Glossary of SheerWind Terms

Capacity Factor: The capacity factor is a ratio that compares the actual output of a system compared to its nameplate power if it were to operate at full capacity over a defined period of time.
The wind industry uses 12 meters per second (26.8mph) to determine their nameplate power. Unfortunately wind speed does not always travel at these speeds. Therefore the traditional wind industry has experienced an average capacity factor of about 30%. The INVELOX system is able to increase this capacity factor substantially.

Cut-in Speed: This is the minimum wind speed at which the wind turbine starts turning and begins to generate power. If the speed ratio of INVELOX is 4, and the cut-in free stream wind speed of the traditional turbine is 4 meter per second, the cut-in free stream wind speed for INVELOX turbine will be about 1 meter per second.

Cut-out Speed:  This is the maximum speed that the turbine can withstand. At free stream wind speeds larger than the cut-out speed, the turbine will shut down in order to prevent damage to the turbine-generator system. The cut-out speed is activated only in very windy conditions. A typical traditional wind turbine has a cut-out wind speed of about 25 meters per second. INVELOX does not have cut-out wind speed because when wind speeds are higher than the rated wind speed, the excess wind is bled off.

Diffuser: The diffuser is the last section of the INVELOX which helps to broaden the airflow and reduce its speed. The diffuser is an important part of the INVELOX system.

Dynamic Pressure: The quantity of air measured by most airspeed instruments and equal to the product 12 ρV2 where ρ is the density of the air and V is the relative speed of the air. Source:

Free Stream Wind Speed: The speed at which air travels when it is free from obstructions.

Installed/Rated/Nameplate Capacity: The nameplate capacity of a wind turbine is the normal maximum output that can be produced, typically expressed in megawatts (MW) at 12 meters per second free stream wind speeds.

Kinetic Energy: The energy of motion of a body, equal to the work it would do if it were brought to rest.

Omnidirectional Intake: An intake that can capture wind from any direction which avoids the need to turn the intake. An omnidirectional intake is ideal for locations where the wind direction often varies.

Rated Wind Speed: The speed at which the turbine-generator reaches it maximum power referred to as the nameplate power or rated power. The rated wind speed for traditional wind turbines is about 12 meters per second. To be consistent with the industry, INVELOX systems are rated at 12 meters per second. however, INVELOX has the ability to have lower or higher rated wind speed.

Pitch: Refers to when blades are turned, or pitched, out of the wind to control the rotor speed and keep the rotor from turning in winds that are too high or too low to produce electricity.
The pitch system is a common failure point with traditional wind. The INVELOX system has no need for a pitch system and therefore doesn’t experience the same downtime issues that the traditional wind industry faces. Source: U.S. Department of Energy

Speed Ratio: The speed ratio is the ratio of wind speed inside the Venturi section of INVELOX to the free stream wind speed. For example, if the speed ratio is 3 and the free stream wind speed is 6 meters per second then the air in the Venturi section will be traveling at 18 meters per second. This is the critical factor which differentiates the INVELOX system from traditional wind turbines. The speed ratio allows us to provide electricity in places where traditional wind turbines would be ineffective. This allows us to create electricity much closer to where it is being consumed.
The speed ratio design for  INVELOX systems depends on several factors; wind speed, environmental conditions, height limitations, and expected power, energy output, and capacity factor. In the case of our commercial scale demo in Chaska, MN the speed ratio is 2 (SR=2) due to space, height, and cost limitations. To date, INVELOX can be designed to have a speed ratio up to 12 suitable for very low (or ultra-low) wind speed areas.

Static Pressure:  The pressure exerted by a fluid that is not moving or flowing. Source:

Uni-directional Intake: When the intake that captures the wind is only open to one direction. A unidirectional intake can be used in a number of circumstances including but not limited to:
• When wind primarily travels in one direction
• When certain height, design, or other limitations exists

Venturi Effect: When a fluid such as water flows through a tube that narrows to a smaller diameter, the partial restriction causes a higher pressure at the inlet than that at the narrow end. This pressure difference causes the fluid to accelerate toward the low pressure narrow section, in which it thus maintains a higher speed.

Wind Class: Wind classes are a system designed to rate the quality of wind resource in an area, based on the average annual wind speed. The scale ranges from 1 to 7 with 1 being the poorest wind energy resource and 7 representing exceptional wind energy resources. Source: *Energy Bible
An outstanding feature of the INVELOX system is that it is able to perform in low wind class conditions by increasing the speed ratio of the wind.

wind speed chart


Yaw system/ Yaw Drive: A yaw system is often used in traditional wind turbine applications in order to angle the turbine into the direction of the wind.
The INVELOX system does not use a yaw system in its design because the wind energy is channeled in the tower. The yaw system is often responsible for downtime experienced by traditional wind turbines.

Watts, Kilowatts, Megawatts, and Gigawatts: Power measurements i.e., the rate at which energy is generated.

Kilowatt (kW): 1Kilowatt=1,000 Watts. A wind farm’s turbine generator’s size or production capacity is measured in kilowatts or megawatts and represents the rate at which the turbine can produce electricity at a given wind speed.

Megawatt (MW): 1 Megawatt= 1,000 Kilowatts= 1,000,000 Watts. Megawatt is the standard measure of electric power plant generating capacity.

Gigawatt (GW): 1 Gigawatt= 1,000 Megawatts= 1,000,000 Kilowatts= 1,000,000,000 Watts

Kilowatt-Hour (kWh): A measure of the amount of electricity produced over time. A wind farm’s turbine generator that is rated at 1 MW (1,000 kw), operating for 1 year (8,760 hours), with a net generating capacity of 40%, produces 3,504 megawatt hours (MWhrs) per year. (1 MW x 8,760 hours x 0.40 = 3,504 MWhrs) The average United States home electric bill is expressed in kWh to reflect the amount of electricity consumed during the previous month.
In 2012, the average annual electricity consumption for a U.S. residential utility customer was 10,837 kWh, an average of 903 kilowatthours (kWh) per month.

Megawatt-hour (MWh): 1,000 kilowatt-hours or 1 million watt-hours. The U.S. Energy Information Administration reports that the total U.S. demand for power was 3.8 billion megawatthours (mWh) in 2012 and is expected to increase to 5 billion mWh by 2040.


History of Wind Energy