Wave Basin Tests of a Novel Offshore Macroalgae Farming System

Macroalgae cultivation in the ocean stands as a promising source of feedstock for biofuels and chemicals. It is particularly attractive because of the efficiency of these marine plants in converting sunlight into biomass and because this type of farming can be done without the risk of displacing land and freshwater from their essential role in feeding the human population. However, there are challenges to achieving this potential due to the limitations of present farming methods. In order to compete economically with land-based biomass production, the bioeconomics of seaweed farming must improve and the areas where it can be practiced must be expanded. Present methods of growing seaweeds are confined to narrow strips along the coasts that are both protected and sufficiently shallow. In order to meaningfully exploit the US Exclusive Economic Zone (EEZ), engineered systems must be developed for high-energy locations in deep water and at an unprecedented scale. This paper will present an innovative design for the farming seaweed in the open ocean and will describe a series of tests conducted at Ohmsett - The National Oil Spill Response Research & Renewable Energy Test Facility - in Leonardo, NJ. The facility was used for these tests because the capabilities matched well testing needs and because the facility uses seawater. Actual fronds of kelp were needed for testing in order to correlate their hydrodynamic characteristics with the scaled materials in 1/20th-scale testing of the structure that was the prime focus of the tests. The results on the resistance testing of single and multiple fronds of kelp will be reported as well as those for the model materials. The results of the tests on various structural models both in currents and in currents and waves will be presented. These tests allowed the measurement of system drag and loads internal to the structure. Accelerations were also measured to determine motions and to predict inertial loading. These tests have allowed us to more confidently design prototype systems that have the potential to revolutionize the domestic seaweed-farming sector.