Solid oxide fuel cell (SOFC) developer Versa Power Systems said a bench-top study of its technology conducted by engineers at Imperial College London validated the performance of a hybrid engine under conditions simulating the rigors of a commercial truck’s operation.
The engineering team built a hybrid engine that pairs a fuel cell with a specialized electric battery to overcome known limitations of each power source. Versa Power chief executive officer Robert Stokes noted that fuel cells generate clean and steady power, but said sporadic driving patterns – start/stop, cruise, decelerate, etc. – can force severe design inefficiencies onto them. Batteries cope better with normal driving variations, but can’t carry a charge that provides an acceptable vehicle range.
The solution devised and tested at Imperial College is a “Big Battery, Small Cell” design that “flip-flops” the two components’ traditional roles. Other experimental fuel cell hybrids tend to minimize the battery’s size and output by using it mainly to supply “extra power” such as needed during acceleration. In the study at Imperial College, a larger battery served as the primary energy source and an on-board fuel cell – smaller than needed to run the vehicle – constantly charged the battery.
The ABSOLUTE Hybrid (Advanced Battery Solid Oxide Linked Unit to maximize Efficiency) prototype engine paired a 300 W Versa Power “stack” (the element of a fuel cell that generates electricity) with a Beta Research & Development Ltd. Zebra sodium nickel-chloride battery that provided 45 amp hours of electricity.
Researchers used software to mimic the conditions experienced by a commercial vehicle over a 12-hour to 16-hour day. Stokes said that despite the mechanical stresses placed on the Versa Power stack, it operated reliably and generated the power output that researchers required. Engineering team members concluded that the stack’s performance makes full-scale prototypes viable in commercially relevant uses.
Stokes said the research clearly demonstrated the durability and predictable performance of the solid oxide fuel cells. “Developers don’t need to be overly concerned with the core SOFC technology,” he said. “They can integrate our stack into their project and be up and running quickly. It speaks to the maturity of our technology.”