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Ce travail présente un modèle mathématique d'onduleur pour les applications photovoltaïques connectées au réseau pendant le fonctionnement du système PV. L'étude a été réalisée pour les trois onduleurs du système photovoltaïque du Centre de Développement des Energies Renouvelables (CDER, Bouzaréah). Dans cette étude, le modèle d'onduleur Sandia (Sandia National Laboratories) a été utilisé. Un modèle simplifié est proposé. Il calcule la puissance de sortie AC de l'onduleur en fonction de sa puissance d'entrée DC

Highlights • A method is proposed to improve the input power of the linear compressor. • Electrical analyses show the requirements of achieving a high input power. • Mechanical analyses show the methods to meet the demands of a high input power. • Changing the compression volume is adopted to improve the input power. Abstract Working characteristics of a linear compressor affected the performance of a pulse tube cryocooler significantly. However, its input power and efficiency need to be analyzed together in the optimization of a cryocooler. In this study, the electrical and mechanical characteristics of a linear compressor have been investigated to show how to achieve a high input power and a high efficiency. The electrical analyses show that a high input power requires the current and the displacement reaches the maximum simultaneously at the mechanical resonant point. The mechanical analyses show how to adjust the mechanical resonant point to meet these requirements. Changing the compression volume is adopted and verified by experiments. While it changes from 19 L to 17 L, the input power increases from 6.8 kW to 9.6 kW and the efficiency decreases a little from 59% to 57%. The study is helpful to take advantage of a linear compressor. [ABSTRACT FROM AUTHOR]

The Stirling machine has many successful applications mainly thanks to its high efficiency, fast cool-down, small size, light weight, low power consumption and high reliability (heating and cooling). A Beta type Stirling refrigerator is studied experimentally and numerically. The mathematical model takes into account complex phenomena related to compressible fluid mechanics, thermodynamics and heat transfer losses. A special attention is paid to the effect of geometric parameters such as dead and swept volumes respectively in compression and expansion spaces. Regenerator length, diameter and porosity are also discussed and optimal parameters are proposed. The effect of speed on the cold end temperature and refrigerator's performances is also investigated. Net cooling capacity, input power and COP were estimated at different conditions. Results allow understanding the physical processes occurring in the refrigerator and for predicting its performance. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a test method for determination of energy consumption of bus HVAC unit. The energy consumption corresponds to a bus engine fuel consumption increase during the HVAC unit operation period. The HVAC unit energy consumption is determined from the unit input power, which is measured under several levels of bus engine speeds and at different levels of testing heat load in the laboratory environment. Since the bus engine fuel consumption is incrementally induced by powering an HVAC unit, the results are subsequently recalculated to the unit fuel consumption under the defined road cycles in terms of standardized diesel engine. The method is likewise applicable either for classic or electric HVAC units with a main consumer (compressor or high voltage alternator) mechanically driven directly from the bus engine and also for electric HVAC units supplied from an alternative electric energy source in case of hybrid or fully electric buses. [Copyright &y& Elsevier]