Originating with the NSF-funded Living Bridge Project, a floating tidal energy conversion (TEC) system has been deployed at Memorial Bridge in Portsmouth, NH since 2018. The bridge crosses the Piscataqua River, in Great Bay Estuary, between downtown Portsmouth and Kittery, ME. The TEC system consists of a 15 m x 6m turbine deployment platform moored to one of the bridge piers and a modified New Energy Corp model EVG-025 vertical axis cross flow turbine (3.2m diameter x 1.7m tall). The turbine is coupled to a 25kW direct drive permanent magnet generator and the platform is equipped with a 25kW Voltsys rectifier and a 36kW Solis solar inverter, which synchronizes and connects to the 480V-3 phase bridge grid. The tidal currents at the deployment location exceed 2.5 m/s during spring ebb tides and provide an excellent open water flow environment to test tidal energy conversion devices.
A recent project conducted in collaboration with the National Renewable Energy Laboratory (NREL) had the objective of making concurrent power performance, thrust load and tidal current resource measurements, while the turbine is in grid-synchronous operation. To prepare the system for this measurement campaign, maintenance and upgrades were required to the existing power equipment and a new data acquisition system based on the NREL Modular Ocean Data Acquisition System (MODAQ) architecture was developed. These efforts led to a significant continuous turbine operation and data acquisition campaign during the fall of 2021 supplying renewable energy to the local grid. Data sets that were recorded include turbine power performance, tidal current velocities with Acoustic Doppler Current Profilers (ADCPs) and Acoustic Doppler Velocimeters (ADVs), turbine thrust load, platform motion with an Inertial Measurement Unit (IMU) and weather and environmental data.
Results of these data sets will be presented including experimentally determined power vs tidal current speed, power coefficient (CP) vs Tip Speed Ratio (λ) and thrust coefficient (Cd) vs λ. Operational characteristics of grid-synchronized vs non-synchronized operation will be analyzed. Additionally, important lessons learned from the operation and maintenance of this TEC installation will be discussed. After Quality Control (QC), the data are now available through the DOE Portal and Repository for Information on Marine Renewable Energy (PRIMRE).
Follow-on work, including the design, installation and testing of an instrumented turbine blade will be discussed in the METS contribution by Bharath et al.
This work is supported by the National Renewable Energy Laboratory (NREL), the Pacific Northwest National Laboratory (PNN), the University of New Hampshire, and the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE) under the Water Power Technologies Office (WPTO) Award Number DE-EE0009450.