How Do We Compare to Fuel Cells?

Compared with Fuel Cells
Fuel cells convert the stored energy in fuels like natural gas or hydrogen gas into electricity without combustion. The result is electric power generation with near zero emissions of NOx or CO. Commercial fuel cells are certified to the strict NOx and CO emissions requirements of the California Air Resources Board (CARB), as are Capstone microturbines. CO2 emissions depend on the fuel used, and are the same as for any combustion-based power system with the same efficiency. Several fuel cell technologies are commercially available, but those used for the stationary power market are typically molten carbonate or solid oxide types. These technologies have good electrical conversion efficiencies of around 40 to 45%, and have the advantage of relatively high temperature in their fuel cell stacks that allows them to recover heat to achieve 80% total system efficiencies. Capstone microturbine solutions can also achieve 80% total system efficiency in heat recovery applications. Both fuel cells and microturbines can operate on a variety of fuels, including natural gas and renewable fuels such as landfill gas and digester gas.

While stationary fuel cells are clean and efficient, they have the disadvantage that they are not well suited to changes in power output. The high temperatures in their fuel cell stacks require careful adjustment to avoid life-limiting thermal stresses. So these fuel cells can take hours to start, and must remain at relatively constant output 24 hours-a-day thereafter. Compare this with a Capstone microturbine that can go from zero to full power in just a few minutes during a cold start, can load follow by the minute as needed to meet changing facility conditions, and can automatically start and stop every day to operate only when economic conditions are optimal for best financial payback. Fuel cells are also expensive, and require significantly higher government incentive levels to stimulate customer investment.

And the societal benefits of NOx reduction, CO2 reduction, and reduced fuel consumption operating a fuel cell with heat recovery are essentially the same as for a Capstone microturbine system with heat recovery having the same total system efficiency.

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