Photovoltaic cells produce electric energy in a short interval during a period of low demand and show high levels of intermittency. One of the well-known solutions is to store the energy and convert it into a more stable form, to transform again into electricity during periods of high demand, in which the energy has a higher value. This process provides economic viability for most energy-storage projects, even for the least efficient and most common, such as batteries. Therefore, this paper aims to propose a storage system that operates with gravitational potential energy, considering a small-scale use. The development of this methodology presents the mathematical modeling of the system and compares the main characteristics with other systems. The dimensions of the considered system are 12-m shaft, 5-m piston height, and 4 m of diameter; it presented an energy storage of 11 kWh. Also, it has an efficiency of about 90%, a lifetime of 50 years, and higher storage densities compared to other systems.

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Biomass has a large share in the energy generation matrix, due to the regional economic benefits. This work has as main objective to evaluate the parameters used in the manufacture of briquettes produced with forest residues and the economic engineering for the manufacturer. The forest residues were: wood chips and chips of Eucalyptus spp. and barks of Pinus taeda. The evaluations were the chemical characterization of forest residues and the costs involved in the briquetting process. The forest residues presented extractive chemical composition and lignin. The production costs of the briquettes were affected mainly by the equipment, being the Pinus taeda barks the one that presented higher production cost. However, the production costs obtained in this study are approximately 20% lower than the production costs using traditional methods for forest firewood. The energy value from biomass allows the reduction of the dependence of energy, which can be used for the generation of steam or electricity, for subsistence. A fact for energy conversion is to evaluate the material moisture. It is suitable to burn residues with moisture between 45 to 55%. The consumed electric energy is important to evaluate the total costs. The energy required depends on the quality of raw material and the system employed. Forest residues is an important source for eco firewood production, contributing to energy generation and decreasing of the solid waste stored at the company. In this way, the new parameters for briquetting biomass forest wastes shown in this work, which is an important stage of the process, make economically viable and environmentally suitable the eco firewood production.

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O trabalho tem como tema a análise do limite de inflamabilidade de uma solução de etanol em água e da segurança da combustão dessa mistura. O trabalho foi desenvolvido utilizando o etanol produzido na UFSM, onde a concentração do produto final é de aproximadamente de 90% de pureza. Através do etanol foi realizado o procedimento de análise das características de temperatura, tempo de queima e coloração da chama. Essas características foram determinadas a partir de diferentes concentrações, começando em 90% e indo na direção de um valor menor, a cada 5% até que se atingisse o ponto de inflamabilidade para as condições de pressão, umidade e temperatura ambientes. As análises buscam os limites de inflamabilidade do etanol hidratado e garantia da segurança do emprego do biocombustível. O volume final da mistura para todos os testes foi constante. A pesquisa se caracteriza como experimental, aplicada, descritiva e quantitativa. Com as análises concluiu-se que o tempo de combustão das amostras diminui à medida em que se aumenta a concentração de água, e que há ignição nas amostras, numa temperatura ambiente, até 35% de etanol em água. E também, a dosagem máxima de radiação é de 5 kW/m² por 60 s para pessoas e equipamentos.

Interest in biofuels is growing, and ethanol has been the most used biofuel as an additive and as a gasoline substitute and, it is considered a potential alternative to traditional fuels. Ethanol represents 17% of energy consumption in transportation in Brazil, the transport sector's share in the energy matrix is 32.4%, which is the second most energy-consuming sector. The production of first and second-generation ethanol in the same industrial plant presents better financial results compared to the isolated processes. Also, ethanol obtained from the sugarcane has renewability, biodegradability and provides CO2 emissions mitigation. The objective of the work is to perform an analysis of the ethanol with several levels of hydration in terms of energetic, economic, environmental and safety. The results showed that each 10% of water in ethanol dilution the temperature in the flame surround decreases by 4%. Besides, the ethanol with 20% of water dilution emits 20% less radiation compared to 10% of water dilution. Indeed, the energy consumed in the distillation to produce ethanol with 10% of water is double. On the other hand, this energy difference in the production of ethanol diluted with 30% of water is not enough to compensate for the losses in the energy use process. Also, large amounts of water in ethanol dilution might be unfeasible the use due to the total cost of transportation. Therefore, ethanol with 20% of water represents the more efficient, cleaner and safe fuel in free flame applications.

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