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With the increasing constraints on energy and resource markets and the non-decreasing trend in energy demand, the need for relevant clean energy generation and storage solutions is growing and is gradually reaching the individual home. However, small-scale energy storage is still an expensive investment in 2022 and the risk/reward ratio is not yet attractive enough for individual homeowners. One solution is for homeowners not to store excess clean energy individually but to produce hydrogen for mutual use. In this paper, a collective production of hydrogen for a daily filling of a bus is considered. Following our previous work on the subject, the investigation consists of finding an optimal buy/sell rule to the grid, and the use of the energy with an additional objective: mobility. The dominant technique in the energy community is reinforcement learning, which however is difficult to use when the learning data is limited, as in our study. We chose a less data-intensive and yet technically well-documented approach. Our results show that rulebooks, different but more interesting than the usual robust rule, exist and can be cost-effective. In some cases, they even show that it is worth punctually missing the H2 production requirement in exchange for higher economic performance. However, they require fine-tuning as to not deteriorate the system performance.

Hydrogen has been identified as a very promising vector for energy storage, especially for heavy mobility applications. For this reason, France is making significant investments in this field, and use cases need to be evaluated as they are sprouting. In this paper, the relevance of H2 in two storage applications is studied: a domestic renewable electricity production system connected to the grid and a collective hydrogen production for the daily bus refill. The investigation consists of the sizing of the system and then the evaluation of its performance according to several criteria depending on case. Optimizations are made using Bayesian and gradient-based methods. Several variations around a central case are explored for both cases to give insights on the impact of the different parameters (location, pricing, objective, etc.) on the performance of the system.Our results show that domestic power-to-power applications (case 1) do not seem to be competitive with electrochemical storage. Meanwhile, without any subsidies or incentives, such configuration does not allow prosumers to save money (+16% spendings compared to non-equipped dwelling). It remains interesting when self-sufficiency is the main objective (up to 68% of energy is not exchanged). The power-to-gas application (case 2, central case), with a direct use of hydrogen for mobility, seems to be more relevant according to our case study, we could reach a production cost of green H2 around 5 €/kg, similar to the 3–10 $/kg found in literature, for 182 houses involved. In both cases, H2 follows a yearly cycle, charging in summer and discharging in winter (long term storage) due to low conversion efficiency.

International audience; This study presents an experimental comparison of three characterization methods for phase change materials (PCM). Two methods were carried out with a calorimeter, the first with direct scanning (DSC) and the second with step scanning (STEP). The third method is a fluxmetric (FM) characterization performed using a fluxmeter bench. For the three methods, paraffin RT58 and polymer PEG6000, two PCM suitable for domestic hot water (DHW) storage, were characterized. For each PCM, no significant difference was observed on the latent heat and the total energy exchanged between the three characterization methods. However, DSC and STEP methods did not enable the accurate characterization of the supercooling process observed with the FM method for polymer PEG6000. For PEG6000, the shape of the enthalpy curve of melting also differed between the experiments on the calorimeter—DSC and STEP—methods, and the FM method. Concerning the PCM comparison, RT58 and PEG6000 appeared to have an equivalent energy density but, as the mass density of PEG6000 is greater, more energy is stored inside the same volume for PEG6000. However, as PEG6000 experienced supercooling, the discharging temperature was lower than for RT58 and the material is therefore less adapted to DHW storage operating with partial phase change cycles where the PCM temperature does not decrease below 52 °C.

This research focuses on the potential of greenhouse cultivation in circumpolar territories. It begins with a survey that encompasses most of the northern greenhouses in North America. This review emphasizes the need for appropriate data and for the right energy system design. Next, the paper focuses on a case study located in Nunavik, which is the northern Inuit territory of the province of Quebec. The Kuujjuaq cooperative greenhouse has been instrumented since June 2016 to collect data on temperature and relative humidity throughout the growing season. These measures have highlighted a major problem: a temperature difference between day and night that is too large, hindering crop development. To counteract this thermal behavior, a heat storage system was designed, built and installed in October 2018. It is the first time that a rock and air-based sensible thermal energy storage system, taking into account local materials and resources, has been designed and built in a northern greenhouse. This paper presents its main characteristics as well as records of temperature changes throughout the growing season. Moreover, an energy balance is presented for three days at the beginning of June 2019.

In the north of Québec (Canada), off-grid aboriginal communities rely on diesel for both space heating and electricity production. Renewable alternatives are therefore necessary to reduce the impact of burning diesel in a region with strong population growth and increasing energy needs. The main challenges are the subarctic environment (more than 8000 heating degree days), the presence of permafrost and the lack of local expertise on drilling and installation of borehole heat exchangers.The communities of Kuujjuaq (58 °N) and Whapmagoostui-Kuujjuarapik (W-K, 55 °N) were chosen as case studies to evaluate the shallow geothermal potential and predict the long-term behaviour of ground source heat pumps (GSHP) and underground thermal energy storage systems (UTES). Local geology mainly consists of low permeable and thermally conductive crystalline bedrock (thermal conductivity of 2-4 W/mK) underlying highly permeable, frost-susceptible and poorly conductive marine sediments (thermal conductivity of 1-1.5 W/mK), generally not thicker than 30-40 m. Electrical resistivity tomography and ground penetrating radar surveys have been carried out to locally evaluate the presence of ice-rich ground that strongly depends on the local hydrogeological conditions. Average underground temperature in the first 100 m is around 1 °C in Kuujjuaq and 2 °C in W-K. Geothermal gradient and heat flux were estimated to be on average 15 °C/km and 40 mW/m2, respectively.Results of the studies carried out in these villages show that both GSHP and UTES are viable technologies to replace part of the current diesel consumption of residential buildings and drinking water facilities, with 10% to 50% primary energy saving depending on the technology. Fifty years’ life-cycle cost analyses demonstrated that the levelized cost of energy for GSHP and UTES is as low as 0.10 and 0.19 USD$/kWh, respectively, compared to the business-as-usual scenario standing at 0.21 USD$/kWh. It also turned out that the energy and drilling costs are key obstacles to a widespread deployment of these technologies in the North. A cost of 110 USD$/m has been defined as a threshold for getting interesting paybacks on the initial financial investment. UTES is also a valuable technology aiming to extend the growing season of community greenhouses in place in both Kuujjuaq and W-K. In Kuujjuaq, a coupled daily and seasonal heat storage is under study to provide renewable heat and help increase the food security in Nunavik.Future activities aim at the set-up of a first demonstration plant to be tested in a subarctic environment with underground close to permafrost conditions. A 200-m well will be drilled in 2020 in W-K and the installation of a borehole heat exchanger will be showcased for technological transfer. Conventional thermal response tests (TRT) and a novel approach of oscillatory TRT will also be carried out to evaluate the in-situ thermal conductivity and heat capacity.

Demand-side management and load-shifting strategies can reduce peak loads as well as temporal production/consumption mismatch, two classic issues in district energy networks that integrate solar sources. Nevertheless, the classic current sizing methods for such networks only consider the total demand, and not the possible loads after use of such techniques. The present paper aim is so to ascertain the connection between the possible demand reductions and the capacity design of generation sources. The study proposes an iterative sizing method with demand-side management as the central pillar. It retro-fits production units by assessing the network's overall performance through several criteria, both energetic and economical and with operational considerations. Exergy, which accounts for the quality of energy and is especially useful for multi-energy networks, is also considered. The method is illustrated on a mixed grid coupling a standalone heating network with a local electrical grid. Thousands of residential dwellings, with haphazard demands covered by solar-assisted technologies and a heat-pump are used in a series of ten scenarios with various management strategies, pricing policies and types of end-user contracts. In summary, the iterative method reduced the number of installed solar thermal collectors and photovoltaic panels by 13–38 % and 8–30 %, respectively. Furthermore, the method is stable: results converged after 2 iterations, in all scenarios. We also discuss the influence of low or high demand-side management penetration rate, and the final sizing selection by the decision-maker.

Solar thermal energy storage is used in many applications, from building to concentrating solar power plants and industry. The temperature levels encountered range from ambient temperature to more than 1000 °C, and operating times range from a few hours to several months. This paper reviews different types of solar thermal energy storage (sensible heat, latent heat, and thermochemical storage) for low- (40–120 °C) and medium-to-high-temperature (120–1000 °C) applications.

Dendritic growth is one of the most common microstructures in metal and solution solidification. The subject of dendritic growth has received much attention from both scientific and industrial points of view. On the one hand, dendritic growth has become a deeply investigated subject in non-linear dynamics field. On the other hand, its understanding became essential for some engineering applications, mainly in metallurgy and latent thermal energy storage where phase change materials are used. Therefore, understanding and modeling the mechanisms which result the dendritic structures has been the objective of much research over the last decades. In order to understand the formation of dendrites, it is essential to understand the physical mechanisms on the interface separating the two phases. This paper reviews and discusses the available theories of dendritic growth, and then introduces the Gibbs-Thomson condition which has to be taken into account to handle all interfacial effects. Based on the Gibbs-Thomson condition, a complete mathematical model describing the dendritic growth problem for pure substances is formulated. This model includes the heat equation in both liquid and solid phases, the heat conservation equation at the interface separating these two phases, and the proposed Gibbs-Thomson equation. In order to solve this complex non-linear problem, several numerical methods have been developed. Hence, in its last section, the paper reviews these numerical methods distinguishing between two major classes involving the explicit and the implicit tracking of the moving interface.

The determination of both the thermal and thermodynamical properties of a composite material containing phase change material is done thanks to an inverse method, which combines experimental measurements and numerical computations. Given first an in-house experiment, which allows us to test samples at a macroscopic scale (i.e., close to the real conditions) and to set various types of thermal stresses, and secondly the simulation of the corresponding thermal behavior, relying on an accurate thermodynamical modeling and taking into account the real operating parameters (e.g., thermal contact resistances and non-symmetric heat fluxes on each side), it is possible to characterize the solid and liquid thermal conductivities and heat capacities, as well as the temperature range associated with a non-isothermal phase transition and the associated latent heat. The specificity of the present approach is to allow, in a single step, a characterization of all the involved thermo-physical parameters that are usually required in simulation tools (e.g., EnergyPlus&hellip, ). Moreover, the hitherto studies dealing with repeatability and uncertainties of the enthalpy characterization are generally very scant and not encountered very often or only with qualitative assessments. This is a clear caveat, especially when considering any system design. Therefore, for the first time ever, the present paper pays a special attention to the repeatability of the identification method and studies the scedasticity of the results, that is to say the deviations of the determined enthalpy curves, not only from a qualitative point of view but also by proposing quantitative arguments. Finally, the results are very promising since the agreement between all trials is excellent, the maximum error for all parameters being lower than 4%. This is far below the current quality thresholds admitted when characterizing the enthalpy of a phase change material.

International audience; Disruptions in the way of life of indigenous peoples from the Far North have greatly affected their ability to meet their food needs. The implementation of community greenhouse and gardening projects is one of the initiatives taken to address this issue in Nunavik. Through a mixed-method approach, we analyze social benefits and challenges, as well as the potential food productivity and nutritional contributions of these projects. We discuss the potential of current greenhouse energy optimization scenarios and we address the benefits of Kuujjuaq's greenhouse in terms of carbon dioxide mitigation. Discussions with the local stakeholders highlighted technical challenges regarding the energy supply, its efficient management and the supply of soil in sufficient quantities. Our results highlight the interconnectedness and complexity of food and energy systems in Nunavik. They show that the establishment of local fresh food production corresponds to a need expressed by the residents and could bypass some of the difficulties associated with the conveyance and freshness of food sold at the supermarket. They also indicate that the implementation of such production poses many challenges that require taking into account the geographical isolation, the arctic climate and the availability of local resources.

International audience; Adjusting to global climate and socio-environmental changes has become a major issue for many societies, especially in the Arctic. Many Inuit wish to better understand the changes taking place. In 2013, an international Observatory of Human–Environment Interactions (OHMi) was established in Nunavik to identify these changes, study their cumulative impact on the socio-ecosystem and to help develop adaptation measures to improve the well-being of Inuit communities. To this end, a team of academics and local Inuit partners joined forces to develop an integrated, interdisciplinary, collaborative research program. Using a participatory action research (PAR) approach, the OHMi Nunavik set the following research priorities: elder-youth knowledge transmission, northern agriculture, preservation of Inuit culture, language and identity, protected areas, mining employment, natural hazards and risks, and wildlife vulnerability. By strengthening the collaborations between multidisciplinary Canadian and French research teams, the OHMi Nunavik program integrates local and scientific knowledge both in planning the research and in disseminating the results; L’adaptation aux changements climatiques et socio-environnementaux est devenue un enjeu majeur pour de nombreuses sociétés, notamment dans l’Arctique. De nombreux Inuit souhaitent mieux comprendre les changements qui se produisent. En 2013, un Observatoire international sur les interactions Homme-Milieu (OHMi) a été mis en place au Nunavik pour identifier ces changements, étudier leur impact cumulatif sur le socio-écosystème et pour aider à élaborer des mesures d’adaptation afin d’améliorer le bien-être des communautés inuit. À cette fin, une équipe d’universitaires et de partenaires Inuit locaux ont uni leurs forces pour développer un programme de recherche concerté, intégré et interdisciplinaire. En utilisant une approche de recherche-action participative, l’OHMi Nunavik a défini les priorités de recherche suivantes: transmission des connaissances entre les aînés et les jeunes, agriculture nordique, préservation de la culture, de la langue et de l’identité inuit, aires protégées, emplois dans les mines, risques naturels et vulnérabilité de la faune. En renforçant les collaborations entre les équipes de recherche multidisciplinaires canadiennes et françaises, le programme de l’OHMi Nunavik intègre les connaissances locales et scientifiques dans la planification de la recherche et la diffusion des résultats

Modeling the thermal behavior of a plant or devices using Phase Change Materials (PCM) requires to know their thermophysical properties. The Differential Scanning Calorimetry (DSC) is a technic largely used to investigate them. However, under the pretext to experiment with small samples, some authors consider the DSC curves as directly representing the properties of the materials without realizing that this interpretation is very often incompatible with the thermodynamics laws: as an example, although a pure substance melts at a fixed temperature T F , it is proposed a melting through a temperature range higher than T F and depending on the experiments (heating rates, sample masses...), for solutions the suggested characteristic temperatures are incompatible with the phase diagram, and also a hysteresis phenomenon is invented... In this paper, we demonstrate by a model coupling thermodynamics and conduction heat transfers, that the DSC curves are exactly compatible with the thermodynamics of phase changes (melting at fixed temperature for pure substances, in conformity with phase diagrams for solutions...). The cases of pure substances, saline solutions, substances with impurities or solid solutions are detailed. We indicate which information can, however, be given by the curves. We also propose a more sophisticated method by inverse calculations to determine the specific enthalpy whose all the thermodynamical properties can be deduced. Finally, we give some indications to understand and use the results indicating supercooling.

Modeling the thermal behavior of a plant or devices using Phase Change Materials (PCM) requires to know their thermophysical properties. The Differential Scanning Calorimetry (DSC) is a technic largely used to investigate them. However, under the pretext to experiment with small samples, some authors consider the DSC curves as directly representing the properties of the materials without realizing that this interpretation is very often incompatible with the thermodynamics laws: as an example, although a pure substance melts at a fixed temperature T F , it is proposed a melting through a temperature range higher than T F and depending on the experiments (heating rates, sample masses...), for solutions the suggested characteristic temperatures are incompatible with the phase diagram, and also a hysteresis phenomenon is invented... In this paper, we demonstrate by a model coupling thermodynamics and conduction heat transfers, that the DSC curves are exactly compatible with the thermodynamics of phase changes (melting at fixed temperature for pure substances, in conformity with phase diagrams for solutions...). The cases of pure substances, saline solutions, substances with impurities or solid solutions are detailed. We indicate which information can, however, be given by the curves. We also propose a more sophisticated method by inverse calculations to determine the specific enthalpy whose all the thermodynamical properties can be deduced. Finally, we give some indications to understand and use the results indicating supercooling.

International audience; When dealing with high-pressure releases, be it needed by some operating conditions or due to an emergency protocol or even to the occurrence of an accident, one has to consider the relevant risks associated to this leakage. Indeed, in addition to the mechanical and blast effects, the dispersion of the released fluid is of primary importance if it is hazardous, as an example for toxic gases or flammable ones (where explosions or fires may be expected).In fact, despite the numerous studies dealing with underexpanded jets, many aspects of their structure are not clearly described, particularly when one seeks for quantitative predictions. By performing an exhaustive overview of the main experimental papers dealing with underexpanded jets, the present paper aims at clarifying the characteristics which are well known, from those where there is clearly a lack of confidence. Indeed, and curiously enough, such a work has never been done and no review is available on such a topic.Two particular regions have drawn most of the attention so far: the nearfield zone, where the shocks/rarefaction pattern that governs the structure of the jet is encountered, and the farfield zone, where the flow is fully developed and often approximated by an equivalent flow.Finally, some clues are given on the numerical methods that may be used if one wants to study such jets numerically, together with an emphasis on the specific thermodynamical difficulties associated to this kind of extreme conditions.

The main challenge of working with thermoelectric generators lies in their low efficiency, so finding the optimal design to achieve the best thermoelectric generator (TEG) performance under the working conditions becomes a strong problematic. In this study, a numerical transient simulation tool was developed using different modelling techniques to achieve the performance improvement of a TEG. This TEG is composed of thermoelectric modules wrapped between two heat exchangers. A three-dimensional heat transfer transient model was first developed for the heat exchanger using the finite volume method and then coupled with a thermoelectric generation model. Materials properties vary as a function of temperature and the Thomson effect is taken into account to be able to get numerical results close to reality. Thermoelectric modules properties used in this model are those given by the manufacturer. The originality of this study is that it takes into account unsteady-state conditions, necessary for simulating a multitude of processes like the automobile (engine and exhaust systems), combustion processes, turbines working conditions and energy production. The use of this numerical tool can help maximize the TEG performance and possibly reduce material cost. In order to validate the model, the TEG has been built with the capacity of using different module quantities for different configurations. Experiments have been conducted at different inlet gas conditions (mass flow rate and inlet temperature). A comparison of experimental and predicted values of temperatures and output electrical power has been done in steady state regime. Using the three dimensional model for the heat exchanger, a good precision of the thermoelectric power generation model is obtained.

International audience; In the building field, the topic of thermal storage is generally studied with assistance from dedicated software programs. To generate transient thermal simulations, these software programs use enthalpy functions h (T) to describe the thermal behaviour of the different parts of a modelled structure. Unfortunately, the mathematical form of these functions is often extremely unrealistic due to an erroneous interpretation of the calorimetric experiments that were performed to determine these functions. The purpose of this study was to evaluate the energy-related errors that occur if a misinterpreted enthalpy function is used and to thereby assess the impact that these inaccurate functions generate with respect to thermal simulations of buildings.

The use of phase change materials (PCMs) to increase solar domestic hot water (SDHW) system efficiency has been already studied by different ways. Some studies place the storage material in the water tank, others directly in the solar thermal collector. However both of them show that the effectiveness of such a use is not relevant. This paper is devoted to a new approach: the PCM is placed in the heat transfer fluid solar loop from the SDHW system. This configuration is studied under different weather conditions and system parameters. On the contrary to previous results, this parametric study highlights a significant increase of the system efficiency due to the PCM. Then, a genetic algorithm allows proposing an optimized system configuration.

Recent studies concerning phase change material (PCM) characterization show that important errors occur if differential scanning calorimetry (DSC) experiments are misinterpreted. Therefore, it is important to know the influence of such misinterpretation on system modeling. The present work deals with phase change materials integrated in building structure to reduce overheating. The objective is to evaluate the discrepancies consequences (temperatures, heat fluxes), due to the use of the misinterpreted DSC experiments at different heating rates to determine the enthalpy, in comparison with those determined with the actual value of the enthalpy of the PCM determined by a proven inverse method. A numerical model of a single-family house with a phase change material mortar is developed to evaluate the thermal comfort in the building. The results show that for free-running temperature, none of the enthalpy curve deduced directly from DSC can predict correctly the thermal behavior of the house and the thermal comfort. Moreover, the more the DSC heating rate and the more the discrepancy with the results from the reference inverse method.

Thermal energy storage is now a key parameter to overcome the delay between energy supply and demand in many applications. To address this issue, the use of phase change materials (PCM) tends to be more and more common. Given the attempted objectives of such applications, performances of the PCM are a cornerstone of the whole system. Therefore, a correct determination of their intrinsic properties is crucial. To perform this step, one may use a calorimetry experiment. Unfortunately, the interpretation of the thermogram is not straightforward and consequently, when not feasible at all, estimations may be wrong. As an example, pure substance as sometimes said to melt at a non-uniform temperature (their enthalpy being smeared over several degrees), and binary solutions are associated with liquidus temperature and latent heat that do not match the correct form of their enthalpy. The present work proposes a new method to avoid such issues. To summarize the novelty of our approach, the main idea is to use an inverse method to identify the thermodynamical parameters of the sample through a matching step between the experimental curves and theoretical ones. It means that contrary to many others methods, we do not directly extrapolate the thermodynamical properties ( e.g. the enthalpy) from the thermogram. Instead, we suppose an a priori formulation of the enthalpy, based on thermodynamical principles. Thus the thermodynamical parameters are inputs of which only values are computed from the experiments. Capabilities of the method are shown on pure substances and binary solutions examples.

This paper presents some results obtained by Differential Scanning Calorimetry (DSC) for characterizing the phase transition within an emulsion. The dispersed substances are either hexadecane, octadecane, water or binary solution. A non-equilibrium model taking into account the inter-phase heat transfer between the emulsifying medium and the dispersed droplet is proposed and explains the main experimental features.

International audience; The support of this study is a cement mortar containing a micro-encapsulated phase change material (PCM). The aim of this article is to identify by an inverse method the thermophysical properties of this composite material and all the parameters that are needed to build a physical model able to simulate the thermal behavior of a material containing PCM with accuracy. This approach consist in estimating different parameters that take place in the analytical relation of the enthalpy as a function of the temperature (h(T)) by comparing the response of the model with experimental results (here, heat flux measurement). A simplex algorithm allowed to minimize the quadratic criterion associated. The results obtained by inverse method are then analyzed and compared by experimental results obtained by direct method.

International audience; The objective of this study is to evaluate three different phase change models used to predict the energy behaviour of a PCM cement mortar sample. Reference data are measured on large samples of composite material using a special experimental set-up. The phase change models tested are: the apparent specific capacity method, the enthalpy method assuming a pure body and the enthalpy method assuming a binary mixture. Numerical results are compared to the reference data of heat flux and energy stored/released. The main conclusions of the study are: (1) the thermodynamically inconsistent apparent specific capacity method is not suitable, (2) the enthalpy method gives better results than the specific capacity method and (3) the enthalpy method gives better results with an appropriate guess of the enthalpy curve.

We present a new technique to globally optimize stirring and mixing in three-dimensional spatially periodic laminar flows. This technique includes a recently developed mapping method and the use of an optimization method. The method gives the opportunity of the statistics of scalar dissipation for multiple stirring protocols. Exhaustive tests, first conducted for a large number of stirring protocols show that finding a stirring protocol which produces a uniform mixture is rare for the specific geometries studied. The results indicate that a global approach is necessary to handle the problem of concentration homogenization. It is shown that Genetic Algorithms enable us to rapidly find the best stirring protocols. Thus, the method described in this paper could be an efficient computational tool for chaotic mixing optimization in other types of periodic flows (2D or 3D).

A new method of determination of the nucleation probability of undercooled liquid dispersed within an emulsion is presented. The nucleation probability is a nonlinear function of the temperature depending on two parameters acting very differently. The aim of this paper is to present a method to determine these parameters by an inverse analysis of the heat transfer during the cooling of the emulsion. Information about the precision of the identification is also presented.

International audience; This article deals with the study of a mixture of a cement mortar with a phase change material. We performed together an experimental analysis and a theoretical modeling of the sample associated with transient simulation of its behavior when a heating or a cooling is imposed to this later one. A non pure enthalpy profile is supposed, which permits to better describe the measurements. Furthermore, the drawbacks no to use such a method in order to prefer a more classical one are pointed out.

In this paper, a model is developed in order to determine the melting thermogram of a binary mixture, presenting a solid solution. Considering the case of an ideal solution, whose enthalpy function is analytically derived, we highlight the large differences existing between the thermogram and the derivative of the enthalpy function. The influence of the heating rates and the mass of the sample are analyzed for different concentrations. Finally, in the case of a thermodynamical equilibrium, we describe how to construct the phase diagram of the solution (liquidus and solidus temperatures, total latent heat).

International audience; It is known that when studying the fusion of phase change materials (PCM) in differential scanning calorimetry (DSC) experiments, the geometry of the samples is not well known. Yet, some studies show that a numerical model, needing obviously to clearly define the shape of the sample, may reproduce the experimental DSC curve. In particular, such methods are currently applied to identification process based on inversion methods applied to the thermodynamical parameters governing the numerical model. Consequently, it means that if several numerical models are able to reproduce the thermal behavior of a PCM undergoing phase transition, the best one is the simplest one, that is to say the one which is the fastest to solve.Recently, we have thus shown that for pure substances PCM, a reduced model based on a spherical assumption for the shape of the sample leads to similar DSC curves that a more general model based on cylindrical shape.Clearly, if this result may be extended to other kinds of PCM, this will promote the capability of this method to be used in inversion process involved by identification process. The aim of the present paper is therefore to further study this method by considering non-pure materials, i.e. binary solution in the present case.

International audience; A two dimensional front-tracking method is developed in order to model dendritic growth during solidification processes of pure substances. The method uses a sequential set of moving marker points to describe and track the liquid-solid interface which evolves over a fixed background mesh describing the whole medium. The code behaviour is first checked by a simple stable case of solidification to provide homogeneous velocity at the interface. Then, test examples of unstable solidification cases considering different modes of anisotropy are performed. Finally, interface evolution, with primary and secondary branches, is described, showing the ability of the code to study realistic dendritic growth characteristics.

International audience; The aim of this paper is to present an inverse identification method to determine specific enthalpy of PCM from calorimetry experiments. We will focus on the cases of pure substances and ideal binary solutions including the eutectic equilibrium. The corresponding direct model, based on energy balance, is first presented. A classical enthalpy method is then used, which presents the advantage of easily decoupling the thermal transfers from the specific energetic behavior of the material (i.e. thermodynamical phenomenon). In the second part of the paper, we will present the used inverse method (genetic algorithms). The sensibilities of the different parameters for the identification are analyzed. Finally, we will present the identification from DSC experiments (1) at different rates of heating for pure substances and (2) at different concentrations of aqueous solutions of N H 4 Cl. In each case, we identify the thermodynamical parameters of the model and compare the corresponding thermograms with the experimental ones. A good agreement is obtained for both cases

Among the various ways to simulate compressor behaviour, using efficiency definitions such as volumetric, isentropic or effective is relatively easy to perform and rapid when dynamic simulation is required. Calculating these efficiencies and their dependence on operating pressure, refrigerant type, and temperature is on the contrary relatively difficult to estimate. The approach presented here supposes that they depend essentially on two parameters, the dead volume ratio, having a particular influence on volumetric efficiency, and a friction factor mainly influencing both isentropic and effective efficiencies. The bases of the model are tested for a reversible and for a non-reversible reciprocating compressor when simulated over a compression cycle and dead volume ratio and friction factor influence is studied and discussed. Finally, the model is compared to experiments and allows validating the method, giving quite accurate results.

We present in this paper a new method of determining the nucleation probability J(T) of a supercooled liquid dispersed within an emulsion, based on the analysis of the thermogram obtained during a regular cooling. The thermal behaviour of the sample during the cooling is modelled in order to calculate the thermogram and so to compare it with the experimental thermogram. A genetic algorithm (GA) is then used to identify the parameters of the J(T) function by minimizing a least squares objective function comparing calculated and measured thermograms. This identification procedure is used to determine the crystallization probability of two samples of same composition but of different manufacture. The results are compared with each other as well as with the results obtained through a traditional calorimetric method. These various tests show that GA associated with calorimetry is a useful and easy tool for the determination of the nucleation probability J(T).

Due to the difficult access to their territories, Northern Canada’s Inuit have faced major adaptation challenges in recent decades, notably in terms of food and energy. Traditional food from hunting, fishing and gathering activities is increasingly difficult to obtain, while European and Canadian foods brought by air or by sea are increasingly expensive. Culture in greenhouses appears as a solution allowing to improve access to fresh vegetables by reducing the ecological and financial costs linked to the transportation of these.The scientific literature on the physical study of northern greenhouses and energetic data (temperature, electricity consumpion, etc.) is scarce. The first part of this thesis has to do with the pinpointing of northern greenhouses existing in North America and shows that this subject is relatively recent. On the other hand, this literature review revealed that the majority of counted greenhouses are not adapted to a cold climate, hence short growing seasons.The second part of this work focuses on the experimental aspect. Data coming from an instrumentation campaign in a northern greenhouse were analysed to demonstrate the relevance of the establishment of a daily thermal energy storage (TES) system. The dimensioning and construction of this system using air as a coolant fluid and local rocks as storage material are also presented. The instrumentation of the rockbed which stores heat has allowed to study energetical data during charge and discharge phases of the stock. This analysis demonstrated the positive impact of the set up of the TES system on the thermal behavior of the greenhouse.The last part of this work concerns the modeling of the thermal behavior of the greenhouse and the TES system. As a matter of fact, the numerical simulation of the climate in a greenhouse is basic in order to understand the improvement mechanisms of existing greenhouses and/or to optimize the conceiving of enclosures for vegetable production in a northern environment. Indeed, a nodal model of the greenhouse and an independent model of the TES system are detailed and validated. A process of calibration about the numerical values of the models’ parameters is also developed to improve the performances of these models.; Vivant sur des territoires isolés où aucune route terrestre ne permet de se rendre, les Inuits du nord canadien (Nunavik) font face, depuis les dernières décennies, à de grands défis d’adaptation, notamment sur le plan de l’alimentation et de l'accès à l'énergie. La nourriture traditionnelle issue des activités de chasse, de pêche et de cueillette est de plus en plus difficile à obtenir, tandis que les aliments euro-canadiens apportés par avion ou par bateau coûtent de plus en plus cher. La serriculture apparaît alors comme une solution permettant d'améliorer l'accès aux légumes frais en réduisant les coûts écologique et financier liés au transport de ces légumes.La littérature scientifique portant sur l'étude physique des serres nordiques et les données énergétiques (température, consommation d’électricité, etc.) sur le sujet sont rares. Dans un premier temps, nous avons recensé les serres nordiques existantes d'Amérique du Nord, et nous avons montré que le sujet est relativement récent. Par ailleurs, cette revue de littérature a révélé que la majorité des serres dénombrées ne sont pas adaptées au climat froid, conduisant à des saisons de cultures courtes. Ensuite, nous avons abordé l'aspect expérimental. Les données issues d'une campagne d’instrumentation de la serre nordique de Kuujjuaq ont été analysées afin de démontrer la pertinence de l'installation d'un système de stockage thermique journalier. Le dimensionnement et la construction de ce dernier, utilisant l'air comme fluide caloporteur et des roches locales en tant que matériau de stockage, sont également présentés. L'instrumentation du lit de roches stockant la chaleur a permis l'étude des données énergétiques durant les phases de charge et de décharge du stock. Cette analyse a démontré l'impact positif de l'installation du système de stockage sur le comportement thermique de la serre. Enfin, nous avons modélisé le comportement thermique de la serre et du système de stockage. En effet, la simulation numérique du climat sous serre est essentielle afin de comprendre les mécanismes d'amélioration des serres existantes et/ou d'optimiser la conception des enceintes de production végétale en milieu nordique. Ainsi, un modèle nodal de la serre et un modèle du système de stockage sont détaillés et validés. Un processus de calibration portant sur les valeurs numériques des paramètres des modèles est également développé afin d'en améliorer les performances.