Wind Energy (19,20,21,22)

What are the four parts of a wind generation facility

• access driveway

• facility substation

• wind turbine tower

• wind turbine assembly

Total wind power is equal to…

the rate of incoming kinetic energy of the wind stream

wind power is proportional to what? Why does this matter?

the cubic power of wind —> small increase in wind velocity is a large increase in power

doubling wind velocity does what to the power?

8x

Betz limit

wind turbine’s maximum efficiency (.59)

typical capacity factor range on wind farm

.3 to .5

what is the typical material and height of a wind tower

steel tube, 80 meters (has to be less than 30 to be transported by flatbed truck)

what are the 3 most common tower designs

• steel tube

• ladder

• concrete

most common materials for wind turbine blades

aluminium, carbon fiber composite, fiber glass

what are the most important factors in blade design

material strength to weight ratio and fatigue life

What is included in the nacelle

low/high speed shafts, generator, gear box, controls, yawing system

Challenges for wind energy

• transmission of harvest to use location

• economic viability of large scale grid connections

• decrease investment and maintenance cost —> increase operating revenues

• wildlife and aesthetic complaints

what drives the physical orientation of nacelle and blades

yaw and pitch —> maximize v3

what is typical wind turbine speed and what increases it

.5hz increased by gear box (120x amplification required)

What is blade pitch angle control vs stall control

in stall control, blade orientation remains constant, where in blade pitch angle control the blades can be rotated around their longitudinal axis

cut in speed

wind speed below which there is insufficient power to turn the blades

rated speed

speed at which the turbine generates its rated power

cut out speed

turbine gets shut town, speeds to high

where in the wtg power curve do turbines operate

between cut in and rated wind speed

generator power is equal to…

turbine power x gear box efficiency x electric generator efficiency

higher density air results in (blank) wind power

greater

an increase in blade length (r2) leads too…

a considerable increase in power

different wind turbines have different maximum….

theoretical efficiences (betz limits)

increase in windspeed leads to a significant increase in…

capacity factor

height increases blank and therefore also increase blank

wind speed, power

mass flow rate

mass of air which passes through a surface per given unit of time

how does the conservation of mass apply to wind turbines

inside the stream tube, flow rate is all the same

wind velocity is equal to…

distance over unit time

wind stream velocity ratio is blank for a a given turbine and condition

fixed (v2 over v1)

what equation does capacity factor depend on

a = v2/v1 (can be altered by orientation, location, etc)

what are the three factors that effect wind power extracted

• design - length of turbine blade

• environmental factors - air density and wind speed

• control factors effecting performance coefficient - pitch and tip speed ratio

what is the most common control strategy

opperate at maximum energy extraction to prevent wind “spills”

why is cut in speed greater than zero

because at low speeds turbine generates less power than internal consumption

3 characteristics for wind turbine blade material

material stiffness, low density (reduce oppositional force), long fatigue life