R. Rubin

The DIAPR: A High-Pressure, High-Temperature Solar Receiver

A solar central receiver absorbs concentrated sunlight and transfers its energy to a working medium (gas, liquid or solid particles), either in a thermal or a thermochemical process. Various attractive high-performance applications require the solar receiver to supply the working fluid at high temperature (900--1,500 C) and high pressure (10--35 bar). As the inner receiver temperature may be well over 1,000 C, sunlight concentration at its aperture must be high (4--8 MW/m{sup 2}), to minimize aperture size and reradiation losses. The Directly Irradiated Annular Pressurized Receiver (DIAPR) is a volumetric (directly irradiated), windowed cavity receiver that operates at aperture flux of up to 10 MW/m{sup 2}. It is capable of supplying hot gas at a pressure of 10--30 bar and exit temperature of up to 1,300 C. The three main innovative components of this receiver are: a Porcupine absorber, made of a high-temperature ceramic (e.g., alumina); a Frustum-Like High-Pressure (FLHIP) window, made of fused silica; a two-stage secondary concentrator followed by the KohinOr light extractor. This paper presents the design principles of the DIAPR, its structure and main components, and examples of experimental and computational results.

Performance of the Directly-Irradiated Annular Pressurized Receiver (DIAPR) Operating at 20 Bar and 1,200°C

The Directly Irradiated Annular Pressurized Receiver (DIAPR) is a volumetric (directlyirradiated) windowed cavity receiver, designed for operation at a pressure of 10 ‐30 bar, exit gas temperature of up to 1,300°C, and aperture radiation flux of up to 10 M W/m 2 . This paper presents test results obtained under various irradiation conditions and flow rates. Inlet aperture flux was up to 5 M W/m 2 ; exit air temperatures of up to 1,200°C were obtained, while operating at pressures of 17 ‐20 bar. Estimated receiver efficiency in these tests was in the range of 0.7‐0.9. The absorber and window temperatures were 200‐400°C below the permitted maximum, indicating that higher air exit temperatures are possible. @DOI: 10.1115/1.1345844#

Solar energy storage via a closed-loop chemical heat pipe

Abstract The performance of a solar chemical heat pipe was studied using CO2 reforming of methane as the vehicle for storage and transport of solar energy. The endothermic reforming reaction was carried out with a reactor packed with a supported rhodium catalyst and heated by the concentrated solar flux from the Schaeffer solar furnace at the Weizmann Institute (Rehovot, Israel). The maximum absorbed power was 8.5 kW. The reforming was run under variable insolation conditions, including partly cloudy days. The flux input was regulated by opening the doors of the concentrator building. The product gas temperature followed a predetermined set point that automatically controlled the flow of reactants to ensure constant composition of the reformer products. The exothermic methanation reaction was run in a multistage methanator filled with the same Rh catalyst and fed with the products from the reformer. High conversions were achieved for both reactions. In the closed-loop mode, the products from thereformer and from the methanator were compressed into separate storage tanks. The two reactions were run consecutively, and the whole process was repeated for over 60 cycles. The overall performance of the closed loop was satisfactory; scale-up work is in progress.

Chemical reactions in a solar furnace 2: Direct heating of a vertical reactor in an insulated receiver. Experiments and computer simulations

The performance of a solar chemical heat pipe was studied using CO2 reforming of methane as the endothermic reaction. A directly heated vertical reactor, packed with a rhodium catalyst was used. The solar tests were carried out in the Schaeffer solar furnace of the Weizmann Institute of Science. The power absorbed was up to 6.3 KW, the maximal flow rates of the gases reached 11,000 1/h, and the methane conversions reached 85%. A computer model was developed to simulate the process. Agreement of the calculations with the experimental results was quite satisfactory.

Simulation of Thermal and Chemical Processes in Annular Layer of ZnO–C Mixtures

A special setup, electrically heated, enabling the simulation of the process conditions encountered in a solar chemical reactor, is described. The setup allows us to study the thermal and chemical processes in different solid (powder or granules) reactant layers from the beginning of the heating until the reaction is completed, in a heating condition typical for indirectly, externally heated solar reactors. The particular case of the ZnO carboreduction process is analyzed in this paper as an example. Tests were executed using different powder mixtures of ZnO-C to demonstrate the layer-wise nature of the process. The results show that the reactivity and the behavior of mixtures strongly depend on their components structures, impurities, and stoichiometry. This method can be generally applied for studying endothermic chemical reactions involving other solid reactants.

Simulation of Thermal and Chemical Processes in Annular Layer of ZnO-C Mixtures

A special setup, electrically heated, is described, enabling the simulation of the process conditions encountered in a solar chemical reactor. The setup allows studying of the thermal and chemical processes in different solid (powder or granules) reactant layers from the beginning of the heating until the reaction is completed, in heating condition typical for indirectly, externally heated solar reactors. Tests were executed with ZnO carboreduction process, using different powder mixtures of ZnO-C to demonstrate the layer-wise character of the reaction. The results show that the reactivity and the behavior of mixtures strongly depend on their components structures, impurities and stoichiometry. This method can be generally applied for studying endothermic chemical reactions involving other solid reactants.Copyright