This invention relates to the generation of electrical energy, and particularly to a piezoelectric electric generator of the rotary type.
Piezoelectric electrical energy generators of the rotary type, e.g., comprising a rotating armature within a stator, are known and described, for example, in U.S. Pat. No. 3,101,420 (Hufferd, et al., Aug. 20, 1963), U.S. Pat. No. 3,208,443 (Hurwitz, Sep. 38, 1965) and U.S. Pat. No. 3,350,583 (Schiavone, Oct. 31, 1967) and in Soviet Union Patent 699,590 (Nov. 25, 1979), the subject matter of which U.S. patents is incorporated herein by reference.
The piezoelectric materials used in these patents are alternately mechanically strained and destrained for generating electrical energy. What occurs is that the mechanical strainings of the materials cause displacements of electrical charges within the materials. The charges resist such displacements, and the energy required to force the charge movement is stored in the form of electrical energy which can be extracted from the materials. In terms of efficiency, practically all the energy required to overcome the resistance by the charges to movement can be stored and recovered. However, the charges are embedded within piezoelectric host materials which themselves resist movement. The energy required to mechanically alternately strain and destrain the piezoelectric materials is generally quite significant, and to the extent that the energy required to mechanically strain and destrain the piezoelectric materials is not recovered, the efficiency of the mechanical energy to electrical energy conversion process is generally very low. The present invention addresses this problem.