| NSF Org: |
ECCS Division of Electrical, Communications and Cyber Systems |
| Recipient: |
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| Initial Amendment Date: | August 6, 2015 |
| Latest Amendment Date: | August 6, 2015 |
| Award Number: | 1509592 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Radhakisan Baheti
ECCS Division of Electrical, Communications and Cyber Systems ENG Directorate for Engineering |
| Start Date: | August 1, 2015 |
| End Date: | July 31, 2019 (Estimated) |
| Total Intended Award Amount: | $345,581.00 |
| Total Awarded Amount to Date: | $345,581.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
2601 WOLF VILLAGE WAY RALEIGH NC US 27695-0001 (919)515-2444 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
911 Oval Dr. - 3407 EB III Raleigh NC US 27695-7910 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | EPCN-Energy-Power-Ctrl-Netwrks |
| Primary Program Source: |
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| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.041 |
ABSTRACT
The objective of this project is to enable scalable arrays of damless oscillating hydrofoil turbines that will offer higher efficiencies, higher power output levels, and wider applicability than current hydropower technologies. The proposed work will take advantage of unique, recently uncovered wake-structure interactions that can increase power output and efficiency in densely packed arrays of oscillators. The approach of using oscillating hydrofoil devices that can be closely arranged together will open new markets for hydropower in locations previously considered too shallow or cluttered to be feasible. With many population centers located on coastlines and along rivers, this new source of clean energy would have minimal transmission costs and losses. Such devices could also be invaluable in off-grid sites like remote villages or temporary shelters for people displaced by disasters. Smaller scale applications could create flow-powered sensing stations that do not rely on short-term and environmentally hazardous consumable batteries for applications like monitoring critical infrastructure. At the utility grid scale, when compared to other renewable energy sources like wind and solar power, oscillating turbine hydrokinetic power arrays will offer more convenient integration into the power grid due to the predictable nature of the energy source. While wind and solar power are subject to daily variation and intermittency due to weather changes, tidal flows in particular can be accurately predicted well in advance, allowing the various sources in the utility grid to be readily balanced to cost-effectively meet demand and production allocations. In addition, the proposed education activities will serve to help broaden participation in engineering and inspire children to Science, Technology, Engineering, and Math (STEM) studies. North Carolina middle school and junior high school students will learn about flow energy harvesting and engineering design in a hands-on lab activity the researchers will develop and run as part of the popular NC State University summer camp program. The researchers will also broaden participation in research by providing opportunities for underrepresented undergraduate students from public colleges across North Carolina to engage in mentored research activities in the PI's and Co-PI's labs.
Unlike traditional spinning turbines, which must be widely spaced to perform most effectively, our preliminary experiments have shown that oscillating energy harvesting devices actually perform most effectively when they are closely packed together and their motions become coupled by the wake flow. This work will determine how arrays of oscillating turbines can be modeled, controlled, and optimally configured to take advantage of these synergistic interactions between the wakes of upstream and downstream devices. Current wind and hydrokinetic energy research largely focus on the performance of individual devices from a mechanical or fluid dynamics standpoint, or the interaction and combination of power sources in a "smart grid" from an electrical perspective. The work proposed will leverage a different approach that exploits and optimizes interactions between devices at the mechanics level. Specifically, experimental and analytic studies will (1) investigate the parameters that govern the occurrence, strength, and scaling of the synergistic wake-structure coupling and how it can be used to enhance the performance of 2D arrays of hydropower energy harvesters. The researchers will also (2) quantitatively compare active, passive, and hybrid actuation and control approaches for the oscillating turbines, and (3) quantify the influence of the shallowness of the water body on the wake structure formation of individual and collective energy harvesters.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
Overview: This project investigated arrays of oscillating-wing turbines that could be used to harvest energy from water flows or wind. The approach sought to take advantage of unique, recently uncovered wake-structure interactions that can increase power output and efficiency in densely packed arrays of oscillating-wing turbines. Unlike traditional rotary turbines, which must be widely spaced to perform most effectively, our experiments have shown that oscillating-wing aeroelastic energy harvesting devices actually perform most effectively when they are closely packed together and their motions become coupled by wake-structure interactions. The project aimed to determine how arrays of these oscillating energy harvesters could be configured to take advantage of synergistic interactions between the wakes of upstream and downstream devices and how the wake of an upstream body influences the energy transferred to a downstream oscillating wing.
Intellectual Merit: This research work has made the following contributions to the scientific and engineering community:
- We demonstrated how wing pitch stiffness modulates the sensitivity and the wake energy capture in downstream aeroelastic wing energy harvesters.
- We developed an aeroelastic inverse method to calculate the aerodynamic forces and moments during limit cycle oscillations.
- We determined how the pitch-heave phase difference not only controls the aerodynamic efficiency but also the energy distribution throughout the structure.
- We investigated and characterized the limit cycle kinematic behavior for bluff body wake disturbances on a downstream aeroelastic wing.
- We identified significant wing-wake interaction parameters, like the ratio of bluff body shedding frequency to wing oscillation frequency, which effected the wake energy transfer to the downstream wing.
- We showed that placing a bluff body near an oscillating does not necessitate significant aerodynamic energy reduction.
- We established the conditions sufficient for wake-induced aeroelastic limit cycle cessation.
Broader Impacts: The research effort benefited society through the STEM outreach and education activities carried out at the PI's laboratory:
- Over the duration of the project, thirteen NCSU undergraduate students and three visiting undergraduate students participated in the project. These undergraduates gained access to the research topics, materials, and laboratory equipment through mentored research activities in the PI's lab.
- The outreach activities also included participation of a local high school student in a semester-long mentored research internship where the student received hands-on training to design and fabricate conceptual prototypes. The student also gave several presentations on his internship activities at his high school, helping to further disseminate the research and encourage interest in STEM.
- The participating students included individuals traditionally underrepresented in STEM fields including four female undergraduate students.
- This research also inspired four undergraduate students to pursue graduate level engineering degrees, adding further depth to the national STEM workforce.
- The project also contributed support for the graduate education of three doctoral students and three master's students at NCSU and led to the publication of several technical papers in conference proceedings and journals. The project also led to publication of a doctoral dissertation and a master's thesis.
The technology and techniques developed here may also benefit society and the environment by quantifying the potential for beneficial wing-wake interactions among multiple oscillating wing energy harvesters and how unsteady inflow conditions alter the energy transfer to the wing. These findings provide information on how to optimize the placement and design of oscillating turbines in river or tidal flows. This may help create a previously untapped energy source for communities where wind turbines, dams, or other renewable energy resources are not a viable option.
Last Modified: 10/04/2019
Modified by: Matthew J Bryant
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