Efficiency of two-step solar thermochemical non-stoichiometric redox cycles with heat recovery

Lapp, Justin; Davidson, Jane H.; Lipiński, Wojciech

doi:10.1016/j.energy.2011.10.045

Cited by 179 publications

(180 citation statements)

References 36 publications

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“…We further allow for the possibility of both solid state and gas phase heat recovery. Again, heat recovery is treated simply by reducing the enthalpy input to achieve a given DT by a fraction, f. While more detailed analyses have appeared in the literature, 19 the methods pursued here are sufficient for the purpose of comparing the two cycling strategies. Representative results are presented in Fig.…”

Section: Computational Resultsmentioning

confidence: 99%

High-temperature isothermal chemical cycling for solar-driven fuel production

Hao

Yang

Haile

2013

Phys. Chem. Chem. Phys.

127

129

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The possibility of producing chemical fuel (hydrogen) from the solar-thermal energy input using an isothermal cycling strategy is explored. The canonical thermochemical reactive oxide, ceria, is reduced under high temperature and inert sweep gas, and in the second step oxidized by H 2 O at the same temperature. The process takes advantage of the oxygen chemical potential difference between the inert sweep gas and high-temperature steam, the latter becoming more oxidizing with increasing temperature as a result of thermolysis. The isothermal operation relieves the need to achieve high solidstate heat recovery for high system efficiency, as is required in a conventional two-temperature process.Thermodynamic analysis underscores the importance of gas-phase heat recovery in the isothermal approach and suggests that attractive efficiencies may be practically achievable on the system level.However, with ceria as the reactive oxide, the isothermal approach is not viable at temperatures much below 1400 1C irrespective of heat recovery. Experimental investigations show that an isothermal cycle performed at 1500 1C can yield fuel at a rate of B9.2 ml g À1 h À1 , while providing exceptional system simplification relative to two-temperature cycling.

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Section: Computational Resultsmentioning

confidence: 99%

High-temperature isothermal chemical cycling for solar-driven fuel production

Hao

Yang

Haile

2013

Phys. Chem. Chem. Phys.

127

129

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“…1. They differed in their approaches to reduce the oxygen partial pressure in the reduction chamber, namely: three mechanical schemes using i) sweep gas (scheme a) [14,15], ii) vacuum pump (scheme b) [18], and iii) the combination thereof (scheme d); and two combined mechanical-chemical schemes using i) sweep gas and a chemical scavenger (scheme c), and ii) using the combination of sweep gas, vacuum pump, and a chemical scavenger (scheme e). All five systems used two continuously and simultaneously operating reaction chambers for the separated reduction and oxidation reactions.…”

Section: Model Developmentmentioning

confidence: 99%

“…(1), operates with reasonable conversion at temperatures ranging between 1400 K and 2100 K. The exothermic oxidation reactions, eqs. (2) and (3), favor lower temperatures in order to ensure a complete oxidation of ceria [12] with a typical temperature range of around 700 Ke1100 K. The temperature difference between the two steps requires solid phase heat recovery in order to maintain a high solar-to-fuel efficiency [14], which is difficult to realize and increases the system complexity. Therefore, isothermal cycling has been proposed [16,22,23].…”

Section: Introductionmentioning

confidence: 99%

“…[3,13,14,17,24]. Panlener et al studied the reaction enthalpy of non-stoichiometric ceria in a large range of temperatures and pressures by thermogravimetric measurements [25].…”

Section: Introductionmentioning

confidence: 99%

“…Particularly two-step, non-volatile metal oxidebased cycles show promise in avoiding gas separation issues, working at lower temperatures compared to direct thermolysis, enabling relatively simple design and operation, and theoretically achieving high solar-to-fuel efficiencies [10e14]. Ceria nonstoichiometric redox cycling has attracted interest due to its nonvolatile characteristics even at high operating temperature, fast kinetics causing high hydrogen generation rates [12,15,16], theoretical high solar-to-fuel efficiencies [13,14,17], and practical demonstration of reasonable efficiencies in working prototypes [18e21]. The two steps water and CO 2 …”

Section: Introductionmentioning

confidence: 99%

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Solar fuel processing efficiency for ceria redox cycling using alternative oxygen partial pressure reduction methods

Lin

Haussener

2015

Energy

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a b s t r a c tSolar-driven non-stoichiometric thermochemical redox cycling of ceria for the conversion of solar energy into fuels shows promise in achieving high solar-to-fuel efficiency. This efficiency is significantly affected by the operating conditions, e.g. redox temperatures, reduction and oxidation pressures, solar irradiation concentration, or heat recovery effectiveness. We present a thermodynamic analysis of five redox cycle designs to investigate the effects of working conditions on the fuel production. We focused on the influence of approaches to reduce the partial pressure of oxygen in the reduction step, namely by mechanical approaches (sweep gassing or vacuum pumping), chemical approaches (chemical scavenger), and combinations thereof. The results indicated that the sweep gas schemes work more efficient at nonisothermal than isothermal conditions, and efficient gas phase heat recovery and sweep gas recycling was important to ensure efficient fuel processing. The vacuum pump scheme achieved best efficiencies at isothermal conditions, and at non-isothermal conditions heat recovery was less essential. The use of oxygen scavengers combined with sweep gas and vacuum pump schemes further increased the system efficiency. The present work can be used to predict the performance of solar-driven non-stoichiometric redox cycles and further offers quantifiable guidelines for system design and operation.

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Hydrogen (or Syngas) Generation – Solar Thermal

McCord¹,

Gordon²

2022

Advances in Energy Storage

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Efficiency of two-step solar thermochemical non-stoichiometric redox cycles with heat recovery

Cited by 179 publications

References 36 publications

High-temperature isothermal chemical cycling for solar-driven fuel production

High-temperature isothermal chemical cycling for solar-driven fuel production

Solar fuel processing efficiency for ceria redox cycling using alternative oxygen partial pressure reduction methods

Hydrogen (or Syngas) Generation – Solar Thermal

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