66 DECEMBER 2023 • WORLD AQUACULTURE • WWW.WAS.ORG requires further study. The fiberglass rods break at a specific bending radius, so wrapping or knotting around flukes, flippers, jaws, etc. would be minimized. We targeted a breaking radius that is greater than the typical whale appendage and are actively designing custom composite rods for these desired characteristics. The grid system was held in place by 36 helical anchors that ranged from 3-7m in length. Tensioning floats were used to keep the submerged grid taught throughout the tidal range. The system is shown in Figure 4, which combines an actual surface picture with a rendering of the submerged gear. It was deployed, seeded, and monitored at the site from November 2021 – May 2022. Though nearshore, the site is exposed to the open ocean; a maximum wave height of 5.9 m was measured at the site while the farm was deployed. Over 562 m of fiberglass kelp cultivation rod were planted over the farm. In addition to addressing entanglement risks, the farm featured: (1) minimized scope to reduce required seabed footprint, (2) novel helical anchor design that supports multiple mooring attachments from a single anchor, (3) integrated modular design to maximize horizontal growing area per farm area and provide flexibility for piecemeal farm expansion, (4) reduced mooring equipment and installation infrastructure scales through distribution of hydrodynamic loads to localized mooring points and (5) wavepowered upwellers to enhance nutrient availability to maximize growth rates. Modeling Efforts Prior to deployment, Kelson Marine analyzed the proposed structure at an exposed site subject to wind, waves, and currents. The aquaculture system was comprised of flexible components subject to nonlinear wave and current forces. The composite structure was evaluated in a 50-year storm event with wave period and current conditions (Fig. 5). The modeling informed the engineering of the kelp farm, ensuring that it would survive extreme storm conditions in the Gulf of Maine. Robotic ROV to Deploy Helical Anchors Conventional anchoring in deep water is slow, expensive, imprecise, and highly sensitive to the nature of the seabed. Existing marine anchoring solutions include gravity anchors, drag embedment anchors, and helical anchors installed with submersible hydraulic rigs. For this project, an innovative underwater ROV was developed to drive 4 m long helical anchors into the bottom (Fig. 6). Helical anchors can hold as much as 100 times or more their own weight and can be low-cost in the right context. They can also sustain vertical loads allowing for lower anchor line scope and, consequently, smaller mooring footprints. The ROV can weigh even less than the anchor and might install a large anchor in as little as ten minutes. A prototype ROV was deployed in NH and ME to conduct sea trials, including spinning helical anchors into the sea bottom. Deployment was hindered by sufficient battery power to spin the helical anchors more than 3 m into the bottom. As a result, the ROV was brought back to Otherlab for further development. Currently, the ROV has evolved to deploy 5-ton helical anchors in 30 m depth. It is designed for 100 m depth and will be tested at this depth soon. In addition, Otherlab is developing 10- and 25-ton versions. This is a critical enabling technology for aquaculture, floating solar, offshore wind, and general marine anchoring. Upweller Device to Provide Nutrients to the Farm Nutrients in the open ocean during certain times of the year can be limited (Brown et al. 2023). To overcome this challenge, a prototype wave-powered upweller device was fabricated to provide deep, nutrient rich water to the surface to fertilize the kelp. Artificial upwellings can bring cool nutrient rich water to the surface, greatly increasing biological productivity and reducing surface water temperature (Yao et al. 2020). Aquaculture yield can be greatly increased, and it could be possible to enable year-round kelp growth normally limited by warmer summer water temperatures. The project’s upweller innovation used a large open rotor with flapping blades that is suspended beneath a surface wave-following float and is capable of ~100 times the flow rate for a given weight and cost when compared to existing wave-powered valved pipe approaches. The rotor moves up and down with each passing wave and directly converts this vertical motion into rotation. It effectively operates like an inverted ceiling fan, creating a large diameter jet of water that can extend up to ten times the diameter of the rotor, enabling operation from significant depths. The rotor itself is bridled such that it scales with similar mass and cost as a wind turbine rotor. Rotor diameters beyond 100 m are possible, although upwelling from as little as 30 m depth can have a big impact. Solar- and waveFIGURE 5. Hydro-Structural Dynamic Finite Element Analysis model of the Ram Island prototype farm used to design and de-risk the farm structure. FIGURE 4. A composite image: with a 3D rendering of the mooring and cultivation pilot scale system deployed in Saco Bay, ME with an overlaid photo of the actual surface components at the site.
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