NEW YORK CITY’S EAST RIVER typically conjures images of a hard working river flowing past a hard working city— certainly not visions of clean energy and a hydraulic lab in Minnesota. Yet this is the latest in SAFL’s ever-increasing list of renewable energy research projects: to help bring tidal power to the Big Apple, via the East River.
In a collaborative project with Verdant Power (as well as national labs and private industry) to generate clean energy from tidal, river, and ocean currents, the current focus on the Roosevelt Island Tidal Energy (RITE) project is jointly funded by the U.S. Department of Energy and the University’s Initiative for Renewable Energy and the Environment (IREE).
For Verdant, a world leader in developing free-flow turbine technologies, the road hasn’t been easy— over $2 million has been spent on aquatic life and regulatory studies, and the strengths of the currents in the East River (which is a tidal strait, with tides that reverse direction every six hours) wreaked havoc on earlier turbine models. But last summer, a pilot-scale project with six newer, stronger turbines was installed and has powered a nearby parking garage and supermarket.
Now that the test array has proven successful, the challenge is to improve the current turbine blade design structure which will allow for larger, more-powerful, and more cost-effective tidal power turbines. This will increase overall efficiency and performance of a field-scale array, which is where SAFL’s expertise comes in. SAFL director, Fotis Sotiropoulos, will lead a team of researchers in developing computational models for optimizing the multi-turbine arrays for the Roosevelt Island site and elsewhere.
Using SAFL’s CFD models, researchers can analyze the design and enhance the environmental compatibility of the system at the rotor, turbine, and array levels. Turbine wakes will be analyzed in order to determine turbine-turbine and turbine-channel interactions on the macro level for array optimization and feedback to the turbine design process. With improved technical design and site arraying factors, the development of cost-effective commercial projects becomes a more immediate reality.
“I think that this new project, along with our recent Xcel Energy wind-power project, places SAFL, IREE, and the Institute of Technology in a great position to provide national research leadership in wind- and water-based renewable energy systems,” said Sotiropoulos.
The source funding, which comes from the DOE’s newly expanded Advanced Water Power Projects program, resulted in the selection of just 14 research teams who will receive up to $7.3 million for advanced water power projects that will advance commercial viability, cost-competitiveness, and market acceptance of new technologies that can harness renewable energy from oceans and rivers.
UNDERWATER WINDMILLS
At the East River site, the current six-turbine array has been a demonstration and test project intended to lead to larger commercial projects— specifically, a 30-turbine field that has been proposed to the Federal Energy Regulatory Commission.
In the current test array, five of the six 5m diameter 35kW turbines have grid-connected generators and one turbine is a dynamometer. The turbines have axial-flow rotors with three fixed pitch blades, and downstream rotors which allow passive turbine yaw to capture energy in both flow directions. The most critical subsystem of the Kinetic Hydropower System (KHPS) is the rotor itself— the kinetic energy capture prime mover. The rotor is uniquely designed to accomplish several simultaneous objectives: It has high power conversion efficiency, fixed pitch for simplicity and scalability, and even in a variable water flow resource can operate at near constant speed with high load-matching efficiency. This allows it to directly drive a high-reliability, low-cost, direct grid-connected induction generator, which is necessary for providing competitively priced electricity.
In order to reach the commercialization of the KHPS, it is necessary to extend these state of the art rotors to capture energy from higher water velocities and deeper resources that can accommodate larger rotor diameters, changes which are significant enough to require a completely new blade hydrodynamic design cycle. This new cycle will include hydrodynamic and structural modeling, analysis, and design, along with design for manufacture and fabrication technique development (which will be followed by extensive strength and fatigue testing and full-scale hydrodynamic testing). As part of this collaborative process, SAFL’s role will be CFD modeling of the rotor and turbine system.
The new rotor design will involve a new structural design and manufacturing technique, and a new hydrodynamic design including a new airfoil shape to allow for thicker sections, requiring a thorough and careful full blade redesign to maintain the present high performance of the rotor. Required factors will be strength, fatigue resistance, corrosion resistance, cost-effective manufacture, cost-effective logistics, final assembly, and deployment capability.
In order to succeed in this challenging engineering undertaking, SAFL will play an important role in a team of organizations with specialized capabilities, whose interactive collaboration is designed to ensure a successful and timely result for this ground-breaking project
“The purpose of the research is not just to bring power to NYC, but to help advance the technology which will be able to provide far greater amounts of power from appropriate tidal, river, and ocean current resources all over the world,” said Dean Corren, director of Marine Current Technology at Verdant.
Maia Homstad |
