Wind energy development is picked up as a part of electricity generation in different parts of India. Although it was initiated a decade back, there is still enough scope for its improvement in this technology. The reality is that our life-style in the early twenty-first century requires huge energy and wind turbines are one of the least environmentally harmful ways of generating electricity. Of the installed capacity, wind turbines have a large share among the other grid connected renewable sources, close to 66.66%¹. Obviously wind turbines need to be built where the wind blows reliably and strongly. The society is certainly not willing to give up private cars, air conditioning, computers, television, refrigeration, and all the other energy consuming equipment of the modern life-style. Accordingly, we must build sustainable energy supply systems. Earlier works promoted wind energy in many ways [1] [2] . In our study we have worked on grid tied rooftop micro wind turbine. The major problem with such a system is synchronization largely due to wind variability. Due to this problem, the stability of available grid gets reduced. This can somehow be achieved by the output power control of the turbine. India is the fifth largest wind power producer in the world. As of March 2014, the installed capacity of wind power in India is 21136.3 MW [3] [4] , mainly spread across Tamil Nadu (7154 MW), Gujarat (3093 MW), Maharashtra (2976 MW), Karnataka (2113 MW) and Rajasthan (2355 MW). Wind power accounts for 8.5% of India’s total installed renewable power capacity, and it generates 1.6% of the country’s power. Still it is not very much popular at domestic level due to the high initial investment and other problems as discussed above. Our goal is to achieve stable power supply to the grid from wind source. To this issue, we suggest a new method of small external motor that will provide momentary impulse or external torque to the rotor through relay switch or voltage controller that helps to maintain the momentum of blades for sufficient time and provide stable power supply. In this method, the light weight external motor has been attached at the hub of the wind turbine and it works on the method of spring balance system. The motor aligns itself with the axis of rotation of blades when a mass of around 10 pounds is put to the groove attached to motor. This is done so as to not disturb the aerodynamics of the blades and the yaw system. The motor provides external torque to the rotor only during moderately low wind speeds, i.e., around 2.5 - 4 m/s. At other times, when the wind speed is self sufficient to produce stable power supply, the motor remains off-axis from the rotor and doesn’t interfere in its motion. This mechanism is currently mechanical but could be automated for better performance. The concept presented in this paper is implemented and tested.

In our method, we attached an external motor to the turbine rotor that provides sufficient external torque to the rotor to rotate at its rated rpm value when the wind speed is less than the rated speed so that the wind generator can generate a stabilized power supply.

We have addressed a few issues related to wind turbines and suggested solutions for the same. Hopefully our suggested method will yield into a product that would help changing the wind power scenario at domestic level. SNT-1 wind turbine installed on rooftop of our energy building―GERMI at PDPU campus (Figures 10-12)―is

specially designed for low wind speed regime and for the first time attempted and installed a grid tied rooftop micro wind turbine. Further improvement is needed to reach to a level to work on concrete proof. We need to test our suggested method’s usefulness to the society as well as to the industry. In this respect, more exhaustive experiments could be devised with data logging facilities. The wind braking and motor system will be upgraded and automated in near future for better results. A control system could also be attached which disconnects the generator to grid when the grid supply is off. During the monsoon season, when the wind velocity is fair enough, our method can be a real asset at least for rooftop wind turbines [14] . The only limitation being it will be commercially beneficial only when the wind speed ranges from 3 to 6 m/s.

We would like to thank all the GERMI staff for their full cooperation to execute this task. Full support provided by Dr. Sagar Agarvat, Scientist C, Solar Research Wing, GERMI is greatly acknowledged. His coordination and help is very much appreciated without which we could have not completed this work. Thanks are due to Mr. Manyam Telukuntla from UPES Dehradun, a summer intern student at GERMI for assisting in the experimental work. Mr. Ankur Bhatnagar, Mr. Dharmik Lay, Mr. Prashant Gopiyani, Mr. Nilesh Patel and Mrs. Sandhya Radhakrishnan have helped in many ways for successful completion of this project.