants from the outside to the inside (buildings), to assess the ratio between the health benefits and the 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 implemented in this theme are, on the one hand, experiments under controlled conditions and in situ and, on the other hand, phenomenological modelling, thermodynamic analyses, asymptotic methods and optimisation (thermodynamic approach, genetic algorithm etc).

Specific scientific objectives

One of the objectives is to improve the performance of trithermal absorption machines, used in different modes of operation (production of cold, heat, work, thermal energy storage, or hybrid operation), through a multi-scale approach. Numerical and thermodynamic modelling will be carried out at the three process scales: characterisation 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. An issue that will be addressed for the integration of these machines in solar buildings is the variable regime modelling 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 allowing a fine analysis of the phenomena and statistically resolved 3D simulations at the scale of an exchanger element. On the scale of an exchanger, robust and experimentally validated sizing laws must be obtained.

A second objective is theoptimisation of solar production and sensitive or latent storage. The development of solar energy in NZEB (Nearly Zero Energy Buildings) type buildings requires maximising 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 problems are related to the study of mass/heat transfer and photo-conversion phenomena. The methodologies developed are based on dimensional analysis, modelling of isolated phenomena (CFD, radiation, phase change) and experimental studies under controlled conditions (PIV, artificial lighting). On the other hand, the aim is to characterise and optimise the performance of the components and systems developed. The modelling concerns coupled phenomena (complete system), and prototype tests 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 sorbents for the treatment of micropollutants and for energy storage. The modelling work undertaken in recent years will be extended to sensitivity studies and the use of dimensional analyses. These studies should make it possible to justify the choice of the most suitable models. All of these tools can be studied for our borderline cases, i.e. for low adsorbate concentrations and/or very strong competition between compounds (water-pollutant).

Persons responsible for the theme

• Michel ONDARTS
  
• Anne-Laure PERRIER
  

Projects and collaborations

In connection with the "absorption machines" objective, we maintain collaborations with the L2ST laboratory (Solar Systems and Thermodynamics Laboratory) of the CEA-INES, as well as with laboratories of the HES-SO in Switzerland (Lesbat, LTE...). In addition, we are actively involved in the GDR Transinter. A platform for the characterisation of falling film heat and mass exchangers under controlled conditions is being finalised and should be fully operational by 2021-2025.

Concerning the "high-performance adsorbents" objective, existing collaborations with laboratories specialising in the synthesis and characterisation of adsorbent materials (LCME USMB, IS2M UHA, LMI UCBL, LMCPA UPHF, IPRA UPPA) and the experimental means developed within the laboratory (test benches for the dynamic characterisation of adsorbents, thermogravimetric analysis) are used in numerous projects at research (ANR, Carnot project, etc.). A special effort is planned to consolidate the devices used to measure micropollutants.

Concerning 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 initiated on the combined issues of solar drying and PVT hybrid collectors.

Finally, an ANR project (WINFIL) is starting on the issue of the joint control of indoor air quality, comfort and energy consumption in residential and tertiary buildings. This project, carried out in partnership with LaSiE, aims to develop and characterise the performance of a new generation parietodynamic window equipped with an electrostatic particle filtering module.

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