What is the image that pops into your mind when you hear the word ‘windmill’? Hilltops where the wind blows hard, long shafts of the windmill fitted with horizontal blades rotating vigorously in the wind? As energy crisis has hit a high and the world looks to wind as a potential source of renewable energy, a new type of efficient windmill design is slowly gaining attention- vertical axis windmills (VAWM).
This is the very basis of a project set up by students of the Bhavan’s Adarsha Vidyalaya, Kakkanad. This project qualified for the state-level finals of the National Childrens’ Science Congress, to be held in Thiruvananthapuram on November 12 and 13. With a total of 161 marks out of 200, the team stands first among the five teams in the senior category that qualified for the finals from the Ernakulam district. The teams members are Sahla Sathar, Jithu Vijayakumar, M V Viswajith, Rohan Mathew George and Aiswarya Martin.
This project aims in the development of a ‘Vertical Axis Windmill with Inverter’ (VAWMI). The present world scenario calls for sustainable energy tapping for meeting energy demand. Solar, wind, and bio-energy are three forms of energy that can be used in residential buildings.
Solar energy and bio-energy have gone a long way in the extraction of power but so far, no proper method has been devised for tapping of wind energy for residential applications. This is where this project comes into the picture, says Mary Sorna Rani, teacher in charge of the project. This project addresses the development of Vertical Axis Wind Mill with inverter for tapping of wind energy on the roof tops or balconies of our own homes.
In July this year, the local media was filled with news of the controversial horizontal axis windmill installed by the Greater Cochin Development Authority (GCDA) at the Marine Drive in Kochi, which fell off within hours of its first installation. Well, this disastrous incident inspired Mary and her students to come up with this project idea. “In a state like Kerala, which has a large coastline, we thought this is a good idea to help tap the energy of the strong winds in coastal areas,” states Mary.
This project is a demonstration of a VAWMI made out of economic materials like PVC pipe and wood. The blades of this type of wind turbine are arranged vertically, unlike common horizontal axis windmills that we usually see. Wind moving around the vertical-axis turbines speeds up and the vertical arrangement of the blades allows the turbines to effectively catch that wind, speed up, and generate more power, explains the team.
This particular arrangement of the vanes makes it possible to pack more turbines onto a piece of land. The advantages of VAWMI as compared to Horizontal Axis wind mill are high efficiency, low noise, better response to lower wind speeds and easy maintenance, says Sahla Sathar, leader of the team.
In this working model set up by the team, the blades or vanes are made of plastic pipes coupled to a vertical shaft mounted on bearings.
The blade rotates due to wind force and rotates the shaft. The shaft is provided with a pulley. With a belt drive, the power is transferred to a smaller pulley whose speed is 10 times more than that of the pulley in the shaft. The smaller pulley is coupled to a generator which produces electrical energy which is fed to an inverter. This design satisfies the 40 per cent of power requirement of residential buildings, says Mary.
So, now let us look at how energy conversion takes place in this windmill project. The blades capture the kinetic energy of the wind and generate mechanical energy which rotates the vanes. This is finally converted to electrical energy, using a DC generator. This electrical energy is converted from DC to AC using an inverter.
Explaining the design of this special design of windmills, the students say, the purpose of the shaft is to transmit the wind rotation from the vanes, whereas the ball bearing helps in friction-less transmission of wind power from the shaft. The shaft is coupled directly to the DC generator which rotates with the same speed and converts mechanical energy to electrical energy.
The students and Mary have gone a long way in testing their windmill project to see how it works in real-time situations. They first tested this vertical windmill on the Cherai beach. After the test at Cherai beach, students improvised the project with certain structural modifications.
Later, this little prototype was transported all the way to the wind catchment areas of Pollachi in Tamil Nadu. Mary who hails from Tamil Nadu had observed that the horizontal axis windmills set up there were mostly dysfunctional. And so, she and Sahla travelled with the project to Pollachi. It was observed that the wind speed was insufficient to rotate the wind mills there but VAWM operated efficiently producing a voltage of 550 mV.
“We felt really happy. We had gone there to compare our project with the existing windmills. It felt all the more fulfilling when we realised that our project was actually working and producing real results,” says an excited Sahla.
“We also discussed our project with the KSEB officials in Kochi recently. They were very encouraging and suggested tips to improve it. P Keshavadas, deputy chief engineer, also said that he would recommend this project for the Startup village here,” says Mary.