Katarina Yuen

Matching a Permanent Magnet Synchronous Generator to a Fixed Pitch Vertical Axis Turbine for Marine Current Energy Conversion

Extracting energy from a free-flow marine current using a vertical axis fixed pitch turbine requires a generator that can handle varying speeds and loads, since such a turbine gives maximum power capture for a fixed tip speed ratio. A prototype of such a generator has been designed and constructed. In this paper, its variable speed and load operation is evaluated, both in terms of how the constructed generator performs in relation to simulations, and in terms of how the generator could perform with three different fixed pitch turbines. Measurements of root mean square (RMS) voltage and current differ 10% from simulations. Performance analysis with example turbines shows that the generator can match fixed tip speed ratio operation of several turbines for current speeds between 0.5 and 2.5 m/s.

A low-speed generator for energy conversion from marine currents – experimental validation of simulations

Abstract A low-speed permanent magnet (PM) cable wound generator for electrical energy conversion from marine or tidal currents has been designed and constructed. A key feature of this variable speed direct drive generator is its capability to efficiently generate electricity from tidal currents with very low velocities, in the order of 1 m/s. In arriving at an appropriate design for the generator typical characteristics of tidal currents were considered. Using these characteristics as input, and accounting for the electromagnetic losses, detailed computer simulations using a finite-element method software were carried out to come up with the final design. Various parameters that can influence the generator design are presented. An experimental set-up has been constructed based on the above-mentioned design in order to study the electrical and mechanical performance of the generator through a variety of experiments. The power input for this set-up is a variable speed motor, capable of operating the generator at rotational speeds of 0–16 r/min, representing tidal currents with very low velocities. The generator presented in this paper may be beneficial for a better understanding of an appropriate design and layout of tidal energy conversion systems.

Efficiency of a Directly Driven Generator for Hydrokinetic Energy Conversion

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.

Implementation of control system for hydrokinetic energy converter

At Uppsala University, a research group is investigating a system for converting the power in freely flowing water using a verticalaxis turbine directly connected to a permanent magnet generator. An experimental setup comprising a turbine, a generator, and a control system has been constructed and will be deployed in the Dalalven river in the town of Soderfors in Sweden. The design, construction, simulations, and laboratory tests of the control system are presented in this paper. The control system includes a startup sequence for the turbine and load control. These functions have performed satisfactorily in laboratory tests. Simulations of the system show that the power output is not maximized at the same tip-speed ratio as that which maximizes the turbine power capture.

A Permanent Magnet Generator for Energy Conversion from Marine Currents: No Load and Load Experiments

This paper presents experiments and measurements on a low speed permanent magnet cable wound generator for marine currentenergy conversion.Measurements were made for no load and nominal load (4.44Ω ...

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

An experimental station for marine current power has been installed in a river. The station comprises a vertical axis turbine with a direct-driven permanent magnet synchronous generator. In measure ...

A Design Study of Marine Current Turbine-Generator Combinations

Marine currents are an offshore source of renewable energy of increasing importance, with the development of technology for electricity generation from tidal currents or low-head river currents advancing at a quick pace. Two of the major components of a marine current power plant are the generator and the turbine. It is not sufficient to design these components separately, but a system approach, where the power plant is seen as one entity, must be taken to achieve best overall efficiency. In the present paper, the performance of three different combinations of direct-driven permanent magnet generator with cross-stream axis marine current turbine is examined numerically under the variation of water flow speed. The design case chosen is that of a shallow river or tidal channel, where the cross-sectional area limits the physical size of the power plant. The units are designed for a power output of 10 kW at a water current velocity of 1 m/s. Turbines for three different rotational speeds are considered, each in combination with a corresponding generator. The three turbine-generator systems are designed according to similar design criteria to allow for comparisons. The turbines are modelled using an in-house code, based on the double multiple streamtube model. Corrections are made due to the finite aspect ratio and tip losses of the blades. Experimental data for the lift and drag coefficients for different Reynolds numbers are used in the model. The generators are modelled using a FEM tool that has been validated with experimental results. The three generators are designed for the same nominal voltage and with a low load angle to allow for overload operation. The overall performance of each of the three systems is studied under varying flow velocity. The main conclusion is that all three machines exhibit essentially the same performance behaviour, which means that the choice of nominal operational speed for a power plant will not be a major design constraint. Turbines with higher rotational speed allow for a more compact generator design within the limits of the design parameters used in this study. However, this also entails certain mechanical constraints on the turbine. Due to the restricted cross-sectional area in the channel, it is clear that at least one of the three systems would have to be placed with the axis of rotation in a horizontal rather than vertical position.Copyright

Experimental Setup: Low Speed Permanent Magnet Generator for Marine Current Power Conversion

Marine currents, e.g. tidal currents, ocean currents and unregulated water courses are characterized by a fairly steady or regular flow and pose a significant potential for electricity generatio ...