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Authors
Abstract(s)
In this study, energy production for autonomous underwater vehicles is investigated. This project
is part of a bigger project called TURTLE. The autonomous vehicles perform oceanic researches
at seabed for which they are intended to be kept operational underwater for several months. In
order to ful l a long-term underwater condition, powerful batteries are combined with \micro-
scale" energy production on the spot. This work tends to develop a system that generates
power up to a maximum of 30 W. Latter energy harvesting structure consists basically of a
turbine combined with a generator and low-power electronics to adjust the achieved voltage to
a required battery charger voltage. Every component is examined separately hence an optimum
can be de ned for all, and subsequently also an overall optimum. Di erent design parameters as
e.g. number of blades, solidity ratio and cross-section area are compared for di erent turbines, in
order to see what is the most feasible type. Further, a generator is chosen by studying how
ux
distributions might be adjusted to low velocities, and how cogging torque can be excluded by
adapted designs. Low-power electronics are con gured in order to convert and stabilize heavily
varying three-phase voltages to a constant, recti ed voltage which is usable for battery storage.
Clearly, di erent component parameters as maximum power and torque are matched here to
increase the overall power generation. Furthermore an overall maximum power is set up for
achieving a maximum power
ow at load side. Due to among others typical low velocities of
about 0.1 to 0.5 m/s, and constructing limits of the prototype, the vast range of components
is restricted to only a few that could be used. Hence, a helical turbine is combined in a direct
drive mode to a coreless-stator axial-
ux permanent-magnet generator, from which the output
voltage is adjusted subsequently by a recti er, impedance matching unit, upconverter circuit
and an overall control unit to regulate di erent component parameters. All these electronics are
combined in a closed-loop design to involve positive feedback signals. Furthermore a theoretical
con guration for the TURTLE vehicle is described in this work and a solution is proposed that
might be implemented, for which several design tests are performable in a future study.