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

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

Simulation of a solar hybrid absorption/thermochemical refrigerationsystem for a residential application

Further improvement of solar refrigeration systems depends strongly on development of more efficient energy storage systems. A hybrid absorption / thermochemical refrigeration system is proposed in this work, where both subsystems share the same condenser, evaporator and refrigerant fluid, making the overall system more economic and better performing than operating both parts separately. Performance of the system is evaluated by means of a simulation in a sample scenario, consisting of a demand of refrigeration for a single-family residence. The influence of varying the number of solar thermal collectors and the mass of refrigerant fluid available for storage at the thermochemical subsystem is studied

Stockage thermochimique inter saisonnier : caractérisation des transferts de masse au sein d'un sel réactif

National audienceCet article présente la caractérisation des transferts de masse au sein d'un sel réactif (cinétique de réaction, perméabilité du lit de sel, …) destiné au stockage thermochimique inter saisonnier, dans le but d'optimiser à la fois la densité énergétique du lit de sel et sa perméabilité (caractéristiques qui ont des évolutions antagonistes). Un modèle et une expérimentation ont donc été réalisées autour du couple SrBr 2 /H 2 O et leurs résultats ont été comparés

Transformation, Conversion, Stockage, Transport de l'énergie thermique par procédés thermochimiques et thermo-hydrauliques

The research presented aims to meet the major challenges of sustainable management and rational use of energy (transport and storage of heat energy), to develop thermodynamic analysis tools and propose appropriate solutions for minimizing environmental impacts resulting from the transformation or conversion of thermal energy. The different developed themes are based on three axes. The first part concerns the development of thermodynamic analysis tools for the assessment, design and optimization of thermodynamic process transformation/conversion of thermal energy. The second part is specifically related to thermochemical transformers based on reversible solid / gas reactions, by taking into account the various scales of the process according to application objectives : choice and implementation of solid reactant, optimal configuration of S / G reactor and dynamic management of the thermochemical cycle. This approach is illustrated through various applications : pseudo-continuous production of heat and / or cold, heat or cold production with high thermal power, solar cooling for buildings, solar deep freezing, solar heat storage with high energy density and transportation of heat or cold over long distances. The last part of this work concerns the development of new thermo-hydraulic processes more specifically adapted to the thermal energy conversion into work and whose potential seems promising for applications in power generation from solar energy or ocean thermal energy, or efficient production of cold in motor vehicles.Les travaux de recherche présentés visent, de manière générale, à répondre aux enjeux majeurs de gestion rationnelle et de maîtrise de l'énergie (transport et stockage de l'énergie thermique), à développer des solutions pertinentes et proposer des outils d'analyse thermodynamique pour la minimisation des impacts environnementaux induits par la transformation ou la conversion de l'énergie thermique. Les différentes thématiques développées s'articulent selon trois axes. Le premier volet concerne le développement d'outils d'analyse thermodynamique pour l'évaluation, la conception et l'optimisation de la qualité thermodynamique des procédés de transformation/conversion de l'énergie thermique. Le second volet est lié aux problématiques spécifiques des transformateurs thermochimiques, basés sur la gestion de la thermicité de réactions solide/gaz, en tenant compte des interactions existantes aux diverses échelles du procédé en fonction d'objectifs applicatifs fixés : choix et mise en œuvre du solide réactif, configuration optimale du réacteur S/G et sa gestion dynamique au cours du cycle. Cette approche est illustrée à travers diverses applications de finalité énergétique différente : la production pseudo-continue de chaleur et/ou de froid, la production de chaleur ou de froid de forte puissance instantanée, le rafraîchissement solaire pour l'habitat, la congélation solaire, le stockage de chaleur solaire de forte densité énergétique et de longue durée, le transport de chaleur ou de froid à longue distance. Le dernier volet de ces travaux concerne le développement de nouveaux procédés thermo-hydrauliques plus spécifiquement adaptés à la conversion énergie thermique/travail et dont le potentiel semble prometteur pour des applications de production d'électricité à partir d'énergie solaire ou de l'énergie thermique des mers, ou la production performante de froid/chaleur dans les véhicules automobiles

Potabilization of water with zero-liquid discharge using low temperature solar thermal energy

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Design of a thermochemical process for deep freezing using solar low-grade heat

International audienceA deep-freezing process has been designed and experimented to cool a cold box down to about −30 °C using only low-grade heat produced by simple flat plate solar collectors operating at 70 °C. The original process involves two cascaded thermochemical systems using BaCl2 salt reacting with ammonia. It works discontinuously, with one day phase of regeneration at high pressure and one night phase of cold production at low pressure. A global dynamic model allows the simulation of the different system components functioning depending on the hourly weather conditions. It takes into account the transient periods and shows the temperature changes of the components, the chemical reactions in the system and its performances. This system will cover the cooling needs of a 560 L cold box at −20 °C during the 3 sunniest months of the year and provide more than 60% of the total yearly cooling needs of this box for the weather conditions of Perpignan (South of France). The prototype is expected to show a system coefficient of performance (COP) of about 0.07 over the 10 sunniest months of the year, and a net solar COP of 0.05, taking into account the collectors efficiencies

Modelling and performances of a deep-freezing process using low-grade solar heat

International audienceA solar deep-freezing process has been designed. It aims at cooling down a cold box to about −20 °C, using simple flat plate solar collectors operating at 70 °C. This original process involves two cascaded thermochemical systems based on the BaCl2/ammonia reaction. Its working mode is discontinuous as it alternates between a regeneration mode during daytime and a cold production mode during nighttime. A global dynamic model involving the various system components allows the simulation of the process; it predicts the evolution of the components temperatures and the rates of chemical reactions of the system. It also allows the dimensioning of the system components to maintain a 500 l cold box at −20 °C during the 6 sunniest months of the year under typical Mediterranean weather conditions and provide over 80% of the total yearly cooling needs of this box. This requires a solar collector area of 5.8 m2 and 39 kg of reactive salt. The predicted coefficient of performance (COP) is about 0.1 over the year, and the net solar COP, taking into account the collector efficiencies, is 0.05

Conception d'un procédé thermochimique de congélation solaire à partir de chaleur basse température

National audienceUn système de production de froid très basse température (de l'ordre de -30°C) a été conçu en utilisant uniquement de la chaleur disponible à basse température (de l'ordre de 70°C) et issue de capteurs solaires plans. Le procédé original défini dans ce but met en oeuvre 2 dipôles thermochimiques fonctionnant en parallèle et produisant du froid en cascade. Le sel réactif sélectionné pour cette utilisation est le BaCl2, réagissant avec l'ammoniac. Le procédé fonctionne de façon discontinue, avec une phase diurne de régénération (haute pression) et une phase nocturne de production de froid (basse pression). Une modélisation dynamique mettant en oeuvre l'ensemble des différentes composantes du système permet de simuler son fonctionnement sur une journée puis sur l'ensemble de l'année en prenant en compte les phases transitoires du fonctionnement. La simulation du procédé a permis de faire évoluer sa conception pour contrôler les échanges gazeux entre les différentes parties du système. Par ailleurs, un dimensionnement optimal (fonctionnement d'avril à septembre) du système et d'un stockage de froid par matériau à changement de phase a été atteint en fonction de la position géographique et des données météorologiques du site. Ce concept original de production de froid à -30°C permet d'atteindre un rendement énergétique de l'ordre de 11%, ce qui est comparable aux performances des procédés de production de froid solaire existants, mais pour des températures de l'ordre de -10°C. Un prototype de chambre froide de 566l pour la conservation des aliments congelés est en cours de construction pour valider la modélisation réalisée et démontrer la faisabilité du procédé de congélation utilisant des capteurs solaire plans simples