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The Organic Rankine Cycle (ORC) is a promising technology for power generation from low-grade heat. The selection of working fluids is one of the important key points to improve the performance of an ORC system. Zeotropic mixtures show promising performances as working fluids. In fact, their temperature glide during phase change enables better match between the working fluid and the heat source/sink temperatures. In order to reveal the performance of mixture in ORC system, this paper deals with the thermodynamic model of the subcritical Organic Rankine Cycle (ORC) systems driven by low grade heat source while using zeotropic mixture working fluids with a special consideration to the interaction between phase change glides and the pinch value and their location in both the evaporator and the condenser (HEXs). Zeotropic mixtures of seven pure fluids are evaluated as working fluids for a subcritical ORC system. The mass fraction effects of mixtures on the thermal efficiency are analyzed. For given working conditions (working fluid mass flow, pressure and bubble temperature) the results show that for each considered zeotropic mixture there exist mass fraction ranges that are not consistent with the pinch values constraint in the HEXs and leads to so-called ‘infeasible zones’ with unreal HEXs dimensions. Results shows also that, out of these “infeasible fractions” zone, keeping unchanged the working conditions, the thermal performances of ORC system using zeotropic mixture are always better than the thermal performances of the same systems using the correspondent pure fluids. In addition, out of these highlighted “unfeasible zones” it was found that mixture with high temperature glide improve the thermal efficiency of ORC system.

The lower productivity of the conventional solar still requires bringing modifications to this system. The proposed modification in this work consists of coupling water spray and ambient air injection, which may enhance the water–air surface contact area as it plays a crucial role in the performance in such a device and, consequently, increases the still performances. Response surface methodology (RSM) model is derived from an experimental test set up using the design of experiment procedure to investigate the binary interaction effects of the operating parameters, i.e., spraying height, inlet water temperature, and water and air flowrates. Based on RSM results, a simple polynomial statistical model is stated in this investigation to determine and maximize the amount of evaporated water from solar still based on the four considered input factors. An excellent fitting is attained between the predicted results derived from the statistical model and the experimental results. The performance of this model was also validated using the variance analysis approach. The findings indicate that the main influencing parameters in the order of impact on the system productivity is ambient air mass flow, saltwater temperature, sprayed water mass flow and sprayer height. The binary interaction effects of the variables were considered and illustrated for design recommendations. Within the studied ranges, the hourly productivity varies from 1.91 to 7.9 kg/h m2 for a water temperature between 40 and 70 °C.

In this paper, a study of the energy performance of a solar powered vacuum membrane distillation was investigated on four typical days that represent the four seasons of the year namely: the equinoxes (March 21st and September 21st) and the solstices (June 21st and December 21st), through the widely used energy criteria such as specific energy consumption, gained output ratio and heat recovery factor. The results indicate that the energy performance of the process is strongly linked to the solar irradiation and as long as the VMD is coupled with solar energy, the process could be competitive with industrialized desalination technologies such as RO, MSF and MED. Besides, the effect of the applied vacuum level on the specific energy consumption was examined. Obviously, the results reveal that for minimum SEEC an optimal vacuum pressure is between 5000 and 10000 Pa. As well a technique to optimize the energy performance by recycling hot cooling water, used for steam condensation, was discussed. An amelioration of about 35%, 26% and 31%, during the hottest day (June 21st) and of about 22%, 19% and 21%, during the coldest (December 21st) in the GOR, the SEC and the daily production could be achieved.

The choice of heating systems in buildings is primarily guided by the desired comfort level and energy saving concerns. Radiant floor heating systems are suitable for satisfying these requirements by considering the trade-off between minimizing the thermal inertia of the radiant slab and maintaining the surface temperature below a certain value. In this study, a new simplified model based on an analytical correlation is proposed to evaluate the heating radiant slab surface temperature and examine its thermal behavior under dynamic conditions. A full-scale test cell, monitored by a set of sensors, was used to obtain measurements under transient conditions. In addition, numerical models based on the finite difference method and the finite volume method were developed and validated under transient conditions. The design of experiments method is used to derive meta-models for the time constant and the delay time in order to compute the surface temperature. The sensitivity analysis indicated that the specific heat capacity of the slab material and the heating water flowrate significantly affect the time constant as opposed to the insignificant effect of the thermal conductivity and the heating water pipe inner diameter. In addition, it was found that all of these parameters, except for the heating water flowrate, have a significant impact on the delay time. Compared to the experimental results, the maximum relative deviations on the computed surface temperature were within 2% for the numerical model and 4% for the semi-analytical model.

New thermal insulation materials made from textile waste based on acrylic and wool were developed using needle punching method. The aim of this work is to investigate the thermal performance of an external building wall outfitted with the developed insulation materials and submitted to the real climatic conditions of Casablanca, Morocco. A numerical finite volume model is developed and validated against the experimental results of a thermally controlled cavity at reduced scale. The numerical model is used to study the thermal performance of the considered wall in winter and summer season and to compute the annual heating and cooling loads. The thermal and energetic performances of the developed insulation materials are compared to the ones of some classical thermal insulation materials (i.e. Rock wool and Expanded polystyrene). Furthermore, a Life Cycle Cost (LCC) analysis is conducted with the local market cost in order to investigate the competitiveness of the new insulation materials and to seek the optimal insulation thicknesses. The results show that the developed thermal insulation materials are a competitive solution in terms of annual loads compared to the conventional thermal insulations. The optimum insulation thicknesses of the new materials and of the considered classical thermal insulations materials are determined using the LCC analysis. The effect of the specific cost of the developed insulation materials is studied and findings show that, the developed insulation can be a competitive solution if their initial cost don’t exceed 590 MAD/m3.

In this chapter, a theoretical study relying on the thermal modelling of a Curie wheel, used for the conversion of low-grade waste heat into electrical power, is presented. It allows understanding the thermal behaviour of a Curie wheel operating in steady state in order to optimise its design. To this end, a stationary one-dimensional analytical thermal model, based on a Lagrangian approach, was developed. It allows determining the local distribution over time of the temperature in the magnetocaloric material exposed to a periodic sinusoidal heat source. Thanks to this model, the effects of different parameters (nature of the magnetocaloric material, nature and temperature of the fluid) were determined and analysed.

Enhancing the glazing areas in buildings could save energy by increasing solar gain and thus decreasing the demand for heating and artificial lighting during the cold season. However, relatively large glazed buildings often cause thermal discomfort to occupants due to the midseason heating, especially in the case of inertial heating systems. This study was conducted to examine the impact of direct solar radiation on the dynamic thermal behavior of a floor heating system. A series of experiments were conducted on a monitored full-scale controlled test cell facility simulating a dynamic sun patch on a radiant heating slab. A previously published bi-dimensional dynamic model based on the finite difference method was extended and validated to consider the additional heat flux brought by the sun patch. The findings show that the overheating time induced by the sun patch exposure was approximately 8.5 h after the disappearance of the solar patch. The average heating floor surface temperature attained 33.91 °C, whereas the indoor air temperature reached 26 °C. The conducted numerical parametric study revealed that when the sun patch occurs, ventilation remarkably decreases the indoor air temperature but keeps the average surface temperature almost unchanged and primarily over the standard upper limits. In contrast, water-based cooling technique appeared to be efficient under sun patch exposure since the average surface temperature and indoor air temperature can be decreased and maintained under acceptable limits in the average comfort zone.

The present work proposes a continuous solar adsorption refrigerator for a positive cold storage room of 231 m3 used for fruits and vegetables preservation and installed in the south of Tunisia. After the estimation of the storage room cooling load which is equal to 13 kW, a parametric study, aims to improve the performance of the chiller is done in order to achieve the storage room need and to estimate the required heat in the refrigerator generator. A theoretical model, based on the thermodynamics of the adsorption process, heat and mass transfer within the porous medium and energy balance in the system components, is developed and a simulation with Matlab/Simulink, is carried out. The model was established and validated with the literature experimental data.A maximum coefficient of performance of 0.52 and cooling load of 22 kW are reached at cycle time of 800 seconds. The inlet temperatures of heating, cooling and chilled water are 85°C, 22°C and 15°C, respectively.

A new simplified model based on a semi-analytical correlation is proposed in this paper to evaluate the heating radiant slab surface temperature and to examine its thermal behavior under dynamic solicitations. In fact, the surface temperature is a normative design parameter and shall be kept under an upper limit whatever are the running conditions. Experimental measurements and a two-dimensional finite difference model (2D FDM) were carried out to validate the developed simplified model based on two characteristic parameters that are the time constant and the delay time. A Design of Experiments (DoE) method is employed to derive meta-models for the time constant and the delay time in order to compute the surface temperature. The sensitivity analysis shows that the specific heat capacity of the slab material and the heating water flow rate affect significantly the time constant compared to the thermal conductivity and the heating water pipe inner diameter. Moreover, it was found that all these parameters, except the heating water flow rate, have a substantial impact on the delay time. Compared to the experimental results, the maximum relative deviations from the computed surface temperature are within 2.4% for the numerical model and 1.75% for the simplified semi-analytical model. Consequently, the proposed simplified model may be utilized by engineers and designers to quickly estimate the radiant slab surface temperature and heat flux as well as to study its thermal behavior under dynamic running conditions. This model may also be integrated in the thermal building simulation software.

This study aims to find the optimal way to integrate a parabolic trough solar field into a gas fired combined cycle. The combined cycle studied here is composed of a gas turbine and a triple pressure bottoming Rankine cycle. A general layout is proposed and allows the integration of the solar source at all levels of temperature. A thermodynamic model is proposed to evaluate the performance of the system and then coupled to a constrained nonlinear optimization algorithm that uses a hybrid optimization technique combining Particle Swarm Optimization (PSO) and Gravitational Search Algorithm (GSA). This gives the optimal configuration of the heat exchanger networks used to harvest the solar source and the exhaust gases of the gas turbine. The effect of the system’s main parameters on the solar integration performance was investigated such as the amount of the solar heat rate injected to the bottoming cycle, the mass flow rate of the solar source, the inlet temperature of the solar source and the outlet temperatures of the high pressure super-heater n°1 and the re-heater n°1. The approach used here is general and gives finally the real potential of the integration of a parabolic trough solar field into a combined cycle.

Located on the Southern shore of the Mediterranean, and at the same time at the gates of Europe and the North of the African continent, Morocco is distinguished by its richness in terms of climate and geography which constitute specific features providing a diversity of local materials required in the eco-construction and renovation. In this regard, the Kingdom of Morocco has launched a transition to a new development model that is more respectful of its human and natural resources through the strategy of energy and energy efficiency. This leads it to deploy an important part of research and development to choose innovative and pragmatic solutions adapted to different sectors. Including the building and thermal comfort. The innovative solutions are based on the choice of an energy mix associated with local materials. The objective of this communication is to realize the variety of materials potentially available in the northern region of Morocco and to evaluate their contribution in terms of thermal comfort and by listing the constraints of short circuit, environmental preservation and possible fields (concrete, wood, bricks...). Then comes the scientific contribution which consists in quantifying, characterizing, understanding and certifying between Universities and other organizations. Focusing on multi-physical characterization methods. The reflection closes with a study about the cost and the global socio-economic benefits of this approach and the implementation of a methodology for the selection of eco-materials in order to establish later a chain of eco-renovation and eco-construction operating on the trans-border area of northern Morocco.

Radiant floor heating systems (FHS) are considered as reliable heating systems since they ensure maintaining inside air temperature and reduce its fluctuations more efficiently than conventional heating systems. The presented study investigates the dynamic thermal response of an experimental FHS equipped with an anhydrite radiant slab. A new simplified model based on an analytical correlation is proposed to evaluate the heating radiant slab surface temperature and examine its thermal behavior under dynamic conditions. In order the validate the developed analytical model, an experimental scenario, under transient conditions, was performed in a monitored full-scale test cell. 2D and 3D numerical models were also developed to evaluate the accuracy of the analytical model. The method of Design of Experiments (DoE) was used to both derive meta-models, to analytically estimate the surface temperature, and perform a sensitivity study.

In this study, experimental and comprehensive multidimensional numerical models are developed for the analysis of the thermal behavior of an anhydrite slab floor heating system (FHS). Three different modeling approaches are employed, including a one dimension (1D) Modelica® method based on an object-oriented approach, a two dimension (2D) finite difference method (FDM), and a three dimension (3D) finite volume method (FVM), using the ANSYS/Fluent® software. The comparison between the numerical results and the measured data is performed for the inlet and outlet water temperatures, the average slab surface temperature, the depth local temperatures, and the average total heat flux. Experiments and simulations were in agreement regarding the thermal response of the FHS in accordance to the well-known 2D FDM. A multi-objective sensitivity study is then performed, based on a design of experiments method (DoE) in order to analyze the effects of the design and physical control factors and their interactions on the average surface temperature and the thermal time constant. A full factorial design, generating 128 simulations based on our validated 2D FDM model is used to construct polynomial meta-models using the aforementioned thermal parameters. As a result, the water volume flow rate and the inner diameter are the most influential factors on the surface temperature, whilst the thermal time constant is shown to be considerably influenced by the slab thickness, density, and specific heat, as well as their interactions. The elicited results may be exploited in order to help practicing building engineers to optimize the FHS, and to enhance its energy performance.

Phase change materials (PCMs) used in the building walls constitute an attractive way to reduce the energy consumption and to increase the occupant's thermal comfort. However, there are some challenges to be faced among which the critical one is the PCM layer location allowing the greater heat flux reduction. In this work, the potential of PCM wallboards is evaluated experimentally using a heated reduced scale cavity including walls with or without PCM in a laboratory conditions. The cavity at reduced scale provides the flexibility to test most kinds of wall constructions in real time and allows faster installation and dismantling of the test walls. Three different PCM layer locations inside the walls are examined in terms of heat flux reduction and outside surface temperatures. The results confirm that the PCM layer reduces the peak heat flux compared to a reference wall (wall without PCM). Indeed, the PCM layer hugely affects the peak heat flux when it is placed on the inner face of the walls, near to the heat source. At this location, the peak heat flux reduction, compared to the reference wall, is 32.9%. Furthermore, for numerical validation purpose, the outside overall heat coefficient of the cavity outside walls is determined based on the experimental data.

The potential applicability of a developed recycled textile material, based on acrylic spinning waste, as thermal insulation is conducted. The prepared acrylic spinning waste (AS) is thermo-physically characterized in terms of density, air permeability, and thermal conductivity. The results show that the density and air permeability are 10.583 kg/m3 and 1100 L/m2/s, respectively. In addition, the thermal conductivity is found to be 38.27 mW/(m K). The developed thermal insulator is then tested in a thermally controlled reduced scale cavity. Two walls of the cavity are outfitted with AS at two different locations and compared to the walls without AS. The comparison is made based on the wall surface temperature and heat flux. A reduction in surface temperature is observed in the walls outfitted with AS, compared to wall without AS. Indeed, compared to a control wall, the peak heat fluxes are reduced by 27.23% and 18.67%, respectively, related to the walls with AS at location 1 and location 2. The obtained results show that the AS is a competitive thermal insulation material and can increase the thermal performance of the building walls.

In Morocco the thermal insulation of buildings envelop was not a common practice until it becomes obligatory since 2015 to meet the requirements of the Moroccan construction thermal regulation (RTCM) depending on six climate zones. The aim of this paper is to determine the optimum thickness of expanded polystyrene (EPS) and rock wool (RW) of walls constructed of brick for different Moroccan climate zones: Agadir (first zone), Tanger (second zone), Fes (third zone), Ifrane (fourth zone), Marrakech (fifth zone), Errachidia (sixth zone). A numerical model of a multilayered wall is developed to compute the annual heating and cooling loads. These loads are used as input to life cycle cost analysis using the energy and insulation costs. The liquefied petroleum gas (LPG) and electricity are used as energy source, respectively, for heating and cooling. For each case, the calculation is carried out for annual heating and cooling loads and total cost including insulation and energy costs. Results show that the optimum thermal insulation depends on climate zones and insulation types. The lowest value of energy savings is obtained for climate zone 1 which are 289.55 and 300.55 dh/m² respectively for EPS and RW.

International audience; This paper presents a validated model based on the object-oriented modeling tool based on Modelica approach for the radiant floor heating system, located in thermal laboratory in a test building. The system consists of heat pump, radiant slab, circulation pump, three way valve and hydraulic loop. Single circuit radiant slab was the main component in our Modelica model. A comparison of simulated and measured data for two case studies resulted in maximum absolute error for room temperature, surface temperature, convective heat flow and radiative heat flow as 0.914°C, 0.772°C, 2.5W/m² and4.5W/m² for the first case study and 1.192°C, 1.463°C, 2.275W/m² and 3.9W/m² respectively for the second case study. The simulated results agreed very well with the measured data by taking the measurements errors and the simulation assumptions into account. Therefore, the developed model was validated to be applicable in other projects.

International audience; A theoretical study relying on the thermal modelling of a Curie wheel, used for the conversion of low-grade waste heat into electrical power, is presented in this paper. It allows understanding the thermal behaviour of a Curie wheel operating in steady state in order to optimise its design. To this end, a stationary one-dimensional analytical thermal model, based on a Lagrangian approach, was developed. It allows determining the local distribution over time of the temperature in the magnetocaloric material exposed to a periodic sinusoidal heat source. Thanks to this model, the effects of different parameters (nature of the magnetocaloric material, nature and temperature of the fluid) were highlighted and studied.

International audience; A packed bed thermal storage tank is modeled using a single phase perturbation model which leads to a single advection–convection differential equation. This equation is derived using the Generalized Integral Transforms Technique (GITT). This approach allows us to obtain an analytical solution for a major case in solar applications where the fluid mass flow rate is time dependent and the inlet temperature is constant. We obtain also a semi-analytical solution for the general case where both fluid mass flow rate and inlet temperature are time-dependent. Analytical solutions for this thermal stock permits any afterwards optimization of solar power plants.

International audience; In Stirling engines designed for continuous work conditions, clearance seals are usually used to avoid excessive wear and hence to extend the service life. This causes a gas leakage between the compression space and the expansion space through the displacer's clearance and also a gas leakage between the compression space and the bounce space through the power piston's clearance. In this study, we propose an unsteady analytical model to calculate the gas leakage mass flow rate by considering an oscillating flow in the annular clearance and to evaluate the power lost in both locations. Finally, the sensitivity to some relevant parameters is discussed.

Different configurations of organic Rankine cycle (ORC) systems are potential thermodynamic concepts for power generation from low grade heat. The aim of this work is to investigate and optimize the performances of the three main ORC systems configurations: basic ORC, ORC with internal heat exchange (IHE) and regenerative ORC. The evaluation for those configurations was performed using seven working fluids with typical different thermodynamic behaviours (R245fa, R601a, R600a, R227ea, R134a, R1234ze and R1234yf). The optimization has been performed using a genetic algorithm under a comprehensive set of operative parameters such as the fluid evaporating temperature, the fraction of flow rate or the pressure at the steam extracting point in the turbine. Results show that there is no general best ORC configuration for all those fluids. However, there is a suitable configuration for each fluid.

International audience; This paper presents the system efficiency optimization scenarios of basic and regenerative supercritical \ORCs\ (organic Rankine cycles) using low-GWP (global warming potential) organic compounds as working fluid. A more common refrigerant, i.e. R134a, was also employed to make the comparison. A 150-°C, 5-bar-pressurized hot water is used to simulate the heat source medium. Power optimization was equally performed for the basic configuration of supercritical ORC. Thermodynamic performance comparison of supercritical \ORCs\ using different working fluids was achieved by ranking method and exergy analysis method. The highest optimal efficiency of the system (ηsys) is always obtained with \R152a\ in both basic (11.6%) and regenerative (13.1%) configurations. The highest value of optimum electrical power output (4.1 kW) is found with R1234ze. By using ranking method and considering low-GWP criterion, the best working fluids for system efficiency optimization of basic and regenerative cycles are \R32\ and R152a, respectively. The best working fluid for net electrical power optimization of basic cycle is R1234ze. Although \CO2\ has many desirable environmental and safety properties (e.g. zero \ODP\ (Ozone Depletion Potential), ultra low-GWP, non toxicity, non flammability, etc.), the worst thermodynamic performance is always found with the cycle using this compound as working fluid.

International audience; An analytical model has been developed to evaluate displacer gap losses in the clearance between the displacer and the cylinder in both β and γ configurations of Stirling engines. Displacer gap losses are the sum of the "shuttle heat transfer" and the "enthalpy pumping". The present model takes into account the pressure gradient in the gap, the gas compressibility and real gas effect. Gas velocity and temperature distributions in the displacer, in the gap and in the cylinder were determined by solving momentum and energy balances in a concentric tubes geometry. Our model is then introduced in a whole engine model and the effect of the clearance thickness and engine's speed on total displacer gap losses are investigated. Novel tendencies of the solution are observed and new ways for optimization are demonstrated.

International audience; This paper carried out the thermodynamic and economic optimizations of a subcritical \ORC\ (Organic Rankine Cycle) using a pure or a zeotropic mixture working fluid. Two pure organic compounds, i.e. n-pentane and R245fa, and their mixtures with various concentrations were used as \ORC\ working fluid for this study. Two optimizations, i.e. exergy efficiency maximization and \LCOE\ (Levelized Cost of Electricity) minimization, were performed to find out the optimum operating conditions of the system and to determine the best working fluid from the studied media. Hot water at temperature of 150 °C and pressure of 5 bars was used to simulate the heat source medium. Whereas, cooling water at temperature of 20 °C was considered to be the heat sink medium. The mass flow rate of heat source is fixed at 50 kg/s for the optimizations. According to the results, the n-pentane-based \ORC\ showed the highest maximized exergy efficiency (53.2%) and the lowest minimized \LCOE\ (0.0863 /kWh). Regarding \ORCs\ using zeotropic working fluids, 0.05 and 0.1 \R245fa\ mass fraction mixtures present the comparable economic features and thermodynamic performances to the system using n-pentane at minimum LCOE. The \ORC\ using \R245fa\ represents the least profitable system.

Using Phase-Change Materials (PCM) for lightweight building applications can increase equivalent thermal mass and provide energy savings. In the present experimental work, the heat transfer performance testing of some building walls, with or without PCM, is carried out using a reduced-scale cubic room (the test-cell). The cubic cell is heated by an incandescent bulb placed on its centre, and it is housed in an air-conditioned large-scale room that allows to control the ambient air temperature. The effect of the double PCM layer and of its location relatively to the outside surface of the wall is tested and discussed in terms of overall transmitted heat flux and in terms of reduction of the inside and outside surface temperatures. Findings shows that the additional inertia introduced by the PCM leads to a reduced overall heat flux transmission by the wall and to a lesser daily temperature amplitude on the surface of the wall that enhances the thermal comfort inside the building. In the next step of this work, the case of sandwich walls with air gap, and with wood and PCM layers will be considered.

The paper presents an analysis of a recuperative gas turbine system used for micro-cogeneration based on energetic and exergetic principles. The system is composed of two compressors (one for the fuel, the other for air), a combustion chamber, a gas turbine, a recuperator used to preheat the air before entering the combustion chamber and a heat exchanger for heating water. The analysis compares three different configurations obtained by placing the recuperator upstream of, downstream of, or in parallel with the water heater. It is subject to the following assumptions: the fuel is injected steadily and ideally (without irreversibility), the air is a perfect gas, the heat exchangers are adiabatically isolated from the surroundings and the compressors and the turbine are adiabatic. A detailed analysis of the thermal and mechanical irreversibilities of the cycle is also presented. The optimization goal is to minimize the entropy generation or to maximize the useful exergy output of the system. With this approach the best configuration for a specified operating regime of micro-cogeneration can be determined.Copyright © 2012 by ASME

This work deals with the modelling and the optimization of thermodynamic solar power plants intended to supply electricity to isolated locations. Firstly, a state of the art of solar collectors is achieved and a model for parabolic trough collectors is proposed. This model is used for actual collectors identification. It is used also to propose correlations to be introduced in the whole system model. In a second time, a state of the art of energy storage technologies is conducted and an original model of a packed bed storage tank is proposed. This model gives an explicit solution of the temperature inside the tank without using a time step based numerical resolution. Two alternatives for the power block are given: Stirling engines and Organic Rankine Cycles. For Stirling engines, a critical review of existing models is performed. Some losses occurring in Stirling engines are not well documented in the literature as leakage losses at the power piston and displacer gap losses. Therefore, original models are proposed to estimate these losses. When compared to former models in the literature, the new model of the displacer gap losses demonstrates clearly that it is very important to use decoupled models with caution. Concerning the ORC, an optimization-oriented model is proposed. Finally, a mono and multi-objective optimization of a solar power plant is performed. The optimized system is composed of a solar field, a packed bed heat storage, a power block and an auxiliary fired heater. Objective functions used in this study are: the Levelized Cost of Electricity (LCOE), the energetic efficiency of the power plant and CO2 emission per kilowatt hour of electricity, Ce travail traite la modélisation et l'optimisation des centrales solaires thermodynamiques à concentration produisant de l'électricité pour l'électrification des zones rurales isolées et mal raccordées au réseau électrique. D’abord, un modèle optique et thermique détaillé des concentrateurs solaires cylindro-paraboliques est présenté permettant l'identification de capteurs existants et la création de corrélations qui peuvent être injectées dans un modèle plus global. Dans un second temps, un modèle original d'un stock de chaleur stratifié de type « lit de roche » est développé. Le nouveau modèle proposé permet de déterminer analytiquement le profil de température dans le stock à n'importe quel instant dans le cas d'une température d'entrée régulée. Ensuite, deux alternatives de bloc moteur sont modélisées : le moteur Stirling et le Cycle Organique de Rankine (ORC acronyme anglais pour Organic Rankine Cycle). Concernant le moteur Stirling, une revue critique des modèles existants a été effectuée. Certains de ces modèles ont été implémentés et complétés par des modèles originaux des pertes par fuite de matière et par effet navette. Le cycle organique de Rankine, lui, est modélisé par un modèle orientée vers l'optimisation. Enfin, une optimisation mono et multicritère d’une centrale solaire est effectuée. La configuration étudiée est équipée d’un stock de chaleur et d’une chaudière d’appoint. Elle est optimisée selon trois critères : le coût moyen actualisé de l'électricité (LCOE acronyme anglais pour Levelized Cost Of Electricity), le rendement énergétique de la centrale et la quantité de CO2 émise par Kilowatt heure d'électricité produite

This thesis concerns the feasibility study of subcritical and supercritical organic Rankine cycles for industrial waste heat recovery at relatively low temperature. Initially, a state of the art of ORCs (Organic Rankine Cycles) and their working fluids has been achieved. We conducted a preliminary comparison of several configurations from the scientific literature. In a second step, methods of energy and exergy analysis were applied to evaluate and optimize the performance of the ORCs. Indeed, sole energy analysis is not enough to access the proper use of the energy potential of the available heat source that corresponds to an industrial waste heat. Exergy analysis, in a complementary way to the energy analysis, enables us to locate the energy resources losses in the various components of the system and to determine their true magnitude and their causes. A thermo-economic optimization of waste heat recovery systems using a subcritical or supercritical Rankine cycle has been performed. According to the results, the industrial waste heat recovery at low temperature (e.g. heat source 150 ° C) using a subcritical ORC is more interesting on economic point of view than the system using a supercritical Rankine cycle, Ce travail de thèse concerne l’étude de la faisabilité des cycles organiques sous-critiques et supercritiques de Rankine pour la valorisation de rejets thermiques industriels à basse température. Dans un premier temps, un état de l’art des cycles ORC (acronyme anglais pour Organic Rankine Cycle) et leurs fluides de travail a été réalisé. Nous avons réalisé une comparaison préliminaire de plusieurs configurations à partir de la littérature scientifique. Dans un second temps, les méthodes d’analyse énergétique et exergétique ont été appliquées pour évaluer et optimiser les performances des cycles ORC. En effet, la seule méthode d’analyse énergétique n’est pas suffisante pour juger de la bonne utilisation du potentiel énergétique de la source de chaleur disponible correspondant à un rejet industrielle de chaleur (chaleur fatale). L’analyse exergétique, intervient en complément de l’analyse énergétique du système, afin de permettre de localiser les pertes des ressources énergétiques dans les différentes composantes du système et de déterminer leurs importances relatives et leurs causes. Une optimisation thermo-économique des installations de valorisation de rejets thermiques utilisant un cycle sous-critique ou supercritique de Rankine a été effectuée. Nos résultats montrent que la valorisation de rejets thermiques industriels à basse température (ex. source thermique de 150 °C) en utilisant un cycle ORC sous-critique est plus intéressante sur le plan énergétique que celle opérée en utilisant un cycle supercritique de Rankine.

This thesis concerns the feasibility study of subcritical and supercritical organic Rankine cycles for industrial waste heat recovery at relatively low temperature.Initially, a state of the art of ORCs (Organic Rankine Cycles) and their working fluids has been achieved. We conducted a preliminary comparison of several configurations from the scientific literature.In a second step, methods of energy and exergy analysis were applied to evaluate and optimize the performance of the ORCs. Indeed, sole energy analysis is not enough to access the proper use of the energy potential of the available heat source that corresponds to an industrial waste heat. Exergy analysis, in a complementary way to the energy analysis, enables us to locate the energy resources losses in the various components of the system and to determine their true magnitude and their causes.A thermo-economic optimization of waste heat recovery systems using a subcritical or supercritical Rankine cycle has been performed. According to the results, the industrial waste heat recovery at low temperature (e.g. heat source 150 ° C) using a subcritical ORC is more interesting on economic point of view than the system using a supercritical Rankine cycle., Ce travail de thèse concerne l’étude de la faisabilité des cycles organiques sous-critiques et supercritiques de Rankine pour la valorisation de rejets thermiques industriels à basse température.Dans un premier temps, un état de l’art des cycles ORC (acronyme anglais pour Organic Rankine Cycle) et leurs fluides de travail a été réalisé. Nous avons réalisé une comparaison préliminaire de plusieurs configurations à partir de la littérature scientifique.Dans un second temps, les méthodes d’analyse énergétique et exergétique ont été appliquées pour évaluer et optimiser les performances des cycles ORC. En effet, la seule méthode d’analyse énergétique n’est pas suffisante pour juger de la bonne utilisation du potentiel énergétique de la source de chaleur disponible correspondant à un rejet industrielle de chaleur (chaleur fatale). L’analyse exergétique, intervient en complément de l’analyse énergétique du système, afin de permettre de localiser les pertes des ressources énergétiques dans les différentes composantes du système et de déterminer leurs importances relatives et leurs causes.Une optimisation thermo-économique des installations de valorisation de rejets thermiques utilisant un cycle sous-critique ou supercritique de Rankine a été effectuée. Nos résultats montrent que la valorisation de rejets thermiques industriels à basse température (ex. source thermique de 150 °C) en utilisant un cycle ORC sous-critique est plus intéressante sur le plan énergétique que celle opérée en utilisant un cycle supercritique de Rankine.