This research studies the performance of a salinity gradient solar pond driving an absorption cooling system, as an alternative to a conventional electrically powered cooling system, to provide cool air for a modern single family house in the hot dry climate of Baghdad, Iraq. The system comprises a salinity gradient solar pond, a hot-water-fired absorption water chiller, a chilled-water cooling coil which cools the air in the house, and a cooling tower which rejects heat to the ambient air. Hot brine from the pond circulates through a heat exchanger, where it heats water that is then pumped to the chiller. This arrangement protects the chiller from the corrosive brine. The system is controlled on-off by a room thermostat in the house. The system performance is modelled by dynamic thermal simulation using TMY2 hourly typical weather data. TRNSYS software is used for the main simulation, coupled to a MATLAB model of heat and mass transfer in the pond and the ground beneath it. The model of the pond and the ground is one-dimensional (only vertical transfers are considered). Radiation, convection, conduction, evaporation and diffusion are considered; the ground water at some depth below the pond is treated as being at a fixed temperature. All input data and parameter values in the simulation are based on published, standard or manufacturer's data. Temperature profiles in the pond were calculated and found to be in good agreement with published experimental results. It was found that a pond area of approximately 400 m2 was required to provide satisfactory cooling for a non-insulated house of approximately 125 m2 floor area. It was found that varying the pond area, ground conditions and pond layer thicknesses affected the system performance. The optimum site is one that has soil with low thermal conductivity, low moisture content and a deep water table. It is concluded that Iraq's climate has a potential for solar-pond-powered thermal cooling systems. It is feasible to use a solar-pond-powered cooling system to meet the space cooling load for a single family house in the summer season. Improving the thermal performance of the house by insulation could reduce the required solar pond area.

Cette thèse s’inscrit dans le cadre du projet SCRIB (“dispositif Solaire de Climatisation Réversible Intégré au Bâti”) porté par la société Helioclim. Ce projet est financé par l’état français dans le cadre des « Investissements d’avenir » pilotés par l’ADEME (Agence de l’Environnement et de la Maîtrise de l’Energie). Le but de ce projet est de développer une solution de climatisation solaire réversible capable de répondre à l’ensemble des besoins thermiques des bâtiments industriels et tertiaires (climatisation, chauffage, production de froid industriel, eau chaude sanitaire). Le système est constitué d’une machine à absorption réversible, alimentée par un système de capteurs solaires innovants. Le cycle de la machine à absorption est en configuration GAX (Generator-Absorber heat eXchange – échange de chaleur entre le générateur et l’absorbeur).Ce travail de thèse s’est intéressé au développement d’un outil logiciel aidant à la conception et au contrôle d’une telle machine. Un modèle de connaissance prenant en compte les paramètres de fonctionnement et de dimensionnement a été ainsi mis en œuvre. L’originalité de ce travail repose sur les points suivants :- L’outil logiciel propose plusieurs modules qui permettent de simuler différentes configurations de machine à absorption (mono ou multi-étagée).- Les propriétés thermodynamiques des mélanges ont été modélisées à l’aide de modèles basés sur l’utilisation d’une équation d’état ou d’un modèle d’enthalpie libre d’excès. Ainsi, le couple fluide pourra être facilement changé.- Un modèle de « Flash Positif » permet de prédire l’état de chaque courant (liquide sous-refroidi, liquide-vapeur ou vapeur surchauffée) sans poser d’hypothèses a priori. Chaque courant est considéré multiconstituant.- Les bilans matière et d’énergie sont écrits pour les différents appareils (évaporateur, absorbeur, détenteur,…).- Le générateur est modélisé par un empilement d’étages théoriques. Les équations MESH (Mass balance, Equilibrium, Summation, Heat balance) ont été écrites pour chaque étage.- Les inerties thermiques et de matière sont prises en compte.Les résultats de simulation obtenus à l’aide de cet outil logiciel ont été comparés avec succès à une étude publiée qui concernait un cycle GAX fonctionnant avec le couple ammoniac/eau. A l’aide de cet outil, le régime permanent et le comportement dynamique du système soumis à une perturbation peuvent être simulés, ce qui peut constituer une aide importante dans le développement de la politique de contrôle du système. / This PhD thesis was carried on in the framework of the SCRIB project (“dispositif Solaire de Climatisation Réversible Intégré au Bâti”) led by the Helioclim company. This project is funded by the French government (“Investissements d’Avenir” operated by the French Agency for Energy and Environment, ADEME). The goal of this project is to develop a reversible solar cooling system which can respond to a set of thermal requirements in industrial and tertiary building sector (cooling system, heating system, industrial cooling system and domestic hot water). Thus an ammonia/water absorption chiller prototype, powered by innovative thermal solar concentrators, has been built. This absorption chiller has a GAX (Generator-Absorber heat eXchange) configuration.This PhD work focused on the development of a support tool for the conception and the control of such device. A software tool has been developed implementing knowledge-based model, which took into account the operating and design parameters of the absorption chiller. The key originalities of the proposed work are as follows:- The software has been designed in a modular way allowing the simulation of various absorption chiller configurations (single or multi-stage).- The thermodynamic properties of the mixture have been modeled by equation of state or excess Gibb’s energy model. The working fluids can then be changed easily.- A “Positive Flash” model allows the description of all the possible states (sub-cooled, super-heated, biphasic…) of the various streams which are all considered as multicomponent mixtures, without a priori assumptions.- The various devices (evaporator, absorber, valves, etc.) are modeled from balance equations (mass, energy). - The generator is modeled using the concept of theoretical plates. MESH equations (Mass balance, Equilibrium, Summation, Heat balance) have been written for each stage.- Both thermal and material inertia are considered.Simulation results obtained with this software have been successfully compared to an earlier published experimental study for a GAX configuration absorption chiller which used ammonia/water as working fluids. Thanks to this tool, the steady state and the transient behavior of the system submitted to a perturbation can be simulated, which can be helpful for the development of the control policy of the absorption chiller.

The work is focused on the issue of cold production using absorbent circulation driven by thermal energy solar collectors recovered. The work can be divided into several main parts. In the first part of this work is given an overview of the possible principles of solar cooling system. In the next section followed by a description of the principle of absorption cycles. In the practical part is solved design proposal absorption refrigeration units with a cooling power of 6 kW. This is followed by a proposal to link solar cooling system with the absorption unit. Final section is made of basic technical-economic comparison of solar refrigeration unit with the compressor refrigeration units.

This thesis presents work on a holistic approach for improving the overall design of solar cooling systems driven by solar thermal collectors. Newly developed methods for thermodynamic optimization of hydraulics and control were used to redesign an existing pilot plant. Measurements taken from the newly developed system show an 81% increase of the Solar Cooling Efficiency (SCEth) factor compared to the original pilot system. In addition to the improvements in system design, new efficiency factors for benchmarking solar cooling systems are presented. The Solar Supply Efficiency (SSEth) factor provides a means of quantifying the quality of solar thermal charging systems relative to the usable heat to drive the sorption process. The product of the SSEth with the already established COPth of the chiller, leads to the SCEth factor which, for the first time, provides a clear and concise benchmarking method for the overall design of solar cooling systems. Furthermore, the definition of a coefficient of performance, including irreversibilities from energy conversion (COPcon), enables a direct comparison of compression and sorption chiller technology. This new performance metric is applicable to all low-temperature heat-supply machines for direct comparison of different types or technologies. The achieved findings of this work led to an optimized generic design for solar cooling systems, which was successfully transferred to the market.