Lamark de Oliveira

SOLAR HYDROGEN PRODUCTION BY A TWO-STEP CYCLE BASED ON MIXED IRON OXIDES

A very promising method for the conversion and storage of solar energy into a fuel is the dissociation of water to oxygen and hydrogen, carried out via a two-step process using metal oxide redox systems such as mixed iron oxides, coated upon multi-channeled honeycomb ceramic supports capable of absorbing solar irradiation, in a configuration similar to that encountered in automobile exhaust catalytic converters. With this configuration, the whole process can be carried out in a single solar energy converter, the process temperature can be significantly lowered compared to other thermo-chemical cycles and the re-combination of oxygen and hydrogen is prevented by fixing the oxygen in the metal oxide. For the realization of the integrated concept, research work proceeded in three parallel directions: synthesis of active redox systems, manufacture of ceramic honeycomb supports and manufacture, testing and optimization of operating conditions of a thermochemical solar receiver-reactor. The receiver-reactor has been developed and installed in the solar furnace in Cologne, Germany. It was proven that solar hydrogen production is feasible by this process demonstrating that multi cycling of the process was possible in principle.

Green photochemistry: solar-chemical synthesis of Juglone with medium concentrated sunlight

Dye sensitized photooxygenations of 1,5-dihydroxynaphthalene were investigated with soluble and solid-supported sensitizers and moderately concentrated sunlight. Moderate to good yields up to 79% of 5-hydroxy-1,4-naphthoquinone (Juglone) were achieved on multiple gram-scales after just 4 h of illumination. The mild and environmentally friendly reaction conditions make this application particularly attractive for ‘green photochemistry’.

Construção e estudos de perfomance de um reator fotoquímico tipo CPC ("Compound Parabolic Concentrator")

A CPC (Compound Parabolic Concentrator) reactor was projected and constructed aiming to promote the degradation of the organic matter present in considerable volumes of aqueous effluents, under the action of solar radiation. The essays were done using a model effluent which consists of a mixture of fragments of a sodium salt of lignosulphonic acid possessing a mean molecular weigth of 52,000 Daltons, and a real effluent, from a chip board industry. The volume of effluent in each test was about 50 L. The tests involved heterogeneous (TiO2 P25 Degussa and formulations made from the association of TiO2 with a photosensitiser), and homogeneous (thermal and photochemical Fenton reactions) catalysis of the effluents. The results demonstrate the viability of application of this kind of reactor even when the load of organic pollutants is high.

Experimental proof of concept of a pilot-scale thermochemical storage unit

An efficient heat storage system, which allows disposal of the energy independently of the weather conditions, is a key factor on the development of Concentrated Solar Power (CSP). In this respect thermochemical heat storage could play an important role. Despite being still at early development stage, the number of recent studies dealing with thermochemical systems for high temperature storage shows that the interest on this topic is largely increasing. Among the reactive materials studied, certain multi-valent metal oxides seem to be a promising option, especially for air-operated CSP plants.

A solar receiver-storage modular cascade based on porous ceramic structures for hybrid sensible/thermochemical solar energy storage

The current state-of-the-art solar heat storage concept in air-operated Solar Tower Power Plants is to store the solar energy provided during on-sun operation as sensible heat in porous solid materials that operate as recuperators during off-sun operation. The technology is operationally simple; however its storage capacity is limited to 1.5 hours. An idea for extending this capacity is to render this storage concept from “purely” sensible to “hybrid” sensible/ thermochemical one, via coating the porous heat exchange modules with oxides of multivalent metals for which their reduction/oxidation reactions are accompanied by significant heat effects, or by manufacturing them entirely of such oxides. In this way solar heat produced during on-sun operation can be used (in addition to sensibly heating the porous solid) to power the endothermic reduction of the oxide from its state with the higher metal valence to that of the lower; the thermal energy can be entirely recovered by the reverse exothermic oxidation...

Solar Hydrogen Production by a Two-Step Cycle Based on Mixed Iron Oxides

A very promising method for the conversion and storage of solar energy into a fuel is the dissociation of water to oxygen and hydrogen, carried out via a two-step process using metal oxide redox systems such as mixed iron oxides, coated upon multi-channeled honeycomb ceramic supports capable of absorbing solar irradiation, in a configuration similar to that encountered in automobile exhaust catalytic converters. With this configuration, the whole process can be carried out in a single solar energy converter, the process temperature can be significantly lowered compared to other thermo-chemical cycles and the re-combination of oxygen and hydrogen is prevented by fixing the oxygen in the metal oxide. For the realization of the integrated concept, research work proceeded in three parallel directions: synthesis of active redox systems, manufacture of ceramic honeycomb supports and manufacture, testing and optimization of operating conditions of a thermochemical solar receiver-reactor. The receiver-reactor has been developed and installed in the solar furnace in Cologne, Germany. It was proven that solar hydrogen production is feasible by this process demonstrating that multi cycling of the process was possible in principle.Copyright

Solar Aluminum Recycling in a Directly Heated Rotary Kiln

South Africa currently is experiencing an electricity constraint due to economic growth and lack of investment in generation capacity, resulting in power blackouts in 2008. With increased electricity prices, the economic sustainability of energy intensive industries is threatened. The aluminum smelting industry is a significant consumer of electricity.