Plasma flow control linked in

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Introduction20 kW DemonstrationKey Accomplishments

Plasma Flow Control for Wind TurbinesNeal E. Fine, PhDJuly 2015Neal E. Fine, PhD 07/06/151/10

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Introduction to Plasma Flow Control

Neal E. Fine, PhD 07/06/152/10Surface mounted plasma actuator:High sectional lift, low dragSolid state, no moving partsLeads to improved aerodynamic efficiencyCan be used to increase wind turbine AEP

This video was shot in Navateks wind tunnel. It shows a wing section which is a geosym of a wind turbine blade built by Renewegy, at the seven-tenths radius. On the left of the frame, just off camera, is a low-voltage hot wire. When the wire is coated with oil and heated electrically, the oil vaporizes, forming the white streak lines. A pair of plasma actuators is mounted on the suction side of the blade between mid-chord and the trailing edge. As you can see, when the plasma is on, the flow goes from stalled to fully attached. Because this is a low-speed demonstration, it is in a sense an exaggeration of what goes on at full scale Reynolds numbers. Nevertheless, it is a very quick way of demonstrating what we are trying to do with active flow control mitigate boundary layer separation, delaying stall and increasing the maximum lift coefficient. 2


Introduction to Plasma Flow ControlNeal E. Fine, PhD 07/06/153/10Advanced proprietary plasma actuatorProven technologyHigh control authorityConformal to bladeLow powerHigh reliabilityFast reacting and adaptiveControllable

Plasma Actuator

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BenefitsImproved aerodynamic performance, leading to increased energy captureIncreased sectional lift leads to increased CPIncreased CP in Region 2 of 5-15% or higherIncreased AEP of 5-10%, or higher

Reduced reliance on pitch for pitch-controlled turbines

Reduction in fatigue loads in Region 3

Neal E. Fine, PhD 07/06/154/10

The graph on the right shows a sample lift polar for the VP20 section shown in the previous slide. The improved aerodynamic performance leads to an increased energy capture. Depending on the platform and system design, we project an increase in CP in Region 2 between 5 and 15%, resulting in increased AEP of 5-10%. For pitch-controlled turbines, we expect that plasma flow control would reduce the dependence on pitch control. Ultimately, we envision a Region 3 role as well in reacting to gusts to reduce fatigue loads. This is an area that has not been fully explored.4


Leveraging $3M in Government R&D

ONR-sponsored demonstration project, 2012-2015Demonstrated on a Renewegy VP20 turbine mounted on the wing walls of Navateks dry dock in HonoluluSupported by wind tunnel testing and performancepredictionsNeal E. Fine, PhD 07/06/155/10

The Office of Naval Research sponsored a demonstration project during the 2012-2015 time frame, performed by Navatek with Neal Fine as the PI. Navatek purchased a pair of Renewegy VP20 wind turbines and mounted them on the wing walls of the Companys dry dock in Honolulu. The demonstration project began with laboratory testing and performance predictions, and culminated with a series of full-scale demonstrations.5


VP20 DemonstrationShore-side turbine is outfittedwith the demonstration system.Renewegy VP209.5 m diameter20 kW nameplate ratingVariable speedPitch controlledRated wind speed 14.5 m/s


The picture shows the two identical VP20 turbines mounted on the wing walls of a drydock in Honolulu. The shore side turbine (on the right) includes the prototype plasma flow control system. A hydraulic lift kit allows the tower to be tilted down for installation and servicing. The VP20 is a variable-speed, pitch controlled turbine, which is unusual for this size. We chose this turbine in part because the manufacturers attempted to incorporate control and monitoring technology usually only seen on the large industrial turbines.6


System Architecture


This schematic shows the general layout of the system. The power inverter and controller are mounted near the base of the tower. We also use a variable autotransformer (commonly known as a Veriac) for manual voltage control. The inverter connects to a trunk cable carrying a high frequency signal at roughly 200 V and 3 kHz. That passes through a slip ring and connects to a set of HV transformers mounted in the hub. This design prevents us from passing a high voltage signal through the slip ring (in exchange for higher current). Each transformer serves one blades worth of actuators, which consisted of five independent actuators daisy-chained from roughly 20% span to roughly 95% span.7


System Architecture


This picture shows transformers and inductor mounted in the hub beneath the nose cone. The red component beneath the blades is the custom slip ring.8


System Architecture


This picture shows the actuators glowing against the night sky, following our second-phase installation.9


Key AccomplishmentsFacilitiesState-of-the-art plasma lab with custom-built low-speed wind tunnelActuatorsImproved control authority and longevityLow cost, flexible peel-and-stick constructionPower SupplyCustom inverterWorking towards low-profile, integrated transformersDemonstrationFull-scale demonstration with first-generation actuatorMeasured increased CP, projected to yield a 13% increase in AEPNeal E. Fine, PhD 07/06/1510/10

These are some of the key accomplishments to date. We have put together a state-of-the-art plasma lab at Navatek, including a custom-built low-speed wind tunnel. We have advanced actuator technology along a track that will lead to a low-cost, flexible peel-and-stick actuator with the highest control authority and longevity in the nascent industry. We developed a new inverter that is also designed to keep costs low, and could support a future design where the transformers are integrated with the actuators. We performed a full-scale demonstration with the first-generation actuator, and measured an increase in CP thats projected to yield a 13% increase in AEP.10

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