Table 4.

Heat recovery concepts for sensible heat of thermochemical reactors

Heat recovery concepts	Designs	Reduction temperature	Oxidation temperature	Oxygen partial pressure in reduction step	Redox material and its shape	Heat transfer medium and its shape	Heat exchange style	Maximum heat exchanger efficiency	Maximum solar-to-syngas efficiency	Reference
Solid phase sensible heat recovery	Moving brick receiver-reactor solid-solid heat exchanger	1800K	1100K	10Pa	Ceria porous brick	/	Radiation	/	∼25%	Siegrist et al.243
	Quasi-counter-current heat exchanger	1400°C	1000°C	/	Ceria particle	Alumina sphere	Conduction	>70%	/	Felinks et al.247
	Counter-flow particle heat exchanger	1800K	1000K	/	Ceria particle	/	Conduction	>80%	/	Falter and Pitz-Paal248
	Quasi-countercurrent heat recovery system	1500°C	900°C	100Pa	Ceria particle	Particle	Conduction	∼70%	/	Brendelberger et al.249
	Counter-flow solid heat exchanger	1800K	1000K	10−3atm	Ceria reticulated porous ceramic brick	/	Radiation	∼70%	∼12%	Falter and Pitz-Paal250
	Heat recovery based on dual heat storage system	1450-1500°C	900-650°C	20-22mbar	Ceria porous eight side brick		Conduction, convection, and radiation	∼70%	∼2.83%	Lidor et al.254
	Counter-flow solid heat exchanger	1800K	1000K	10−5atm	Ceria porous brick	/	Radiation	∼80%	/	Falter et al.258
	Solid–solid heat exchanger	1773.15K	1073.15K	10−3bar	/	/	/	/	/	Holzemer-Zerhusen et al.259
	Reactor train system for heat recovery	1773K	1073K	10Pa	Ceria porous brick	/	Radiation	∼80%	∼30%	Patankar et al.251
	Counter-rotating inert solid heat exchanger	/	/	/	Ceria porous medium	Inert material cylinder solid	Radiation	>50%	/	Lapp et al.202
Gas phase sensible heat recovery	Reticulated ceramic foam heat exchanger	1773K	1773K	/	Ceria porous particle	/	Conduction and convection	/	∼2.4%	Bala Chandran et al.257
Simultaneous solid and gas phase sensible heat recovery	Simultaneous solid and gas phase heat recovery design	1980K	1073K	0.01atm	Ceria	/	Conduction convection and radiation	/	∼40.8%	Lapp et al.19