UC San Diego

Wirewalker vertical profilers have become a common tool for oceanographic research, but the energy required by onboard sensors sets up a maximum horizon for deployment before ongoing recovery and re-deployment becomes impractical and expensive. Given that the Wirewalker mechanically harnesses energy from ocean surface waves to drive propulsion, a natural next step for the Wirewalker system is using ocean wave energy to power the onboard sensors. This paper documents the design process for a 3-wheel power take-off system that merges the submersible motor-generator (Livewire), designed by Dr. Michael Goldin and Prof. Drew Lucas, within a Wirewalker frame. The as-tested “omega-configuration” power take-off relies on the grip of a single wheel on the mooring wire to both cam in one direction (allowing profiling mechanically driven by the surface waves, as in the present generation Wirewalker, and also efficiently generating power. Basic profiling dynamics and experimental results inspired a design that pushes the generator wheel between two sheaves, while allowing it to hinge up and down to passively increase grip on the wire as the power available in any particular wave cycle increases. Tests in the Scripps pool generated a peak power of 1 Watt, with a time average 0.1 Watts. However, this result was likely related to slipping and frictional losses, which also was observed to inhibit 1-way camming motion. Future iterations of the 3-wheel power take-off should wrap the wire further around the wheel, investigate wheel surfaces with a higher coefficient of friction, and reduce internal friction losses with better constrained sheaves.