Volumetric receivers in Solar Thermal Power Plants with Central Receiver System technology: A review

Coupled radiation and flow modeling in ceramic foam volumetric solar air receivers

Thermochemical water and carbon dioxide splitting with concentrated solar energy is a technology for converting renewable solar energy into liquid hydrocarbon fuels as an alternative to fossil fuels, which are dominating in today's energy mix. For the conversion reaction to be efficient, special redox materials are necessary to perform the necessary chemical reactions in a thermochemical cycle. Through this review we carefully examine perovskite oxides to design and optimize next generation solar-to-fuel conversion materials operating on thermochemical cycles. To date efforts have primarily been directed to binary oxides among which most prominently ceria was selected. Despite the promise, ceria has an unfavorable high reduction temperature and is restricted in its opportunities to manipulate through extrinsic doping the oxygen nonstoichiometry and thermodynamic properties for oxygen exchange towards H2O and CO2 splitting. In contrast, recent reports highlight new opportunities to use and alter perovskite oxides in terms of elemental composition over a wider range to affect reduction temperature, oxygen exchange characteristics needed in the catalytic reactions and fuel yield. To further foster perovskites for solar-to-fuel conversion, we review basic concepts such as the lattice structure and defect thermodynamics towards CO2 and water splitting, discuss the role of oxygen vacancies and present strategies for an efficient search for new perovskite compositions. Summarizing, recent efforts on perovskite oxide compositions investigated are based on Fe, Mn, Co, or Cr with reported fuel yields of up to several hundred μmol per g per cycle in the literature. This article reviews the underlying principles, the latest advances and future prospects of perovskite oxides for solar-to-fuel technology.

Perovskite oxides – a review on a versatile material class for solar-to-fuel conversion processes

An experimental and numerical investigation of premixed methane combustion within a nonhomogeneous porous ceramic was performed. The burner consisted of two porous ceramic cylinders of equal length and diameter that were stacked together and insulated around the circumference. Four series of experiments were carried out to determine the lean limit using three different pore sizes in the downstream ceramic cylinder (SBR). The pore size in the upstream ceramic cylinder was constant in all four cases. A new definition of the lean limit was introduced to account for the effects of the porous ceramic. The burners were tested over the range of lean limit 0.41 < φ≤ 0.68 and the numerical simulations were performed over 0.43 < φ ≤ 1.0. The results demonstrated that porous ceramic burners provide a range of stable burning rates at a constant φ, The maximum flame speed inside the burners was much higher than the premixed, freely burning adiabatic laminar flame (free flame) speed. The lean limits in the por...

Experimental and Numerical Study of Premixed Combustion Within Nonhomogeneous Porous Ceramics

Fully coupled transient modeling of ceramic foam volumetric solar air receiver

Combined radiative, conductive, and forced convective heat transfer through a packed bed composed of two spectrally dissimilar slabs of particles is analyzed on the basis of the two-flux model. Taking into account the variation of absorption and scattering of the layers in the visibles and infrared spectral ranges, the selectivity of such a system is proved theoretically. Experiments are run using a bed composed of glass and silicon carbide particles as a solar absorber for gas heating. Good agreement is shown in comparison of predictions with experimental data.

T. Menigault

Papers

Combined Heat Transfer in a Semitransparent Multilayer Packed Bed