Efficiency of a Directly Driven Generator for Hydrokinetic Energy Conversion

Abstract

An experimental setup for hydrokinetic energy conversion comprising a vertical axis turbine, a directly driven permanent magnet generator, and a control system has been designed and constructed for deployment in the river Dalälven in Sweden. This paper is devoted to discussing the mechanical and electrical design of the generator used in the experimental setup. The generator housing is designed to be water tight, and it also acts as a support structure for the turbine shaft. The generator efficiency has been measured in the range of 5–16.7 rpm, showing that operation in the low velocity range up to 1.5 m/s is possible with a directly driven generator.

Marine Current Energy Converters to Power a Reverse Osmosis Desalination Plant

“…The turbine is connected to a permanent magnet synchronous generator (PMSG). The design of the generator makes it efficient at the low rotational speeds [18]. The efficiency of the generator is in the experiments in [18] found to be at least 80% for all rotational speeds and gives an output line-to-line voltage of 150 VRMS at nominal operation.…”

“…The added extra weight of using ferrite magnets instead of Nd2Fe14B magnets is not an issue for the converter as it is placed on the bottom of the river or sea, but may introduce difficulties related to the deployment. The large Uppsala MCC generator with many magnetic poles (here almost 2 m in diameter [17] and 112 poles [18]) generates power from lower water flow velocities than most TECs and MCCs.…”

“…Energies 2018, 11, 2880 3 of 13 In fact, in contrast to many other hydro-kinetic energy converters, this device is built to be efficient at water speeds lower than those regarded to low by most other marine current technologies, 2 m/s, with a rated water velocity of 1.4 m/s [18]. Vertical axis turbines (VATs) are not as common as horizontal axis TECs.…”

Experimental Results of a DC Bus Voltage Level Control for a Load-Controlled Marine Current Energy Converter

“…A more detailed description of the generator can be found in [13]. Further details of the control and measurement system can be found in [14].…”

Experimental demonstration of performance of a vertical axis marine current turbine in a river

“…To obtain the power P t captured by the turbine, electrical and mechanical power losses were calculated through known parameters of the conversion unit (the efficiency of the generator is discussed in Ref. 24, and frictional losses in bearings and seals were measured before the unit was deployed). The corresponding power coefficients were then computed.…”