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A new packed-bed reactor coupled with thermal energy storage (TES) for solar pyrolysis of biomass is developed to overcome the shortcomings of solar energy. The numerical model of a 3.5 kW reactor is formulated by coupling heat and mass transfer balances to chemical kinetics for biomass pyrolysis. It is solved numerically by finite element techniques. The model is applied to analyze the influence of the storage component on the thermal and chemical performance of the pyrolysis process. A new criterion Ydefined as the ratio of the char yield and the effective solar power input is proposed to evaluate the effectiveness of solar power input. Under different solar radiation conditions, the coupled TES reduces the solar energy consumption for the char production by over 16%. The storage component can alleviate the overheating and thermal cyclic stresses on the absorption surface. As compared to the non-TES design, the new design can decrease the temperature fluctuation on the absorption surface for over 300 K during solar intermittencies. Moreover, the latent heat in the storage component makes the pyrolysis process stable. Under short-term interruptions, the variation of char yield in the terminal temperature range of 623–673 K is as large as 34.9% in the non-TES design, and it can be decreased to 16.5% after coupling TES. This value can also be decreased from 66.8% to 17.0% under long-term interruptions by coupling the storage.

The high-performance PLTES basically relies on the heat transfer inside the sphere capsule. To achieve a high cost-performance enhancement, the sphere capsule with the copper foam partially filled is proposed, depending on the full utilization of the foam enhancement and natural convection. The melting performance of the partly filled sphere capsule and the optimization, including the geometric shape and foam material usage, is numerically investigated. The economic assessment of these initial cases and the optimized cases is also conducted to evaluate the economic feasibility. The numerical results indicate the partially filled strategy is effective and the optimal design is the spherical capsule with a copper foam geometric shape that resembles a high cone with a prominent center. This is because the buoyancy-driven natural convection is fully used to enhance the heat transfer in the upper section and the foam is used to enhance the heat transfer in the bottom section. Based on this analysis, a better effect can be obtained by maintaining consistent angle size while changing the height of the vertex of the high cone. Through this optimization, the usage of copper foam is reduced by 24.48 % at the same melting rate.