This project emerged in 2006 from a very simple idea: cross-fertilization among scientists in different disciplines at the CNRS. In practice taking advance of colleagues from the newly born INES we figured out a project to build an exemplary zero net energy building in the Mediterranean area with a very low environmental impact and at reasonable costs.
Briefly the conceptual scheme is based on precise architectural choices coupled to innovative energetic solutions in the aim to optimize energy consumption and ideally to approach the construction of a zero net energy building. The project includes from the beginning an experimental ambition. In fact the experimental validation of performances and realizations is part of the exercise from its very beginning
Architectural choices are simple: a compact design, an inner concrete nucleus highly inert and an efficient insulation by light exterior walls (refer to photos below). These elementary concepts are coupled to solar panel production of hot water for heating and sanitary uses. The theoretical estimation approaches 100% efficiency by a precise optimization of concrete surfaces and reservoir balloons.
Seasonal comfort in summer is provided by natural ventilation coupled to air fan and solar fences.
Specific studies were realized to evaluate precisely the energetic potential with respect to needs so that the building can definitely be considered as an energetic node able to produce, stock and use energy according to seasons.
Natural ventilation and its optimization are crucial aspects around which we could gather a number of scientific projects. Indeed in the context of the project ADN-bati, part of the interdisciplinary CNRS program on ENERGY, simulation exercises on the air fluxes the rooms of Charpak building were object of a national benchmark. The ADN-bati project associates several CNRS laboratories - LIMSI (CNRS/UPMC/Université Paris Sud), LOCIE (CNRS/Université de Savoie) and PIMENT at Reunion island, Its goal is to develop and optimize theoretical models enabling efficient simulation of air fluxes. Indeed existing models are not adapted to this particular exercise reduced to the scale of a building.
The figure below illustrates the results from the benchmark. In practice a precise estimation of the size and position of openings could be achieved (L.Stephan, A.Bastide, E.Wurtz, Optimizing opening dimensions for naturally ventilated buildings Applied Energy, 88 (2011), pp. 2791-2801).
Charpak building has been chosen as an example of application of the program « solar heating and cooling » from the international agency for energy « net zero energy building » (www.iea-shc.org/task40/) and is also integral part of the project ANR 4C (Confort en Climat Chaud sans Climatiser) again dedicated to the optimization of natural ventilation performances.
As for now the optimization and experimental validation of the solution put in place in Cargèse are studied by two PhD students at the laboratories G2elab (CNRS/Université Grenoble I/Institut polytechnique de Grenoble) and LOCIE supervised by INES and IESC.
In the actual societal reality where buildings represent approximately 50% of energetic consumption and 70 % of electric consumption, the charpak building, with its precise attention to summer comfort in hot Mediterranean climate, has gathered several international and national laboratories participating to IEA.
Simulation of natural ventilation describing air fluxes in a room of Charpak building (A.Bastide, PIMENT)
A: Description of limit conditions
B: The field of temperature variation in the room. Pseudo color blue to red identifies minimal to maximal temperature fields.
C: Evolution of air speed fields, in pseudo color scale from bleu to red are indicated minimal to maximal speeds.
