SOFC Power Generation from Biogas: Improved System Efficiency with Combined Dry and Steam Reforming

Abstract

Solid oxide fuel cell systems (SOFC) can improve the efficiency of electrical power generation from biogas compared to small scale CHP units. The SOFC requires a reforming step converting biogas into synthesis gas (hydrogen and carbon monoxide). . Dry reforming of methane with the carbon dioxide contained in biogas is a promising approach to produce high caloric SOFC fuel gas, but carbon formation is predicted for all typical biogas compositions. To avoid carbon formation and to compensate fluctuating biogas compositions additional supply of steam is essential leading to a combined dry and steam reforming. The paper describes the system approach, upfront analysis, biogas monitoring results, process unit design and evaluation as well as the system setup to demonstrate a biogas to electricity route with a gross efficiency of 45 % using a commercial 1 kW SOFC stack.

A critical review of key materials and issues in solid oxide cells

“…[17,18] It should be noted that the cited round trip efficiency is for the cells only (mainly lab scale) and for commercial systems the efficiency will be lower (<55%). [19,20] Due to these unique traits, SOCs technology will be an indispensable part of our future energy system. Therefore, it is important to keep up to date with the latest progress and development of SOCs key materials, that is, electrode, electrolyte, interconnect and sealant, and fundamental understanding of critical issues, including the surface chemistry, segregation, electrode/electrolyte interface and varying material degradation mechanisms under reversible operation of SOCs.…”

“…[ 17,18 ] It should be noted that the cited round trip efficiency is for the cells only (mainly lab scale) and for commercial systems the efficiency will be lower (<55%). [ 19,20 ]…”

Alternative Fuel Cell Technologies for Cogenerating Electrical Power and Syngas from Greenhouse Gases

“…Solid oxide fuel cells (SOFCs) provide a viable way to simultaneously address the issues associated with clean energy sources and environmental pollution (Figure ) because it has the potential to produce electrical power and syngas with little or zero GHG emissions of CO 2 and CH 4 , the two primary components of global GHGs . Because of the high working temperature (500–800 °C) and fuel flexibility, SOFCs can directly convert the chemical energy in fossil fuels into electricity with high efficiencies (typically 50–80%), , and more importantly, SOFCs are able to perform the in situ dry reforming of methane (DRM, eq ) reaction and simultaneous H 2 selective electro-oxidation in their anode compartments. The typical working temperature of an intermediate temperature (IT) SOFC ranges from 500 to 800 °C, which is beneficial for the DRM according to the theoretical calculation illustrated in Figure . Such working temperatures help achieve high CO 2 equilibrium conversion (Figure a) while restraining the water–gas shift reaction (Figure b).…”

“…Solid oxide fuel cells (SOFCs) provide a viable way to simultaneously address the issues associated with clean energy sources and environmental pollution (Figure 1) because it has the potential to produce electrical power and syngas with little or zero GHG emissions of CO 2 and CH 4 , the two primary components of global GHGs. 4 Because of the high working temperature (500−800 °C) and fuel flexibility, SOFCs can directly convert the chemical energy in fossil fuels into electricity with high efficiencies (typically 50−80%), 5,6 and more importantly, SOFCs are able to perform the in situ dry reforming of methane (DRM, eq 1) reaction and simultaneous H 2 selective electrooxidation in their anode compartments.…”