Estimate electrical potential of municipal wastewater through a micro-hydroelectric plant

Renewable energy is extracted from Ultra Low Head (ULH) hydraulic resources through a turbine-generator set, which converts only the kinetic energy of the water to electrical one. However, these resources have a little or no water storage, which require operations over a wide range of water flow conditions throughout the day and the year. As the natural fluctuations of the resources avoid a constant energy exchange, the system needs to be evaluated with different flow rates to be as efficient as possible. Thus, this paper focuses on designing and evaluating the capability of a Permanent Magnet Synchronous Generator (PMSG) working at a variable rotational speed due to coupling with a Propeller Hydraulic Turbine (PHT). The methodology established to reach this design was set up in three steps: First, to define the maximal available energy of the water resource. Second, to calculate the rotational speed range of the PHT. Third, to design a PMSG able to transforms all the variable mechanical energy delivered by the shaft. Finally, with this methodology different magnet's capabilities of the PMSG could be analyzed to better exploit the available hydraulic energy of a variable hydraulic resource.