Dynamic modeling of an air source heat pump water heater

International audienceThis paper presents a dynamic simulation model to predict the performance of an air source heat pump water heater (ASHPWH). The mathematical model consists of submodels of the basic system components i.e. evaporator, condenser, compressor, and expansion valve. These submodels were built based on fundamental principles of heat transfer, thermodynamics, fluid mechanics, empirical relationships and manufacturer's data as necessary. The model simulation was carried out using MATLAB software. Refrigerant R134a with two different reservoir volumes 150L & 200L are investigated. Additionally, different ambient air temperatures are considered. Results show that the rate of hot water production increases as the water reservoir volume decreases and the integrated COP increases as the ambient temperature increases

Electricity of Lebanon: Problems and Recommendations

AbstractThis paper presents a detailed review of EDL (Electricité du Liban). It displays the institution's technical problems at the level of electricity generation, transmission and distribution as well as the administrative and financial states and suggests several recommendations. It is obvious that EDL suffers a great shortage in its generating capacity and human resources and would not be effective without conducting a national strategy that includes radical solutions

Investigation of exhaust gas heat recovery unit for diesel power generator

The aim of this paper is to find a proper heat recovery unit that recovers lost energy from a diesel power generator exhaust. This process is performed by inserting the exhaust gas of a 20 kVA power generator into a specifically configured shell & tube exchanger, and transferring its energy into circulating water. The carried energy is then stored in a thermal storage tank so that it would be used for a selected residential energy demand. This method is called “cogeneration”. Different configurations of heat exchanger and tank volumes are considered and flow simulations are performed in order to select a suitable recovery unit for the given design conditions

Phase Change Materials (PCM) for cooling applications in buildings: A review

International audienceCooling demand in the building sector is growing rapidly; thermal energy storage systems using phase change materials (PCM) can be a very useful way to improve the building thermal performance. The right use of PCM in the envelope can minimize peak cooling loads, allow the use of smaller HVAC technical equipment for cooling, and has the capability to keep the indoor temperature within the comfort range due to smaller indoor temperature fluctuations. This article presents an overview of different PCM applications in buildings for reducing cooling loads under different climate conditions, and the factors affecting the successful and the effective use of the PCM. Many drawbacks have been found in PCM applications, mainly the intense impact of summer weather conditions over the PCM performance, which prohibits its complete solidification during night, and thus, limiting its effectiveness during the day. Proposed solutions are reviewed in this article. Finally, a topology diagram is presented to summarize the steps leading to an effective use of PCM in building applications

Optimization approaches and climates investigations in NZEB—A review

International audienceThe conception of net zero energy buildings (NZEB) has been introduced to limit energy consumption and pollution emissions in buildings. Classification of NZEB is based on renewable energy (RE) supply options, energy measurement process, RE-sources location, and balances whether are energetic or exergetic. In general, it is traditionally agreed that there are three main steps to reach the NZEB performance, starting through the use of passive strategies, energy efficient technologies, and then RE generation systems. Then, these three steps could be accompanied with the smart integration of advanced efficient energy technologies. A state of the art shows that the main ZEB studies are related to: energy savings, reduce electric bills, energy independence, pollution reduction, and occupants comfort, in addition, others are more interested in the aesthetic aspect by combining modern technologies with innovations to achieve high energy and sustainability performance. Building optimization is a promising technique to evaluate NZEB design choices; it has been adopted to choose the perfect solution to reach the zero energy performance through the optimization of an objective function related to energy (thermal loads, RE generation, energy savings) and/or environment (CO2 emissions) and/or economy (life-cycle cost (LCC), net-present value (NPV), investment cost). This paper starts by presenting the global energetic and pollution challenges the world faces. Moreover, it shows, to the best to the author’s knowledge, the existing NZEB definitions and the corresponding case studies investigated in 8 different climatic zones (humid continental, humid subtropical, Mediterranean, moderate continental, moderate continental, marine west coast, tropical, semi-arid and hot), the paper also focus on the importance to treat each climate separately. Even in the same country, two or more climates may co-exist. NZEBs drawbacks are also presented. Furthermore, different optimization problems are reviewed in the last section. Building energy optimization methods are employed to obtain the ideal solution for specific objective functions which are either related to energy, and/or environment and/or economy. Optimization variables are distributed between passive and/or RE generation systems. Finally, a table summarizing the most commonly used electric and thermal RE applications which yield to the zero energy balance in each climate, as well as three flowcharts are presented to summarize the whole three-stage procedure, to reach NZEB, starting from building designing, passing through the optimization procedure, and lastly categorizing the zero energy balance

Investigation of exhaust gas heat recovery unit for diesel power generator

The aim of this paper is to find a proper heat recovery unit that recovers lost energy from a diesel power generator exhaust. This process is performed by inserting the exhaust gas of a 20 kVA power generator into a specifically configured shell & tube exchanger, and transferring its energy into circulating water. The carried energy is then stored in a thermal storage tank so that it would be used for a selected residential energy demand. This method is called “cogeneration”. Different configurations of heat exchanger and tank volumes are considered and flow simulations are performed in order to select a suitable recovery unit for the given design conditions

Modèle simplifié pour la prise en compte de la convection naturelle dans la modélisation du changement de phase solide-liquide

International audienceUn modèle simplifié basé sur l'approche de la conductivité efficace ainsi que sur la théorie d'échelle est présenté dans ce travail pour modéliser la convection naturelle pendant le processus de fusion d'un matériau à changement de phase. Le modèle mathématique est codé sous MATLAB en utilisant la méthode des volumes finis en deux dimensions. Les résultats du modèle simplifié sont ensuite comparés à ceux d'un modèle CFD complet créé dans COMSOL, et aux résultats numériques des benchmarks trouvés dans la littérature. En particulier, une corrélation du nombre de Nusselt correspondant à notre cas d'étude est trouvée, sur la base du modèle CFD, et est ensuite implémentée dans le modèle simplifié. Les résultats montrent que, pour un temps de calcul largement plus court que celui de la CFD, les valeurs de fraction liquide moyenne et de la position du front de fusion sont acceptables. De plus, Les résultats du modèle de conductivité efficace proposé ont montré un très bon accord avec les résultats numériques des benchmarks

Passive designs and renewable energy systems optimization of a net zero energy building in Embrun/France

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