The Development of a Backup SOFC Generator at Upstart Power

Abstract

Upstart Power is developing a state-of-the-art SOFC generator that provides backup power solutions for residential and industrial customers. The Upgen NXG™ fuel cell enables grid independence and pairs seamlessly with solar and/or standalone battery storage to provide extended backup power and 24/7/365 energy solutions. The system has dual fuel capability using either propane or natural gas and exports AC power via Enphase micro-inverters. Field trials are being conducted including a batch of 10 units in Puerto Rico running on propane in collaboration with Sunnova.The key technologies enabling the Upgen NXG™ system’s fast cycling and overall simplicity include:1) Integrated Hot Zone with advanced Thermal Management2) Custom dry CPOx reactor (waterless)3) Control strategy based on two thermocouple setpointsThe core of the NXG system is the Hot Zone which integrates the CPOx reactor, fuel cell stack, heat exchanger, flame sensor, spark ignitor and exhaust system. Figure 1 shows the complete subsystem layout of the NXG system, including the fuel filter, blowers, power electronics and controls. The core component of the Hot Zone is a single piece structure that comprises a thermally conductive element that conducts heat from the combustion chamber to the stack inlet. This enables both rapid start-up and enhanced performance from the stack, without the risk of cell failure due to thermal stress. Figure 2 shows a Hot Zone demonstrating 1000 rapid thermal/power cycles from operating temperature down to 200°C. The chart shows power per cycle with a heat-up time of 40 minutes. Power output was increased after 800 cycles with higher power test cycles run throughout the test.The dry CPOx reactor converts fuel gas into hydrogen and carbon monoxide for use in the fuel cell without the use of any additional water. The CPOx can operate at very low O:C ratios (< 1.2) providing stack fuel efficiencies up to 40% and is controlled by a single thermocouple in the reactor core. The other system control setpoint is the temperature in the core of the hot zone which provides a simple system control scheme with minimal yet reliable sensors.Figure 3 shows real time cycle data from the Upgen NXG™ system, with a start-up time of less than 60 minutes with 9 hours of steady state AC power exporting to the grid via Enphase micro-inverters. The cathode air flow is controlled by the thermocouple in the core of the Hot Zone (Radiated).In summary, the Upgen backup power systems outperform ICE generators and battery-only backup by providing unlimited backup solar + storage systems that are more robust, cost-effective and have lower emissions. The single wall mounted unit minimizes connections and simplifies installation over an ICE generator that typically sits on an outdoor concrete pad. With near silent operation and the absence of deadly CO emissions, the Upgen NXG™ is a safe and environmentally friendly backup power solution for residential solar and industrial customers. Figure 1