Calcium carbonate is promising thermochemical heat storage material for next-generation solar power systems due to its high energy storage density,low cost,and high operation temperature.Researchers have tried to impr...Calcium carbonate is promising thermochemical heat storage material for next-generation solar power systems due to its high energy storage density,low cost,and high operation temperature.Researchers have tried to improve energy storage performances of calcium carbonate recently,but most researches focus on powders,which are not suitable for scalable applications.Here,novel granular porous calcium carbonate particles with very high solar absorptance,energy storage density,abrasive resistances,and energy storage rate are proposed for direct solar thermochemical heat storage.The average solar absorptance is improved by 234%compared with ordinary particles.Both cycle stability and abrasive resistances are excellent with almost no decay of energy storage density over 25 cycles nor apparent particle weight loss over 24 h of continuous operation insides a planetary ball mill.In addition,the decomposition temperature is reduced by 2.8%–5.6%while the reaction rate of heat storage is enhanced by 80%–205%depending on the CO_(2) partial pressure.The decomposition process of doped granular porous CaCO_(3) particles is found to involve three overlapping processes.This work provides new routes to achieve scalable direct solar thermochemical heat storage for next-generation high-temperature solar power systems.展开更多
Hydrogen production via a two-step thermochemical cycle based on solar energy has attracted increasing attention.However,the severe irreversible loss causes the low efficiency.To make sense of the irreversibility,an i...Hydrogen production via a two-step thermochemical cycle based on solar energy has attracted increasing attention.However,the severe irreversible loss causes the low efficiency.To make sense of the irreversibility,an in-depth thermodynamic model for the solar driven two-step thermochemical cycles is proposed.Different from previous literatures solely focusing on the energy loss and irreversibility of devices,this work decouples a complex energy conversion process in three sub-processes,i.e.,reaction,heat transfer and re-radiation,acquiring the cause of irreversible loss.The results from the case study indicate that the main irreversibility caused by inert sweeping gas for decreasing the reduction reaction temperature dominates the cycle efficiency.Decreasing reduction reaction temperature without severe energy penalty of inert sweeping gas is important to reducing this irreversible loss.A favorable performance is achieved by decreasing re-oxidation rate,increasing hydrolysis conversion rate and achieving a thermochemical cycle with a lower equilibrium temperature of reduction reaction at atmosphere pressure.The research clarifies the essence of process irrrversibility in solar thermichemical cycles,and the findings point out the potential to develop efficient solar driven two-step thermochemical cycles for hydrogen production.展开更多
This review investigates the effect of different dopants on the oxygen evolution and carbon dioxide splitting abilities of the lanthanum manganites.Particular focus was placed on the lanthanide,alkaline earth metals,r...This review investigates the effect of different dopants on the oxygen evolution and carbon dioxide splitting abilities of the lanthanum manganites.Particular focus was placed on the lanthanide,alkaline earth metals,redox-active transition metal,and non-redox active Group 3 metals.The review suggests that a small ionic radius lanthanide on the A-site can increase the size discrepancy,leading to Mn-O_(6) octahedra tilting and more facile Mn-O bond breaking.Doping the A-site with a divalent alkaline earth element can increase the valance of the transition metal,leading to greater reduction capabilities.A transition metal with one electron in the e_(g) orbital is the most effective for reduction while for oxidation,zero electrons in the high-energy e_(g) orbitals is optimal.Finally,doping of the B-site with metals such as gallium or aluminium aids in sintering resistance and allows reactivity to remain constant over multiple cycles.Higher reduction temperatures and moderate re-oxidation temperatures also promote higher fuel yields as does the active reduction of the perovskite under hydrogen,although the total energy consumption implications of this are unknown.Far more is known about the mechanism of the reduction reaction than the oxidation reaction,therefore more research in this area is required.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.51820105010 and 52076106)the support from Natural Science Foundation of Jiangsu Province(Grant No.BK20202008).
文摘Calcium carbonate is promising thermochemical heat storage material for next-generation solar power systems due to its high energy storage density,low cost,and high operation temperature.Researchers have tried to improve energy storage performances of calcium carbonate recently,but most researches focus on powders,which are not suitable for scalable applications.Here,novel granular porous calcium carbonate particles with very high solar absorptance,energy storage density,abrasive resistances,and energy storage rate are proposed for direct solar thermochemical heat storage.The average solar absorptance is improved by 234%compared with ordinary particles.Both cycle stability and abrasive resistances are excellent with almost no decay of energy storage density over 25 cycles nor apparent particle weight loss over 24 h of continuous operation insides a planetary ball mill.In addition,the decomposition temperature is reduced by 2.8%–5.6%while the reaction rate of heat storage is enhanced by 80%–205%depending on the CO_(2) partial pressure.The decomposition process of doped granular porous CaCO_(3) particles is found to involve three overlapping processes.This work provides new routes to achieve scalable direct solar thermochemical heat storage for next-generation high-temperature solar power systems.
基金the financial support provided by the National Natural Science Foundation of China(No.52090061)the Basic Science Center Program for Ordered Energy Conversion of the National Natural Science Foundation of China(No.51888103)。
文摘Hydrogen production via a two-step thermochemical cycle based on solar energy has attracted increasing attention.However,the severe irreversible loss causes the low efficiency.To make sense of the irreversibility,an in-depth thermodynamic model for the solar driven two-step thermochemical cycles is proposed.Different from previous literatures solely focusing on the energy loss and irreversibility of devices,this work decouples a complex energy conversion process in three sub-processes,i.e.,reaction,heat transfer and re-radiation,acquiring the cause of irreversible loss.The results from the case study indicate that the main irreversibility caused by inert sweeping gas for decreasing the reduction reaction temperature dominates the cycle efficiency.Decreasing reduction reaction temperature without severe energy penalty of inert sweeping gas is important to reducing this irreversible loss.A favorable performance is achieved by decreasing re-oxidation rate,increasing hydrolysis conversion rate and achieving a thermochemical cycle with a lower equilibrium temperature of reduction reaction at atmosphere pressure.The research clarifies the essence of process irrrversibility in solar thermichemical cycles,and the findings point out the potential to develop efficient solar driven two-step thermochemical cycles for hydrogen production.
基金support to the work under EP/T031379/1,EP/T022981/1 and EP/S032622/1.Harriet Kildahl acknowledges the University of Birm-ingham Centre for Energy Storage and School of Chemical Engineering for a PhD scholarship.
文摘This review investigates the effect of different dopants on the oxygen evolution and carbon dioxide splitting abilities of the lanthanum manganites.Particular focus was placed on the lanthanide,alkaline earth metals,redox-active transition metal,and non-redox active Group 3 metals.The review suggests that a small ionic radius lanthanide on the A-site can increase the size discrepancy,leading to Mn-O_(6) octahedra tilting and more facile Mn-O bond breaking.Doping the A-site with a divalent alkaline earth element can increase the valance of the transition metal,leading to greater reduction capabilities.A transition metal with one electron in the e_(g) orbital is the most effective for reduction while for oxidation,zero electrons in the high-energy e_(g) orbitals is optimal.Finally,doping of the B-site with metals such as gallium or aluminium aids in sintering resistance and allows reactivity to remain constant over multiple cycles.Higher reduction temperatures and moderate re-oxidation temperatures also promote higher fuel yields as does the active reduction of the perovskite under hydrogen,although the total energy consumption implications of this are unknown.Far more is known about the mechanism of the reduction reaction than the oxidation reaction,therefore more research in this area is required.
