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Energies 2012, 5(8), 2794-2817; doi:10.3390/en5082794

On the Efficiency of a Two-Power-Level Flywheel-Based All-Electric Driveline

* ,
Division for Electricity, Department of Engineering Sciences, Uppsala University, Uppsala 75105, Sweden
* Author to whom correspondence should be addressed.
Received: 13 June 2012 / Revised: 20 July 2012 / Accepted: 26 July 2012 / Published: 2 August 2012
(This article belongs to the Special Issue Electrical Power and Energy Systems)
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This paper presents experimental results on an innovative electric driveline employing a kinetic energy storage device as energy buffer. A conceptual division of losses in the system was created, separating the complete system into three parts according to their function. This conceptualization of the system yielded a meaningful definition of the concept of efficiency. Additionally, a thorough theoretical framework for the prediction of losses associated with energy storage and transfer in the system was developed. A large number of spin-down tests at varying pressure levels were performed. A separation of the measured data into the different physical processes responsible for power loss was achieved from the corresponding dependence on rotational velocity. This comparison yielded an estimate of the perpendicular resistivity of the stranded copper conductor of 2.5 × 10−8 ± 3.5 × 10−9. Further, power and energy were measured system-wide during operation, and an analysis of the losses was performed. The analytical solution was able to reproduce the measured distribution of losses in the system to an accuracy of 4.7% (95% CI). It was found that the losses attributed to the function of kinetic energy storage in the system amounted to between 45% and 65%, depending on usage.
Keywords: kinetic energy storage; flywheel; electric machine; driveline; electric vehicle; losses kinetic energy storage; flywheel; electric machine; driveline; electric vehicle; losses
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Abrahamsson, J.; de Oliveira, J.G.; de Santiago, J.; Lundin, J.; Bernhoff, H. On the Efficiency of a Two-Power-Level Flywheel-Based All-Electric Driveline. Energies 2012, 5, 2794-2817.

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