Diamond Capacitors for Power Electronics
Energy storage systems are increasingly important in achieving the efficiency targets of power electronics systems including: transportable storage systems for grid applications, hybrid electric vehicles, aerospace power systems, renewable power generation, and inverter-based equipment to connect renewable energy sources to the electric grid. Capacitors are a crucial component dictating the efficiency of these systems. With an ever increasing share of U.S. electricity being processed through power electronics, even a modest efficiency increase from high-performance capacitors would result in significant annual energy and cost savings.
Project Innovation + Advantages:
Cree Fayetteville will develop high voltage (10kV), high energy density (30 J/cm3), high temperature (150 °C+) capacitors utilizing chemical vapor deposition (CVD) diamond capable of powering the next generation of high-performance power electronics systems. CVD diamond is a superior material for capacitors due to its strong electrical, mechanical, and materials qualities that are inherently stable over varying temperatures. It also has similar qualities of single crystal diamond without the high cost. Commercial CVD diamond deposition will be utilized to prove the feasibility of the technology with consistent, low cost, high-resistivity diamond films. The CVD diamond will be used as an optimal dielectric for today's demanding power electronics applications. Most power electronics systems require large capacitors to filter switching noise and provide sufficient energy to loads during transient periods. But present-day film and ceramic capacitor technologies are quickly becoming obsolete as the switching frequency and operating temperature of power electronic systems continue to increase. Using CVD diamond for this purpose may provide a capacitor technology that does not experience lifetime-limiting overheating, at both low frequency (high energy) and high frequency (low equivalent series resistance) conditions, and with reasonable size and cost. In conjunction with a robust electrode metallurgy and proven high-temperature packaging techniques, energy densities in excess of 80 J/cm3 have been modeled; the proposed specification of 30 J/cm3 will be a drastic improvement over current technologies. The team’s effort will primarily focus on the development and characterization of multi-layer CVD diamond capacitor design, packaging, and fabrication techniques, resulting in proof of concept prototypes to demonstrate the technology feasibility.