Investigation of a Hydrogen Admixture in a Natural Gas Powered Phosphoric Acid Fuel Cell (PAFC)

Gas-fired power plants make a major contribution to the security and stability of the global energy system. For the transformation of the energy sector towards climate neutrality, the expansion of renewable energies is essential, but also a challenge. During the period when solar and wind power generation is limited and direct power storage is depleted, electrical energy must be provided through the use of gas. Natural gas (CH4) will be replaced by biogas and hydrogen (H2) due to climate impacts, resource scarcity and rising CH
4
prices, such as those seen in Europe as a result of the Ukraine war. The fuel switch from CH
4
to H2, biogas or other green gases places new demands on power generation plants that have to operate with different gases or gas mixtures. As part of the energy transition some regions, such as Europe, allow H2 to be blended into CH
4
pipelines to support H2 production and use. Therefore, generation plants like gas turbines, engines, or fuel cells must be able to operate with different gas compositions. Although fuel cells do not have a large market share in power generation, they are one of the most promising technologies in a pure electricity and H2 world. In this work, various H2 admixtures up to 25 percent are investigated in a CH4-fueled phosphoric acid fuel cell (PAFC) system, commonly used for stationary applications and power generation. The effects on internal parameters such as gas flow rate or gas composition and the change in electrical efficiency are determined. A detailed process engineering model of a PAFC system at steady state shows that with 25 percent H2 admixture, fuel utilization increases by 2.1 percentage points and electrical efficiency increases by 0.8 percentage points.