Numerical modelling of a hemp concrete wall

In a global warming context associated to the abuse of energy consumption, actual researches focus more and more on reducing energy costs in the building sector. This target could be achieved by using innovative building materials, such as hemp concrete, due to its positive impacts on thermal and environmental levels. The aim of this work is to carry out a numerical study of a hemp concrete wall subjected to several indoor and outdoor conditions of temperature and relative humidity using the program object oriented SPARK. The hygrothermal behaviour of the wall is investigated taking into account heat and moisture transfer within the wall as well as hysteresis phenomenon between the sorption and desorption curves and their temperature dependency

Seasonal Coefficient of Performance of Heat Pumps

International audienc

Optimisation des performances non nominales des pompes à chaleur réversibles pour le secteur tertiaire

Maître de thèse : Philippe RivièreSeasonal performance optimization of reversible heat pumps contributes to the reduction of energy consumption in the commercial building sector. A detailed thermodynamic model of a commercial heat pump (compressor, condenser, expansion valve, evaporator) at off-design conditions is developed. The heat pump model, validated by experiments in laboratory and in-situ, is coupled to a building thermal load model to evaluate the seasonal performance of the heat pump and to improve its design according to this criterion. Seasonal performance optimization is then led to respond to two different objectives: - Local perspective optimum: optimization with respect to a specific installation with focus on heat output regulation or prioritizing design optimal design in heating or in cooling mode. The seasonal optimization of the heat pump is carried out on an office building for different building characteristics (new and existing) simulated under different climates in order to test the sensitivity of the results. - Industrial point of view optimum: integration of innovative devices to support competition and to increase the product ranking for performance labeling. The performance improvements are completed with a technical-economic study, based on the heat pump main components costs decomposition. Finally, the payback time of the optimized heat pump is determined for the different building and climates.L'optimisation des performances non nominales des pompes à chaleur réversibles contribue à la réduction des consommations énergétiques du secteur tertiaire. Une modélisation thermodynamique détaillée d'une pompe à chaleur destinée au secteur tertiaire (compresseur, condenseur, détendeur, évaporateur) en régime non nominal est réalisée. Le modèle de pompe à chaleur validé par expérimentation en laboratoire et in-situ est couplé à un modèle de calcul des besoins thermiques de bâtiment afin d'évaluer les performances saisonnières de la PAC et d'améliorer la conception en fonction de ce critère. Des voies d'optimisation des performances saisonnières sont évaluées suivant deux axes principaux : -Optimum du point de vue local : optimisation par rapport à une courbe de besoins donnée ; interviennent la régulation de puissance, la conception orientée mode chaud ou orientée mode froid. Ces simulations sont réalisées sur un bâtiment tertiaire de type neuf ou existant. Une étude de sensibilité des résultats au climat du lieu d'installation est également réalisée. -Optimum du point de vue industriel : par l'intégration de composants innovants à fort enjeu concurrentiel pour un bon positionnement vis-à-vis de l'étiquetage européen des systèmes de climatisation. Les améliorations de performance sont complétées par une étude technico-économique, basée sur la décomposition des coûts de la PAC selon ses principaux composants. On détermine finalement le temps de retour de la machine optimisée en fonction du type de bâtiment et du climat

Analysis of Building-integrated Photovoltaic Systems: A Case Study of Commercial Buildings under Mediterranean Climate

AbstractIn the last decades, due to the significant increase in energy consumption in the building sector, many engineering strategies were developed to benefit from the use of renewable energy, particularly the solar energy. Today, building-integrated photovoltaic (BIPV) is being considered by building designers as an innovative technique for clean energy production and reduction of green house gases. Integration of PV cells in the building envelope can help in overcoming many economical and social barriers that are preventing a wider dissemination of the technology in the Mediterranean area. The BIPV components are multifunctional elements that can be used not only as energy converters, but also as shading devices, cladding, façade or roofing elements, etc. The Mediterranean countries are located in a relatively sunny area with a global horizontal radiation of 7.5–8 kWh/m2 in summer. However, the temperature in these countries can reach high levels for the same period. This can affect the performance of the BIPV cells. In this paper, BIPV systems are analyzed through a literature review where the BIPV systems that are most suitable for Mediterranean climate are investigated according to architectural constraints. The case of commercial buildings is considered where different integration scenarios are compared and analyzed. The energy performance of BIPV systems is assessed through modeling and simulations by a simplified approach taking into account various parameters such as the climate, tilt angle, azimuth angle, and types of cells. Prospects for the development of this sector are discussed at the end of this paper

Seasonal coefficient of performance of heat pumps

International audienc

Reversible heat pump model for seasonal performance optimization

International audienceBuilding is one of the economical sectors where solutions are available to significantly reduce energy consumption and greenhouse gases emissions. Electric heat pumps are one of the solutions favored in Europe. Europe recently adopted a conventional primary energy to electricity ratio which enables to compare electric heat pumps and fossil fuel boilers. This leads to an increased consideration for the evaluation of the seasonal performances of heat pumps. Nowadays, the design and sizing of heat pumps are still based on full load performance in order to fulfill thermal comfort under extreme conditions. However, the HVAC industry is switching to designs based on improved seasonal performance. The objective of this work is to model an air to water reversible heat pump that can re-design its components for seasonal performance improvement. In this context, we will present a system model including detailed sub-models of each component of the system: heat exchangers, compressor, and expansion valve. The model converges with the system thermodynamic equilibrium after simulating each component separately. Results obtained are validated through experimental data per component and for the whole cycle. Modeling requirements for the purpose of simulating seasonal performance improvements are discussed