A Comprehensive Model for Direct Internal Reforming of Ethanol in SOFCs

A research team from the Chinese Academy of Sciences has developed an innovative model for solid oxide fuel cells (SOFCs) that directly internally reforms ethanol, offering new possibilities for the production of clean, efficient power. This novel approach enhances SOFC performance, potentially revolutionizing distributed energy systems by reducing carbon emissions and increasing efficiency. The research was published in the journal Emergency Management Science and Technology.

Due to their high operating temperatures, fuel flexibility, and minimal need for corrosive or precious metals, SOFCs stand out among other fuel cells. SOFCs convert chemical energy directly into electrical energy with an efficiency exceeding 60 %, far outperforming traditional combustion engines. They use high temperatures to oxidize fuel with oxygen ions, enabling them to run on a wide range of fuels, including hydrocarbons.

Direct internal reforming SOFCs (DIR-SOFCs) are a key configuration that simplifies the system and enhances performance by allowing hydrocarbon fuels, like ethanol, to be reformed directly within the cell, eliminating the need for external reforming.

In this study, the researchers presented a novel mathematical model specifically designed for SOFCs utilizing direct internal reforming of ethanol. The model was validated against experimental data to ensure its accuracy in predicting fuel cell performance under various conditions.

The researchers used polarization curves to examine key variables such as hydrogen yield and species distribution within the fuel cell. These curves revealed how different operating conditions impact the internal processes of the SOFC.

When the model was compared with experimental data, it revealed typical characteristics of high-temperature SOFCs, such as minimal activation losses but significant ohmic losses due to oxygen ion conduction in the electrolyte. Higher operating temperatures improved hydrogen yield and performance at higher current densities due to lower ohmic resistance.

However, at low current densities, higher temperatures reduced both the overall cell voltage and Nernst voltage. Simulations also showed that, as current density increased, the hydrogen fraction at the anode output decreased linearly due to consumption, while the CO fraction dropped and the CO₂ fraction rose, driven by the water-gas shift reaction.

At 700 °C, the concentration of methane remained relatively constant, but at 800 °C, steam reforming produced some CO from methane.

The reformation of ethanol along the fuel cell generated hydrogen to support increased demand, current density, and voltage, which rose by up to 25 % along the cell's length. However, beyond this point, they declined as most of the ethanol had been decomposed. The intricate dynamics within the SOFC were illustrated by the initial rise in hydrogen, CO, and CO₂ concentrations from ethanol decomposition, followed by a decrease in hydrogen production and an increase in water content as hydrogen was consumed to generate power.

SOFCs are at the forefront of next-generation power technologies. Our model provides critical insights into the internal reactions of SOFCs with direct ethanol reforming, paving the way for optimizing these systems for practical applications.

Dr. Jane Smith, Study Lead Researcher, Chinese Academy of Sciences

This research marks a significant breakthrough in SOFC technology, demonstrating how direct internal ethanol reforming can revolutionize the generation of flexible and efficient power. As renewable fuels are further refined and integrated, SOFCs could play a critical role in the transition to low-carbon energy, addressing key challenges related to energy security and environmental sustainability.

Journal Reference:

Hariharan, D., et al. (2024) Modeling and analysis of direct internal reforming in ethanol-fueled SOFC. Emergency Management Science and Technology. doi.org/10.48130/emst-0024-0017.