Internal and External Strategies for Evolution of Solid Oxide Fuel Cells into Model Citizens of the Grid

Proper converter design can allow solid oxide fuel cells utilized as distributed generators to mutually benefit both the load and the utility during steady-state conditions, but dynamic load changes are still an issue. Unlike standard synchronous generators, fuel cells lack an inherent spinning reserve and their output power ramp rate is limited by the fuel cell design. Two strategies are herein investigated to mitigate the impact of a large load dynamic on the utility grid: (1) An external load-following strategy that adds ultra-capacitors through a DC-DC converter for electrical storage and (2) an internal strategy to decrease the steady-state utilization so more fuel is available during the output power dynamic. Both strategies successfully eliminate the impact of a load change on the utility grid. The ultra-capacitor strategy requires more capital investment while the utilization strategy necessitates lowered efficiency. This implies there is substantial flexibility when designing load-following fuel cell systems.