Reversible Solid Oxide Cell (ReSOC) as flexible polygeneration plant integrated with CO₂ capture and reuse

Dipartimento Energia, Politecnico di Torino – C.so Duca degli Abruzzi 24, 10129 Torino (Italy)

^* Corresponding author: giulio.buffo@polito.it

Abstract

This work presents the concept of a Reversible Solid Oxide Cell (ReSOC) system localized in an urban residential district. The system is operated as a polygeneration plant that acts as interface between the electricity grid and the local micro-grid of the district. The ReSOC plant produces hydrogen via electrolysis during periods of low electricity demand (i.e., low-priced electricity). Hydrogen is used for multiple city needs: public mobility (H₂ bus fleet), electricity production delivered to the micro-grid during peak-demand hours, and heat (accumulated in a storage) provided to the local district heating (DH) network. An additional option analyzed is the use of part of the H₂ to produce DME using CO₂ captured from biogas obtained from municipal solid wastes. The DME is used for fueling a fleet of trucks for the garbage collection in the residential district. A traditional CO₂ removal process based on liquid MEA thermally integrated with the ReSOC system is studied. A time-resolved model interfaces the steady-state operating points with the thermal storage and the loads (electrical, H₂ buses, DME trucks, heat), implementing constraints of thermal and H₂ self-sufficiency on the system. Neglecting the DME option, the average daily roundtrip electric efficiency is about 38%, while the annual efficiency, which includes H₂ mobility and thermal energy to DH, reaches 68%. When the DME option is considered, the thermal demand for CO₂ removal and conversion process reduces the heat availability for DH, while the need for additional H₂ for DME synthesis increases the electricity consumption for water electrolysis: both these phenomena imply a reduction of system efficiency (-9%) proportional to DME demand.