Diversos estudos realizados nos últimos anos têm apontado as implicações e impactos sócio-ambientais do consumo de energia. As fontes renováveis de energia são apresentadas como a principal alternativa para atender as demandas da sociedade com relação à qualidade e segurança do atendimento da demanda de eletricidade com a redução dos danos ambientais decorrentes do consumo de energia. Este artigo apresenta uma revisão dos conceitos físicos relacionados ao emprego da energia cinética dos ventos na geração de eletricidade. Inicialmente, o artigo descreve a evolução do aproveitamento da energia eólica, incluindo dados e informações sobre a situação atual do uso desse recurso para geração de energia elétrica. O artigo apresenta uma descrição dos aspectos dinâmicos dos ventos e circulação atmosférica na Terra, incluindo a descrição dos fatores que influenciam a velocidade e direção dos ventos nas proximidades da superfície de nosso planeta. A modelagem e previsão dos ventos são discutidas apresentando os principais resultados obtidos com as metodologias empregadas no Brasil. Os aspectos relacionados à estimativa e previsão da potência eólica são abordados ressaltando a importância de uma base de dados de vento de qualidade para a determinação da confiabilidade dos resultados fornecidos pelos modelos numéricos.

Several studies have been pointed out the energy consumption implications and impacts on environment and human society. Renewable sources of energy were identified as the major alternative to assure the confidence and the quality required to fulfill the energy demands from human society by reducing the environmental impacts. This paper presents a short review of knowledge and technological evolution related to conversion of wind energy into electricity. First of all, the paper describes the time evolution and the present status of the wind energy deployment. After that, a brief discussion on atmospheric circulation is presented including the main factors that affect the wind velocity and direction near the surface. The wind energy assessment methodologies adopted in Brazil that uses regional climate models and wind data acquired in ground sites spread throughout the Brazilian territory were discussed. Finally, the issues related to the wind power are depicted and special attention is given to the importance of database reliability to the wind power plant design and management.

Este trabalho apresenta uma revisão dos aspectos ligados à influência das nuvens sobre o clima como também seus impactos no desenvolvimento científico, tecnológico e econômico de diversos setores da atividade humana. Conceitos básicos da física de nuvens são discutidos. Também são apresentadas as metodologias mais modernas para a determinação da cobertura de nuvens a partir de medidas feitas na superfície e por satélite.

This work is a review on the clouds influence on the weather/climate as well as on its impacts in applied sciences, technology and economic sectors. Basic concepts on cloud physics and its role in the climate system are presented, followed by current methods to determine the cloud cover amount from satellite images. A new method to determine the sky cloud cover, developed by the authors is also presented with its first results.

The objective of this study was to evaluate the immobilization of lipase on a chitosan support by physical adsorption, aiming at its application in hydrolytic and synthetic reactions. Two types of chitosan (flakes and porous) were used for immobilizing lipase from a microbial source (Candida rugosa) and animal cells (porcine pancreas). The best results for recovery of total activity after immobilization were obtained for microbial lipase and porous chitosan beads. This set was selected for further immobilization studies, including full characterization of the immobilized derivative in aqueous and organic media. In aqueous medium, the operational and thermal stabilities of this preparation were quantified. In organic medium, the direct synthesis of n-butyl butyrate in organic solvent was chosen as a model reaction. The influence of several parameters, such as temperature, initial butyric acid concentration and amount of enzyme in the reaction system, was analyzed. Production of n-butyl butyrate was optimized and an ester yield response equation was obtained, making it possible to predict ester yields from known values of the three main factors. Use of this immobilized preparation was extended to the direct esterification of a large range of carboxylic acids (from C2 to C12) with a variety of alcohols (from C2 to C10).

The enzymatic synthesis of selected low molecular weight esters such as acetate esters by direct esterification using acetic acid as acyl donor usually display low yields. The acetic acid changes the polarity of the reaction medium, which in this turn modifies the partitioning of water between the solid phase (enzyme preparation) and the liquid phase (substrate), resulting in its accumulation on the enzyme solid phase. This may reduce the enzyme´s local pH. Therefore, the enzyme active site is modified and the reaction became nearly impossible. Our previous work showed that there is a negative relationship between enzyme activity and substrate partition coefficient (Ps); that is, the higher the substrate partition coefficient the lower the amount of product formed. This work investigated the feasibility of minimizing this inhibition by replacing the esterification reaction for alcoholysis reaction using several acetate esters. This approach enhanced the reaction yields to 46%, which is about 3 times higher than that one obtained in the esterification route.