Triple-mode grid-balancing plants via biomass gasification and reversible solid-oxide cell stack: Concept and thermodynamic performance

Abstract

Biomass-to-electricity or -chemical via power-to-x can be potential flexibility means for future electrical grid with high penetration of variable renewable power. However, biomass-to-electricity will not be dispatched frequently and becomes less economically- beneficial due to low annual operating hours. This issue can be addressed by integrating biomass-to-electricity and -chemical via ''reversible'' solid-oxide cell stacks to form a triple-mode grid-balancing plant, which could flexibly switch among power generation, power storage and power neutral (with chemical production) modes. This paper investigates the optimal designs of such a plant concept with a multi-time heat and mass integration platform considering different technology combinations and multiple objective functions to obtain a variety of design alternatives. The results show that increasing plant efficiencies will increase the total cell area needed for a given biomass feed. The efficiency difference among different technology combinations with the same gasifier type is less than 5% points. The efficiency reaches up to 50%–60% for power generation mode, 72%–76% for power storage mode and 47%–55% for power neutral mode. When penalizing the syngas not converted in the stacks, the optimal plant designs interact with the electrical and gas grids in a limited range. Steam turbine network can recover 0.21–0.24 kW electricity per kW dry biomass energy (lower heating value), corresponding to an efficiency enhancement of up to 20% points. The difference in the amounts of heat transferred in different modes challenges the design of a common heat exchange network. ; L. Wang, M. Pérez-Fortes and J. Van herle have received funding from the European Union's Horizon 2020 under grant agreement No 826161 (Waste2GridS), 826234 (Waste2Watts), 815284 (BLAZE) and 735692 (CH2P), and support from the Fuel Cells and Hydrogen Joint Undertaking, Hydrogen Europe and Hydrogen Europe research. T.- E. Lin thanks the Young Scholar Fellowship Program by the Ministry of Science ...