6.6 Flashcards by Catherine Cordova

is air moving from an area of high pressure
to an area of low pressure and results
chiefly from natural convection driven by
uneven heating of the earth’s surface and
to a certain extent from the rotation of the
earth.

Wind

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*is the velocity of the wind in relation to the
ground

Wind Speed

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was expressed using the direction of a 32-
point compass

Wind Direction

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is a bearing from true north in degrees
clockwise in the direction from which the
wind is blowing

*Wind azimuth

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is the direction from which the
wind blows

*windward

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is the direction in which the wind
is blowing

*leeward

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is
used to detect wind direction

*wind vane, windsock, or wind sensor

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A ____________ has a vertical axis and
three cups that catch the wind and cause it
to rotate about its axis

cup anemometer

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is measured with an
anemometer or wind sensor

Wind speed

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detect wind speed and
direction

*Ultrasonic sensors

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t or f
Wind speed and direction are always
fluctuating

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t or f
wind tends to change direction more
frequently and be more turbulent during
the nightime hour

f ( daytime hour)

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is a polar bar graph that
illustrates the distribution of winds at a
specific location

wind rose

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t or f
The roughness of the surface over which
the wind blows affects its speed

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most familiar wind energy system

Dutch windmill

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collects kinetic energy from the wind and
converts it to electricity with its sleek
aerodynamic blades and tall tower

Wind turbine

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*has a rotor with an axis of rotation that is
horizontal with respect to the ground and
parallel to the wind stream
*designed to operate in an upwind mode,
with the blades upwind of the tower

Horizontal-Axis Wind Turbines (HAWT)

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is usually used to keep the blades
facing into the wind

*tail vane

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*has blades with an axis of rotation that is
vertical with respect to the ground and
roughly perpendicular to the wind stream
*basic VAWT designs are the Darrieus,
Giromill, and Savonius

Vertical-Axis Wind Turbines(VAWT)

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has a rotor section that has
multiple curved blades that look like an
eggbeater.

Darrieus VAWT

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is similar to the Darrieus VAWT
except that it has straight vertical axis
blades

Giromill

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has a rotor section that is
S-shaped when viewed from above. A welldesigned Savonius turbine can have a tip
speed ratio of slightly greater than 1

Savonius VAWT

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converts the energy in the
wind to rotational shaft energy

blade or rotor

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usually including a gearbox and a
generator

drive train

*collects energy from the wind

Rotor

blades are attached to the rotor hub, which in turn is attached to the ___________ which includes the gearbox, low- and highspeed shafts, generator, controller, and brake

nacelle,

*In ______ design, the wind pushes the rotor blades out of the way

drag

The ______design is aeronautically designed as an airfoil or wing that makes use of the principle that enables airplanes, kites, and birds to fly

lift

is the minimum wind speed at which the blades will turn and generate useable power

*Cut-in speed

is the minimum wind speed at which the wind turbine will generate its designated rated power

rated speed

identify wind turbine output versus wind speed.

power curves

is the wind speed at which shutdown occur

cut-out speed

is the relationship between rotational speed of the tips of the rotor blade to the wind speed

speed ratio

is an electromechanical device that converts mechanical energy into electrical energy

Generator

A ________ transmission is used to step up rotational speed of the wind turbine to speeds required for operation of the generator

gearbox

a structure that elevates the wind turbine so it can reach stronger winds at higher elevations and to provide blade-to-ground clearance.

Tower

is built on a stable and substantial foundation and stands in place without the use of guy wires

freestanding tower

is held in place with guy wires anchored to the ground on three or four sides of the tower

guyed tower

Most stand-alone systems fall into one of 3 categories: *_______ systems (100 W or less) *_____ systems (100 W to 10 kW) *_____ systems ( 10 kW to 50 kW)

*Micro systems (100 W or less) *Mini systems (100 W to 10 kW) *Small systems ( 10 kW to 50 kW)

refers to the practice of selecting ideal sites or locations for wind turbines.

Siting

* The main criterion for a good wind power site is ______________.

average speed

__________ on the site may limit the allowable tower height, requiring of a conditional permit from your city planning department

Zoning restrictions

– Produces power independently of the utility grid. – This system can be more cost-effective than extending a power lone to the electricity grid. – They are especially appropriate for remote, environmentally sensitive areas, such as national parks, cabins, and remote homes.

Stand-Alone Systems

need no electrical storage because they operate only during daylight hours.

Direct-coupled systems

can supply the owner with reserve power whenever energy demand exceeds delivered by the WECS

Battery systems

interface with the utility grid. – It supplies surplus power back through the grid to the utility and obtain power from the utility grid when the buildings system’s power supply is low. – These systems eliminate the for battery storage.

* Grid-connected systems–

Some utilities only use a __________ where it turns backwards when the system is producing more power than it is consuming. This measuring technique is called ____________

single meter, net metering

*is a measure of the energy available in the wind over a period of time

Theoretical Wind Power

*is the unit power (W/m2 ) in moving air at a specific speed (v), in mph or m/s

Wind Power Density

if wind speed is doubled, power in the wind increases by a factor of 8 (2 3=8); if wind speed is tripled, wind power increases by a factor of 27 (3 3=27)

Law of the Cube

*the maximum aerodynamic efficiency of a wind turbine rotor is 0.593 (or 59.3%)

Betz Limit

Able to maintain high efficiency

Flat Curve

Experiences a drastic efficiency drop

Sharp Curve

*A complete wind energy system will produce between__and ___% of the energy available in the wind

5 and 30%

*The power available in the wind is related to the speed of the wind and the density of the air

Wind Turbine Power

is a useful way to assess the wind energy available at a potential wind turbine site.

Wind power density

The _________ capacity of a wind turbine for a particular installation depends on the maximum overall load and on the wind conditions at the site

generating