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

Barriers of solar energy uptake and the potential for mitigation solutions in Barbados

Understanding the barriers that inhibit the deployment of renewable energy technologies to achieve long-term reductions in carbon emissions from the use of fossil fuels is paramount to Barbados. Although there are targets towards renewable energy (solar, wind, biomass, geothermal) uptake, the share of these technologies in the energy mix does not exist in Barbados due to the total dependence on fossil fuels. In this paper, a review of potential challenges and the main problems for deployment of alternative energy sources is presented. Through interviews, questionnaires with a focus group of key personnel’s, the paper documents the lack of renewable energy sources (with emphasis on solar energy) as one of the main alternatives to meet the carbon emission targets set by the country. The barriers and challenges facing the implementation of solar energy deployment have been clarified. From the results, it is evident that significant policy barriers still exist at the country level, which has reduced the effectiveness of a concerted national effort to deploy renewables. The current policy landscape which benefits from fossil fuel imports, the lack of technical know-how and the lack of research and development in the renewable energy space are amongst the key barriers identified. The paper also outlines the key policy’s frameworks, regulatory environment and the lack of incentives, which encompasses the renewable energy sector, and presents a critical analysis of the barriers faced by the industry. A mitigation framework is proposed to bridge the gap of solar energy (renewable energy) deployment

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

Impact of urban heat island mitigation measures on microclimate and pedestrian comfort in a dense urban district of Lebanon

International audienceThe interaction between microclimate and buildings is predominant in urban areas. Thus, the urbanization constitutes the main cause of UHI formation. During the last years, several studies exposed the critical effects of UHI in the Mediterranean climate. As a result, there is a need for sustainable systems and urban policies to reduce heat islands in urban areas. This paper aims to present the impact of some UHI mitigation strategies in a Mediterranean city, Beirut Lebanon. Numerical microclimate simulations of an existing Lebanese district of Dora in Beirut, are performed using ENVI-met software. The study focuses on the potential of UHI mitigation scenarios to create freshness in summer conditions. The strategies are based on the increase of green surfaces, on the installation of water spray and fountains, and on the increase of the albedo of the facades and roofs of the buildings. A focus is carried out on white models, dealing with the albedo modification of roads and buildings. The effect of the proposed strategies on the pedestrian comfort is also evaluated by using the physiologically equivalent temperature PET. Results pointed out that implementation of water features contributes to a significant reduction of ambient temperature reaching a maximum of 5 °C. In term of outdoor thermal comfort, the results showed the important role of green areas on the improvement of pedestrian comfort during daytime. Finally, this research supports a set of actions that could be helpful for urban designer to create cool islands in the Lebanese neighborhoods

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

Model of a Reversible heat Pump for Part Load Energy Based Optimization Design.

International audienc

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

Energy and economic analysis on retrofit actions for Italian public historic buildings

According to the recent EU Directives on building energy efficiency, the Italian government is paying particular attention to energy refurbishments of buildings by enacting energy measures and obtaining significant results. In particular, the Italian government is providing economic incentives to citizens or public administrations that improve the envelope of the energy performance of a building. However, according to strict national regulations concerning building heritage, most actions cannot be applied to historic buildings, even though they represent approximately 30.1% of all buildings. In this context, the energy retrofits for Italian buildings are not simple but necessary. Therefore, in this work, a public historic building was simulated, and some permitted retrofit actions were applied to analyse the effectiveness of national measures in four different climatic zones. The results showed that the same applied action that reduces the primary energy consumption in some zones will significantly increase consumption in other zones, even if the zones fall within the same case-law. Finally, the results highlight two main unsolved issues: the renewable energy source installation of a historic building and a strong distinction between measures and economic incentives around the Italian peninsula, which has very different climate conditions