Counter-Rotating Type Power Technologies to Exploit Offshore Energies

Counter-Rotating Type Power Technologies to Exploit Offshore Energies

Toshiaki Kanemoto (Kyushu Institute of Technology, Japan)
Copyright: © 2012 |Pages: 20
DOI: 10.4018/978-1-4666-1625-7.ch012
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For the next leap in power-generating technologies, the world is obligated to not only cope with the warming global environment but also to conserve the natural ecosystem. This chapter discusses the advances in technology designed to successfully exploit offshore marine and wind resources. (1) The Counter-Rotating Type Hydro/Tide Power Unit, which is composed of the tandem runners and the peculiar generator with double rotational armatures, is applicable to both rising and falling tides at the power station with the embankment, in place of the traditional bulb type turbines. (2) The Floating Type Ocean Wave Power Station, where a pair of floats lines up at the wavelength spacing, can get the superabundant velocity energy. (3) The Intelligent Wind/Tide Power Unit, which is composed of the tandem wind/tide rotors and the double rotational armatures, is suitable for offshore wind and the tidal stream.
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Double Rotational Armature Type Generator

The author has prepared the peculiar generator composed of the inner and the outer rotational armatures, without the traditional stator. Figure 1 shows the performances of the model synchronous generator (3-phase, 4-pole, permanent magnet, AC generator with double rotational armatures), where the rated output P = 1kW at the induced frequency f = 50Hz and the induced voltage E = 100V while the relative rotational speed NT = 1500min-1. Figure 1a shows the relation between the outer armature rotational torque TF* and the inner armature rotational torque TR*, in keeping the rotational speed of the outer armature constant at NF = 750 min-1, while changing the rotational speed of the inner armature NR at the various external loads. These rotational torques do not include the mechanical torques such as the bearings in the generator, and TR* is given by the absolute value though the direction of TR* is against TF*. It is obvious that TR* coincides with TF* irrespective of the relative rotational speed (NT = NFNR) and the output/load, because the rotational torque should be always dynamically counter-balanced between both the armatures. That is, the rotational torque counter-balances dynamically between the inner and the outer armatures. The relative rotational speed affects the output P and the induced voltage E against IG, as shown in Figure 1b. The output increases with the increase of the induced voltage E at the same IG, while E is in proportion to the relative rotational speed NT.

Figure 1.

Performances of the model double rotational armature type generator: (a) rotational torque, (b) output, induced voltage, and electric current

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