Wind is simply air in motion. It is caused by the sun’s uneven heating of the Earths surface: This happens when the Earth s surface which is made of different types of land and water, absorbs the sun s heat at different rates. The presence of clouds can also locally reduce the effectiveness of the sun’s rays.
During the day, the air above the land heats up faster than the air over water. The warm air over the land expands and rises up in the atmosphere, and the heavier, cooler air rushes in to take its place, creating winds. At night, the small-scale winds are reversed because the air is getting cool more rapidly over land than over water.
In the same way, the large scale atmospheric winds that circle the Earth are created because the land and sea near the earth’s equator is heated more by the sun than the land and sea near the North and South Poles.
The use of the wind as a prime mover ceased only in the 20th Century, the age when coal and conventional liquid fuels were expanding rapidly and electricity was being extended even to the most remote areas.
The oil crisis and the Ecological Movements at the beginning of the 1970s brought Aiolic energy to prominence again. From that time up to the present, there has been very rapid development which has been reinforced by the urgent need to protect and save the environment due to threat of world climate change. More and more people realized that the wind is a clean and inexhaustible source of energy and not at all “old fashioned”. After all, wind is called a “renewable energy source” and it will blow as long as the sun exists.
This article focuses on windmills for farming applications like water pumping or small electric generators, and contains guidelines on constructing windmills. However, this is not a complete construction manual.
Building a wind generator is not that difficult. You will need a shop with basic power and hand tools and, of course, dedication.
Large wind generators of 2,000 watts and up are a major projects needing very strong construction and exact calculations, but smaller ones up to 1,000 watts with 3-4 m diameter range can be built easily from scrapped car parts and be up and flying in a week. It is highly recommend that you make a smaller windmill before even thinking of building a large one.
The research on windmills derived many types of machines which can be separated into two major categories: windmills of vertical axle and windmills of horizontal axle.
author: Stefanos Sakellaridis, Agriculture Magazine, photo from flixya.com