The Archimedes screw generator (ASG) is an emerging form of microhydro power generation. This technology is particularly suited for exploiting low head sites at existing dams and weirs, and has been found to have high efficiencies, low environmental impact, and moderate maintenance, installation and manufacturing costs. Models are presented in the literature to evaluate the power and the efficiency of the ASGs however, they are either largely empirically-based or used to study ideal screws. Furthermore, little knowledge is present in the scientific community about the losses at the outlet section of the screw because of the complexity of the physical processes that occur at that location. In this thesis a theoretical model is developed to analyze the efficiency and the power produced by ASGs. The new model is only minimally based on empirical correlations. It is implemented as a MATLAB code and it is able to predict the power losses for screws of different geometries and sizes working under a wide range of operating conditions. The validation of the new model, as well as previous ones (Kozyn and Lubitz 2017 and Nuernbergk’s equation for variable outlet level losses) is performed using data from three different screw sizes. Data from the Archimedes screw laboratory of the University of Guelph (Canada) were collected by the candidate specifically for this study. This data is used together with numerous other data that were already available of the 16 screws present in the lab. Field data is also used from a full-scale two-screw ASG system installed near Ferrara, (Italy) by Hydrolab s.r.l., and from a smaller single screw plant installed near Waterford (Canada) by Greenbug Energy. The validation process showed that the new model provides predictions of power and efficiency with low error levels that scale correctly across the different plant sizes and dimensions.
La coclea idraulica utilizzata come turbina (AST) è una forma emergente di produzione elettrica tramite piccolo idroelettrico. Questa tecnologia è particolarmente adatta a sfruttare luoghi con dighe o sbarramenti a piccoli salti ed è caratterizzata da alte efficienze, basso impatto ambientale e moderati costi di manutenzione, istallazione e produzione. In letteratura sono presenti modelli per predire la potenza e l’efficienza delle viti di Archimede, ma sono tuttavia ampiamente empirici o usati per studiare viti ideali. Poco è conosciuto inoltre in ambito scientifico riguardo le perdite nella sezione in uscita della turbina, a causa della complessità dei fenomeni fisici che la caratterizzano. In questa tesi è sviluppato un modello teorico per analizzare l’efficienza e la potenza prodotta dalle coclee. Il nuovo modello è solamente in minima parte basato su correlazioni empiriche. È implementato in codice MATLAB ed è in grado di stimare le perdite di potenza per turbine di diversa taglia. La validazione del nuovo modello, assieme a quella di modelli precedenti (Kozyn e Lubitz 2017 e l’equazione di Nuernbergk per il livello variabile in uscita) è eseguita con l’utilizzo di dati provenienti da turbine di diversa scala. Dati provenienti dal laboratorio di viti di Archimede dell’Università di Guelph (Canada) sono stati raccolti dalla candidata specificatamente per questo studio. Queste misurazioni sono state utilizzate assieme a numerosi altri dati precedentemente raccolti dalle 16 turbine presenti nel laboratorio. Sono inoltre analizzati dati provenienti da un impianto reale di grande taglia costituito da due viti istallato vicino a Ferrara (Italia), gestito da Hydrolab s.r.l. e da un impianto più piccolo istallato vicino a Waterford (Canada), gestito da Greenbug Energy. Il processo di validazione ha mostrato che il nuovo modello predice potenza e efficienza con bassi errori che scalano correttamente su impianti di diverse dimensioni e taglie.
Investigation of energy losses in laboratory and full-scale Archimedes screw generators
PASSAMONTI, ARIANNA
2016/2017
Abstract
The Archimedes screw generator (ASG) is an emerging form of microhydro power generation. This technology is particularly suited for exploiting low head sites at existing dams and weirs, and has been found to have high efficiencies, low environmental impact, and moderate maintenance, installation and manufacturing costs. Models are presented in the literature to evaluate the power and the efficiency of the ASGs however, they are either largely empirically-based or used to study ideal screws. Furthermore, little knowledge is present in the scientific community about the losses at the outlet section of the screw because of the complexity of the physical processes that occur at that location. In this thesis a theoretical model is developed to analyze the efficiency and the power produced by ASGs. The new model is only minimally based on empirical correlations. It is implemented as a MATLAB code and it is able to predict the power losses for screws of different geometries and sizes working under a wide range of operating conditions. The validation of the new model, as well as previous ones (Kozyn and Lubitz 2017 and Nuernbergk’s equation for variable outlet level losses) is performed using data from three different screw sizes. Data from the Archimedes screw laboratory of the University of Guelph (Canada) were collected by the candidate specifically for this study. This data is used together with numerous other data that were already available of the 16 screws present in the lab. Field data is also used from a full-scale two-screw ASG system installed near Ferrara, (Italy) by Hydrolab s.r.l., and from a smaller single screw plant installed near Waterford (Canada) by Greenbug Energy. The validation process showed that the new model provides predictions of power and efficiency with low error levels that scale correctly across the different plant sizes and dimensions.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/139659