Wind energy has been harnessed by human beings for thousands of years for the purpose of sailing, lifting water, grinding grains, etc. From the start of the 20th century, wind power has been used to generate electricity with the help of windmills. Generally, windmills are tall structures, say 120m tall, with turbines located on top of it. At these heights, there is enough wind speed required for the blades in order to run turbines. This speed is known as cut-in speed which is generally 15kmph.
The problems with these mega sized windmills are-
- They can be installed only in those places where for most part of the year the available wind speed is more than the cut-in speed . These places are generally away from the cities. In cities there are more obstructions for wind.
- Even, if a suitable site is found, the wind turbine remains idle for the rest of the year as strong winds are available only for about 200 days in a year.
- These huge structures are to be transported to those sites. The site must have proper road accessibility.
- There must be grid connectivity available at the site in order to evacuate the generated power.
- These turbines tend to produce noise, thus might raise objections from the local people.
- Wind turbines cause bird deaths, thus disturbing ecology.
- The huge windmills are prone to accidents when the wind speed is very high during cyclones or tornadoes.
All these problems can be overcome by a new innovation known as ‘Arbre à Vent’ or ‘Wind Tree’ and ‘Aeroleaves’ developed by a French startup Newwind.’Wind Tree’ has been designed to look like a tree with branches and leaves. It is about 10m tall and has 72 micro wind turbines called ‘Aeroleaves’, thus biomimicing natural trees. The tree trunk and branches are made up of steel, whereas the leaves are 3D printed with plastic. They are easy to install and can be installed even in cities, where generally wind speed is low.
The ‘Aeroleaves’ are vertical axis wind turbines which are aerodynamically designed to rotate even at low wind speeds such as 7kmph. Urban winds are not very strong but they are turbulent. Thus they seem to be the best-suited wind power harnessing devices for urban areas. Moreover, they make less noise and work for more number of days in a particular area when compared to a conventional windmill. The highlight is that the power can be produced right at the place where it will be used, avoiding the transmission and distribution losses.
A ‘Wind tree’ has a rated capacity of about 3.1kW. According to the developers, it can power 15 street lamps of 50W or can meet 83% of the electricity needs of a French household excluding heating or run an electric car for 10,168 miles per year.
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The first prototype was installed on the streets of Paris in 2014 and since then the number of installations has gone up. The cost of the prototype was about $35,000, but would ultimately decrease when production cost decreases and technology develops. Alternatively, the ‘Aeroleaves’ alone can be used for smaller power applications. Generating about 2400kWh per year, one ‘Wind Tree’ can offset 3.2 tonnes of CO2 emission every year.
Check the wind tree in action !
Image Source: trueactivist.com