CHAPTER – 1: INTRODUCTIONIn recent days, mobile phones have become an omnipresent personal electronic device in people’s daily lives. In our current gadget-centric culture, one limiting factor for mobile devices is the capacity of the batteries that power them, and while we haven’t seen any massive improvements in battery technology which would help us to go for days without charging. However, the difficulty to charge the phone battery which is commonly due to the power supply problem has not yet been resolved satisfactorily.
To meet the energy crisis, new renewable and sustainable energy source technologies are being developed in the world. A genuine way of converting renewable energy into electrical energy is one of the most of environment friendly and effective way of charging one’s mobile phones. There are several resources of renewable energy such as solar, wind, wave, geothermal and biomass. The wind power is among the best candidates due to its wide availability. Money can also be saved and air pollution can be reduced by using renewable energy sources such as wind power.
1.1 Target – DomainThe main target domain of people that can benefit directly from this project are discussed below- Adventurers can use it for charging mobile phones, emergency lights where power supply is not easily available at high altitudes. This project has the potential to charge powerful devices like laptops. Portable wind turbine can be used in divider on the highways as they can power up display boards provided a powerful back-up is present; the turbine blades will be rotating due to the wind draft produced by the fast-moving vehicles.
Can be used on boats when sailing, the wind speed is thus sufficient to make the blades rotate at suitable speed for charging.1.2 Overview of Technical AreasThere are two primary physical principles by which energy can be extracted from the wind; these are through the creation of either lift or drag force (or through a combination of the two). The difference between drag and lift is illustrated by the difference between using a spinnaker sail, which fills like a parachute and pulls a sailing boat with the wind, and a Bermuda rig, the familiar triangular sail which deflects with wind and allows a sailing boat to travel across the wind or slightly into the wind. Drag forces provide the most obvious means of propulsion, these being the forces felt by a person (or object) exposed to the wind.Lift forces are the most efficient means of propulsion but being subtler than drag forces are not so well understood.The basic features that characterize lift and drag are: Drag is in the direction of air flow. Lift is perpendicular to the direction of air flow. Generation of lift always causes a certain amount of drag to be developed. With a good aero foil, the lift produced can be more than thirty times greater than the drag. Lift devices are generally more efficient than drag devices.1.3 The Basic Wind Power TheoryThe wind systems that exist over the earth’s surface are a result of variations in air pressure. These are in turn due to the variations in solar heating. Warm air rises and cooler air rushes in to take its place. Wind is merely the movement of air from one place to another. There are global wind patterns related to large scale solar heating of different regions of the earth’s surface and seasonal variations in solar incidence. There are also localized wind patterns due the effects of temperature differences between land and seas, or mountains and valleys. Wind speed data can be obtained from wind maps or from the meteorology office.Unfortunately, the general availability and reliability of wind speed data is extremely poor in many regions of the world. However, significant areas of the world have mean wind speeds of above 3m/s which make the use of wind pumps an economically attractive option. It is important to obtain accurate wind speed data for the site in mind before any decision can be made as to its suitability. The power generated depends on- The area of windmill being swept by the wind The cube of the wind speed The air density – which varies with altitude The formula used for calculating the power in the wind is shown below_Pw=1/2 AV 3 Equation No.1.1Where, Pw is power in watts available in the wind (W) is the air density in kilograms per cubic meter (kg/m3)A is the swept rotor area in square meters (m2) V is the wind speed in meters per second (m/s)The fact that the power is proportional to the cube of the wind speed is very significant. This can be demonstrated by pointing out that if the wind speed doubles then the power in the wind increases by a factor of eight! It is therefore worthwhile finding a site which has a relatively high mean wind speed.1.4 Wind into WattsAlthough the power equation above gives us the power in the wind, the actual power that we can extract from the wind is significantly less than this figure suggests. The actual power will depend on several factors, such as the type of machine and rotor used, the sophistication of blade design, friction losses, the losses in the pump or other equipment connected to the wind machine, and there are also physical limits to the amount of power which can be extracted realistically from the wind. It can be shown theoretically that any windmill can only possibly extract a maximum of 59.3% of the power from the wind (this is known as the Betz limit). In reality, for a wind pump, this figure is usually around 30% to 40% and for a large electricity producing turbine around 45% maximum. So, modifying the formula for ћPower in the windџ we can say that the power that is produced by the wind machine can be given by_Pw= 1/2 Cp AV 3 Equation No.1.2Where, Pw is power (in watts) available from the machineCp is the coefficient of performance of the wind machine.In recent years, wind energy has become one of the most economical renewable energy technologies. Today, electricity generating wind turbines employ proven and tested technology, and provide a secure and sustainable energy supply. At good, windy sites, wind energy can already successfully compete with conventional energy production. Many countries have considerable wind resources, which are still untapped.A wind turbine is a device that converts kinetic energy from the wind into electrical power. A wind turbine used for charging batteries may be referred to as a wind charger. Wind turbine can be separated in to two basics types determined by which way the turbine spins. Wind turbines that rotate around a horizontal axis are more common, while vertical axis wind turbine is less frequently used.1.5 Vertical Axis Wind TurbineFig- 1.1 Vertical axis turbineVertical Axis Wind Turbines are designed to be economical and practical, as well as quiet and efficient. They are great for use in residential areas. Vertical-axis wind turbines (VAWTs) are a type of wind turbine where the main rotor shaft is set transverse to the wind (but not necessarily vertically) while the main components are located at the base of the turbine. This arrangement allows the generator and gearbox to be located close to the ground, facilitating service and repair. VAWTs do not need to be pointed into the wind, which removes the need for wind-sensing and orientation mechanisms.A VAWT tipped sideways, with the axis perpendicular to the wind streamlines, functions similarly. A more general term that includes this option is “transverse axis wind turbine” or “crossflow wind turbine.1.6 Types Of Blades For Vertical Axis Wind Turbines (a) Savonius rotor (b) Darrieus rotor (c) H-Darrieus rotor (d) Rotor Darrieus HelicoidalFig- 1.2 Types of Blade1.7 Overview of Choosing Gorlov Rotor Ease of construction Minimal maintenance Gorlov turbine is always facing into the wind, no matter what direction the wind is blowing. The Gorlov turbine can be operated at lower elevations from the ground. It is not greatly affected by turbulence. The Gorlov turbine also turns at relatively low speeds and does not stick out very far. These two things make the design less dangerous to birds, wildlife, and children than a lift turbine.1.8 Horizontal Axis Wind TurbineFig- 1.3 Horizontal axis wind turbineHorizontal-axis wind turbines (HAWT) have the main rotor shaft and electrical generator at the top of a tower and must be pointed into the wind. Small turbines are pointed by a simple wind vane, while large turbines generally use a wind sensor coupled with a servo motor. Most have a gearbox, which turns the slow rotation of the blades into a quicker rotation that is more suitable to drive an electrical generator.In high winds, the blades can also be allowed to bend which reduces their swept area and thus their wind resistance. In upwind designs, turbine blades must be made stiff to prevent the blades from being pushed into the tower by high winds.1.9 Advantages of VAWT Over HAWT They are mounted lower to the ground making it easy for maintenance if needed. They start creating electricity at speeds of only 6 mph. They may be able to be built at locations where taller structures, such as the horizontal type, can’t be. Higher power utilization– 20% higher than HAWT. Lower noise level–only 27- 37 dB, suitable for your living condition. Safer operation spins at slower speeds than horizontal turbines, decreasing the risk of injuring birds and also decreasing noise level. Simpler installation and maintenance. Not affected by orientation variation. Wind energy system avoids fuel provision and transport. On a small scale, up to a few kilowatt systems is less costly. On a large-scale cost can be competitive conventional electricity and lower costs could be achieved by mass production. Produces less noise – low speed means less noise.