Thermodynamic analyses on hybrid sorption cycles for low-grade heat storage and cogeneration of power and refrigeration

International audienceThis paper investigates three ways of coupling a solid/gas sorption refrigeration cycle with a Rankine cycle to create innovative hybrid cycles enabling power and refrigeration cogeneration with intrinsic energy storage. A new methodology has been developed to analyze these hybrid cycles and assess five relevant performance criteria (required heat source temperature, energy efficiency, exergy efficiency, power production ratio, and exergy storage density). Screening of 103 reactive salts implemented in the different hybrid cycle configurations highlights the most favorable configuration and reagent to meet the requirements of various applications. Analyses show that energy and exergy efficiencies can reach 0.61 and 0.40, respectively. Exergy storage density ranges from 142 to 640 kJ/kg NH3 when the heat source temperature is increased from 107 °C to 250 °C

Hybrid thermochemical cycles for low-grade heat storage and conversion into cold and / or power

International audienceIn order to recover low grade heat (available at temperatures under 250 °C) provided for instance by an industrial plant or solar energy, innovative thermodynamic cycles are investigated. These cycles are based on the hybridization of a solid/gas chemical sorption cycle (thermochemical cycle) with a power cycle (Organic Rankine Cycle (ORC)), they enable converting a low grade heat input into cold and / or power while providing an intrinsic energy storage feature. Four hybrid configurations are considered, a thermodynamic analysis allows comparing their performances with those of existing ORC through several criteria: energy and exergy efficiencies, specific exergy output and power production ratio. For each of the five systems, potential applications, advantages and weaknesses are summarized

Le test des gestes et de la parole dans la communication politique télévisée

Interview de Denis Muzet, directeur de l'institut Médiascopie, par Jean Mouchon sur la prise en compte de l'image et du geste dans les enquêtes d'opinion menées par les Instituts d'études

Solar-driven thermo-hydraulic process for reverse osmosis desalination

International audienceExisting distillation-based desalination processes are highly thermal energy consuming. Reverse osmosis (RO) technique is more efficient than thermal-based processes but it remains a solution that still induces high operating and maintenance costs. In this paper, an innovative thermally powered RO-based desalination process is presented. This new RO thermo-hydraulic process enables the pressurization of the salty water beyond its osmotic pressure to allow the permeation water through a semi-permeable membrane, thanks to a piston or an elastic bladder that is set in motion in a reservoir by a working fluid following a thermodynamic engine cycle similar to an Organic Rankine Cycle. The evaporator is heated by low grade heat (70 to 80°C) such the one delivered by plate solar collectors, while the condenser is cooled by the concentrated salty water. In order to enable a continuous drinkable water production, this process needs to implement two reservoirs, alternatively connected either to a high pressure evaporator or to a low pressure condenser. Such installation, designed here for brackish water desalination (5 g/liter), should enable an average daily production of 300 liters of drinkable water per m² of solar collectors with a production cost below 4€/m 3. That technology seems to be relevant for small scale (5 to 10 m 3 /day) the daily water needs of people living in remote areas, in accordance to the location and the solar resource. A modeling of the whole process, considering a quasi-steady state approach has been developed in order to study its dynamic behavior, optimize its design and maximize its performances. This paper presents the preliminary results relative to the performance of such solar-driven desalination process

Electrostatic complementarity in an aldose reductase complex from ultra-high-resolution crystallography and first-principles calculations

The electron density and electrostatic potential in an aldose reductase holoenzyme complex have been studied by density functional theory (DFT) and diffraction methods. Aldose reductase is involved in the reduction of glucose in the polyol pathway by using NADPH as a cofactor. The ultra-high resolution of the diffraction data and the low thermal-displacement parameters of the structure allow accurate atomic positions and an experimental charge density analysis. Based on the x-ray structural data, order-N DFT calculations have been performed on subsets of up to 711 atoms in the active site of the molecule. The charge density refinement of the protein was performed with the program MOPRO by using the transferability principle and our database of charge density parameters built from crystallographic analyses of peptides and amino acids. Electrostatic potentials calculated from the charge density database, the preliminary experimental electron density analysis, DFT computations, and atomic charges taken from the AMBER software dictionary are compared. The electrostatic complementarity between the cofactor NADP+ and the active site shows up clearly. The anchoring of the inhibitor is due mainly to hydrophobic forces and to only two polar interaction sites within the enzyme cavity. The potentials calculated by x-ray and DFT techniques agree reasonably well. At the present stage of the refinement, the potentials obtained directly from the database are in excellent agreement with the experimental ones. In addition, these results demonstrate the significant contribution of electron lone pairs and of atomic polarization effects to the host and guest mechanism.Instituto de Física de Líquidos y Sistemas BiológicosFacultad de Ciencias Exacta

Electrostatic complementarity in an aldose reductase complex from ultra-high-resolution crystallography and first-principles calculations

The electron density and electrostatic potential in an aldose reductase holoenzyme complex have been studied by density functional theory (DFT) and diffraction methods. Aldose reductase is involved in the reduction of glucose in the polyol pathway by using NADPH as a cofactor. The ultra-high resolution of the diffraction data and the low thermal-displacement parameters of the structure allow accurate atomic positions and an experimental charge density analysis. Based on the x-ray structural data, order-N DFT calculations have been performed on subsets of up to 711 atoms in the active site of the molecule. The charge density refinement of the protein was performed with the program MOPRO by using the transferability principle and our database of charge density parameters built from crystallographic analyses of peptides and amino acids. Electrostatic potentials calculated from the charge density database, the preliminary experimental electron density analysis, DFT computations, and atomic charges taken from the AMBER software dictionary are compared. The electrostatic complementarity between the cofactor NADP+ and the active site shows up clearly. The anchoring of the inhibitor is due mainly to hydrophobic forces and to only two polar interaction sites within the enzyme cavity. The potentials calculated by x-ray and DFT techniques agree reasonably well. At the present stage of the refinement, the potentials obtained directly from the database are in excellent agreement with the experimental ones. In addition, these results demonstrate the significant contribution of electron lone pairs and of atomic polarization effects to the host and guest mechanism.Instituto de Física de Líquidos y Sistemas BiológicosFacultad de Ciencias Exacta

Hybrid system combining mechanical compression and thermochemical storage of ammonia vapor for cold production

International audienceThis paper studies a hybrid system for cold production consisting of a compression cycle combined with a thermochemical process 10 by sharing the same condenser, evaporator and refrigerant fluid. The aim of this hybridization is to solve mismatch issues between 11 the demand of cold and the source of energy (availability and/or price) with a system as compact as possible. One important side 12 benefit is that the interaction between the compressor and the thermochemical reactor reduces the activation temperature for 13 ammonia desorption in the thermochemical reactor. To study this interaction a quasi-steady simulation model for both storage 14 and de-storage phases has been developed and experimentally validated by means of a small scale (approx. 300 Wh of cold 15 storage) experimental bench with ammonia as refrigerant and barium chloride (BaCl2) as reactant salt. Experiments proved a 35 16 K reduction in the activation temperature of the desorption reaction with respect to desorption without compressor. Model 17 validation by adjusting permeability and thermal conductivity of the reactive composite showed an acceptable agreement between 18 predicted and experimental reaction advancement-time curves. The validated model was used for simulation of the system in a 19 preliminary case study, representative in power (40 kW) and temperature (-25°C) of an industrial cold demand. It is shown that 20 during ammonia de-storage, the hybrid achieves a higher COP than a conventional mechanical vapor compression system. It 21 increases exponentially with the relative share of thermochemical storage in the cold production. 2

Experimental comparison of autodyne and heterodyne laser interferometry using a Nd:YVO4 microchip laser

Using a Nd:YVO4 microchip laser with a relaxation frequency in the megahertz range, we have experimentally compared a heterodyne interferometer based on a Michelson configuration with an autodyne interferometer based on the laser optical feedback imaging (LOFI) method regarding their signal to noise ratios. In the heterodyne configuration, the beating between the reference beam and the signal beam is realized outside the laser cavity while in the autodyne configuration, the wave beating takes place inside the laser cavity and the relaxation oscillations of the laser intensity then play an important part. For a given laser output power, object under investigation and detection noise level, we have determined the amplification gain of the LOFI interferometer compared to the heterodyne interferometer. LOFI interferometry is demonstrated to show higher performances than heterodyne interferometry for a wide range of laser power and detection level of noise. The experimental results are in good agreement with the theoretical predictions