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Updated: October 11, 2013 16:07 IST
GREENSENSE

Power from terrace

SATHYA PRAKASH VARANASHI
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While there are wind turbine clusters with hundreds of them dotting the landscape, we are discussing here mainly the small-scale unit practical for typical urban public buildings.
The Hindu While there are wind turbine clusters with hundreds of them dotting the landscape, we are discussing here mainly the small-scale unit practical for typical urban public buildings.

A wind energy unit is a one-time investment. So, across years of operation, the cost per unit goes on reducing, making it a sustainable source of energy

If we think energy from wind mills is new technology, we are totally wrong. They existed in Babylonia 2,500 years ago, Persians tried them out 1,200 years ago and Europe in general has had windmills for over 700 years. Generally, the rotating blades were used to move simple mechanical parts for lifting water, pounding grains or extracting oil in mills. Wind power to move sail boats and later to explore the world by larger ships has been in vogue for thousands of years. During the 20 century, it caught up in the U.S. and rest of the world for more diverse applications.

While there are wind turbine clusters with hundreds of them dotting the landscape, we are discussing here mainly the small-scale unit practical for typical urban public buildings. They supply power for lights, TV, battery charging and such needs. With blade diameter ranging from 0.5 to 7.0 metres, and average wind speeds upwards of 2.5 metre per second, we can generate power in the range of 0.5 kW to 10 kW per hour.

For routine household needs, even smaller units with blade diameter less than 3 metres, generating up to 2 kW, can be considered. DC generators in the 12 to 24 volts range are adequate for household needs.

For such small scale, magnetic alternator-type generator serves the function. Also, horizontal axis devices deliver maximum coefficient of efficiency. These can be easily mounted atop any well-designed building. The legs of the tower cannot be directly placed on a slab, but preferably need RCC pillars or an inverted beam arrangement to transfer the load down.

Technically speaking, periodic records of wind speed across one year taken through anemometer is required to accurately assess the power generation. Altitude, air density, topography, speed, wind direction, trees, buildings and such others increase the air turbulence, reducing the power generation. Using scientific formulae based on density, velocity and wind sweep area, technical experts can advice on the installation of the turbine.

The choice of rotor depends upon the purpose of generation – slow running multiple blades are good enough for water pumps while the fast running ones with fewer blades, with wind blowing perpendicular to the blades, are required for electricity.

If the wind can create a drag and lift effect, it further boosts power generation. Of course, there will be the tail vane to rotate the blades in wind directions. Generally, the blades need to have aerodynamic design, good strength and light weight material. Accordingly, aluminium and fibre are preferred over steel.

India, on an average, has around 3 metres per second speed, making it a viable nation for tapping wind energy. Of course, this average has no meaning, for the spot speeds are important. Wind energy unit is a one-time investment, so across years of operation the cost per unit goes on reducing, making it a sustainable source of energy.

The writer is an architect working for eco-friendly designs and can be contacted at varanashi@gmail.com

To the consumer, no technical detail is of importance. All he would be
bothered about is,

1. What is the initial investment?
2. What maintenance charges will be incurred?
3. When will the costs incurred reach break-even. i.e. when will one
start getting returns on investment?
I doubt solar and wind are still not popular just because the cost/kW
is high and apart from being eco-friendly it does not actually yield
any returns on investment.

from:  Arun Karuppaswamy B
Posted on: Oct 12, 2013 at 12:03 IST

There needs a good marketing approach for these technologies.
People though are aware of the technological approach in a nascent
way, are not ready to shift considering the implementation
difficulties.
The aspect of wind speed monitoring needs upfront investment which
doesn't seem to make logical sense with people not being aware of the
potential in their area. If the distribution company comes out with a
wind speed map and approach, then people might show interest.
Also it should be bundled as a single package with offer for
maintenance for a long period which will make the package attractive.

from:  Ashok
Posted on: Oct 12, 2013 at 11:46 IST

Can I know the cost.

from:  Irshad
Posted on: Oct 12, 2013 at 11:35 IST

I cant imaging blades on terrace like dish antennas nowadays. wind has
to be captured through something that enhances beauty of the
building/bungalow

from:  Aayush
Posted on: Oct 12, 2013 at 06:44 IST

Which companies install rooftop windmills? What is the cost?

Thanks for a very useful article.

from:  swami
Posted on: Oct 12, 2013 at 01:53 IST

While the author has explained the wind mill, he has not mentioned other
electrical/electronics requirement. A cost comparison with solar and
diesel set would have been more educative. Lastly he has not mentioned
anything about the disadvantages and the annual or periodical
maintenance.

from:  SARANATHAN
Posted on: Oct 11, 2013 at 20:09 IST

There was a CSIR sponsored research project in our college ,PSG College
of Technology, Coimbatore ,1964 on wards handled by Mr G Shanmgham, then
Professor of Mechanical Engineering in our college..There was a windmill
atop the college building...but I do not know what happened to it
later..What I say is the tapping wind energy was on anvil of CSIR aound
50 years ago and in Indian tradition it faded away..

from:  S BHARGAVAN
Posted on: Oct 11, 2013 at 18:58 IST

It will be of great help if cost of installation is also mentioned in the articler. Also details about hybrid generating station harnessing both wind and solar can also be shared.

from:  karthik
Posted on: Oct 11, 2013 at 18:40 IST
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