Increasing hydraulic energy storage capacity: Flywheel-accumulator

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15 Scopus citations


The energy storage density of hydraulic accumulators is significantly lower than energy storage devices in other energy domains. As a novel solution to improve the energy density of hydraulic systems, a flywheel-accumulator is presented. Energy is stored in the flywheel-accumulator by compressing a gas, increasing the moment of inertia of the flywheel by adding hydraulic fluid, and by increasing the angular velocity of the flywheel. Through a numerical model of the energy flows in the system, the energy storage of the flywheel-accumulator was demonstrated to be approximately 10 times greater than a conventional accumulator. Furthermore, the flywheel-accumulator allows the hydraulic system pressure to be independent of the quantity of energy stored. The integral flywheel-accumulator presents numerous future research challenges, yet offers the potential to transform and enable numerous applications including plug-in hydraulic hybrid vehicles.

Original languageEnglish (US)
Pages (from-to)41-50
Number of pages10
JournalInternational Journal of Fluid Power
Issue number3
StatePublished - 2009
Externally publishedYes


  • Accumulator
  • Flywheel
  • Hydraulic energy storage
  • Hydraulic hybrid vehicle

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