SBIR-STTR Award

APEI, Inc. is proposing in this Phase I effort to design and build a scalable, high-efficiency, high-power density, gallium nitride (GaN)-based DC-DC converter for grid-tied energy storage applications. The project approach will utilize a soft switching dual active bridge DC-DC converter with state-of-the-art GaN power semiconductor switches and advanced power packaging techniques to efficiently transform energy from a battery energy storage system to a three-phase voltage-source inverter for subsequent insertion to the AC grid. This converter can work with any renewable or alternative energy source that produces an unregulated or uncontrolled DC voltage at its terminals. The goals of the Phase I project are to: i) compare several candidate DC-DC soft-switching converter topologies for high voltage, high power energy storage applications, ii) design a custom GaN-based power module demonstrating optimal thermal, electrical, and mechanical characteristics, iii) design and build a representative scalable prototype to demonstrate the efficacy of the selected GaN power module-based soft-switching converter topology, and iv) target the preliminary performance specifications provided in the solicitation in order to commercialize this technology for existing and emerging energy storage power conversion systems used for facility load peak shaving, energy arbitrage, renewable energy smoothing/buffering, and coincident peak reduction. APEI, Inc. will use its expertise in power electronics miniaturization and packaging to design and build a minimum volume and weight, high efficiency electronic converter that converts a DC voltage from a battery energy storage system at its input to a desired DC voltage at its output.

Power generation and transmission limits manifest themselves in the inability to respond to dynamic peak power demand. Load leveling can effectively support dynamic demand changes by having additional standby power generating capabilities. This is achieved by either having a generation and distribution infrastructure that matches the peak demand and it is operated under its full capacity or having additional power plants that can be brought online to provide additional power. These methods are economically costly because power generators are underutilized, likely operating at a lower efficiency point, or because power generating infrastructures are left unused for large portions of time. Grid-connected energy storage systems are intended to enhance performance and reliability of the utility infrastructure. By storing energy during off-peak power demand and releasing it during peak demand, grid-tied energy storage systems can effectively shift the dynamic power demand profile seen by the grid infrastructure. There is currently a need to develop high efficiency power electronics to interface with grid-tied energy storage systems. Consequently, APEI is proposing to develop a high efficiency, high power density, modular (>50 kW at > 2 power density of state-of-the-art Si designs), high frequency (> 20 kHz; 100 kHz target), GaN-based DC-DC converter with > 800 Vdc output, for interfacing with grid-level energy storage elements, such as batteries. A high frequency, GaN-based modular power topology will be designed to enable bi- directional power flow to support energy storage. One of the key benefits of high frequency operation is the significant reduction in size of the transformer used in the power conversion system. APEI has successfully implemented GaN-based systems capable of operating in the MHz range while still providing high efficiency. Smaller magnetic components result in an overall system cost reduction while delivering operational cost improvement through higher efficiency Commercial Applications and Other

Benefits:
The United States consumed approximately 3,800 TWh of electricity in 2012. At such a massive level, even small increases in efficiency can have a prominent impact. Assuming that 30% of the yearly total is processed by power electronics at 85% efficiency, for every 1% average efficiency increase, there would be an annual cost savings of over $2 billion (at $0.15 per kWh) and a reduction of 25 billion lbm of CO2 emissions (assuming 1.77 lbm of CO2 per kWh) in the United States alone. The significance of efficiency is ever important as renewable sources such as wind, solar, and tidal energy become more prevalent. Grid-tied energy generation and storage to transportation-based power systems will be.