1. How does INVELOX work?
It is very simple, a large intake captures wind, funnels it down using tapered pipes leading to a concentrator that ends in Venturi section and finally wind exits from a diffuser. Turbine(s) are placed inside the Venturi section of the INVELOX. Inside the Venturi the dynamic pressure is very high while the static pressure is low. The Turbine converts dynamic pressure or kinetic energy to mechanical rotation and thereby to electrical power using a generator.
2. How do you make more energy?
INVELOX does not create or add energy to the natural wind; it is a passive mechanism that converts part of existing static pressure energy into dynamic pressure or kinetic energy. INVELOX captures, accelerates, and concentrates wind. For example: the power density of wind at 7 m/s mph is less than 200 W/m2 while a power density of about 12,000 W/ m2 can be realized at 27 m/s.
3. What size is the intake?
The size of the intake depends on the power output needed. A size comparison and land use of INVELOX to traditional wind power systems of the same power is shown in the below table.
Blade Diameter [m]
Tower Height [m]
Intake Diameter [m]
Land Use [Acres]
Cut-in Speed [m/s]
1.8 MW INVELOX System
Passive Omnidirectional (i.e. no active yaw control)
1.8 MW Traditional System
85 (Sweep Diameter)
passive unidirectional or unidirectional with active yaw control
4. Do you have a “power curve” to show the generating power of the turbine at rising wind speeds?
Yes, we have power curves. (VIEW HERE) It is important to understand SheerWind is not creating a new turbine or generator. Rather, it has developed a “fuel injection” system for wind. The wind “fuel” is concentrated and accelerated, and then injected over WTGs (wind turbine-generators). The key is INVELOX increases wind speed. So the power curves that exist for the “off-the-shelf generators” that we place in the INVELOX system hold true, however, with the INVELOX system we begin to produce power much earlier and can operate much longer with much smaller blades.
5. Is the location of the system a factor and how does it affect test results?
INVELOX is a passive system that captures, concentrates, and accelerates wind. The location does not effect results except that it is best to not have obstructions like trees or buildings that block or move the wind too close to the intake.
6. How long of a test is sufficient to validate the technology?
We have not developed a new turbine generator that requires many hours of operation to test, therefore we can use the manufactures’ turbine data for performance and data. At best INVELOX needs to be tested for seasonal weather conditions, which we have done and found that weather does not adversely effect the system. If need be snow and ice can is removed through a trap door at the bottom of the intake.
7. How do you plan to assemble and ship your equipment/materials?
SheerWind plans to assemble and build on site. SheerWind will hire locally and outsource and license most of our work.
8. Will there be any noise from the towers?
Moving parts (turbines or generator) are enclosed at or below ground level; thereby eliminating excess noise generated by the traditional turbine-generator systems. Tower noise is not anticipated to be a problem. With the INVELOX system rotating blades are inside an enclosure at the ground level, the low frequency blade noise/vibration can be more effectively managed and suppressed.
9. Will INVELOX system harm birds?
The INVELOX system should not kill any birds or flying creatures since it has no moving components at the intake, on the top of the tower. If need be a net can protect birds and flying creatures from entering the turbine generator area.
10. Will INVELOX harm wildlife?
a) The intake does not have a suction effect, it is not like a vacuum. It does not suck birds in. In fact, the wind speed at the intake is far less (up to half) than wind speed in the free stream. If natural wind or free stream wind is at 10 mph, the wind speed at the intake could be 5 to 8 mph.
b) The INVELOX system bends below the intake and captures wind vertically then turns it horizontally. Birds are much heavier than air and will fall right at the first turn and will not fly into the turbine. The wind speeds will not be fast inside the INVELOX until they reach Venturi section where the turbine is placed.
c) If a bad boy bird decides to explore and actually fly in, one can place net right at the bottom of the intake to prevent them from entering.
d) Birds have difficulty with moving objects, compared to a traditional wind blade that can travel at speeds of 150 to 200 mph at the tips, INVELOX has no moving components exposed. It is a stationary tower that birds have learned to avoid. It is much like having a window of 3 or 4 story building open. How many birds fly in an open window in a year?
e) The issue with traditional wind turbine systems is not the number of birds they kill, it is the type of birds they kill or disturb. The traditional wind power plant often has 100 to 200 towers spread over 10,000 acres. Because they must be placed where wind is and away from human development, they are often placed on the path of bird migrations. INVELOX does not need to be installed in the middle of bird migration areas, and can be closer to people since no rotating parts are exposed.
f) The top of INVELOX could potentially be a rest area or nesting area for birds.
g) Traditional wind turbines radiate a low frequency (below 20 Hz) airborne vibration (it is not noise since it is not audible). These low frequency airborne vibrations come from large blades (30 to 60 m in radius) interacting with wind and turning at 200 to 1000 rpm. This low frequency airborne vibration has negative influence on wildlife, livestock, and humans. In Europe, there is a minimum distance (2 to 3 Km) between wind power plants and residential areas. Even if this may protect people to some degree, it does nothing for wildlife running around the wind power plants. INVELOX does not have large blades running at the top of a tower, and therefore there is no low frequency to be radiated in and around the tower.
11. What about Wind Turbine Syndrome? Is there less of that as well?
See item 10g above. It is the low frequency and optical flickering that causes problem for people and animals. INVELOX has none of those.
12. What are the details of the system inside?
Sorry, we do not comment on the details of the inside of our INVELOX system because they are part of our trade secret.
13. What about Betz limit?
Betz limit has nothing to do with energy production. Betz only worked on power coefficient, in other words, he worked on efficiency of blades and his theory was that the blades cannot capture more than 59% of the wind power. Energy production has to do with how low the cut in speed is and how fast the turbine reaches its power rating. Betz has been silent on these subjects. Betz work was on traditional turbines in open flow, free stream wind. He did not do formulations for ducted turbines.
14. How do you explain 600% more energy?
INVELOX system is able to produce 600% more energy:
• Low cut in speeds as low as 2mph (much lower than traditional turbines which are 8mph or more).
• Comparing the output energy with the same turbine-generator-load system mounted on the top of tower at the same height as our intake.
• Turbines in the INVELOX system reach high power output at much lower wind speeds. When comparing free stream wind speed at about 15 mph, the turbine on the top of a tower generated less than its maximum power. But the same turbine inside INVELOX will increase the wind speed from 15 mph to 30 mph at the Venturi, allowing the same turbine-generator to reach its maximum power.
• The combination of the above factors results in an energy production improvement between 85 to 620%, with an average of about 314% more energy.
15. Do you have an actual test site with proven results at 2 cents per kwh (4 cents is considered low)?
In addition to fully validating the technology through significant laboratory tests, wind tunnel tests, and full-scale computational fluid dynamic models (CFD) from 2009–2012, SheerWind designed, built, commissioned, and evaluated two fielded demonstration units in 2012.
Most of the SheerWind’s tests and evaluations have been conducted in collaboration with other companies or organizations. Our laboratory tests were conducted in collaboration with QRDC, Inc., a highly respected R&D firm working for US government for over 25 years. Wind tunnel tests were conducted at City College of New York (CCNY) and Massachusetts Institute of Technology (MIT). Our two field tests were conducted in collaboration with multiple partners.
The results of the SheerWind field tests have been published in both marketing articles and peer-scientific papers. Examples are: WindTech International in March 2013, and ASME paper published in July 2013. The ASME article was scientifically reviewed and accepted for publication and presentation at ASME conference in Minneapolis in July 2013.
16. What about the fact that the industry successfully has grown using the larger blades on the top of tall towers? Are you claiming they are wrong?
SheerWind has never made the claim that the traditional wind turbine systems with huge blades and very tall towers were wrong— rather we claim it is time to change and make industry changing improvements. Like any other old technology that was replaced with a more cost effective and more efficient system, INVELOX is the next generation and a more effective way of generating wind power. Cars replaced horses, and touch phones replaced rotary phones, and PCs replaced huge mainframe computers not because the old industry was wrong, in fact they were very good for their time, but their useful time came to an end and they were replaced. If one argues that the industry is always right, no new invention should take place and no evolutionary, revolutionary, or disruptive technological advances will be ever made.
Furthermore, if we look at the very basic of reasons why certain energy sources give the impression of being cheaper than others, we realize that INVELOX is doing what is necessary to reduce costs. For example fossil fuel and nuclear material are created through intense natural concentration process’, sun and earth work together over millions of years to concentrate and mix many materials to generate the very natural source of energy we know as natural gas, coal, oil, or radioactive material. Hydro dams, biomass plans, and geothermal plants concentrate the source of energy through a combination of natural and man-made process. In hydro water is concentrated by nature then is concentrated more by placing a dam in a river. Water is collected in a huge mass and concentrated (the source of energy) and is forced through small intakes toward hydro turbines. This technique of concentration by process makes the hydropower very cost effective since capacity is very high.
More recently the solar industry has begun the concentration of solar light using lenses and mirrors. This concentration process has increased solar capacity factor from 25% to more than 65% and rising. This improved capacity comes from concentration.
Wind is the only industry that relies on concentration of equipment instead of concentration of the source of energy. Depending on the power rating of each generator, 200 to 500 turbine-generators are used for a 500MW wind power plant. In contrast only 4 generators (each 880 MW) are used in a 3,500 MW coal power plant (7 times larger than wind power plant.) This is based on concentration of the source of energy (i.e. coal) and the wind power plant is based on concentration of equipment.
INVELOX concentrates wind. It is a passive system to convert static pressure to dynamic pressure where the turbine is located. Static pressure cannot be harvested by traditional turbines, only dynamic pressure or kinetic energy can be harvested. INVELOX converts some of the static pressure to dynamic pressure and therefore there is more energy available to the turbine.
17. Will the technology scale to utility-size turbines, say 2 – 15 MW, for onshore and offshore applications?
Yes, the technology is scalable from community size units to utility rated power ones where the cost of generating power will be significantly lower. We have also submitted several proposals for on- and offshore applications at this power range are pending.
18. How much room or acreage is required per kW?
For utility scale units (over 1MW) about 1.5 to 2 acres are needed per 1 MW. For small wind (below 200 KW) approximately .5 acre per 100 KW in needed.
19. Are your units made out of fiberglass, plastic or composite?
It can be made out of a variety of materials depending on the customer requirements and environmental conditions. The two demos were built of metal (first one) and fabric (same fabric used in large tents) and aluminum. The main supporting of our test structure is steel but it can be anything.
20. How do you protect the intake structure and turbine from adverse weather conditions (rain, sleet, snow, ice, hurricanes, etc.)?
The intake is of a material that can withstand all these effects and will vary based on climate. The structure is constructed from materials that are compatible with the location/conditions. There is a drain or door to let collected water or snow release. The turbine is within the duct and it is protected. In high winds or hurricane winds the turbine/generator can be moved or by-passed.
21. Is the geometry of the intake structure critical to performance? What about skeptics?
Of course the geometry and configuration is critical, this is the whole idea. As with any new technology, there will always be skeptics. Most individuals have no doubts because they see the simplicity, understand, and follow.
22. What about flow-dynamics of the system, will air/wind move around it instead of going in?
Like traditional wind turbines the wind cannot avoid the tower. Some wind hits the tower and baffles and moves in and down the funnel. Unlike traditional turbines, wind that is captured by INVELOX results in a much higher power coefficient.
23. Can INVELOX be in regions where the available wind is insufficient for traditional turbines?
Traditional windmills are not effective in slow wind speed areas (class 1 or 2). Traditional wind works best in class 3, 4, 5, or 6. INVELOX is a wind delivery system that captures, concentrates and accelerates wind. Because SheerWind’s INVELOX speeds up wind, it can work in all classes of winds and be effective.
24. What about other ducted or shrouded turbines, how does INVELOX compare?
Many other ducted concepts have been explored dating back to the 1930′s.
Benefits discovered from past ducted turbine concepts:
• Speed increase was proven
• Power increase was demonstrated
• At small scale, outperformed traditional windmills
• Lower cut-in speed
• Speed increase may result in 8X more power for the same rotor size
Challenges discovered from past ducted turbine concepts:
• Duct & WTG were installed at the same location, high on top of a tower
• For speed increases more than 2X, duct becomes too expensive to manufacture, install, and turn in the direction of wind
• When scaling to utility scale, duct becomes too large to build, install, and operate
• There was very little benefit in terms of environment and wildlife, and influence on people
• O&M cost went up not down
• Land use & cost was not reduced
• CAPEX was increased for the gain in performance
• The systems were limited to small wind applications
• All in all, a solid business case could not be made
INVELOX has resolved challenges of previously attempted ducted concepts. Benefits of INVELOX:
• Intake & wind turbine/generator (WTG) were decoupled
• An intake tower replaces wind turbine generator high on a pole and the wind turbine/generator are located at ground level
• Intake can be increased at a different rate than the turbine diameter
• Speed increase of 10X or more is possible, this means significant increase in output power for the same size rotor
• Speed control is possible
• High speed increase (i.e., 10X) results in ultra low cut-in speed (i.e. 0.4 m/s = 0.90 mph if the traditional cut-in speed is 4 m/s)
• No large rotating blades on the top of the tower eliminates all environmental impacts, such as wildlife, bird migration, people, radar, etc.
• Multi-stage wind energy conversation systems become possible
• Heavy equipment (more than 200 tons) removed from the top of a tower
• Having WTG at the ground level reduces O&M cost by 50%
• 10X speed increase will result in significantly increase in mass flow.
• Increased in mass flow will result in increased in output power
• Ultra low cut-in speed allows capacity factor of 70% up to 95%
• Speed Control results in operation even during high wind speed periods, thereby increasing AEP
• There are many options for material selection/construction
• INVELOX can be combined with other sources of energy
• Given the same capacity, INVELOX rotors can be 75 to 85% smaller than the traditional rotors
• Increased performance while reducing CAPEX & OPEX
• Offering near–zero downtime
Download additional information: SheerWind Ducted Turbine History