Abstract Distributed photovoltaic generation (DPVG) has become a worldwide trend and is experiencing great growth in Brazil, although at a later rate than most of the more developed countries. Brazil has an incentive tariff for distributed electricity generation based on a compensation system, i.e. net metering, therefore DPVG is becoming increasingly popular for low voltage consumers. However, the business model of Brazilian electrical energy distribution utilities is primarily a function of the trade and distribution of energy in addition to the maintenance and expansion of the distribution grid. The objective of this study was to evaluate the business model of electric power distribution utilities and to propose possible improvements in order to make it more robust and maintain the viability of electric distribution utilities, in a context of increased utilization of distributed energy resources. Data and tariff compositions from a Brazilian distribution utility at low voltage were studied. Considering different consumptions possibilities, the annual tariff costs for different types of consumers were simulated, the percentages of tariff reduction for the consumers and for the utilities, if these consumers opted for DPVG. Finally, based on tariff proposals for other countries, a tariff was proposed. With the proposed binomial tariff, which includes charging demand and energy consumption, there was greater attractiveness for smaller consumers to adopt DPVG and reduced bills for consumers with less demand, making the system fairer and more balanced.

Abstract Brazilian scientific production has been mostly developed (90%) by Brazilian universities, mainly graduate programs, which must be assessed and ranked by the Brazilian government for their maintenance. The Qualis system is used for this classification by valuing the scientific production of graduate programs, stratifying journals and assigning grades. Several Brazilian researchers affirm that the Qualis system is inaccurate and subjective because it is carried out by a group of researchers. This work aimed to propose methods to evaluate Brazilian scientific production in order to improve the assessment of graduate programs through multi-criteria methods in addition to Qualis. The application of different metrics presented results significantly different from Qualis, including the over valuation of journals with a low international impact factor. The proposed metrics considered: (i) web of science impact factor of the journals; (ii) Citations from articles; (iii) Citations of citations, i.e., a new metric; and (iv) H-Index for researchers. It was proposed the multi-criteria method, composed of the mentioned criteria, in addition to Qualis. For the sample of researchers, it was demonstrated that multi-criteria methods can assess scientific production more accurately. Therefore, they are more adequate to assess the Brazilian graduate programs, considering several internationally accepted criteria.

ABSTRACT The largest energy losses and voltage variations from electricity suppliers occur at times of peak demand. Daytime peaks are mainly influenced by large industrial and commercial consumers. The installation of photovoltaic systems without energy storage to supply part of the demand can contribute to stabilize the voltage and reduce losses. These and other benefits constitute the so-called externality of the decrease in off-peak demand due to photovoltaic generation. The objective of this study was to investigate the role of this externality in agroindustry, as a consumer of electrical energy, in order to better understand its effects on the consumer and the utility. The implementation of photovoltaic systems was simulated with the objective to reduce the off-peak contracted demand by agroindustries. Both the energy balance and the economic viability of the photovoltaic system implantation were analyzed. It was concluded that the photovoltaic system contributed to the reduction in energy costs, improved the load factor by about 47%, and reduced the off-peak contracted demand by about 20.2% and 54.2% for the small and medium-sized agroindustries considered, respectively.

ABSTRACT The objective of this study was to analyze the feasibility of using agricultural waste from a swine farm to produce biogas, which can be used to generate electricity. For this purpose, the waste production potential was evaluated to determine the biogas production capacity of the farm. This measurement allowed scaling the size of the generator used to the electricity production to meet the needs of the farm as well as surplus electricity. The surplus electricity may be used on the farm when the generator is under maintenance or the electricity consumption is larger than the energy generated. This process is regulated by Normative Resolutions 482 and 687 in Brazil. The results of the analysis of the net present value, internal return rate, payback period and benefit cost ratio indicated that the project was feasible.

Abstract The suitability of the motive force contributes to the efficient use of electrical energy. On the other hand, the inadequate size of electric motors is directly connected to increased investment and running costs. This article presents the theory and mainly the application of a methodology for the adequacy of the motive power. The research was conducted at the Federal University of Viçosa dairy factory. This methodology consists in measuring motor rotation, acquiring technical information from the manufacturer's manual, and identifying the type of motor load. In addition, it uses the linearization method to estimate the resistance torque in steady state. This step is achieved without the need for using additional equipment or sending the motor to a laboratory for measuring the torque. In this sense, the studies can be made during the production process. Thus, this relevant methodology has the advantage of allowing the studies to be carried out at the agro-industry facilities. After getting all the information described above, it was possible to determine whether each motor at the factory was oversized. Then, the suitable motor was selected according to the load type. The application of the methodology described herein could provide around 50.6% savings in the monthly electricity costs at the dairy factory, and an attractive internal return rate.

Resumo Políticas públicas de incentivo à conservação de energia têm sido empregadas em vários países, a fim de reduzir o consumo de energia e as emissões de gases de efeito estufa. Objetivou-se com este trabalho analisar as políticas públicas brasileiras de promoção à eficiência energética, bem como desafios e oportunidades relacionados. Experiências têm demonstrado que é imprescindível que o governo formule um planejamento energético estratégico, que contemple medidas de incentivo ao uso racional de energia, tanto na gestão do lado da oferta quanto na do lado da demanda, para reduzir o risco de uma crise energética no país, como já ocorrido no passado recente.

Abstract Public policies for energy efficiency have been deployed in several countries to reduce energy consumption and the emission of greenhouse gases. This work aims to analyze Brazilian public policies promoting energy efficiency, as well as related challenges and opportunities. It has been shown that governments must develop strategic energy planning, with measures to promote energy management and generate awareness both to the demand and supply sides of the economy and to reduce the risk of another energy crisis in Brazil, as happened in recent past.

A irrigação é de grande importância para a produção de alimentos, e acredita-se que ela seja responsável por boa parte da produção agrícola mundial, mas é grande consumidora de água doce, principalmente na irrigação por aspersão. O objetivo desta pesquisa é avaliar a redução do custo da energia elétrica para irrigação, por meio de sistema automatizado de controle de velocidade em pivô central instalado em encosta. Para tal, foi dimensionado um pivô central com raio de 56,4 metros com 10 emissores com pressão de serviço de 137,8 kPa, representando uma área irrigada de 1,3 ha, e a lâmina bruta de irrigação adotada foi de 10 mm dia-1. Posteriormente, realizaram-se cálculos para determinar as pressões em cada emissor, para as condições de 0; 10; 20 e 30% de declividade média do terreno. Posteriormente, foi montado um protótipo do pivô central em tamanho reduzido, com 6,3 metros de comprimento, com 10 emissores. Foi utilizado um conjunto motobomba de 2,21 kW (3cv), onde as perdas de cargas em cada emissor eram realizadas por meio de registros inseridos na linha lateral. A automação e o controle de velocidade implementada no protótipo possibilitaram a redução dos gastos em energia elétrica entre 18% e 52%. A automação desenvolvida mostrou-se viável e capaz de responder com agilidade a qualquer mudança de pressão.

Irrigation is of great importance to food production, it is believed that it is responsible for much of the world agricultural production, but appears as a villain in the consumption of fresh water, particularly the sprinkler irrigation. The objective of this research was to evaluate the reduction in the electricity costs for irrigation using automated speed control in central pivot irrigation systems, installed in a slope. For this research, a central pivot was dimensioned with a radius of 56.4 m, 10 emitters, pressure of 137.8 kPa, with a irrigated area of 1.3 ha and an the adopted irrigation depth was 10 mm day-1. Afterwards, calculations were performed to determine the pressures at each emitter to the conditions of 0, 10, 20 and30% of average land slope. A mathematical modeling was done, where the hydraulic calculations were made for these conditions. It was later mounted a prototype central pivot in small size with 6.3 long with 10emitters. It was used a motor pump set with 2.21 kW (3 hp), and the pressure drop in each emitter was done by adding flow controller on the lateral line. The automation and speed control implemented in the prototype enabled the reduction of electricity costs from 18% to 52%. The automation developed show to be viable and able to respond quickly to any pressure change.

Os programas de simulação são importantes ferramentas para análise de diferentes alternativas energéticas, incluindo o uso de energias renováveis. O objetivo deste trabalho foi realizar uma análise comparativa das diferentes ferramentas computacionais disponíveis para modelagem de aquecedores solares de água. Entre os principais programas de simulação de sistemas solares térmicos estão: RETScreen International, EnergyPlus, TRNSYS, SolDesigner, SolarPro e T*SOL. Entre as ferramentas citadas, apenas o EnergyPlus e o RETScreen International são livres, mas permitem a obtenção de resultados interessantes quando aplicadas em conjunto. O primeiro possui um módulo de análise energética detalhado de aquecedores solares de água, enquanto o segundo possibilita um estudo detalhado de viabilidade econômica e uma avaliação de emissões de gases de efeito estufa. Os programas EnergyPlus e RETScreen International são destinados a um público-alvo diverso, incluindo projetistas, pesquisadores e planejadores energéticos.

The simulation programs are important tools to analyze the different energetic alternatives, including the use of renewable energy. The objective of this study was to analyze comparatively the different computer tools available for modeling of solar water heaters. Among the main simulation software of solar thermal systems, there are: RETScreen International, EnergyPlus, TRNSYS, SolDesigner, SolarPro, e T*SOL. Among the tools mentioned, only EnergyPlus and RETScreen International are free, but they allow obtaining interesting results when applied together. The first one has a detailed module of energy analysis of solar water heaters, while the second one provides an detailed economic feasibility study and an assessment of emissions of greenhouse gases. RETScreen International and EnergyPlus programs are aimed at a diverse audience, including designers, researchers and energy planners.

Essa pesquisa foi conduzida com o objetivo de avaliar e comparar o comportamento do aquecimento dentro de galpão avícola por meio de campânula a gás e aquecimento pelo piso. O experimento foi realizado em galpão avícola pertencente ao Instituto Federal de Educação, Ciência e Tecnologia de Triângulo Mineiro, Uberlândia-MG. As dimensões do galpão são de 24 metros de comprimento por 9,6 metros de largura e com pé-direito de 3,2 metros. A temperatura foi medida com termômetro óptico da marca Minipa, modelo MT 350. Foi utilizado para a análise do comportamento da temperatura o programa de computador de domínio público FEMM 4.2, que utiliza técnicas de elementos finitos, com dados coletados em dois lotes. O aquecimento pelo piso se dá com a utilização de água quente, passando por um sistema tipo serpentina, que é instalada abaixo da cama, sendo essa água quente proveniente de aquecedor solar. Foi realizada uma avaliação energética e econômica do aquecimento de galpão para criação de frangos. A partir dos resultados obtidos com as simulações, nota-se que o aquecimento através do piso fornece uma distribuição mais homogênea da temperatura quando comparado com o aquecimento tipo campânula. O fluxo de calor dá-se de baixo para cima, suprindo assim a necessidade maior de aquecimento da ave, que é na parte peitoral.

This study was conducted to evaluate and compare the behavior of the heating inside poultry shed through gas hood and underfloor heating. The experiment was conducted in poultry shed belonging to the Federal Institute of Education, Science and Technology of Triângulo Mineiro Region, Uberlândia city – state of Minas Gerais (MG), Brazil. The dimensions of the shed are 24 meters long and 9.6 meters wide and with a ceiling height of 3.2 meters. The temperature was measured with an optical thermometer of Minipa brand, MT 350 model. It was used, to the analysis of temperature behavior, the public domain software FEMM 4.2, which uses finite elements techniques, with data collected from two lots. Underfloor heating is made using hot water flowing through a serpentine type system, which is installed below the bed; this hot water is from solar heaters. An energetic and economic assessment of the warming shed for raising chickens was realized. From the results obtained with the simulations, it may observe that the heating through the floor provides a more homogeneous distribution of temperature when compared with the hood heating. The flow of heat is upwards supplying, thus, the greatest need of heating of the bird, which is the pectoral part.

A minhoca (Eudrilus eugeniæ) é uma espécie adaptada ao clima tropical, razão pela qual é bastante demandada como isca para pesca e tem grande valor econômico na atualidade. Normalmente, a separação de minhocas do húmus é realizada por método manual, mecânico, comportamental e elétrico. O objetivo desta pesquisa foi, caracterizar pulsos elétricos na separação de minhocas (Eudrilus eugeniae) do húmus. Para determinar a eficiência de separação de minhocas do húmus foram utilizados um gerador de pulsos controlados com: frequência de 1 e 5 Hz, tensões de 100 e 200 volts, duração do patamar de 2, 3 e 4 x 10-3 s e tempo de exposição de 15 e 30 min. As características elétricas dos pulsos, que resultaram na maior eficiência de separação, foram: 1 Hz, 2 x 10-3 s e 200 V. O índice de deslocamento máximo foi de 80%, ocorrendo na frequência de 1 Hz, com patamar de pulso de 2 x 10-3 s e tensão de 200 V. O índice de sobrevivência foi de 100% para os pulsos que resultaram em melhores índices de separação.

The worm Eudrilus eugeniæ is a species adapted to tropical climates and is highly demanded as fishing bait, therefore possessing high economic value. Separation of worms from humus is typically performed by manual, mechanical, behavioral and electric methods. The objective of this study was to characterize electric pulses for separation of worms (Eudrilus eugeniæ) from humus. To determine separation efficiency of worms from humus, a controlled pulse generator was used with frequencies of 1 and 5 Hz, voltages of 100 and 200 V, peak widths of 2, 3 and 4 x 10-3 s and exposure times of 15 and 30 min. The electrical pulse characteristics which resulted in greatest separation efficiency were: 1 Hz, 2 x 10-3 s and 200 V; and the maximum displacement index was 80% which occurred under these conditions. The survival index was 100% for the pulses which resulted in the greatest separation indices.

Vários países têm utilizado a energia solar com a finalidade de reduzir a dependência de combustíveis fósseis e as emissões de gases de efeito estufa. Os edifícios comerciais, públicos e residenciais são responsáveis por 47,6% do consumo de energia elétrica no Brasil. O chuveiro elétrico é o equipamento com maior participação de consumo em residências brasileiras, seguido da geladeira e do ar-condicionado. Objetivou-se com este trabalho analisar a eficiência energética de um sistema solar térmico com apoio elétrico para atender diferentes demandas de água quente em uma residência unifamiliar, comparativamente ao uso de chuveiro elétrico. No dimensionamento do sistema solar foram considerados parâmetros do Programa Brasileiro de Etiquetagem de edifícios e da norma técnica NBR 15569/2008. O aquecedor solar foi simulado pelo programa EnergyPlus nas condições climáticas de Viçosa, Minas Gerais. Entre outras variáveis, foram avaliadas a fração solar do sistema, a energia transferida ao coletor solar, a energia armazenada no reservatório térmico e o consumo de energia elétrica pelas duas opções de aquecimento. Foi verificado que a substituição do chuveiro elétrico pelo aquecedor solar com backup elétrico provocou uma redução média de 70% no consumo de energia elétrica destinado a aquecimento de água e 36% no consumo total de energia elétrica da residência.

Several countries have been using solar energy in order to reduce dependence on fossil fuels and to cut greenhouse gas emissions. Commercial, public and residential buildings are responsible for 47.6% of the electricity consumption in Brazil. Electric water heaters are the biggest energy consumers in Brazilian dwellings, followed by refrigerators and air-conditioners. The objective of this study is to analyze the energy efficiency of a solar water heating system with electric backup to meet the different hot water demands of a single-family dwelling, comparing it with electric water heaters. The parameters of the Brazilian Labeling Program for buildings and those of the technical standard NBR 15569/2008 were considered in the dimensioning of the the solar heating system. The solar heating system was simulated using the EnergyPlus software in the climatic conditions of Viçosa, Minas Gerais. The variables analyzed included the solar fraction, the energy transferred to the solar panels, the energy stored in the storage tank and the electricity consumption of the two water heating options. The results indicated that the replacement of the electric shower by the solar heater with electric backup led to an average reduction of 70% in electricity consumption for water heating and 36% of the dwelling's total electricity consumption.

Objetivou-se, com este trabalho, o desenvolvimento de metodologia para diagnosticar energeticamente sistemas de captação de água com vistas ao abastecimento da irrigação e para meio urbano. Foram avaliados: (i) a qualidade da energia elétrica fornecida pela concessionária em relação aos quesitos nível e desbalanceamento do sinal de tensão da rede; (ii) o consumo e a demanda de energia elétrica na estação de captação; (iii) o levantamento das características elétricas e hidráulicas das cargas; (iv) o enquadramento e a otimização tarifárias; (v) a capacidade de armazenamento de água e (vi) o gerenciamento dos horários de funcionamento. Esta metodologia foi testada e validada para a estação de bombeamento de água em uma cidade de cerca de 70.000 habitantes. Dentre as ações propostas e que mais economizaram com gastos com energia elétrica, se encontram: (i) o redimensionamento de bombas e motores e (ii) o enquadramento e a otimização tarifárias. No caso testado observou-se que a metodologia utilizada é simples e de fácil aplicabilidade, havendo um potencial de economia de energia elétrica com valores de até 52%.

This study aimed to develop a methodology to diagnose energetically a water supply system for a irrigation system and for a city. The steps taken were: (i) the energy quality supplied by the utility in relation to level and unbalanced of the supplied voltage; (ii) the electrical energy consumption and demand for the pumping station; (iii) the study of the electrical and hydraulic load's characteristics; (iv) the tariff and demand contracts optimization; (v) the water storage capacity; and (vi) the working hours management. This methodology was tested and validated for the water pumping station in a town of about 70,000 inhabitants. Among the proposed actions, which saved the most, were: (i) the sizing of pumps and motors; and (ii) the optimization of tariff and demand contracts. It was noted that this methodology is simple and easy to apply and there is a great potential for saving energy up to 52%

Sistemas de irrigação demandam quantidades significativas de energia elétrica, o que aumenta consideravelmente o custo de produção. Simularam-se o gasto com energia elétrica e as lâminas de irrigação, para um perímetro irrigado hipotético na região do Jaíba, MG, para as culturas: abacaxi, banana, goiaba, limão, mamão, manga, maracujá, melão, pinha e uva. A partir de dados das necessidades hídricas das culturas, calcularam-se as lâminas de irrigação mensal e para cada um dos lotes, simularam-se as alturas manométricas, as demandas hidráulicas e elétricas e o consumo de energia, para diferentes combinações de culturas nos lotes e, para as combinações, simulou-se o uso do inversor de frequência com restrição do número de horas de funcionamento diário em função da época do ano visando maximizar o índice de carregamento dos motores e o rendimento do conjunto motobomba. Concluiu-se que o uso do inversor de frequência e o gerenciamento do número de horas de disponibilidade da irrigação no sistema de fornecimento de água para irrigação no perímetro estudado, garantiram economia de energia elétrica, que variou em torno de 7% a 62% para as combinações estudadas.

Irrigation systems demand significative electrical energy quantities, that increase considerably the production costs. The electric energy expenditure and the irrigation depth for one hypothetical irrigated perimeter on Jaíba region - MG, Brazil were simulated for the: pineapple, banana, guava, lemon, papaya, mango, passion fruit, cantaloupe, pine cone and grape crops. From the monthly irrigation depth calculated for a hypothetical area the pressure head, the electrical and hydraulic demands and the electrical energy consumption for different crop combination were simulated. The frequency inverter use and the daily restriction to the availability of the number of hours of irrigation were simulated for each combination, in order to maximize the motor´s load and the motor pump set performance. It is concluded that the frequency inverter use and the management of the availability of the number of hours of irrigation secure energy savings that varies around 7 to 62% for the studied combinations.

O manejo da irrigação, com base no monitoramento do teor de água do solo, permite racionalizar a quantidade de água aplicada, tornando o seu uso mais eficiente. Levando-se em conta esses aspectos, foi desenvolvido um sensor capacitivo de teor de água do solo e seu circuito de medição para que sistemas de irrigação possam ser automatizados. Desta forma, problemas que afetam a produtividade, tais como irregularidades no acionamento e aplicação de água de maneira excessiva ou deficiente, podem ser contornados. No desenvolvimento dos sensores, foram utilizadas hastes de aço inoxidável, resina e verniz isolante. O circuito de medição foi baseado em um microcontrolador, que disponibiliza um sinal de saída no formato digital. Os sensores foram calibrados, utilizando-se de solo do tipo neossolo quartzarênico. Um polinômio de terceira ordem foi ajustado aos dados experimentais, para correlacionar o teor de água do solo, obtido pelo método-padrão de estufa, com os sinais digitais correspondentes, medidos pelo circuito. Obtiveram-se um coeficiente de determinação de 93,17% e uma precisão nas medidas de ±0,010 kg kg-1. Com base nos resultados obtidos, concluiu-se que o sensor desenvolvido e o circuito de medição implementado podem ser utilizados no processo de automação de sistemas de irrigação.

The irrigation management based on the monitoring of the soil water content allows for the minimization of the amount of water applied, making its use more efficient. Taking into account these aspects, in this work, a sensor for measuring the soil water content was developed to allow real time automation of irrigation systems. This way, problems affecting crop yielding such as irregularities in the time to turn on or turn off the pump, and excess or deficit of water can be solved. To develop the sensors were used stainless steel rods, resin, and insulating varnish. The sensors measuring circuit was based on a microcontroller, which gives its output signal in the digital format. The sensors were calibrated using soil of the type “Quartzarenic Neosoil”. A third order polynomial model was fitted to the experimental data between the values of water content corresponding to the field capacity and the wilting point to correlate the soil water content obtained by the oven standard method with those measured by the electronic circuit, with a coefficient of determination of 93.17%, and an accuracy in the measures of ±0.010 kg kg-1. Based on the results, it was concluded that the sensor and its implemented measuring circuit can be used in the automation process of irrigation systems.

Este trabalho apresenta o projeto de aterramento elétrico para Sistema Monofilar com Retorno pela Terra (MRT), em solicitações de baixas frequências, utilizando-se o método das imagens e considerando a simplificação do método dos potenciais constantes. Simulou-se o comportamento de três diferentes configurações de aterramento: hastes em triângulo, em quadrado vazio e para nove hastes, formando uma malha com quatro quadrados. A partir da simulação obtiveram-se o valor da resistência de aterramento para cada configuração e os potenciais gerados na superfície do solo. Com base nesses resultados foi possível comparar os valores tabelados para resistências mínimas, em função da potência do transformador, aplicados para diferentes concessionárias de energia que utilizam o Sistema MRT, com os valores calculados que mantêm os potenciais no solo em níveis seguros para seres humanos e animais. Os resultados mostraram que é possível utilizar aterramentos mais simples e mais baratos, pois os gradientes de tensões no solo se mantiveram em níveis seguros.

This work presents a grounding project for a Single Wire Earth Return (SWER) system in low frequency applications, through the use of the image method, a simplification of the constant potential method. The responses of three different grounding configurations were simulated: electrodes in triangular format, electrodes placed in the corners of a square and nine electrodes placed in the corners of a grid with four squares. With the mentioned simulation it was possible to calculate the ground resistance and the surface voltage of each configuration. Based on these results, it was possible to compare the values for minimal resistance, depending on the power of the transformer, applied to various power utilities that use the SWER system with the values that hold the potential in the soil at safe levels for human beings and animals. Results showed that it is possible to use simpler and cheaper grounding configurations due to the fact that the surface voltages were maintained at safe levels.