The target of this research is to develop a micro electric power generator for a low cost small river monitoring device. First, the power generation by VIVs, its efficiency coefficient and the optimum condition of the generator were estimated from energy balance analysis based on the assumption that VIVs can be regarded as a resonance oscillation of a linear system. Second, water tunnel experiments were carried out and it was confirmed that the trailing vortex induced vibration (TVIV) occurs on a cruciform circular-cylinder/strip-plate system over a velocity range about 15 times wider than that of Karman vortex induced vibration (KVIV). Finally, power generation experiments were carried out by utilizing TVIV. The generator circuit consists of coils mounted on the circular cylinder vibrated by TVIV and magnets fixed on rigid supports. The generator is shown to extract energy from the water flow in the same way as a viscous damper over the expected velocity range. Although the efficiency coefficient of TVIV is lower than that of KVIV, it is more appropriate for natural rivers of which flow velocity changes greatly.
