INTRODUCTION

Energy extraction from wind is one of the oldest energy harvesting technologies that is being used for centuries. Winds are caused by the rotation of the earth and the heating of the atmosphere by the sun. The total annual kinetic energy of air movement in the atmosphere is estimated to be about 3 x 105 kWh or about 0.2% of the solar energy reaching the earth. The maximum technically usable potential is estimated to be theoretically 30 trillion kWh per year, or about 35% of current world total energy consumption [1]. The power in the wind blowing at 25.6 km/h is about 200 W/m2 of the area swept by the windmill. Approximately 35% of this power can be captured by the windmill and converted to electricity. The kinetic energy of the air can be transformed to mechanical and then to electrical form of energy using fans, gears, turbine and generator system. Windmills are the modern world electricity harvesting technologies which accounts for more than 2 GW installed capacity worldwide [2]. Electricity generation from wind is directly proportional to the air density, swept area of blades and cube of the wind velocity. Since the wind velocity is more tentative, hence optimizing the blade area, maximum energy can be extracted for particular wind speed at given place [3].

                                                              (1)
where,             P – Wind power                                       – Air mass density
A – Swept area (area of wind flow)       V – Wind velocity

The annual wind speed at a location is useful as an initial indicator of the value of the wind resource. The relationships between the annual mean wind speed and the potential value of the wind energy resource are listed below;

Uttara Kannada district located in the west coast and in Western Ghats region of Karnataka state is blessed with good wind potential. Harnessing of wind energy could play a prominent role in meeting the energy demand in the region since electricity supply is unreliable in most of the times. Wind energy potential in the district could meet the regional electricity demand through wind energy conversion system (WECS) avoiding plenteous greenhouse gas (GHG) emission and fossil fuel. It can be harnessed locally in a decentralized manner for applications in rural areas and remote areas such as water pumping for agriculture and plantations. Wind driven electric generators could be utilized as an independent power source and for purposes of augmenting the electricity supply from grids. In coastal densely populated taluks like Karwar, Kumta and Bhatkal in Uttara Kannada District, decentralized production of electricity would help local industries, especially seasonal agro processing industries like cashew, etc. WECS can be hybridized with solar, biomass and any other available local energy resource to provide cent percent reliable power since wind flow is maximum during monsoon when solar insolation and dry biomass availability is lesser [4].

Wind resource assessment: Wind resource assessment is the primary step towards understanding the local wind dynamics of a region. Wind flow developed due to the differential heating of earth is modified by its rotation and further influenced by local topography. This results in annual (year to year), seasonal, synoptic (passing weather), diurnal (day and night) and turbulent (second to second) changes in wind pattern [5]. Increased heat energy generated due to industries and escalating population in urban areas result in heat islands which affects the wind flow as well.