Riding the Solar Curve – Solar+Second-Life-Storage+EV Charging

Statement of the problem Solar+storage systems, powered by 2nd life EV batteries, can achieve low system-level cost while contributing to sustainable power grid EV charging. However, a system integration gap exists between the highly heterogenous 2nd-life battery packs at 300-410VDC output voltage and the PV DC bus at 800-1200VDC. Available power converter solutions are either cost prohibitive, under-optimized for power and voltage, or not capable of addressing EV battery safety concerns. How this problem will be addressed Smartville proposes to develop a robust solar+storage system with 2nd-life EV battery packs to achieve cost-reduction and improved system functionality. We will: (1) design a non-isolated DC-DC converter to interconnect a variety of EV packs to a common 1200VDC bus; (2) design unique cooling system and a battery-converter-coupled ground fault response to achieve improved battery safety in-lieu of an isolated power converter; and (3) perform system design to investigate the improved value proposition under solar+second-life-storage+EV charging use cases. What is to be done in Phase I During Phase I, the proposed project will: • System Design. Develop a system-level high voltage DC-coupled solar+second-life-storage system, with 1200VDC coupling and high power EV charging. • High Voltage Direct Current Coupling. Develop a unique non-isolated modular power converter to adapt a variety of EV batteries optimized for 1200VDC coupling, with oil-based coolant, and ground-fault detection scheme to achieve improved system safety. • System Modeling and Validation. Model and validate the integrated solar+second-life- storage & high power EV DC charging system at a 1200VDC bus voltage. Commercial applications and other benefits The system-level EV charging application developed and commercialized in Phases II and III will: (1) improve the value proposition of solar generation by integrating low-cost energy storage, (2) provide a low-cost way to mitigate utility demand charges during high power EV charging, and (3) provide a high-value market for second-life EV batteries