太阳能高温热化学反应分解水或二氧化碳是制取太阳能燃料的重要途径，通常以热化学循环的方式进行。鉴于太阳能热化学循环反应腔体温度显著低于太阳表面温度，可以通过光谱选择性透过膜抑制腔体向环境的二次辐射，从而达到显著降低不可逆损失、提升集热效率、降低聚光集热成本的目的。该文对选择性透过膜的特征参数截止波长及其对热化学循环性能的影响进行了系统的研究，进而在氧化铈热化学循环分解二氧化碳实验基础上，分析了选择性透过膜对太阳能-燃料化学能效率的影响。最后，对聚光集热成本相对于选择性透过膜成本的敏感性进行了讨论。结果表明，对于最高温度为1 773 K的太阳能热化学循环，最佳截止波长为1 350 nm，与太阳能光谱（AM1.5）的水蒸气、二氧化碳吸收峰重合。选择性透过膜可以将黑体腔理论集热效率提升34.7%~85.2%，可以较为明显地提升热化学循环分解二氧化碳的太阳能-燃料化学能效率上限。选择性透过膜对缩短还原反应的升温时间和减少辐射损失分别为13.7%和36.7%。当选择性透过膜的单位成本低于碟式聚光镜的单位成本的330倍时，使用选择性透过膜可以有效降低聚光集热成本。
Splitting H2O or CO2 via solar-driven thermochemical redox cycles is important for solar fuel production. Since the reactor chamber temperature in thermochemical redox cycles is much lower than the surface temperature of the sun, secondary radiation from the reactor chamber to the ambient can be suppressed by spectral-selective transmissive coatings. These significantly reduce the irreversible losses, improve the solar thermal collection efficiency, and reduce the solar thermal collection cost. The cutoff wavelength is a key characteristic parameter of spectral-selective transmissive coatings which significantly affect the thermochemical performance of solar-driven thermochemical cycling. This study investigates the effect of the spectral-selective transmissive coatings on the solar-to-fuel efficiency based on experimental data for thermochemical splitting of CO2 using reticulated porous ceria. This work also discusses the economic impact of the spectral-selective transmissive coatings on the solar thermal collector cost. The results show that for a solar-driven thermochemical redox cycle with a high temperature of 1 773 K, the optimal cutoff wavelength is 1 350 nm, which coincides with the steam and CO2 absorption peaks in the solar spectrum (AM1.5). Spectral-selective transmissive coatings can increase the theoretical solar thermal collection efficiency of a blackbody cavity by 34.7%~85.2% and can significantly enhance the upper limit of the solar-to-fuel energy efficiency. The coatings can reduce the reduction half-reaction heating time by 13.7% and radiation losses by 36.7%. Finally, this work analyzes the economic impact of the spectral-selective transmissive coating on the solar thermal collector cost. The spectral-selective transmissive coatings can effectively reduce the solar thermal collector cost when the unit cost of the spectral-selective transmissive coatings is 330 times less than the cost of a dish concentrator.
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