Solar-assisted biomass chemical looping gasification in an indirect coupling: Principle and application

A new configuration of solar-assisted biomass chemical looping gasification (CLG), in which solar heat is indirectly absorbed and stored in the form of sensible heat in solid particles (oxygen carrier and support material), was developed (i.e., indirect coupling). A steam Rankine cycle was integrated to further recuperate the thermal energy of the high-temperature solid particles at the outlet of the steam reactor. Compared with the direct solar energy utilization approach, the proposed configuration can circumvent the fluctuating working conditions of the CLG and downstream processes. Additionally, since the solar receiver and reactor are uncoupled, efficient thermal integration of the developed system is relatively easy to achieve. Thermodynamic analysis of the proposed configuration was conducted, and the indirect coupling of solar energy with CLG was investigated. A case study of methanol synthesis was conducted to compare the annual output of the proposed configuration with that of an auto-thermal CLG. Results indicate that the energy and exergy efficiencies of the present configuration were 66.16% and 77.68%, respectively. The optimal solar multiple was 2.8, which corresponds to the thermal energy storage and designed heliostat size of 10 h and 110.74 × 103 m2, respectively. The case study shows that the present configuration-based methanol synthesis route produced more methanol and electricity but emitted less carbon than the auto-thermal CLG-based method.