Performance evaluation of an air-to-air heat pump coupled with temperate air-sources integrated into a dwelling

ISBN : 978-0-947649-40-1 Disponible à l'adresse : http://www.ibpsa.org/proceedings/BS2009/BS09_2266_2273.pdfInternational audienceAn inverter-driven air-to-air heat pump model has been developped and implemented in the thermal simulation tool COMFIE, in order to compare the seasonal performance of a variable capacity air-to-air heat pump coupled with temperate air sources (crawlspace, attic, sunspace, heat recovery ventilation, earth-to-air heat exchanger) with the performance of a conventionally installed heat pump. The empirical model of the heat pump is presented in this paper, including full-load and part-load model at rating and non rating conditions, and also frosting conditions. Several coupling configurations are studied and applied on a case study: a French typical residential house. The influence of the climatic region is evaluated, giving indications on energy saving using such systems

Simulation of the thermal interaction between a building integrated photovoltaic collector and an airsource heat pump

Disponible à l'adresse : http://leso.epfl.ch/files/content/sites/leso/files/download/publications/cisbat_proceedings_final_download.pdfInternational audienceThe number of buildings simultaneously equipped with air-source heat pumps and photovoltaic collectors is constantly increasing. Nevertheless, both systems are installed independently, and their thermal interaction is not taken into account. In addition to electricity, the photovoltaic collector produces heat which can be used to increase the temperature of the source of the heat pump, thus improving its COP (Coefficient Of Performance). Inversely, the fluid cooled by the external unit of the heat pump can be used to lower the operating temperature of the photovoltaic collector, improving its electrical efficiency. This paper presents the methodology employed to simulate this kind of system and gives some results. The two systems (heat pump and photovoltaic collector) have been modelled and implemented in a thermal simulation tool of buildings. The resulting software enables to take into account the thermal interaction between each physical object (heat pump, PV collector and building) in a dynamic way. Simulations are run for the whole year and with a time step of one hour. The aim of this development is to evaluate the increase of efficiency of the combined system installed in a building compared to the case where both systems are installed independently. The simulation tool is applied on a case study : a single family house with a living area of 135 m2 and recently renovated. The south oriented roof gives enough space to install a 30 m2 photovoltaic collector. The external unit of the heat pump is installed in the attic just beneath the PV collector, which preheats the incoming air. The results illustrate how the thermal interaction between both systems can be taken into account

Étude de la possibilité de récupération de chaleur par voie thermodynamique pour la réhabilitation des maisons individuelles

An air-to-air heat pump performs poorly at low ambient temperatures, and its performance decreases in the coldest part of winter when the heating load is greater. Both the COP and the heating capacity of the system decrease as the outdoor temperature decreases. Auxiliary resistance heaters must then be used as back up, reducing the overall performance of the system. Moreover, defrost cycles are necessary in a specific range of outdoor conditions, lowering the heat pump performance. This is of particular interest for electricity utilities, because peak loads generally coincide with the coldest ambient temperatures. Attempts to improve the heat pump efficiency and to reduce the peak-loading problem have led to the coupling of heat pumps with milder temperature air. Different components of a building envelope can contribute to increase the heat pump's heat-source temperature, as for instance sunspaces or attics, and to some extent crawlspaces and earth-to-air heat exchangers. Other sources such as the exhaust air of a ventilation system can be used to preheat the heat pump air-source. This allows the heat pump to operate in more favourable conditions, with a higher efficiency and a higher sink-source temperature adapted to the heat production needed in dwellings retrofit. A global approach is needed to explore the energy potential of such combination and evaluate the relevance of coupling an air-source heat pump with milder air sources from the building environment. Ambient conditions and solar energy both influence the heating load and the air-source temperature that interact directly with the heat pump running conditions and performance. Besides, the heat pump running conditions, and particularly the air flow rate conditions needed at the outdoor unit, interacts directly with the air flow rate of the milder source, influencing the building heating load. The different models of air sources and heat pumps are presented. Then, different coupling configurations are studied in the case of a typical French dwelling, and typical climates.Les pompes à chaleur disposant d'une source froide sur l'air extérieur sont moins performantes les jours de grand froid, là où les besoins de chauffage sont les plus élevés. Le déclenchement d'une énergie d'appoint d'origine électrique est souvent nécessaire pour couvrir l'ensemble des besoins de chauffage, ce qui réduit les performances globales de l'installation. De plus, des cycles de dégivrage sont nécessaires sur certaines plages de températures afin d'éliminer la formation de givre sur l'échangeur extérieur, contribuant à réduire les performances du système. Ces comportements ont des conséquences sur la gestion de l'électricité, où les pics de demande coïncident généralement avec les températures extérieures les plus froides. Ces constats sont le point de départ d'une réflexion visant à améliorer les performances des pompes à chaleur et à contribuer à la limitation des pointes de demande en électricité, en couplant la source froide de la pompe à chaleur avec des sources d'air tempérées intégrées au bâtiment. Certains dispositifs intégrés aux maisons individuelles peuvent contribuer à augmenter la température de la source froide des pompes à chaleur, comme par exemple un comble perdu ou une véranda, ou encore un vide sanitaire ou un échangeur air-sol. D'autres sources peuvent également être envisagées comme l'air vicié d'un système de ventilation, ou des capteurs solaires hybrides à air. L'utilisation de ces sources peut permettre à la pompe à chaleur de fonctionner à des températures plus favorables, permettant de réduire sa consommation, d'améliorer ses performances saisonnières, et de fournir une chaleur à plus haute température mieux adaptée aux besoins plus élevés des bâtiments existants. Une approche globale par modélisation est utilisée dans le cadre de cette thèse afin d'apporter des éléments de réponse aux possibilités de récupération de chaleur par voie thermodynamique. Ce rapport présente en détail l'ensemble des modèles utilisés, concernant les sources utilisables et les pompes à chaleur. Différentes configurations de couplage sont ensuite étudiées sur une maison type, et pour différents climats