Analysis of continuously variable transmission for flywheel energy storage systems in vehicular application

Abstract

Energy storage devices are an essential part of hybrid and electric vehicles. The most commonly used ones are batteries, ultra capacitors and high speed flywheels. Among these, the flywheel is the only device that keeps the energy stored in the same form as the moving vehicle, i.e. mechanical energy. In order to connect the flywheel with the vehicle drive line, a suitable means is needed which would allow the flywheel to vary its speed continuously, in other words a continuously variable transmission (CVT) is needed. To improve the efficiency and speed ratio range of the variators, a power spilt CVT (PSCVT) can be employed. This paper discusses the kinematics of PSCVT used to connect the flywheel to the driveline. A methodology describing the characteristic equations of speed ratio, power flow and efficiency of the PSCVT for various types including power recirculating and multi regime in both directions of power flow has been presented. An example of a PSCVT for a flywheel energy storage system (FESS) is computed using the derived equations and the results compared.

The Kinetic Energy Storage as an Energy Buffer for Electric Vehicles

“…The energy conversion could be avoided by using a mechanical link between KES and vehicle driven wheels, such as belt drives [11], toroidal transmissions [12], planetary gear sets, PGS, [13][14][15], or power split CVT [16]. This approach is not suitable for BEV application because of its complexity, lacks of flexibility and increased overall BEV mass.…”

Review of battery electric vehicle propulsion systems incorporating flywheel energy storage

“…The common PSCVTs employed in FW hybrid vehicles (FWHV) are electromechanical, hydromechanical and various traction drive PSCVTs. The concept of PSCVT for flywheel in vehicular application has been explored by [66].…”

Theoretical Study and Experimental Validation of a Hydrostatic Transmission Control for a City Bus Hybrid Driveline with Kinetic Energy Storage

“…The weak point of such transmission configurations is the power flow limit through the CVT part, and as a consequence, the inability to use KES in its optimal efficiency range [17]. Based on the achievement of the popular Toyota Prius hybrid drive line [18], power-split continuous variable transmissions (PSCVTs) of various types are considered to be a promising variant in future for KES coupling [19]. Mechanical CVT used in parallel with planetary gear sets and KES was considered for a Zero Inertia powertrain in [20], in which a sophisticated control algorithm was proposed for KES utilization in transient modes.…”