Chigueru Tiba

Resumo Calor de processo industrial representa uma grande parte da demanda energética das indústrias. Setores como têxtil, bebidas e alimentos demandam por volta de um terço de eletricidade e, o restante, calor de processo. Simulações utilizando o software System Advisor Model (SAM) foram realizadas para obtenção do sistema solar termoelétrico que visa atender à demanda energética de uma planta de processamento de leite instalada em três localidades no Nordeste do Brasil com diferentes irradiações diretas normais (DNI). A análise financeira mostrou custos nivelados de calor (LCOH) entre 2,52 e 3,38 ¢/kWh-t para tubos evacuados e entre 5,95 e 11,67 ¢/kWh-t para tubos com ar. Os LCOH com uso de tubos evacuados são comparáveis ou até melhores que os custos de calor a partir de gás natural nos EUA e Europa. Já o custo nivelado de eletricidade (LCOE) para o ciclo de Rankine a vapor e ciclo orgânico de Rankine ficaram entre 0,23 e 0,31 US$/kWh-t para os tubos com vácuo e entre 0,63 e 2,73 US$/kWh-t para aqueles com ar. Os LCOE obtidos para tubos evacuados e ORC são comparáveis aos das plantas de grande porte existentes atualmente, mas ainda altos comparados a outras fontes renováveis.

Este trabalho tem como objetivo modelar, com uma rede neural artificial, a temperatura de funcionamento de um arranjo fotovoltaico partindo apenas de variáveis meteorológicas (velocidade do vento, irradiação incidente e temperatura ambiente) que são facilmente obtidas em banco de dados disponíveis em várias localizações ao redor do mundo. Além disso, também compara temperatura obtida pela modelagem com RNA com a temperatura estimada por uma correlação experimental conhecida na literatura como correlação de Skoplaki. Os desvios percentuais e o erros médios quadráticos normalizados são respectivamente -0,42% e 8,90% para a modelagem com RNA e -0,38% e 9,73% para a modelagem com a correlação de Skoplaki, percebe-se assim que a modelagem que utiliza RNA é mais precisa. O arranjo FV experimental que forneceu os dados utilizados (40 dias de medição) para a modelagem com RNA e com a correlação de Skoplaki estava localizada em Recife-PE.

The objective of this work was to analyze the impacts on the transmission network due to the increase in centralized photovoltaic (PV) generators’ incorporation. A study was carried out in a high-voltage (HV) transmission network, considering adjustments in the simulation environment for more realistic results. ANAREDE software and the static voltage stability evaluation method were used. The simulation was carried out in a steady state, considering an average load and the power of the PV generators corresponding to the base case (70.6 MW), with an increase of 100% of the predicted total (270 MW) for the future. The results showed that, under normal and contingency conditions, small disturbances caused voltage instability. It was observed that the incorporation of PV generators contributes to the improvement of the voltage stability in the bars close to their insertion. However, the greater the PV distribution and generation was, the greater the influence on the attenuations of the voltage profiles through the transmission system was.

The objective of this paper was to analyze the impacts caused by the operation of voltage regulators in electrical distribution networks and to evidence the number of operations in the face of short-duration voltage variation caused by the high intermittency of the connected PV generators. A real LV and MV feeder was used, modeled in OpenDSS software, based on normative standards, adjustments, and technical maneuvers strategically used by the local utility. The analyses considered the temporal variations for the photovoltaic generators and different load demand profiles connected to the feeder. The feeder was submitted to the demand curves varying the load percentage, framing it in high and conventional (nominal) load according to the profiles of consumers and prosumers connected. The simulations made it possible to observe the exacerbated elevation in the number of maneuvers performed by the voltage regulators of the network. The single-phase voltage regulators stood out by the elevation of control operations, causing premature wear of the PV generation equipment connected to the most loaded phase. It was observed that discrepancies in the power flow in the lines and the voltage levels at the busbars. The creation of strategies and decisions to correct these impacts caused to transformers and regulators is possible.

This work aims to highlight and analyze the impacts caused on the transmission network resulting from the increase in the insertion of centralized PV generators in the transmission network. A real high voltage (HT) transmission network was analyzed, working within the normative standards, and considering some adjustments in the simulation environment so that the results could be more realistic. The study was carried out with ANAREDE software, considering the system in steady state for load demand and PV generation. The static stress stability evaluation method was used. The simulated system was subjected to an average load level and the PV generators were injecting the power corresponding to the base case (70.6 MW of PV generation already operational) and as an increase of 100% of the forecast total (270 MW) to be added to the PV complex in the future. Through the results, it was possible to verify that, from small disturbances in normal and contingency operating conditions, there was a voltage instability in the network. Furthermore, it was evidenced that the PV complex contributes to an improvement in the stability of the voltage in steady state, reflecting in better responses in the bars close to the insertion of the PV systems. However, the greater the distribution and the higher the power from the PV generation, the greater the contribution to the attenuation of the voltage profiles along the transmission system. Este trabalho tem por objetivo evidenciar e analisar os impactos causados na rede de transmissão decorrentes aumento da inserção de geradores FV (fotovoltaico) centralizados na rede de transmissão. Foi analisada uma rede de transmissão real de alta tensão (AT), funcionando dentro dos padrões normativos e considerando alguns ajustes no ambiente de simulação, como por exemplo, a substituição de dados de geração médios por dados instantâneos, para que os resultados pudessem ser mais realistas. O estudo foi realizado com o programa ANAREDE, considerando o sistema em regime permanente para a demanda de carga e da geração fotovoltaica. Foi utilizado o método estático de avaliação da estabilidade de tensão. O sistema simulado foi submetido a um patamar de carga média e os geradores FV estavam injetando a potência correspondente ao caso base (70.6 MW de geração fotovoltaica já operacional) e como incremento de 100% do total previsto (270 MW) a ser acrescentada ao complexo fotovoltaico no futuro. Através dos resultados foi possível verificar que a partir de pequenas perturbações nas condições de operação normal e em contingência ocorreu a instabilidade de tensão na rede. Além disso, ficou evidenciado que o complexo FV contribuí para uma melhora da estabilidade da tensão em regime permanente, refletindo em melhores respostas nas barras próximas a inserção dos sistemas FV. No entanto, quanto maior for a distribuição e mais elevada a potência proveniente da geração FV, maior é a contribuição nas atenuações nos perfis de tensão, ao longo do sistema de transmissão.

Calor de processo industrial representa uma grande parte da demanda energética das indústrias. Setores como têxtil, bebidas e alimentos demandam por volta de um terço de eletricidade e, o restante, calor de processo. Simulações utilizando o software System Advisor Model (SAM) foram realizadas para obtenção do sistema solar termoelétrico que visa atender à demanda energética de uma planta de processamento de leite instalada em três localidades no Nordeste do Brasil com diferentes irradiações diretas normais (DNI). A análise financeira mostrou custos nivelados de calor (LCOH) entre 2,52 e 3,38 ¢/kWh-t para tubos evacuados e entre 5,95 e 11,67 ¢/kWh-t para tubos com ar. Os LCOH com uso de tubos evacuados são comparáveis ou até melhores que os custos de calor a partir de gás natural nos EUA e Europa. Já o custo nivelado de eletricidade (LCOE) para o ciclo de Rankine a vapor e ciclo orgânico de Rankine ficaram entre 0,23 e 0,31 US$/kWh-t para os tubos com vácuo e entre 0,63 e 2,73 US$/kWh-t para aqueles com ar. Os LCOE obtidos para tubos evacuados e ORC são comparáveis aos das plantas de grande porte existentes atualmente, mas ainda altos comparados a outras fontes renováveis.

Among the electrical problems observed from the solar irradiation variability, the electrical energy quality and the energetic dispatch guarantee stand out. The great revolution in batteries technologies has fostered its usage with the installation of photovoltaic system (PVS). This work presents a proposition for voltage regulation for residential prosumers using a set of scalable power batteries in passive mode, operating as a consumer device. The mitigation strategy makes decisions acting directly on the demand, for a storage bank, and the power of the storage element is selected in consequence of the results obtained from the power flow calculation step combined with the prediction of the solar radiation calculated by a recurrent neural network Long Short-Term Memory (LSTM) type. The results from the solar radiation predictions are used as subsidies to estimate, the state of the power grid, solving the power flow and evidencing the values of the electrical voltages 1-min enabling the entry of the storage device. In this stage, the OpenDSS (Open distribution system simulator) software is used, to perform the complete modeling of the power grid where the study will be developed, as well as simulating the effect of the overvoltages mitigation system. The clear sky day stored 9111 Wh/day of electricity to mitigate overvoltages at the supply point; when compared to other days, the clear sky day needed to store less electricity. On days of high variability, the energy stored to regulate overvoltages was 84% more compared to a clear day. In order to maintain a constant state of charge (SoC), it is necessary that the capacity of the battery bank be increased to meet the condition of maximum accumulated energy. Regarding the total loading of the storage system, the days of low variability consumed approximately 12% of the available capacity of the battery, considering the SoC of 70% of the capacity of each power level.

The single axis solar tracker based on flat panels is used in large solar plants and in distribution-level photovoltaic systems. In order to achieve this, the solar tracking systems generally need to work by tracking the sun’s position with dozens, maybe hundreds of movements along the day with a maximal known tracking error within the specifications. A novel model is proposed along this work based on the control of the angle deviation within a (polar) single axis configuration. This way an optimization of the harnessing of solar energy can be achieved with as few panel displacements as possible in order to decrease the wear in the mechanical parts of the equipment and the energy consumed by it. This tracking approach was implemented with as few as seven positions along the day and got an estimated theoretical value of 99.27% of the total collected energy in a continuous tracking system. Regarding an annual average basis, it would be about 96.5% of a dual axis system according to the proposed model. The novelty of the model is related to a tradeoff between the gain with the simplicity of a single axis n-position tracking and the solar energy loss associated.