Exergy Analysis applied to a Power to Gas Plant
The share of Renewable Energy Sources (RES) for the European power-generation sector has almost reached 30%. Despite that, in the heating and cooling sectors only 20% comes from RES and in the transport sector, 7% was just exceeded in 2016.
In order to enable higher RES penetration, future energy systems would require further development of relevant infrastructures. Many strategies and technologies are being applied and developed and as a new integral and promising approach, power-to-x (PtX) technologies have attracted more supporters since they not only serve for demand-side management and energy storage but also facilitate the substitution of fossil fuels in the sectors of building, industry and transport.
Nevertheless, these systems are known for high capital costs and low roundtrip efficiencies. The system performance depends on the operating point of the electrolyser and system design, particularly the heat exchanger network.
To understand how the system performance is improved from one design to another, component-based exergy analysis can be employed. This will identify the sources and magnitude of the thermodynamic inefficiencies occurring with each component, highlights the components with the highest inefficiencies, and pinpoints the directions for system improvement.
In this paper, we investigate a Solid-Oxide Electrolyzer (SOE) based PtM plant with a fixed-bed catalytic methanator and a membrane module for methane upgrading. We employed a top-down approach to providing optimal system designs step by step from the system concept to optimal conceptual designs. Furthermore, we carried out an exergy evaluation to the system designs in order to understand how exergy dissipation and performance of the overall system and each component vary from one to another.