Rapid and stable calcium-looping solar thermochemical energy storage via co-doping binary sulfate and Al–Mn–Fe oxides

Solar thermochemical energy storage based on calcium looping(CaL)process is a promising technology for next-generation concentrated solar power(CSP)systems.However,conventional calcium carbonate(CaCO_(3))pellets suffer from slow reaction kinetics,poor stability,and low solar absorptance.Here,we successfully realized high power density and highly stable solar thermochemical energy storage/release by synergistically accelerating energy storage/release via binary sulfate and promoting cycle stability,mechanical strength,and solar absorptance via Al–Mn–Fe oxides.The energy storage density of proposed CaCO_(3)pellets is still as high as 1455 kJ kg^(-1)with only a slight decay rate of 4.91%over 100 cycles,which is higher than that of state-of-the-art pellets in the literature,in stark contrast to 69.9%of pure CaCO_(3)pellets over 35 cycles.Compared with pure CaCO_(3),the energy storage power density or decomposition rate is improved by 120%due to lower activation energy and promotion of Ca^(2+)diffusion by binary sulfate.The energy release or carbonation rate rises by 10%because of high O^(2-)transport ability of molten binary sulfate.Benefiting from fast energy storage/release rate and high solar absorptance,thermochemical energy storage efficiency is enhanced by more than 50%under direct solar irradiation.This work paves the way for application of direct solar thermochemical energy storage techniques via achieving fast energy storage/release rate,high energy density,good cyclic stability,and high solar absorptance simultaneously.

Analysis of radiation heat transfer and temperature distribu- tions of solar thermochemical reactor for syngas production

This paper investigated radiation heat transfer and temperature distributions of solar thermochemical reactor for syngas production using the finite volume discrete ordinate method （fvDOM） and P1 approximation for radiation heat transfer. Different parameters including absorptivity, emissivity, reflection based radiation scatter- ing, and carrier gas flow inlet velocity that would greatly affect the reactor thermal performance were sufficiently investigated. The fvDOM approximation was used to obtain the radiation intensity distribution along the reactor. The drop in the temperature resulted from the radiation scattering was further investigated using the P1 approx- imation. The results indicated that the reactor temperature difference between the P1 approximation and the fvDOM radiation model was very close under different operating conditions. However, a big temperature difference which increased with an increase in the radiation emissivity due to the thermal non-equilibrium was observed in the radiation inlet region. It was found that the incident radiation flux distribution had a strong impact on the temperature distribution throughout the reactor. This paper revealed that the temperature drop caused by the boundary radiation heat loss should not be neglected for the thermal performance analysis of solar thermochemical reactor.

Thermal characteristics and thermal stress analysis of solar thermochemical reactor under high-flux concentrated solar irradiation

Nowadays, using a solar-driven thermochemical reaction system to convert greenhouse gases into high-quality liquid fuels has been proven to be an effective way to address the growing depletion of traditional fossil fuels. However, the utilization of highlyconcentrated solar irradiation runs the high risk of reactor damage issues resulting from thermal stress concentration, which seriously threatens the security and reliability of the total reactor system. In this study, the thermal radiation distribution and thermo-mechanical process in a volumetric reactor were numerically investigated by combining Monte Carlo ray-tracing method with computational fluid dynamics method. Based on the experimental results and thermal characteristic analysis, the formation mechanism of thermal stress concentration and the strategies of improving thermal stress distribution were discussed in detail.The simulation results indicate a great possibility of reactor damage at about 1000℃ operating temperature and 9.0 k W lamp power, which is well-matched with related experimental results. The ceramic damage typically occurs at the inner edges of the through-holes, including the aperture, the gas inlet, and the thermocouple hole, then extends along the lines connecting these holes and finally causes brittle fracture. By reasonable control of the opening direction and the distance between the throughholes, the maximum compressive stress can be reduced by 21.78%.

New Hybrid CHP System Integrating Solar Energy and Exhaust Heat Thermochemical Synergistic Conversion with Dual-Source Energy Storage

For the efficient use of solar and fuels and to improve the supply-demand matching performance in combined heat and power(CHP)systems,this paper proposes a hybrid solar/methanol energy system integrating solar/exhaust thermochemical and thermal energy storage.The proposed system includes parabolic trough solar collectors(PTSC),a thermochemical reactor,an internal combustion engine(ICE),and hybrid storage of thermal and chemical energy,which uses solar energy and methanol fuel as input and outputs power and heat.With methanol thermochemical decomposition reaction,mid-and-low temperature solar heat and exhaust heat are upgraded to chemical energy for efficient power generation.The thermal energy storage(TES)stores surplus thermal energy,acting as a backup source to produce heat without emitting CO_(2).Due to the energy storage,time-varying solar energy can be used steadily and efficiently;considerable supply-demand mismatches can be avoided,and the operational flexibility is improved.Under the design condition,the overall energy efficiency,exergy efficiency,and net solar-to-electric efficiency achieve 72.09%,37.65%,and 24.63%,respectively.The fuel saving rate(FSR)and the CO_(2) emission reduction(ER_(CO_(2)))achieve 32.97%and 25.33%,respectively.The research findings provide a promising approach for the efficient and flexible use of solar energy and fuels for combined heat and power.

Current technology development for CO2 utilization into solar fuels and chemicals:A review

The continuous consumption of fossil fuels causes two important impediments including emission of large concentrations of CO2 resulting in global warming and alarming utilization of energy assets.The conversion of greenhouse gas CO2 into solar fuels can be an expedient accomplishment for the solution of both problems,all together.CO2 reutilization into valuable fuels and chemicals is a great challenge of the current century.Owing to limitations in traditional approaches,there have been developed many novel technologies such as photochemical,biochemical,electrochemical,plasma-chemical and solar thermochemical.They are currently being used for CO2 capture,sequestration,and utilization to transform CO2 into valuable products such as syngas,methane,methanol,formic acid,as well as fossil fuel consumption reduction.This review summarizes different traditional and novel thermal technologies used in CO2 conversion with detailed information about their working principle,types,currently adopted methods,developments,conversion rates,products formed,catalysts and operating conditions.Moreover,a comparison of these novel technologies in terms of distinctive key features such as conversion rate,yield,use of earth metals,renewable energy,investment,and operating cost has been provided in order to have a useful review for future research direction.

New operation strategy and multi-objective optimization of hybrid solar-fuel CCHP system with fuel thermochemical conversion and source-loads matching

Multi-energy hybrid energy systems are a promising option to mitigate fluctuations in the renewable energy supply and are crucial in achieving carbon neutrality.Solar-fuel thermochemical hybrid utilization upgrades solar energy to fuel chemical energy,thereby achieving the efficient utilization of solar energy,reducing CO_(2)emission,and improving operation stability.For hybrid solar-fuel thermochemical CCHP systems,conventional integration optimization methods and operation modes do not account for the instability of solar energy,thermochemical conversion,and solar fuel storage.To improve the utilization efficiency of solar energy and fuel and achieve favorable economic and environmental performance,a new operation strategy and the optimization of a mid-and-low temperature solar-fuel thermochemical hybrid CCHP system are proposed herein.The system operation modes for various supply-demand scenarios of solar energy input and thermal-power outputs are analyzed,and a new operation strategy that accounts for the effect of solar energy is proposed,which is superior to conventional CCHP system strategies that primarily focus on the balance between system outputs and user loads.To alleviate the challenges of source-load fluctuations and supply-demand mismatches,a multi-objective optimization model is established to optimize the system integration configurations,with objective functions of system energy ratio,cost savings ratio,and CO_(2)emission savings ratio,as well as decision variables of power unit capacity,solar collector area,and syngas storage capacity.The optimization design of the system configuration and the operation strategy improve the performance of the hybrid system.The results show that the system annual energy ratio,cost saving ratio,and CO_(2)emission saving ratio are 52.72%,11.61%,and 36.27%,respectively,whereas the monthly CO_(2)emission reduction rate is 27.3%–47.6%compared with those of reference systems.These promising results will provide useful guidance for the integrated design and operational regulation of hybrid solar-fuel thermochemical systems.