MSCA-COFUND-CLEAR-Doc-PhD Position#CD22-34: DECARBONISING CITIES IN THE CLIMATE CHANGE CONTEXT: APPLICATION TO THE TERTIARY BUILDING

Context and Scientific issues

Recent work (Andrić et al. 2021) has shown that the energy demand for heating and cooling buildings will significantly increase, respectively up to 52% and 1050%, depending on the international geographical position. For example in France, the building sector is also one of the largest energy consumers. According to the data recorded by the French energy agencies, the energy consumption, mainly electrical, dedicated to air conditioning, represents, between 2017 and 2020, about 21 TWh/year, i.e. 10% of the total consumption dedicated to the tertiary buildings. Recent IPCC position papers (Dodman et al. 2022) have highlighted urban energy harvesting related to the magnitude of the temperature increase at a higher frequency level resulting from intense heatwave. As a result, air conditioning of tertiary buildings will be increasingly used, generating an increase in energy consumption. For example, the data centre building uses an HVAC (Heating, Ventilation and Air Conditioning) installation that controls the temperature and humidity of the server room to prevent the IT equipment from overheating. These installations account for about 50% of the electricity consumption of such a building. The reduction in the use of HVAC systems in temperate climates is achieved through free-cooling, which involves using outside air that is cooler than the temperature of the data centre's indoor environment. To extend the benefit, we have therefore recently proposed the use of an energy storage system based on sustainable granular materials, which needs to be placed upstream of the air conditioning system (Bouchenna et al. 2021). A packed bed of earthen materials was thermally characterized using multiple heating/cooling cycles according to ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) standards. The results show that particle diameter and the aerodynamic regimes exert significant effects on the energy buffering capacity. A relationship was proposed to link the specific mass power of the energy storage system, the architecture of the internal heat exchanger and the Reynolds number of the pores with the aim of designing mud bricks. The next two main research directions of this PhD proposal are to set up experiments and their numerical twin to define:

- the behavior of thermal hysteresis as a function of material properties and process parameters,

- the role of microporosity in the perspective of latent heat storage.

Scientific program

One of the main objectives of the PhD work will be to conduct numerical simulations at pore- and wall-scales, which will be compared to experiments performed in environmental controlled conditions. The scientific program will follow the four mains stages:

1. The state of art related to the characterization of the heat and mass transfer through earthen materials will be performed.

2. A numerical twin is developing from the French side. The student will bring its computation skills to implement the mass transfer model to capture the moisture buffering kinetics.

3. Validation of the model will be performed from experiments at the wall-scale to measure the heat and mass transfer fluxes using coupled remote sensing techniques. An inverse method will be employed to adjust the real external convective transfer coefficients to the simulations results.

4. The student will produce scientific articles in peer-reviewed journals

Working environment

The student will be inserted in the GPEM Laboratory constituted of a multi-disciplinary researchers teams working on circular economy and sustainable development. The team has a long experience of interdisciplinary and international collaborative works (Brazil, UK, Spain, Taiwan, China, and Czech).

References

Andrić, I., Le Corre O., Lacarrière B., Ferrão P., and Al-Ghamdi S. G. 2021. “Initial Approximation of the Implications for Architecture Due to Climate Change.” Advances in Building Energy Research 15 (3): 337–67. https://doi.org/10.1080/17512549.2018.1562980.

Bouchenna, C., Huchet F., Aramiou C., E. Hamard, Le Guen L., and Paul J. M. 2021. “Heat Exchanger Design Based on Earthen Materials.” Energy 227. https://doi.org/10.1016/j.energy.2021.120385.

Dodman, D., B. Hayward, M. Pelling, V. Castan Broto, W. Chow, E. Chu, R. Dawson, L. Khirfan, T. McPhearson, A. Prakash, Y. Zheng, and G. Ziervogel, 2022: Cities, Settlements and Key Infrastructure. In: Climate Change 2022: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [H.-O. Pörtner, D.C. Roberts, M. Tignor, E.S. Poloczanska, K. Mintenbeck, A. Alegría, M. Craig, S. Langsdorf, S. Löschke, V. Möller, A. Okem, B. Rama (eds.)]. Cambridge University Press, Cambridge, UK and New York,NY, USA, pp. 907–1040, doi:10.1017/9781009325844.008