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Spitz C.,CNRS Laboratory of Design Optimisation and Environmental Engineering | Mora L.,French National Center for Scientific Research | Wurtz E.,French National Solar Energy Institute | Jay A.,French National Solar Energy Institute
Energy and Buildings

Today, simulation tools are widely used to design buildings because their energy performance is increasing. Simulation is used at different stages to predict the building's energy performance and to improve the thermal comfort of its occupants, but also to reduce the environmental impact of the building over its whole life cycle and lower the cost of construction and operation. Simulation has become an essential decision support tool, but its reliability should not be overlooked. It is important to evaluate the reliability of simulation and measurement as well as uncertainty so as to improve building design. This work aimed to evaluate and order the uncertainty of the simulation results during the design process. A three-step methodology was developed to determine influential parameters in the building's energy performance and to identify the influence of parameter uncertainty on the building performance. This methodology was applied at the INCAS experimental platform of the French National Institute of Solar Energy (INES) in Le-Bourget-du-Lac to identify and measure the uncertainty in a simulation hypothesis. The method can be used during the entire design process of a building, from preliminary sketches to operating phase. © 2012 Elsevier B.V. All rights reserved. Source

Si Larbi A.,University Claude Bernard Lyon 1 | Agbossou A.,CNRS Laboratory of Design Optimisation and Environmental Engineering | Hamelin P.,University Claude Bernard Lyon 1
Composite Structures

This experimental and numerical study is related to the repair and strengthening of reinforced concrete beams with TRC (textile-reinforced concrete) and hybrid (TRC. +. carbon and glass rods) solutions that are positioned relative to the more traditional ones such as the CFRP (carbon fibre-reinforced polymer) solutions. Beyond the good performances highlighted experimentally, especially in terms of bearing capacity and different failure modes (e.g., possibility to avoid peeling off), it is clear from this work that the TRC, despite its nonlinear behaviour (multi-cracking), does not allow a significant gain in ductility. From a numerical perspective using numerical modelling (smeared crack approach), the overall behaviour of beams reinforced with TRC (or the hybrid solutions) based only on the textile "efficiency factor" (or the average contribution of the filaments) as a calibration coefficient was found to be significantly satisfactory. Numerical modelling performed on all the beams also highlighted the fact that the axial stiffness of reinforcements (even in the case of a cracking material) governing the overall behaviour of beams could, at least in part, explain the observed failure modes. © 2012 Elsevier Ltd. Source

Perrier G.,CNRS Laboratory of Design Optimisation and Environmental Engineering | De Bettignies R.,DTS | Berson S.,DTS | Lemaitre N.,DTS | Guillerez S.,DTS
Solar Energy Materials and Solar Cells

A study of the optical and impedance behavior of optimized standard and inverted photovoltaic solar cells based on P3HT:PCBM active nano composites is presented. The standard cells sequence is ITO/HTL1/P3HT:PCBM/Ca/Al and the inverted cells one is ITO/ZnO/P3HT:PCBM/HTL2/Ag where HTL1 and HTL2 are Hole Transport Layers. Absorption and action spectra, together with I-V characteristics, are shown to be quite similar and lead to 4.05% and 3.90% energy conversions, for standard and inverted cells, respectively. Built-in potentials of 0.82-0.89 V and acceptor impurities concentrations of 1.6-2.4 10 15 cm -3 are found through capacitance measurements. Impedance spectrometry shows the classical two-circle complex plan curves, one being related to the effective lifetime of charge carriers before recombination at low frequency, and the other one to the diffusion time of these carriers at high frequency. The shape of the curves is identical, showing the ohmic role of the ZnO layer. It is shown that overall resistances in the dark are higher for inverted cells as compared to standard ones, and that this feature is inverted under illumination, with a thousand-time decrease. Global mobilities are in the range 3.8-4.6 10 -3 cm 2 V -1 s -1, which is slightly higher as compared to the literature. Four different equivalent circuit models are tested on experimental results, and it is concluded that the classical RCPE model (or its Garcia-Belmonte variant) is suitable for this kind of cells. © 2012 Elsevier B.V. All rights reserved. Source

Pastor F.,Athenee royal Victor Horta | Kondo D.,University Pierre and Marie Curie | Pastor J.,CNRS Laboratory of Design Optimisation and Environmental Engineering
International Journal for Numerical Methods in Engineering

The first purpose of this paper is the numerical formulation of the three general limit analysis methods for problems involving pressure-sensitive materials, that is, the static, classic, and mixed kinematic methods applied to problems with Drucker-Prager, Mises-Schleicher, or Green materials. In each case, quadratic or rotated quadratic cone programming is considered to solve the final optimization problems, leading to original and efficient numerical formulations. As a second purpose, the resulting codes are applied to non-classic 3D problems, that is, the Gurson-like hollow sphere problem with these materials as matrices. To this end are first presented the 3D finite element implementations of the static and kinematic classic methods of limit analysis together with a mixed method formulated to give also a purely kinematic result. Discontinuous stress and velocity fields are included in the analysis. The static and the two kinematic approaches are compared afterwards in the hydrostatic loading case whose exact solution is known for the three cases of matrix. Then, the static and the mixed approaches are used to assess the available approximate criteria for porous Drucker-Prager, Mises-Schleicher, and Green materials. © 2013 John Wiley & Sons, Ltd. Source

N'Tsoukpoe K.E.,CNRS Laboratory of Design Optimisation and Environmental Engineering | Le Pierres N.,CNRS Laboratory of Design Optimisation and Environmental Engineering | Luo L.,CNRS Laboratory of Design Optimisation and Environmental Engineering

The long-term thermal storage by absorption process studied in this paper is devoted to building heating. A demonstrative prototype that can store 8 kWh of heat and produce a heating power of 1 kW has been designed and built. It has been tested in static and dynamic operating conditions, which are compatible with domestic solar thermal and heating plants. The process operating principle, the prototype design and first experimental results are presented and discussed in this contribution. The charging process has been proved successful. The observed power during the charging phases is satisfactory, according to the process design for a real plant (2-5 kW). Absorption during discharging phase is also verified. Discharging tests show that absorption operates in conditions that could allow house heating as the absorber outlet solution temperature can reach 40 °C. However, some problems related to the absorber design have not allowed observing the heat recovery by the heat transfer fluid as expected. Some avenues are explored prior to a new and more appropriate design and eventually a new operating mode. Various aspects such as the use of a heat and mass transfer enhancement additive and stratification in the solution storage tank have also been addressed. © 2013 Elsevier Ltd. Source

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