Lecture 10 Notes
Part 1: Harnessing the Wind
Part 2: Power Generation
2.2 Wind Turbines
Part 3: Special Topic: Permafrost in SW Hudson Bay
Part 1: Harnessing the Wind
Humans have long yearned to fly as represented in the Greek myth of Icarus. In
the 15 century Leonardo da Vinci designed various flying machines (including designs
for helicopters) but did not have the engineering skills to complete the designs. In the 19
century, Otto Lilienthal performed more than 2000 glider flights using his own designs.
He perished in 1886 after a glider mishap. Manned flight was achieved first by the
Wright Brothers on Dec.17, 1903.
Bernoulli’s principle explains how flight is possible. A fluid that is moving faster
has a relatively lower pressure. The shape of a wing causes air to flow faster over the top
of the wing than it does beneath. This produces a lower pressure above the wind and a
higher pressure below the wing; creating a pressure gradient force pushing upward. The
wing experiences a lift and thus flight is enabled. The invention of flight has revolutionized travel. In 2000, 8,000 commercial
flights were taking place at any given moment, carrying 1,000,000 passengers. There are
some risks involved in flight but these have become smaller and smaller in recent years
as revealed by data compiled by Boeing.
Sailing has a long history, particularly in the Middle East and China. Sailing was
used as an efficient means of transportation, carrying people and goods from port to port
and bringing prosperity to coastal regions.
As ships became more seaworthy, sailing became an effective tool for
exploration. Norse sailors used ships of type known as knarrs or cogs to cross the
Atlantic to North America for the first time around 1000 AD. The “square rigged” sails
on these ships were very sensitive to wind direction; the Norse travelled to Greenland and
Newfoundland by following the Polar Easterly winds across the North Atlantic, returning
to Europe slightly further south via the midlatitude Westerlies.
In contrast, the junk rig used by Chinese ships had the capability of sailing into
the wind as early as 220 BC.
A major advance in European sailing occurred when square rigged sails were
augmented by or replaced by lateen (triangular) sails in a moveable boom. This allowed
greater boat maneuverability – and the ability to sail into the wind. By the 13 century
sailing around the world had sufficiently advanced to allow the exploration of the entire
planet. The age of sail continued until the 1860’s when it was outstripped by steam
technology. It is now largely recreational.
Sailing is based on the same principle as flying. In this case the “lift” or pull is
horizontal rather than vertical. Moveable sails are oriented so that the wind flows faster
over the front of the sail than the back, creating a pressure gradient force that pulls the
sail forward. The use of a keel board (a piece of wood that penetrates into the water
beneath) provides better control of the sailboat path. The sail pulls the boat in the
direction of the front of the sail; the resistance between the water and the keel produces a
force that keeps the motion of the boat in the direction chosen by the sailors. Part 2: Power Generation
Like sailing, windmills have a long history of providing energy for human needs.
Early uses in Persia and China included grain grinding and water pumping. Two styles
emerged, vertical axis and horizontal axis. The horizontal axis has been found to be more
efficient and dominates current and historical design.
In 12 century Europe windmills were developed that could be turned in order to
match the direction of the wind. In its heyday there were 90,000 windmills in England
(“one for every field”), producing a wind-based economy with uses expanded to
threshing grain, sawmills, and land drainage. It was gradually taken over by coal based
energy after the Industrial Revolution which began in the 1820s.
2.2 Wind Turbines
Wind turbines are a natural extension of windmills. Wind turbines are used to
generate electricity rather provide direct energy for end use as wind mills commonly did
and do, such as water pumping and grain grinding. The first wind turbine has been
credited to Charles Brush in Cleveland in 1888. Brush later joined forces with Edison to
form General Electric Company. His wind turbine had 144 blades and produced 12 kW.
Poul la Cour, a Dane, modified the design in 1999 after years of wind tunnel experiments.
Determining that the best design had fewer blades and a rapid rotation speed, la Cour’s
windmill had only four blades and achieved a far more efficient wind turbine. In 1891 la
Cour had also introduced the idea of using some type of battery to produce a constant
power supply from the inconstant wind; his first designs used hydrogen power, although
he later moved on to other chemicals.
Wind turbine use received a boost from the OPEC crisis of the early 1970s, when
high oil prices drove a search for alternative energy sources. Concerns about global
warming and the Kyoto Protocol in the 1990s re-ignited interest in wind power.
At present 1% of Canadian electricity is produced by wind power. This is rapidly
increase and could supply up to 5%, 3 TWh. These efforts have been plagued by NIMBY (Not In My Back Yard) problems, with local residents complaining about the noise and
unattractiveness of the turbines. Melancthan, near Shelburne, is an example of this.
Worldwide wind power is growing rapidly.
2.3 Wind Energy Basics
Basic information on wind energy and wind power technology, resources, and issues of
Wind Energy and Wind Power
Wind is a form of solar energy. Winds are caused by the uneven heating of the
atmosphere by the sun, the irregularities of the earth's surface, and rotation of the earth.
Wind flow patterns are modified by the earth's terrain, bodies of water, and vegetative
cover. This wind flow, or motion energy, when "harvested" by modern wind turbines,
can be used to generate electricity.
How Wind Power Is Generated
The terms "wind energy" or "wind power" describe the process by which the
wind is used to generate mechanical power or electricity. Wind turbines convert the
kinetic energy in the wind into mechanical power. This mechanical power can be used for
specific tasks (such as grinding grain or pumping water) or a gen