3D-Topology Optimization of Nanodielectric Spacer for Capacitive Wireless Charging Applications

The dielectric medium is a key component in an EV Capacitive Wireless Charging System (CWCS) because it influences the effective permittivity system and consequently determining the power and energy density of the system. Epoxy nanocomposites with carbon nanotubes (CNTs) are attractive for this application, as suitably chosen sub-percolation CNT loadings can provide a substantial increase in real permittivity with minimal compromise of the loss tangent in the MHz band, while retaining good mechanical strength and castability into complex three-dimensional shapes. In this work, the dielectric permittivity spectrum and the loss tangent spectrum of epoxy-CNT nanocomposites are characterized over 1 kHz-10 MHz for filler volume loadings of 0%, 0.05%, 0.07%, 0.08%, and 0.1%. In parallel, an analytical material sensitivity expression for enhancing energy density in three-dimensional electrostatic systems is derived using the virtual-void concept, enabling direct evaluation of how local changes in nanodielectric topology can perturb the stored electric energy and peak field. These measured dielectric properties and sensitivity fields are then combined in a topology optimization framework to obtain the optimal geometry of the nanodielectric spacer in a CWCS coupler, targeting simultaneous maximization of average energy density and mitigation of local electric-field hotspots under high power operation.