Paulo Roberto Wander

Este artigo investigou a geração de energia elétrica por células Peltier, explorando o diferencial térmico de fontes domésticas acessíveis, como cafeteira italiana (≈90 °C) e gelo (0 °C). Baseado nos efeitos Seebeck e Peltier, o estudo testou até cinco células em série, paralelo e mistas. A maior potência registrada foi de 1012,93 mW, com diferença térmica de 88 °C, em arranjo série/paralelo de quatro células sob carga resistiva. A maior tensão foi de 4,69 V em circuito aberto com cinco células em série, e a maior corrente, 452,2 µA, com quatro células em paralelo sob baixa resistência. A eficiência máxima foi de 1,57%, calculada pela razão entre a potência gerada e a taxa de calor transferido (Q̇), com valores abaixo de 1% na maioria das configurações. Os resultados demonstram a viabilidade da conversão de calor residual em eletricidade em pequena escala, contribuindo para soluções sustentáveis e de reaproveitamento energético no ambiente doméstico.

Rice husk is considered as a waste in the rice industry but is proficient in manufacturing different materials, such as zeolites, which is produced in large quantities all over the world, for example in Brazil. Zeolite is an adsorbent support material, which can be synthesized from rice husk ash (RHA) with external sources of aluminium (ESA). The scientific community has been conducting several measures to minimize the environmental impacts caused by greenhouse gases. Several mitigation processes are presently investigated, which includes carbon dioxide injections into adsorbent materials (e.g. zeolites). The efficiency of this technology involves a zeolitic material with high crystallinity and high concentrations of SiO₂ and Al₂O₃ (aluminosilicates). In the present work, zeolites have been synthesized from rice husk ash (SiO₂ source) and external aluminium sources (Al₂O₃ - alumina, gibbsite and metakaolin) to fulfill that purpose. With the aid of XRF, XRD, SEM/EDS and FTIR techniques, the zeolitic material was characterized in two distinct crystalline phases: Mordenite and ZSM-5. The synthesis was carried out by the ideal addition of ESA (2.5 g) to RHA. According to the literature, the zeolitic materials formed by the mixture of Mordenite and ZSM-5 can be availed for gas separation and greenhouse gas storage.

Several Carbon Capture and Storage (CCS) techniques have been studied including injections of carbon dioxide (CO₂) into the mature and/or depleted hydrocarbon reservoirs and deep saline aquifers. This work aims to test storing CO₂ into the magnesium-rich evaporite strata and also into the stratigraphic intervals containing Mg-rich brines. The test simulates Mg-carbonation of the synthetic solution obtained from the Mg-evaporite mineral, bischofite – both experimentally in the laboratory condition and also through computerised geochemical simulation. The laboratory experiments, which resulted in the crystallisation of anhydrous magnesite, were analysed. The TOUGHREACT^TM, Geochemist’s Workbench^TM (GWB) and PHREEQC^TM software simulated the experiments as computerised geochemical model and tested the results for natural geological conditions. The geochemical simulations successfully demonstrate the immense CCS potential for the Mg-evaporite (as well as the sedimentary strata charged with Mg-evaporitic brine) at their subsurface geological occurrences at elevated pressure-temperature and high salinity.