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Sistemas hídricos de captação de energia para redes de sensores sem fios
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O presente trabalho teve como objetivo o estudo de soluções de produção de energia elétrica a partir de fontes hídricas com o fim de alimentar nós sensores. Foi feito um estudo geral relativamente a sistemas tradicionais de captura de energia hídrica de grande escala. Foram obtidas as equações de dimensionamento das turbinas de grande escala e das condutas de captura. Foram escolhidos os detalhes para a produção de um protótipo com as ferramentas disponíveis, tendo-se implementado dois sistemas de geração de energia hídrica de pequena escala. O primeiro sistema estudado utilizou uma turbina tipo Propeller, a versão de pás fixas do sistema Kaplan que é muito mais comum, mas mais difícil de produzir à escala desejada. Neste sistema foi usada uma solução comercial, nomeadamente um eixo com rolamento estanque e uma hélice de nylon utilizados em modelismo. Foram testados vários caudais ao variar a diferença de altura entre o nível de água a montante e a jusante da turbina. Foi obtida uma eficiência máxima na ordem dos 62% na turbina, no sistema com bocal divergente. O segundo sistema estudado utilizou uma turbina tipo Pelton. Para este caso foi decidido usar a tecnologia de impressão 3D para fabricar as turbinas, injetores e qualquer outro componente necessário. Foi assumido, propositadamente, que as equações para turbinas de grande escala se aplicavam a sistemas de muito pequena escala. Como tal, foi dimensionada uma turbina à escala seguindo uma forma próxima da geometria das turbinas encontradas em sistemas de grande escala. Foram impressas 19 turbinas distintas, divididas em 3 grupos de dimensão, de modo a testar o efeito de mudar caraterísticas de desenho. Foi também testada uma turbina Pelton feita de metal usada num estudo anterior. Para cada turbina foram extraídos os dados de potência mecânica usando 4 diâmetros distintos de injetor. Destes testes, foi observado que a melhor eficiência nas turbinas de menor dimensão testadas foi de 37%, para as turbinas de dimensão intermédia foi de 42% e para a turbina impressa de maior dimensão foi de 41%. A turbina de metal obteve uma eficiência na ordem dos 48%. De seguida foram escolhidas 2 turbinas de cada escala, para serem testadas usando um gerador trifásico desenvolvido para o efeito, um retificador e uma carga elétrica programável. Os testes foram realizados com 3 diâmetros de injetor. Destes foi observada uma eficiência máxima que variava entre os 25% para a turbina de menor escala e os 36% para a turbina de metal. Posteriormente, a melhor turbina de cada escala foi testada usando um nó sensor desenvolvido para o efeito e 2 diâmetros de injetor. Nestes testes foi observado que a eficiência geral variava entre os 18,1%, para turbinas pequenas, e os 29,2%, para a turbina de metal. Além da diferença de eficiência entre os dois sistemas, foi observado que o sistema tipo Propeller tinha uma gama de potência muito estreita relativamente ao sistema Pelton. Refira-se que os dados para o sistema tipo Propeller foram capturados de forma completamente manual. Como a quantidade de testes realizados para o sistema tipo Pelton foi substancialmente superior, o sistema de captura de dados foi melhorado para permitir a captura semiautomática dos valores de potência mecânica e binário.
This study aimed to develop very small scale hydropower solutions, small enough to effectively supply energy to wireless sensor network nodes. Research was done on traditional, large scale, hydropower systems in order to obtain the equations and ratios for correctly dimensioning the turbines and penstock necessary for this study. Details were chosen for the fabrication of a prototype with the available tools. Two different systems were implemented. The first one was a Propeller style system, similar to the more common Kaplan system, which is very difficult to fabricate at the required scale. For this system a commercial solution was used, namely an airtight axle and bearing tube and a nylon turbine used in scale models. Several flow rates were tested by varying the gross head between the water level upstream and downstream from the turbine. An efficiency of about 62% was obtained by using a divergent draft tube. The second system was based on Pelton systems. In this case it was decided to use 3D printing technology for the fabrication of the turbines, injectors and any other required part. It was deliberately assumed that all of the large scale relations and equations apply directly to very small scale systems. Therefore a primary turbine was created following very closely the geometry of large scale turbines. 19 turbines were fabricated, divided in 3 size groups, in order to test the effect of changing design attributes. A small scale metal Pelton turbine that was used in a previous study was also tested. Each turbine was tested with a set of 4 injectors with different diameters and the data for mechanical power was extracted. From these tests it was found that the smaller scale turbines had a top efficiency of 37%, the average the sized turbines had a top efficiency of 42% and the larger scale turbine had a top efficiency of 41%. The metal turbine achieved an efficiency of about 48%. 2 turbines of each size group were chosen. These were tested using a hand made three phase generator, a rectifier and a programmable electrical load. The tests were made using 3 diameters of injectors. The maximum efficiency ranged from 25% for the smaller scale turbines and 36% for the metal turbine. After that, the best turbine of each scale was tested using a developed sensor node and 2 injectors of different diameters. During these tests the overall efficiency ranged from 18.1% for the smaller turbines and 29.2% for the metal turbine. When comparing the Propeller based system with the Pelton based system it was found that the Propeller system has a much narrower power curve when compared with a Pelton system. It should be mentioned that the data for the Propeller based system was all captured manually. Since the amount of tests for the Pelton system was substantially larger it was decided to improve the dynamometer into a semi-automatic system.
This study aimed to develop very small scale hydropower solutions, small enough to effectively supply energy to wireless sensor network nodes. Research was done on traditional, large scale, hydropower systems in order to obtain the equations and ratios for correctly dimensioning the turbines and penstock necessary for this study. Details were chosen for the fabrication of a prototype with the available tools. Two different systems were implemented. The first one was a Propeller style system, similar to the more common Kaplan system, which is very difficult to fabricate at the required scale. For this system a commercial solution was used, namely an airtight axle and bearing tube and a nylon turbine used in scale models. Several flow rates were tested by varying the gross head between the water level upstream and downstream from the turbine. An efficiency of about 62% was obtained by using a divergent draft tube. The second system was based on Pelton systems. In this case it was decided to use 3D printing technology for the fabrication of the turbines, injectors and any other required part. It was deliberately assumed that all of the large scale relations and equations apply directly to very small scale systems. Therefore a primary turbine was created following very closely the geometry of large scale turbines. 19 turbines were fabricated, divided in 3 size groups, in order to test the effect of changing design attributes. A small scale metal Pelton turbine that was used in a previous study was also tested. Each turbine was tested with a set of 4 injectors with different diameters and the data for mechanical power was extracted. From these tests it was found that the smaller scale turbines had a top efficiency of 37%, the average the sized turbines had a top efficiency of 42% and the larger scale turbine had a top efficiency of 41%. The metal turbine achieved an efficiency of about 48%. 2 turbines of each size group were chosen. These were tested using a hand made three phase generator, a rectifier and a programmable electrical load. The tests were made using 3 diameters of injectors. The maximum efficiency ranged from 25% for the smaller scale turbines and 36% for the metal turbine. After that, the best turbine of each scale was tested using a developed sensor node and 2 injectors of different diameters. During these tests the overall efficiency ranged from 18.1% for the smaller turbines and 29.2% for the metal turbine. When comparing the Propeller based system with the Pelton based system it was found that the Propeller system has a much narrower power curve when compared with a Pelton system. It should be mentioned that the data for the Propeller based system was all captured manually. Since the amount of tests for the Pelton system was substantially larger it was decided to improve the dynamometer into a semi-automatic system.
Description
Keywords
Redes de sensores sem fios Energia hídrica Pelton Propeller Captação de energia de pequena escala Wireless sensor networks Hydropower Small scale energy harvesting Engenharia de Telecomunicações e Redes de Energia . Faculdade de Ciências Exatas e da Engenharia