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AIRBORNE WINDMILL
INTRODUCTION
Today more than 80 per cent of the world’s electric power production comes from fossil-fuelled plants. As the demand for electricity is forecasted to increase, there is an urgent need to find new methods to extract electric energy from renewable sources. Renewable electric energy supply is today one of the highest priorities in many parts of the world.
The Kyoto declaration 1997 and the last agreement at Marrakech 2002 are significant proof of this. Both the EU and the US have set their targets on future greenhouse emissions. Hence Renewable Energy Sources are one of future energy producers. Renewable energy is energy generated from natural resources such as sunlight, wind, rain, tides and geothermal heat, which are renewable(naturally replenished).
In 2006, about 18% of global final energy consumption came from renewable, with 13% coming from traditional biomass, which is mainly used for heating, and 3% from hydroelectricity. New renewable (small hydro, modern biomass, wind, solar, geothermal, and biofuels) accounted for another 2.4% and are growing very rapidly. The share of renewable in electricity generation is around 18%, with 15% of global electricity coming from hydroelectricity and 3.4% from new renewable.
Wind is a form of solar energy. Winds are caused by the uneven heating of the atmosphere by the sun, the irregularities of the earth's surface, and rotation of the earth. Wind flow patterns are modified by the earth's terrain, bodies of water, and vegetation. Humans use this wind flow, or motion energy, for many purposes: sailing, flying a kite, and even generating electricity.
Wind power is growing at the rate of 30% annually, with a worldwide installed capacity of 157,900 megawatts (MW) in 2009, and is widely used in Europe, Asia, and the United States. The terms wind energy or wind power describes the process by which the wind is used to generate mechanical power or electricity. Wind turbines convert the kinetic energy in the wind into mechanical power. This mechanical power can be used for specific tasks (such as grinding grain or pumping water) or a generator can convert this mechanical power into electricity.
But the Conventional Wind Turbines have the disadvantage of being stuck on the ground, consequently dependent on the wind passing through their location and they are not economical. Thus these factors make it unreliable for power production. Hence a new innovative way of delivering clean renewable energy to the world has evolved i.e.
Airborne Wind Turbine is a new design concept for a wind turbine that is floating in the air without a tower. Airborne Wind Turbine was designed and developed by Magenn Power, which is an Ontario based company. It is also called as M.A.R.S (Magenn Air Rotor System).
Airborne Wind Turbines have distinct advantages over existing Conventional Wind Turbines and Diesel Generating Systems including: global deployment, lower costs, better operational performance, and greater environmental advantages.
Hence the new kind wind turbine would be useful in fulfilling the future energy demands with zero emissions.
"There is enough energy in high altitude winds to power civilization 100 times over; and sooner or later, we're going to learn to tap into the power of winds and use it to run civilization." Says Ken Caldeira, Professor of Global Ecology at the Carnegie Institution for Science.
TECHNOLOGY
2.1. Working:
The Airborne wind Turbine is lighter-than-air tethered device that rotates about a horizontal axis in response to wind, efficiently generating clean renewable electrical energy at a lower cost than all competing systems. When wind rotates the turbine's blades, which in turn cause an attached generator to also spin. The generator then converts that moving energy of the wind into electricity using electromagnetic induction. The blades of the MARS turbine are actually part of the three-dimensional blimp itself. The blades catch the wind, causing the entire blimp to spin around. After the generator converts that movement into electricity, it's transferred down the turbine's long tether.
How the lift is created?
The lift for the airborne turbine is created due to two reasons. Primarily it’s due to buoyant lift i.e. due to helium present in the turbine which is lighter than the air. The amount of helium present in the airship decides the altitude of operation. The helium provides at least twice the positive lift versus the overall weight of the MARS unit. The secondary lift is due to aerodynamic effect or MAGNUS EFFECT. Magnus Effect was discovered in the mid 1800, which create lift when a spherical or cylindrical object is spun while moving in a fluid. A dimpled golf ball, hit properly, has a back spin that causes it to lift in flight. A baseball curve ball pitch uses the Magnus effect. Basically, a back spin causes a low pressure region to form above the object and high pressure to form below, resulting in lift. A large object like the Magenn Air Rotor creates substantial lift, so much so that the device should actually work in a wind, without using a lifting gas.
2.3. Components in Airborne Wind Turbine:
The components in Magenn Air Rotary System are:
1) Bladder:
The bag filled with any gas is called bladder, here the airship is filled with inert gas which is non-flammable i.e. Helium. Helium is the second most abundant element in the universe. Helium provides extra lift and will keep MARS at altitude in very low winds or calm air. It is also plentiful, inexpensive and environmentally safe. Helium's inert quality over other lifting gases makes it very acceptable. MARS 10kW unit will require slightly over 32,000 cubic feet of helium. The price of Helium varies from country to country. It is roughly $0.30 cents per cubic foot. But the helium gas leaks out at a rate of 0.5% per month or 6% per year; therefore the MARS units will have to be topped up with Helium every 4 to 6 months. The bladder is made up of Vectran fabric which has high strength, low elongation properties. The bladder is equipped with a radar reflective material that will present an echo to surface radar operating in the 200 MHz to 2700 MHz frequency range. This is useful for ATC (Air Traffic Controller) to identify the Magenn wind rotor, if they interfere the flight path