One of the difficulties in generating electricity from solar and wind energy is its inconsistency. Hydrogen storage systems, which utilize hydrogen created from water splitting, can provide clean electricity. It could be a viable alternative to compensate for problems in power output during poor environmental circumstances. However, these systems usually necessitate large-scale investments to compensate for their inefficiency. The hurdle can be removed only through extensive thermal control is required and reduction in energy and power density.
A new study has presented an alternate electric energy storage device that uses carbon (C) instead of hydrogen as an energy source. The team has named the device "carbon/air secondary battery" (CASB). The novel storage device has the potential to boost the Next-Generation Batteries Market as it could quickly become an alternative to electricity generators that use natural fuels.
The team generated carbon via electrolysis of carbon dioxide (CO2) to develop the current device. They oxidized it with air to produce energy in a solid-oxide fuel and electrolysis cell (SOFC/ECS). Compressed liquefied CO2 is fed into the SOFC/ECS to make up the energy storage system. The team added that to reduce CO2 to C, the CASB is charged using energy provided by renewable sources, like a battery. The C is then oxidized to generate energy during the discharge phase.
The energy density of the CASB is restricted by the amount of carbon it can carry because carbon is stored in a confined region in SOFCs/ECS. Despite this constraint, the CASB had a higher volumetric energy density than hydrogen storage systems, according to the researchers.
The charge-discharge efficiency is another indicator of battery performance. The researchers used a charge-discharge experiment to test this statistic. They discovered that the changes between C and CO2 were caused by "Boudouard reactions," which are characterized by a redox reaction involving a combination of carbon monoxide (CO), carbon dioxide (CO2), and carbon. Specifically, C was deposited on the electrode during the charging phase by the electrochemical reduction of CO2 and the Boudouard breakdown of CO. The C was oxidized to CO and CO2 during the discharge phase by the Boudouard gasification reaction and electrochemical oxidation. The researchers discovered that the CASB's C usage for energy generation depended on the Boudouard equilibrium, the equilibrium between three different carbon species (C, CO2, and CO).
The CASB system is projected to have a smaller size and higher efficiency than hydrogen storage systems. Their novel technique could pave the way for small and efficient carbon energy storage devices that could coexist with renewable energy sources in the future to eliminate the need for fossil fuels.