Cummins Power Generation successfully demonstrated a tubular solid oxide fuel cell (SOFC) in a hybrid-configured auxiliary power unit (APU) configured to power a Class 7/8 truck’s "hotel loads" while running on commercial ultra-low sulfur diesel (ULSD) fuel. The Cummins APU incorporated hybrid power electronics, system controls, and balance-of-plant components combined with SOFC modules supplied by Protonex Technology Corp..
The SOFC power unit was integrated with a modified power electronics section derived from Cummins Power Generation’s Hybrid Quiet Diesel™ (HQD) recreational vehicle power system. The hybrid power electronics provide dynamic load sharing between the SOFC and a battery pack.
The testing replicated the ten-hour rest period that is part of the daily routine of a typical over-the-road truck. Specific achievements demonstrated were: operation on "straight from the pump" ULSD fuel during the entire test; operating a truck cab’s air conditioner and lighting solely from the SOFC sub-system power; hybridization of APU for instant-on capability and increased peak loading capacity-up to 3,800W ac available from the combination of fuel cell and battery boost; combined heat and power (CHP) generation; recharging batteries from the SOFC sub-system; 1,260W net peak demonstrated dc power; 940W net peak demonstrated ac power; average net power produced over test period: 1,100W dc or 820W ac.
This demonstration, held at Cummins Power Generation facilities in Minneapolis, leveraged development supported by the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE). The APU combines Cummins Power Generation’s HQD hybrid power electronics, controls and systems integration expertise with Protonex’ SOFC technology to address increasingly stringent anti-idling requirements aimed at reducing commercial truck emissions, noise and fuel consumption.
The HQD architecture-which can combine power from an engine-driven generator or fuel cell and a battery pack to supply ac and dc loads-potentially provides a versatile platform for a wide range of power system applications such as recreational vehicles, consumer marine, commercial mobile, truck APUs, and off-grid power for telecom or remote residences.
The SOFC APU system form factor and mission capabilities are comparable to commercially available diesel engine-based APU generators, highlighting the ability of the SOFC APU to be integrated into the same form factor as existing production hardware.
The hybrid-configured APU provides both ac power and dc power to the truck’s hotel loads. It intelligently controls charging of the energy storage system by regulating the power output of the SOFC sub-system and dynamically distributing loads between the fuel cell and stored energy. The SOFC sub-system efficiently converts chemical energy in the ULSD fuel directly into useful electrical power.
