• 1) POWER in the wind: (P, watts)• Is proportional to the cube(3) of:

• p = air density • A = area intercepting wind; • v = instantaneous wind velocity• r = blade length

2) ex. If wind speed is 20% (1.2x) greater at one site compared to another, the power will be about_____ greater at that site.3) Show equation to calculate:_______________

Reference wind .ppt on lecture page

r

• 4) POWER in the wind: (P, watts)• Is proportional to the square(2) of:

• p = air density • A = area intercepting wind; • v = instantaneous wind velocity• r = blade length

5) ex. If blade length (r) is 2x greater on one wind machine compared to another, the power will be about____ greater on that machine.6) Show equation:_____________________

Finding Available Wind EnergyFinding Available Wind EnergyIncreasing tower height increases power exponentially.

7) Why?________________________________

…equation for relationship between power and height also, just remember cubed…

V/Vo=(H/Ho)a, where:

Vo is wind speed at original height

V is wind speed at new height

Ho is original height

H is new height

8) a (alpha): What is Alpha?_____________________

Over rough terrain, alpha = 0.25. Over smooth terrain (water/ice), alpha = 0.1

Gipe (1999)

9) At an average annual wind speed of 10mph, what % of the time does the wind blow 8mph?

______

• Batteries and inverters are critical to the success of a hybrid system– Energy storage– Conversion of DC to AC

• 10) What is a hybrid system?______________________

• Improvements of inverter technology have made it easier to live off the grid with AC appliances

Gipe (1999)

Grip-hoistsGrip-hoists

• Tractel’s Super Pull-All is a great model

• If you are going to buy anything for wind turbine, buy a griphoist

• Better than hoists:– Readily portable– Easier to control

11) Used for what?______________

_____________________________

Wind EnergyWind Energy

(Reference Skystream 3.7 data sheet)

POWER• 12) What is the Cut-in wind speed in mph and

meters/sec?• 13) What is the rated wind speed in mph and

meters/sec?• 14) What is the shut-down speed in mph and

meters/sec?

Wind EnergyWind Energy

(Reference Skystream 3.7 data sheet)

ENERGY15) If your daily average watt-hrs is 16.67kwh/dayWhat average annual wind speed do you need to

provide this much power?

16) If your average annual wind speed is 8.5 m/s, how many kwhs/day are produced?