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July 2013 www.sname.org/sname/mt (mt notes) Harnessing Magnetostriction continued of a partially submerged buoy, anchored to a catenary- moored heave plate by taut tethers. ese tethers are largely made up of, or are connected to, discrete, robust power takeo modules (PTOs), which contain iMEC- enabled generators. Hydrodynamic forces on the buoy cause the line tension of each tether to continuously change, resulting in a high-force, low-displacement mechanical energy input that is converted to electrical energy in the PTOs. The MWEH has several advantages over other approaches to wave energy generation, giving it the potential to achieve the following. No moving parts. e MWEH can produce energy from waves with no signicant relative motion between or signicant dimensional change of its components. is eliminates sub-system (for example, lubrication, bearings, and seals for moving components) costs and will signicantly reduce operating and maintenance costs due to the elimination of the need to periodically service or replace components such as joints or bearings. Low cost materials. e MWEHs materials set does not include signicant quantities of any supply-limited or expensive materials. While small quantities of com- mercial rare earth magnets are used, these could be replaced by ferrite magnets if their cost or availability becomes an issue. Low cost manufacturing. All components used in the MWEHs PTO are amenable to low-cost, high-vol- ume, automotive-scale manufacturing. e buoys and anchors have no complex parts. Relative ease of deployment. Standard vessels that do not have to be customized to hold equipment in a specic direction or to deploy devices onto the ocean oor can be used. High eciency across the wave spectrum. Operating substantially below the resonant frequency, the MWEH does not experience steep reductions in eciency on either side of a nominal/rated condition, as is the case with many other WEC technologies that rely on wave motion to move a oating body. While such WEC systems are intrinsically narrow-band? technologies, the MWEH operates as a wide-band device across the wave spectrum. Minimal environmental impact. Broadly speak- ing, the MWEHs impacts should be more manageable than that of other approaches for the following reasons: at least 8 m between individual tethers; EMF leakage below detection limits for marine organisms; anchor design exibility; customizable above-water buoy pro- le to minimize its attraction to sea life; and minimal noise due to lack of moving parts. Technology development Development of our technology has proceeded along three general thrusts: generator design and optimi- zation, including validation and improvement of our performance model; design and optimization of the PTO and overall system, including the buoy and anchor; and e MWEH can produce energy from waves with no signicant relative motion between or signicant dimensional change of its components. Conceptual illustration of OPIs magnetic circuit.