Abstract
A novel variable-pitch (VP), vertical-axis, surface-piercing, marine hydrokinetic (MHK) turbine has been developed through partnership between Bucknell University and Adaptide LLC. The turbine features an alternative to existing stall, speed, or independent pitch control approaches. A passive variable-pitch mechanism will be developed and tested to maximize efficiency in a flow with a Reynold’s regime of below 60,000. Results from prior testing of a small-scale surface-piercing fixed pitch (FP) turbine, wherein 20% efficiency was achieved, were leveraged into the VP turbine design. The scaled tests of the VP turbine will quantitatively indicate if efficiency gains of 30% are attainable with a surface-piercing design. This technology aims to maximize power capacity factor over a range of flow speeds in high-energy density MHK resources, thus enabling reduced levelized cost of energy (LCOE). Current barriers to widespread adoption of conventional MHK turbines include excessive site characterization requirements, inability to survive maximum current speeds of lucrative high-energy density MHK resources, and lack of debris avoidance or mitigation capability.
Following extensive testing of a scaled prototype of the VP turbine, the proposed Adaptide technology will implement a vertical actuation system to vary operating depth or remove the turbine completely from the water, enabling maximization of capacity factor and survival in extreme flow conditions respectively. Implementing prior works, a novel pitching law is being designed, fabricated, and tested to identify optimal tip speed ratio (TSR) for a range of current speeds. The VP mechanism allows for the testing of multiple pitching laws of a single turbine through profile modification of an interchangeable cam. Results of the performance testing for the VP mechanism with fixed-pitch cam and the VP mechanism with variable-pitch cam will be presented and compared to prior FP turbine test results.