(Image: Courtesy Hongkong HIWIN)
Ever played with a pinwheel? If yes, that was your very own windmill there. If not, do not fret. You can make one for yourself. Wind power can be harnessed for various applications other than a pinwheel. It can be used to generate electricity or for water pumping or to sail away some place using a hot air balloon or a sailing vessel on water. To make this possible we need machines called windmills. Windmills consist of vanes that sway with the wind, converting wind energy to rotational energy, like the one in the picture above. Rotational energy is kinetic energy which is then converted into electrical energy. The machine is called a wind turbine in this case, a windmill for power generation. They were used to grind grain and pump water. Solar wind power on the other hand is the power obtained from gases/charged particles from the sun flowing in outer space.
This section of the series will cover the very basic question of this series and it is:
What are winds and how are they formed?
Wind is basically a flow of air/gases. When the sun shines on our planet, it falls directly on the equator, well most part of it, that’s why it is so hot in there. The air at the equatorial region gains heat and rises up. This is because warmer air has lower density than colder air. You can easily test this in a kitchen. This is the reason exhaust fans are placed at the top side of the kitchen. Coming back to the warm air, as it rises, it leaves a void where it was before. This region of void is called ‘low pressure area’. The wind that is relatively colder than the warm air replaces this low pressure area. The cycle continues and you experience winds.
You can see a beautiful global wind map here. It is updated every few hours. Can you notice the Coriolis effect there? Due to the Coriolis effect, the winds in the northern hemisphere spin clockwise, while in the southern hemisphere they spin anti-clockwise. Quiet famous among the sailors is the Intertropical Convergence Zone (ITCZ). It is where the northeast and southeast trade winds come together. Trade winds are the winds on the equator. The Coriolis effect twists them into a certain direction. Check out the map of prevailing winds on Earth. You can see in the global wind map how wind patterns are more dominant over a certain areas. These are the areas where windmills are installed.
One can study aerodynamics (study of air/gases in motion), fluid mechanics (studies fluids and forces on them) and fluid dynamics (studies all kinds of fluid in motion).Wind engineering on the other hand takes all these fields plus meteorology and information systems to study the effect of winds on things around us.
Historical use of wind power:
Archaeologists have found windmills in China and Egypt dating as far back as 500 BC. The following is a snapshot of a watermill/windpump taken from Popular Science, Issue: Oct, 1933.
Windmills were also used as drainage mills for draining land that is below sea level. Animal power was then employed. The Dutch windmills of the Netherlands are known for this. For example, horse-mills. People also used wind power to propel ships & boats on the ocean. At the cusp of 1900s, experiments began on the wind turbines you see now. In between this period and the early watermills, the heat engine that ran on fossil fuels entered the spotlight. It was in 1941 that technological developments lead to the world’s first megawatt-size wind turbine started operating. It was called the Smith-Putnam wind turbine.
In Hindu mythology, there’s an interesting story about a deity called ‘Vayu’ – Lord of the winds. (Vayu translates into ‘air’ in English). His spiritual son, Hanuman, as a kid, mistakes sun for a fruit (a mango). Hanuman can fly. So he sets out to reach the sun, to grab a bite of him. At the same time, Rahu, a deity that causes eclipse is on a chase for the sun. It happens that Hanuman and Rahu clash each other. Rahu complains about the situation to the god of deities, Indra. Indra goes on and throws a thunderbolt (aka Vajra, a weapon) at Hanuman. Bam! Poor Hanuman falls back down to earth. On this, furious father Vayu takes away all the wind there is on the earth. People and animals start to collapse, plants start to wither away. All the deities then bless little Hanuman and revive him. Vayu returns wind to the planet as an act of forgiveness. Phew!
See you in the 2nd part of the series ! Got any questions? Ask away!