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Frequently Asked Questions
Competitive Advantage
There have been other attempts at shrouded concepts, what is different with the FloDesign wind turbine?
FloDesign Wind’s technology is the first to combine mixer pumps, ringed airfoils, and stator rotors into a single system that significantly exceeds the Betz limit and beats the economics of traditional turbine designs. FloDesign conducted exhaustive research on all publicized prior attempts at shrouding wind turbines. There are many names used to describe the shrouds, including ducted fans, concentrators, diffusers, etc. All shrouded designs capitalize on the effects of a diffuser, which Northrop Grumman applied to wind turbine turbines as early as 1970. A diffuser is a duct that starts out at a smaller diameter and gradually opens to a larger exit diameter. Ideal diffusers require diffusion angles of 5-7 degrees; larger angles will cause the flow to separate and the diffuser is useless. Properly designed diffusers also require a substantial length to get good performance. Additionally, conventional diffusers require on-axis flow, meaning the wind should be in line with the diffuser duct. Therefore, when the prior attempts were tested in a wind tunnel, results were exceptional. Once deployed in the field, however, their performance dropped considerably.
FloDesign Wind’s team has pioneered the use of mixer/ejectors in propulsion systems for over 30 years. We have designed such concepts for Rolls Royce, Gulfstream, Sound Solution, Stage III Technologies, Sikorsky Aircraft, UTC, FN Herstal and many others. The application of a mixer ejector in propulsion systems has been widely accepted. FloDesign Wind’s turbine design combines the latest state-of-the-art gas turbine concepts, such as a shrouded propeller and circulation ringed airfoils, with FloDesign’s proprietary multi-stage mixer/ejector pumps. The shrouded design allows for more efficient stator/rotor concepts. The high circulation cambered airfoils in combination with the mixer/ejector system brings significantly more flow through the rotor for extracting more power. As a result, the FloDesign turbine has the potential to increase wind power output by 3x or 4x that of traditional turbines, far exceeding the Betz limit.
In addition to dramatically increasing airflow through the rotor area, FloDesign’s mixer/ejector system provides rapid wake mixing, allowing much closer placement of the wind turbines in the field. The mixer/ejector is also characterized by its ability to accommodate off-axis flow—up to 45 degrees off-axis with no significant dropoff in performance. The combination of these technologies means the shroud is a lightweight and compact diffuser. In a traditional turbine, a diffuser 10x as long would be required to achieve the same efficiency effects.
Given the capital intensity and financing requirements of the wind industry, how will FloDesign Wind compete with established players?
Wind turbine production is a capital-intensive business that necessitates substantial equity financing in early stages. “Me too” turbines face substantial hurdles to market entry, especially in the areas of warranty provision that require strong balance sheet backing. FloDesign Wind plans to limit its equity capital needs in several ways:
FloDesign Wind plans to initially develop a 150 kW unit (FD150) aimed at the community wind and mid-scale markets, which have been traditionally underserved by the big players. This will reduce risk and allow FloDesign to commercially validate its technology while reaching a positive cash flow position thanks to its superior efficiency and cost. FloDesign will concurrently focus on scaling its technology to megawatt-scale turbines.
FloDesign’s technology also means it can compete in less favorable wind regimes, creating significant opportunities currently unavailable to traditional turbines. While these turbines are generally only financially feasible in AWEA class 4+ wind regimes. FloDesign’s turbine is financially feasible in lower Class 3 winds. Since there are 10x more class 3 sites than class 4 and 5 combined, FloDesign’s turbine represents a potential paradigm shift for wind farm development. Rather than simply penetrating the established market, FloDesign’s technology creates a new opportunity 10x larger than the existing market.
FloDesign Wind does not plan to manufacture individual turbine components such as the gearbox, generator, power electronics and tower itself. Instead it will play the role of a less capital intensive “system integrator.” By demanding strong warranty provisions from individual component suppliers, FloDesign Wind will limit/hedge its warranty exposure.
In addition, several insurance companies are available to “wrap” warranties or provide supplemental coverage, especially for serial failures (typical premiums are approximately $30,000 for a 2 MW turbine). If necessary, FloDesign Wind could partner strategically with an established manufacturer of large rotating machinery, whereby the partner would bear the ultimate product performance risks.
Most startup wind technologies have demonstrated only marginal improvements over current designs (e.g. multi-gearbox operation or direct drive PM). The advantages of these technologies have not justified the risk inherent in working with a startup company. In contrast, FloDesign’s turbine provides substantially higher performance than traditional turbiness and opens up many distributed/community sites where traditional turbines are not viable.
How is FloDesign developing its technology for market entry?
First, the underlying mixer/ejector theory was validated by model testing at MIT’s wind tunnel laboratory. The required engineering design and performance criteria have been developed using FloDesign’s aerospace engineering expertise and existing turbine technologies. Over 50 patent applications have been filed to protect the concept. Three journal papers and two conference papers have been submitted for publication, including the paper entitled, “Ducted Wind/Water Turbines Revisited.”
Second, the concept is scheduled to be demonstrated at NREL’s Golden Colorado facility. We also plan to certify the turbine in accordance with all relevant standards in the field of wind energy (i.e. DMV or Germanischer Lloyd). Additionally, FloDesign Wind has identified several wind farm developers interested in placing our prototype units. We realize that the first units are critical to acceptance but believe the benefits of our design will be rapidly accepted upon successful demonstration.
Third, we will rapidly scale manufacturing operations. Current wind turbine designs require custom equipment for both fabrication and transport. This results in long lead times for delivery, the need for custom manufacturing plants and higher costs. Our design uses standard manufacturing techniques used around the world. Our blades are shorter and stubbier, which allows them to be manufactured through simplified fabrication processes such as pull-trusion. We also plan to limit components to the size of standard 40-foot shipping containers.
Additionally, we have chosen a market entry turbine size that could use the ailing automotive industry supply chain. In fact, the FD150 has about the same HP as a Chevy Malibu (200 hp). We plan to align with distributors from around the world to manufacture and sell our design. Thus, we hope to meet the world’s wind power needs through rapid deployment.
Why will people accept the FloDesign wind turbine over standard designs?
FloDesign turbines are smaller, safer, quieter and more aesthetically pleasing, making them more likely to be accepted by stakeholders. As wind turbines become more popular in the landscape, so has opposition. The costs of permitting and site acceptance can cost well into the millions of dollars. A perfect example is the opposition in Massachusetts to the proposed Cape Wind off-shore installation. We feel confident that our turbine will be accepted by communities for the following reasons:
Appearance:
Just as the jet engine has replaced propellers, we believe current designs will be perceived as old fashioned. Additionally, because the FloDesign turbine is half the diameter, it can be placed closer to the ground. Though average wind speed increases with height, some sites such as ridgelines don’t require significant elevation. On ridgelines, FloDesign’s turbines could hug the ground and thus become less visible to the habitants below. For off-shore applications, FloDesign’s turbine will disappear into the horizon faster because it’s lower.
Land Utilization:
Current wind turbines require wide spacing on land due to downstream wake effects. Turbulent mixing requires a distance equivalent to 7-10 diameters downstream to fully develop. In other words, the turbine blade slows the air down and it takes a long time for the wind to fill in down-stream. FloDesign’s turbine is a paradigm shift for wind farm developers. FloDesign turbines can be spaced 4-5 diameters downstream, meaning twice the energy can be extracted per parcel of land.
Safety:
On-shore applications require that turbines be placed far from municipalities due to slinging ice and debris as well as damaged blades. FloDesign’s shroud isolates possible debris slinging, significantly mitigating these safety concerns. Offshore applications require that the distance from the turbine blade be high enough such that sailboat masts don’t collide with the propeller tip, the speed of which can exceed 200 mph. In contrast, the FloDesign turbine rotor is isolated. Therefore, the turbine could be barge mounted. This allows a passive yaw system (wind pointing) without the assist of yaw motors.
Noise:
The FloDesign Wind turbine is quieter since the shrouds provide both acoustic shielding and sound attenuation. The shroud could provide additional noise attenuation by tuning. Small holes could be strategically oriented, providing an acoustic filter or muffler-like effect. Over time, site requirements will continue to become increasingly strict. FloDesign Wind is uniquely positioned to accommodate future legislation.
Technical Questions
How can FloDesign’s turbine provide two or three times the Betz limit?
This question is the key to our invention and can be answered with different degrees of technical complexity as seen below.
Technical Response
The Betz limit is not turbine efficiency. It is a performance anomaly associated with an un-shrouded propeller caused by the flow rate through the propeller and the amount of open diffusion that occurs downstream in the wake of the system. The Betz limit represents the maximum power that can be extracted from the wind by non-shrouded, propeller wind turbines. The 59.3% represents the percentage of the kinetic energy that can be extracted from a stream tube of oncoming wind flow having the same cross section as the swept area of the propeller blades. The Betz limit results from applying conservation of mass, momentum and energy with fluid dynamic, control volume analyses to an un-shrouded wind turbine propeller system. Such first principle, engineering analyses predict that the oncoming wind flow has to slow down as it approaches the propeller, resulting in higher pressures in front of the propeller. This increased pressure region in front of the propeller deflects the oncoming flow outward causing about one half of the wind flow approaching the propeller to flow around, and not through the swept area of the propeller. The flow that passes through the propeller has to use open diffusion (not controlled by a surface) in the downstream wake to reach free stream pressure. The actual efficiency of the propeller in extracting the energy of the flow passing through the swept area is about 80% to 90% for good blade designs. Such efficiencies reflect friction losses, tip vortices and downstream swirl losses with an un-shrouded propeller.
FloDesign’s turbine uses an inward cambered turbine shroud coupled to a downstream mixer/ejector pump to increase both the flow rate through the turbine and the diffusion downstream of the turbine. The cambered turbine shroud uses wing lift principles to lower the pressure on the turbine shroud inner surfaces to draw in more wind flow. This effect is similar to the top surface of a wing. The downstream mixer/ejector pump generates a low pressure area at the turbine shroud exit also helping to significantly draw in more flow through the turbine. The mixer/ejector uses an inwardly cambered shroud along with highly efficient lobed mixers to pump and mix out the low energy flow exiting the turbine shroud with the high energy air that flows around the turbine. The increases in turbine flow rate and flow velocities allow higher blade torque and work potential. They also allow the use of stator/rotor turbine cascade concepts which can increase turbine efficiencies by eliminating tip losses and swirl losses. As a result, the increase in turbine flow rate and velocities, the rapid wake mixing and dispersion, coupled with the potential improvements associated with turbine cascades allow the FloDesign turbine’s performance potential to exceed the Betz limit by factors of two or three times.
Less Technical Response
Above all else, it is first important to understand that the “Betz Limit” of 60% ONLY applies to traditional, bare wind turbines. It has long been known, understood and shown many times that ducted or shrouded wind turbines can exceed this value. The reason for this seeming conflict is contained in the basic physics that apply to bare and shrouded wind turbine operation. Because a bare wind turbine extracts energy from the oncoming wind, it causes it to slow down as it approaches the wind turbine. In fact, it diverts a large portion of the flow around the turbine blades in the same way your open hand did when you hung it outside your parent’s car while driving. As you opened and closed your fingers, more or less air passed through them—thus more or less power was extracted. You no doubt noticed the force on your hand increased or decreased accordingly. Exactly the same happens for a bare wind turbine. As more or less air flows through it, it rotates faster or slower and thus extracts more or less power. Betz showed that there was an optimum configuration for the blades (or your fingers) on either side of which the power extracted is lower. At the optimum state, only about half the approaching air passes through the blades and the remaining half goes around them. If one does not design the blades correctly, more than half the air will go around, less than half will be available to rotate the blades and the power extracted will decrease below the Betz Limit. Nearly all the three bladed wind turbines operating today only achieve about 80% of the Betz Limit (i.e., 48% of the power available) because of the complex aerodynamics associated with the design of those long, skinny blades. For a host of well understood aerodynamic reasons, those designs have virtually reached their limit and cannot be improved upon.
Ducted or shrouded wind turbines are a different aerodynamic entity--as different from the bare wind turbine as a jet engine is to a propeller. Properly designed shrouds, like the nacelles you see surrounding jet engines, have long been known to have a different set of aerodynamic elements that allow it to tailor the flow field through and around it. In particular, through careful contouring, one can cause the flow to accelerate into the shroud, thereby allowing more flow to pass through a given cross sectional area and less to go around it. To do this, the shroud uses some of the same principals as a wing does to create lift. A properly designed wing causes the flow to accelerate over its top surface and decelerate over its bottom surface to produce lift.
Now imagine rolling such a contoured wing into a loop and connecting its two ends into what is called a ring airfoil. If the accelerating portion is on the inside, more will go through the ring than around. If the accelerating portion is on the outside, the opposite will occur. Thus one can design a ring airfoil (or shroud) that will capture more of the flow approaching it and divert less of it around its exterior. Now imagine placing a wind turbine inside such a ring or shroud. One would expect, and it has been shown many times, that because the shroud brings in more air, it allows more power to be extracted. Again, as for the bare wind turbine, the key is to properly design the wind turbine blades aerodynamically so they are able to optimize the amount of power extracted. FloDesign has published several recent papers that show how to calculate this optimum—which can be 2x to 3x the Betz limit because the ring airfoil delivers 2x to 3x time the flow through the turbine.
Will icing and inclement weather affect the performance of FloDesign’s turbine?
Icing is expected to have minimal effect. FloDesign’s turbines are better suited to handling harsh conditions than conventional open blade designs because the rotor blades are shielded from ice, rain and snow by the front stators, shroud and the nacelle. While standard turbines require substantial distance from habitation due to slinging ice or blade damage, FloDesign’s turbine is inherently safer and can be placed on buildings or near people.
Depending on the location and climate, the FloDesign turbine will utilize the following methods to deal with ice and snow:
Because the shroud is arched, certain polymers will naturally shed ice and snow. For larger models, the material for the shroud will be resilient, meaning it will flex under load and break the snow or ice away. FloDesign is currently considering methods using polymer-based materials for use in the FD150. Quonset huts with resilient material have been used in the arctic for years. Each material will naturally shed ice and snow given certain configurations.
The aerodynamic surfaces will use standard techniques used in both the wind turbine and aircraft industry on nacelle inlets. For example, surface embedded resistance wires can be fabricated into the key components. Another method used in traditional wind turbines is to apply black paint to the ice prone surfaces. The black paint may absorb enough solar heat to melt or shed ice. The FDWT shroud could use the same technique. Black blades have historically caused polyester type resins to wear more quickly due to the extreme temperature shifts at the surface.
There are also some novel de-icing methods used in the aircraft industry that can be utilized, such as a bladder wrap around the nacelle that can be inflated to break away ice. Most of the ice prone surfaces on the FloDesign turbine are stationary and easily modified for de-icing.
Will the FloDesign turbine be able to withstand high wind speed?
Yes. This question can be address by considering the key turbine components affected:
How will FloDesign Wind size the generator?
Our design is unique in that it is capable of producing power in both lower and higher wind scenarios, from 11 - 60 mph. This provides expanded opportunities for wind farm developers. However, different component configurations will be optimal for different applications. For instance, generators designed for use in IEC Class I, II and III regions must meet different requirements relating to average wind speed, maximum gust speeds, and turbulence intensity.
As a result, even though we could generate power in high wind conditions, it may not make sense to a use a large generator for the high speed anomalies. Our generator will be sized based on the (Rayleigh curve) average wind velocity available at the site. If higher wind speeds are encountered, our design will be capable of sustaining the gusts and producing power throughout the higher wind speed regime. However, the max power extracted will be limited to the size of the generator.
How will you regulate the rotor speed at max power? Current wind turbine blades change pitch or “feather” into the wind to regulate speed. In our design, the stationary blades or “stators” change pitch to regulate flow. During extreme high wind/gust situations, we would brake to prevent overloading the generator and continue to extract power. Thus, we can withstand high wind gusts without damage and can generate power using a combination of braking and/or stator pitch regulation.
How will your blades sustain such high winds? Our blades are shorter and have a hoop around them, meaning they are supported at both ends. This design generates a strong, durable structure, in contrast to the long cantilevered beams used with traditional turbines. Traditional turbine manufacturers such as Suzlon and Clipper have encountered significant problems with large blades cracking or breaking due to the extreme mechanical stresses inherent in traditional turbine designs. In contrast, FloDesign’s turbine shifts loads to the non-rotating components, reducing wear issues.
How will the shroud sustain high winds? The shroud will use manufacturing materials and techniques utilized in aircraft wings. Wing construction techniques vary depending on application. For example, a glider and jet fighter have entirely different criteria. We are choosing shroud construction techniques to match the end use criteria, such as a spar wrapped with plastic, aluminum, fiberglass or carbon fiber. On-shore applications could also utilize foam core with plastic wrap. Some applications may require that the shroud is stowable (able to retract) or that the fabric be rolled up. Severe applications (such as Mt. Washington) could use aluminum or stainless steel.
Will the FloDesign wind turbine harm migrating bird or bats?
Early indications are no. Though most scientific studies suggest that bird strikes are rare, most people working on wind farms do witness avian fatalities and it remains a controversial topic. The general consensus is that it’s a game of statistics, as birds are unaware that they have entered into the dwell region of a wind turbine blade and then are struck broadside. Raptors such as hawks and eagles are constantly surveying the earth’s surface for prey and have poor peripheral vision, making them exceptionally vulnerable.
We feel confident that our turbine will be safer than traditional turbines. Current open blade designs reach maximum efficiency when the blade tips reach extremely high speeds–as much as 150-200 mph. What birds can’t see, they fly into. Because FloDesign turbines have a shroud, birds can better see the obstruction and simply fly around it. Additionally, our rotating blade is behind a stationary blade (stator). Anecdotally, the stator looks like a venetian blind, and birds don’t fly into windows when the blinds are drawn.
The noise emitted from current 1.5MW designs is low frequency. Birds have difficulty locating the origin of low frequency noise. Birds, unlike elephants and tigers, communicate in high frequency. Therefore, birds cannot avoid what they can’t hear. The noise emitted from our design is a higher, audible frequency easier for birds to hear.
Is the FloDesign wind turbine noisy?
No. As noted earlier, it is predicted to be quieter compared to current designs. The sound that propagates from existing wind turbines is low frequency and thus travels long distances. Some reports indicate that home owners can hear wind farms from up to 5 miles away. The overall noise from a conventional turbine is broadband and this low frequency noise is the most difficult to absorb. This is best demonstrated by the thump of a sub-woofer from a car. One hears the low frequency thump from a distance, yet cannot hear the higher frequency singer’s voice. The low frequency noise from wind turbines comes from the enormous blades rotating at low speed (15 RPM). As the blades pass the tower, deflection occurs. The deflection of the blade acts like a diaphragm and creates noise.
FloDesign’s turbine spins at a higher RPM (20-100 RPM) with more blades, thereby shifting the frequency higher. Higher frequency noise is absorbed and dissipated quickly. Additionally, the shroud can be designed be act like a Helmholtz resonator. Holes around the interior of the shroud can trap high frequency sound. Also, the addition of sound absorption material in the liner of the shroud could drastically reduce noise. FloDesign’s staff is uniquely qualified in the field of acoustics, having worked on noise reduction projects for everything from jet engines to firearms. See the FloDesign website for more details.
Does the FloDesign wind turbine scale with size?
Yes. The problem with performing small scale testing with wind turbines is the scaling factor. This results in the need for high air speeds for small scale models. Therefore, testing becomes difficult at smaller scale. FloDesign has a significant aerospace background and has conducted numerous successful projects based on scale model tests and projections. We have used sub-scale proto types to predict the performance of aircraft systems since 1990.
Why can FloDesign turbines be placed closer together on a wind farm?
Wind turbine spacing has been the topic of many technical papers and is relatively complex. If you think of the propeller as a restriction to the flow, similar to a screen, the conventional turbine requires 8-10 diameters downstream to fully develop the flow to its original profile.
Down-stream turbine performance is a function of mixing the slowed air with the adjacent faster moving air. Our claim to being able to pack the turbines tighter is the result of the rapid mixing provided by mixer-ejector technology. The patented mixer ejector uses an inviscid phenomenon to shorten the length needed to replenish the flow field. Hence, the name, “mixer.”
Additionally, conventional turbines are plagued by lift-induced drag (tip vortices). This is the phenomenon that requires spacing of approaching airplanes on runways. FloDesign’s shielded rotor (propeller) eliminates tip vortices.
Traditional wind farms are very inefficient and extract only a little over 30% of the wind energy approaching them. Frendsen et al recently showed that for a 10 row off-shore wind farm with spacing of 7 diameters by 7 diameters, each of the 9 downstream turbines in a row only produce about 55% of the power of the row’s lead turbine, which itself only extracts 50% of the power approaching it. Spacing of 10 diameters did a little better. Both of these results are to be expected because the turbulent viscous mixing at the edge of their wakes can only slowly blend in some of the higher energy wind that was diverted around the upstream turbines. Such viscous mixing is a classical fluids phenomenon that is known to take very long distances to be effective.
The poor performance of such downstream traditional turbines is directly related to the resulting low velocity voids in the wakes of the upstream turbines. The impact of these low velocities is amplified by the fact that the power extracted is proportional to the cube of the wind speed approaching each turbine. Thus low wake velocity means very low power production. There is no known methodology by which traditional designs can overcome this limitation. That technology is at or near its limit. FloDesign’s wind turbines can be spaced as close as 4 diameters apart in a row because their wake velocities are 2 or more times those of traditional turbines at the same power levels.
FloDesign’s wind turbines do not encounter turbulent mixing limitations because they use advance, proven and proprietary inviscid flow mixing and ejector pump principles. This mixer-ejector technology has been repeatedly demonstrated to reduce the length of mixing from 10 diameters down to roughly one. Additionally, FloDesign’s shielded rotor eliminates the blade tip vortices that traditional turbines spawn, which in turn structurally plague downstream turbines. Thus we have every expectation that our turbines could increase the productivity of new and existing wind farms by a factor of two or more.
How will you accommodate rapid direction change of the wind?
The shroud is designed to fly into the wind, allowing a passive yaw system. The shroud is a winged airfoil designed to withstand heavy broadside loads in the event of yaw system failure. The center of pressure on the shroud is positioned such that the turbine will rapidly rotate to face the wind. It is similar to the way a weather vane, airplane or kite accommodates off-axis gusts. We are currently also evaluating novel umbilical attachments to the tower.
What are the maintenance requirements for your turbine?
Maintenance is a major issue for current turbines. This begins with the fact that current turbines use large cantilevered blades. These flexible, rotating beams propagate vibrations through the gears and eventually to components in the nacelle. People who have been inside the nacelle of an operating turbine equate the vibrations to those experienced in a car when driving down a road with washboard frost heaves. As a result, electrical components are subjected to extreme conditions. Current turbines experience the majority of down time due to control system, gear train and blade failures.
FloDesign Wind’s technology mitigates many of the stresses that plague traditional turbines. First, the FloDesign turbine reduces vibrations due to the smaller, stiff rotor. This substantially reduces vibrations and results in longer life for electrical and mechanical components. We also plan to implement aerospace quality redundant control systems. Second, the FloDesign turbine gear train complexity is greatly reduced. Our design drives the generator directly from the hoop. Third, our blades benefit from hoop strength and simple manufacturing methods. The total substantially reduces maintenance requirements.
Another innovation to be employed in the FloDesign turbine manufacturing process will be designing advanced condition based management (CBM) techniques into the device from the bottom up. Since FloDesign’s technology is new and heretofore untried, conditions measurements of the device and installation will be significantly different–and therefore improved by definition. We have engaged an initial CBM definition with an established CBM systems supplier for the near-term. We have also embarked on an initiative for an advanced, heuristics-based CBM program with the respected manufacturing research organization, TechSolve of Cincinnati, Ohio. TechSolve has been working in intelligent condition technologies as part of a multi-year, multi-million dollar smart machine program under the U.S. Department of Defense Manufacturing Technology (ManTech) program. The technologies and lessons learned will be extended to the renewables and wind arena through this effort and will also strive to design CBM to benefit the wind farm operator, as well as the turbine manufacturer.
What is the FD150’s projected annual energy production?
The FD150 projects to offer higher annual energy production and capacity factors compared to a reference 150 kW unit. And because the FD150 is much smaller, it delivers significant cost savings as well.
609 MWh per year at an IEC class 2 site (8.5 m/s average), yielding 46.3% capacity factor.
503 MWh per year at an IEC class 3 site (7.5 m/s average), yielding 38.3% capacity factor.
Business Economics
How is your design cheaper when you add the extra material for the shroud?
The benefits outweigh the cost. Phrases we often use in the aircraft industry are “figure of merit” and “will it buy itself on?” This involves a numerical analysis (decision matrix) of the characteristics of a device that represents the efficiency or measure of success. We embrace the ultimate figure of merit for a wind turbine as the cost/kWh. This is the point at which the feature or component in question makes sense financially. The additional cost of the shroud is offset by benefits to the farm and lower cost for various components on the turbine. The FloDesign Wind Turbine is ½ the size of conventional Wind Turbines for equal power output. The smaller size means numerous components are lower mass and cost, including the blades, gearbox, generator, and bedplate.
Fabrication for Blades:
Current wind turbine blades require enormous custom machinery to fabricate.
Existing Turbine Blade
Our design uses a stator rotor configuration. The rotating blade is referred to as a rotor. FloDesign Wind’s rotor blade is a simple design. It can be extruded and made from plastic, drastically reducing costs.
Pitch Control:
The traditional rotor consists of the hub, three blades and a pitch regulation system, all of which are located upwind of the tower. Current wind turbines require that the rotating blade change in pitch. Pitch control is essential for conventional turbines to obtain high efficiencies. Pitch control helps the blades get started and regulates the max speed. In gusty situations, conventional turbines will adjust the blade pitch to a neutral position and stop rotation. FloDesign’s stator will pitch, meaning that the rotating component, the rotor, does not need active pitch control. This also reduces blade costs.
Transportation Costs:
As the size of turbines increase, so does the cost for transportation. Transportation can represent 20% of the cost for conventional turbines. FloDesign Wind’s concept is a smaller, modular design that can fit in standard 40-foot shipping containers.
Yaw Drive:
Conventional turbines use a yaw system that turns the nacelle into the actual wind direction using a rotary actuator and a gear mechanism at the top of the tower. A fully automatic microprocessor-based control and monitoring system is a part of the wind turbine. The control system is designed for remote operation from the shore-based operations center via a fiber optic communications system. FloDesign’s rotor configuration has a significant portion of the mass downwind, allowing for a passive yaw system. This would allow the turbine to align itself into the wind without the need for a yaw drive. In other words, the shroud allows a weather vane like action and slip rings provide a full 360 degree rotation. Dampers are used to reduce abrupt changes. Larger configurations can use a simplified yaw to unwind the power cable.
Front Rotor Bearings:
Traditional rotor bearings are expensive and must support the mass of the blades as well as the static thrust from the impinging wind. As a result, they are prone to costly maintenance requirements. The hub must also accommodate pitch control. FloDesign’s rotor experiences very little thrust loading, meaning it’s cheaper and simpler. The stator-rotor can be thought of as a water wheel, helping convert the wind’s energy into higher RPM and torque while experiencing very little thrust loading itself.
Gearbox:
Conventional turbine hubs rotate at 10-20 RPM. Most generators require an input of about 1700-1800 RPM. This amplification in speed is what requires a complex gearbox. The gearbox is prone to failure in locations that experience variable winds. FloDesign’s gearbox is far less complex and can operate at 2x to 3x the RPM of traditional turbines. The FloDesign turbine rotor is connected to the generator from the outer hoop on the blade. This results in both a lower cost and robust connection.
Direct Drive PM Generator:
The higher RPM of the FloDesign turbine allows for simpler gearboxes or more advanced permanent magnet generators (PMG), which have recently been introduced into traditional wind turbines. PMGs have the advantage of potentially allowing direct drive, which would eliminate the traditional gearbox entirely. The criteria for their use is based on torque density and cost/torque. Axial Flux Permanent Magnet Generators (AFPM) are believed to have the highest torque/volume relation of PM generators. The ultimate measure of performance is the cost. PMGs are measured by the amount of active material utilized within; iron, copper, ferrite magnets and rare earth magnets have commodity costs associated to them. The overall amount of active material required is directly related to the input RPM. The slower speeds require a larger diameter to get the pole speeds up. For traditional turbines, the direct drive PMG has the highest energy yield and is cheaper than the electrically excited direct drive generator. However, it is more expensive than the traditional generator with a gearbox. Because our turbine has a smaller, faster spinning blade, the overall amount of active material can be reduced, potentially enabling a PM direct drive on the FDWT with both better performance and lower cost.
What is the going rate capex for a mid-scale turbine? What is the going rate capex for a utility scale turbine?
The Northwind 100 can be $3,000-$3500+ per kW uninstalled, or $5,000+ installed. FloDesign’s wind turbines are much lower cost. Utility-scale turbines average $1,450 per kW uninstalled, but can be up to $1,600 for one-off purchases according to Emerging Energy Research (2008).
How will FloDesign conform to the extensive field testing requirements needed for financing wind projects?
Financing is critical and much more of a challenge for early entrants. However, based on conversations with insurance companies, approximately 8,000 hours of testing time is reasonable for a technology to be considered “commercial” and financeable. We expect to have this completed as our production ramps up, and we are aggressively pursuing early design certification with firms including Germanischer Lloyd, DNV and Garrad Hassan. FloDesign’s turbine also has attributes that make it the only turbine suitable for certain locations.
For our early units, we are pursuing direct purchases by government entities such as the Commonwealth of Massachusetts that will not be leveraged. For later units, we have begun partnerships with several local banks that are interested in financing “community wind” projects of < 5 MW net output and have different lending criteria than are typical for large structurings of project-financed wind farms. In addition, revisions to the Department of Energy loan guarantee program hold potential for government guarantees of wind farm debt in the future. Our turbine will also be available for siting in higher value locations closer to load, providing a higher effective purchase price of power. And finally, the FDWT is the only turbine that has the potential to be deemed “Bird Safe” and reflect ‘Zero Radar Cross Section” for air traffic controllers.
With some established manufacturers lowering prices and margins shrinking, how will FloDesign Wind compete effectively?
FloDesign Wind expects to be able to price very competitively with traditional turbines in the 100-300 kW capacity range, using primarily off-the-shelf components manufactured in relatively small batches. Early financial projections show that strong financial ratios are achieved with selling prices more than $1000/kW lower than current market pricing.
FloDesign Wind can also open up new markets for wind turbines closer to population centers (due to ease of erection, compactness, low noise and shadow flicker, safer operation in icy conditions, etc). These new markets will not face the same price pressures as the commoditized large wind farm applications.
Ultimately, FloDesign will introduce a more advanced turbine concept that incorporates customized features including lightweight shrouds, novel tower configurations, stator/rotor, and a new PM generator. Combined with lean mass production techniques, this will result in significant pricing advantages on both a $/kW and $/kWh basis compared to any size of traditional turbine.
