CEE Oct-Dec 2012

available to facilitate a selection of the best strains. To solve this problem scientists from across the country, belonging to a consortium of nine laboratories, are working on an ambitious project called the 'New Millennium India Technology Leadership Initiative' (NMITLI), to develop a viable and scalable process of producing biofuel from microalgae, undertaken by the Council of Scientific and Industrial Research(CSIR), New Delhi. Courtesy: Renewable EnergyAkshay Urja, June 2012, Pp14-17. The authors are Prof. and Head and Research Scholar, Department ofPharmaceutical Technology; National Institute of Pharmaceutical Education and Research Punjab, respectively. E-mail: ucbanerjee@mper.ac.in ' - •. · . ..,. -· .f'": · Wind ' ·' ' Towers play a critical role in the functioning of a wind turbine project as they carry the weight of the nacelle and the rotor blades as well as help in absorbing the static loads caused due to varying wind speeds. Therefore, it becomes imperative for turbine manufacturers to develop towers that can cater to different types of wind density sites and support new, higher-capacity turbines. The wind turbine size has grown from a little under 1 MW a decade ago to 2 - 7 MW at present. The increasing average capacities of wind turbines require larger blades, which necessitates larger tower dimensions, especially height. Tower manufacturers across the world are exploring new and innovative construction techniques to enable the production of more efficient turbines. Guyed towers: The most economical/least expensive tower type is guyed towers. These have a steel pole with a height of 9 - 30 metres. These towers have three to four guy wires that connect the top of the tower to anchors placed on the ground. These wires are made of steel and provide support to the tower. A variant of the guyed tower, guyed tilt-up towers, are also available. These have a pivot joint at their base that facilitate tilting and movement of the turbine for it maintenance. Due to their low costs, these tower types are suitable for small, residential-scale turbines, especially in countries like India that are yet to tap the off-grid wind segment. However, these towers have high requirements as the guy wires extend well beyond their base. Tubular towers: These are commonly used in large, commercial-scale turbines. These have a tube-like structure which is wider near the base and tapering at the top. Tubular towers usually have a hub height of 60 - 11 0 metres. However, in order to leverage stronger winds at a higher elevation, manufacturers are developing towers with a height of over 110 metres. Tubular towers consist of a built-in , ladder-type structure to enable easy access to the upper parts of the turbine for repair and maintenance works. An alternative to tubular towers is lattice towers, in which, several steel strips are crossed and joined together. These strips provide durability and structural support to the turbine, thereby enabling its use in high-wind sites. Steel is primarily used as the construction material for tubu lar and lattice towers, but manufacturers are also shifting towards the use of concrete given its higher cost effectiveness and structural strength. Floating towers: Floating wi nd towers used at offshore sites are a recent addition to tower designs. Coastal areas witness consistent and stronger winds due to the absence of any topographic or terrain obstructions, which ensures 36