A Linear Generator Power Take-Off System for the VIVACE Hydrokinetic Energy Converter

Abstract

Water is the largest energy storage medium. Of the solar energy available to Earth, 285 ZJoule/year are absorbed by water, 6 ZJoule/year are theoretically available in wind, and 1.8 ZJoule/year are absorbed by biomass. Worldwide energy consumption was 0.471 ZJ in 2004. Marine energy is clean, renewable, abundant, and available worldwide. It comes in five forms: currents, waves, tides, thermal gradient, and salinity gradient. The Challenge: Wave and current/tidal energy pilot devices are environmentally obtrusive and complex. Simpler devices that emulate natural phenomena and fish kinematics are needed. Energy from currents can be harnessed using turbines, which require an average speed of 5-7 knots to be financially viable. The vast majority of currents, however, flow at speeds of less than 3 knots. VIVACE can harness energy from currents even slower than 2 knots. VIVACE is not a turbine; it is an altogether novel concept. The Technology: Flexible bluff structures (particularly cylinders), from fishnet filaments to 120ft diameter SPAR offshore platforms and anything in between, such as car antennas, flagpoles, marine cables, heat exchanger tubes, experience VIV (Vortex Induced Vibration) in a steady flow. Engineers seek to suppress VIV because it causes large motions leading to fatigue and structural failure. The VIVACE (VIV for Aquatic Clean Energy) Converter is designed to do the opposite: maximize and utilize VIV to harness the hydrokinetic energy of flows. Thus, VIVACE takes this natural, destructive, instability phenomenon and transforms it into means of taping into a vast and virtually untapped energy source. VIV is further enhanced using turbulence stimulation and fish-biomimetics. VIVACE models operate in the UM Marine Renewable Energy Lab. VIVACE is modular and scalable from 1kW-1GW.