A Study of Wind-Powered Turbine Generation
Chapter One
Preamble of the Study
Since ancient times, people have harnessed the winds and energy. Over 5,000 years ago, the ancient Egyptians used wind to sail ships on the Nile River. Later, people built wind mills to grind wheat and other grains. The earliest known wind mills were in Persia. These early wind mills looked like large paddle wheels. Centuries later, the basic design of the wind mills was improved. It was given a propeller type blade. The evolution has been slow but continuous, with two major phases. The first in which wind energy was directly use for mechanical work, as in windmills, sawmills, water lifting etc. and a second phase in which mechanical energy was changed into electrical energy.
CHAPTER TWO
CONSIDERATION FOR WIND POWERED GENERATOR
In the 1970s, oil shortage pushed the development of alternative energy source. In 1990s, the push came from a renewed concern for the environment in response to scientific studies indicating potential changes to the global climate if the use of fossils fuels continuous to increase. Wind is a clean fuel; wind farms produce no air or water pollution because no fuel is burnt.
Providing new cost effective advanced and innovative technologies valuation and performance metrics that will enhance environmental performance and greater efficiencies. The basic design concept for a wind powered outfit can be seen as in fig.
inside the wind
This section defines the various part and instrument found inside the wind turbine. Anemometer: This is an instrument which is used to measure the wind speed by rotating in the wind and generates a signal proportional to the wind speed and transmit wind speed data to the controller. Most of which are designed with cups mounted on shaft arms connected to a rotating vertical shaft.
Controller : The controller starts up the machine at wind speed at about 8 to 16 miles per hour (mph) and shuts off the machine at about 65mph. Turbines.
Cannot operate at wind speed above the rate of 65mph because their generators could overheat.
Generators : This is usually an off the shell induction generator that produces 60 cycle .C electricity.
Gear Box: Gear box connect low-speed shaft to the high-speed shaft from about 30 to 60 rotations per minute (rpm) to 1200 to 1500 rpm, the rotational speed required by most generators to produce electricity. This gear box is a costly and heavy part of the wind turbine.
Low-Speed Shaft : This is the connecting pipe between the rotor and the gear box. Rotor: This is made up of the blade and the hub. It is a portion of the wind turbine that collects energy from the wind and rotates about an axis (horizontally or vertically) at a rate determined by the wind speed and shape of the blade. The blade is attached to the hub, which in turn is attached to the main shaft.
Brake: A disc brake which can be applied mechanically, electrically or hydraulically to stop the rotor in emergencies is used.
Yaw Drive: This is an equipment that is used to keep the rotor facing into the wind as the wind direction changes. It is only found in the upwind turbine.
Yaw Motor: This powers the yaw driver.
High Speed Shaft: This drives the generator.
Wind Vane: This is an instrument that measures or decodes the wind direction and communicate with the yaw drive to channel the turbine rotor properly with respect to the wind.
Nacelle: This is the housing or casing which sits on-top of the tower and includes the gear box, low and high speed shafts, generator, controller and brakes. The rotor is being attached to it
Tower: This is being made of steel lattice and is very high because wind speed increase with height and taller towers enable turbines to capture more energy and generate more electricity.
BASIC PRINCIPLES OF WIND POWER GENERATION
Wind power is a measure of the energy available in the wind. It is a function of the cube (third power) of the wind speed, if the wind speed is doubled, power in the wind is increased by a factor of eight (i.e. 23) this relationship means that the small difference in wind speed leads to a large difference in power.
Wind speed is therefore defined as the rate at which airflow past a point above the earth’s surface.
The output of a wind turbine varies with the wind speed through the motor. The “rated wind speed” is the speed at which the “rated power” is
achieved. This corresponds to the point at which the conversion efficiency is near its maximum. In most system, the power output above the “rated wind speed” is mechanically or electrically maintained at a constant level allowing more stale system control.
The power output drops sharply at wind speed. This is better explained by the cubic power law, which states that the power available in the wind increases eight times from every doubling of the wind speed and decreases eight times for every halving of the wind speed.
In a particular wind site, the power output expected at the average wind speed can be determined by the power curve.
CHAPTER THREE
LITERATURE REVIEW
TYPE OF WIND MACHINE
There are two types of wind machine (turbines) used today. This classification is based on the direction of the rotating shaft (AXIS). Horizontal- axis wind machine Vertical – axis wind machine. The size of wind machine varies widely. Small turbines used to power a single home or business. This may have a capacity of 100 kilowatts. Some large commercial sized turbines may be up to 5 million watts or 5 watts. Large turbines are those that provide power to the electrical grid
HORIZONTAL – AXIS WIND TURBINE(HAWT)
Most wind machines being used today are the horizontal – axis type. Horizontal – axis wind have blades like airplane propellers. A typical horizontal wind machine stands as tall as 20 – story building and has three blades that span 20 feet across. The largest wind machines in the world have blades longer than a football field. Wind machines stand tall and wide to capture more wind.
The axis of rotation is parallel to the wind flow. Some very large turbine use a motor driven mechanism that turns the machine in response to wind directionn sensor mounted on the tower. A prime objective in wind turbine design is for the blade to have a relatively high lift-to-drag ratio. This ratio can be varied along the length of the blade to optimize the turbine’s energy output at various wind speeds.
CHAPTER FOUR
DESIGN SPECIFICATION FOR WIND TURBINE
TRENGTH CALCULATION FOR STRUCTURAL ANALYSIS& SAFETY
It is usually the common practice in Engineering field to have prior knowledge of the properties of the materials that will be used in a design so that the design could be carried out with the awareness of the materials properties. With such prior knowledge adequate provision could be made to compensate the inadequacies of the material available for use in design.
It is in the light of the above that the strength calculation of these materials must be done before and during the fabrication process. The most important test will be the strength of wood/aluminum airfoils under centrifugal load as flying broken pieces of airfoils are not welcomed especially in wind tunnel. The airfoils model can be fabricated using either solid woods or aluminum sheets with spar and rib.
Having a wind turbine test model as basic of my estimates and calculation these strength calculation/estimates can be sub-divided into.
different section as;
- Airfoil bending stress
- Bolt tension at Airfoil joint and washed pressure
- Support arm vibration and deflection
- Shaft bending stress and vibration
- Bearing size selection
- Pipe bending stress and vibration
CHAPTER FIVE
VIABILITY IN NIGERIA
Nigeria generates her electric power from two main systems the hydro and the thermal/gas turbines. For now there are three hydro-stations in the country. These are kanji, Jebba and Shiroro and for some reason two of the hydro – stations (Kainji and Jebba) are built in the same river “THE RIVER NIGER”. The rest of the stations are predominantly thermal/gas. These are Afam, Delta, Egbim, and Sapele etc
At present their capacities are shown as seen on table 1. Unfortunately the generated power is not yet adequate for the Nation’s Power Consumers. To worsen the situation there are lots of limitations in both transmission and distribution sectors. Such limitations are transformers, cable’s etc and they make it difficult for the power consumers to enjoy steady electricity supply thus most of the station and substation were built long time ago and needed to be up-graded in other to meet the challenges of the present day.
Most of the prospective consumers are, yet to be connected to the Nations Power Supply System. Many towns and villages have not been privilege to see electric poles and cable in their land, yet need electricity like others.
CHAPTER SIX
CONCLUSION
As the need to stabilize the nation’s energy resource and electricity demands, renewable energy comes into play and also at a time when customers across the country are facing electricity rate hikes due to supply shortage, wind power is an attractive option to consumers and business alike.
Wind energy works because it generates energy without fuel. While providing a reliable edge against rising energy cost. Wind energy works because the wind energy industry is a good steward of the environment and provides pollution-free, domestically generated electricity to support our economy.
Wind energy power generators provides electricity which can be used immediately at the point of production, used to supply isolated loads or supplied into the national grid to alleviate and support other forms of electricity production and as well reduce the cost of electricity.
- To further tap this underutilized, strategic resource, a balance energy policy should.
- Remove current barriers to wind energy development in electric markets rules.
- Support a long-term extension of the wind energy production tax credit to encourage investment in the industry and
- Fully tap wind energy potentials for domestic electricity production through improved access and upgrade the existing transmission lines and creation of new ones.
- Wind energy will work effectively in Nigeria’s economy, environment and energy security and must be part of the nation’s energy policy if we are to achieve our country’s full energy potentials.
REFERENCES
- S.P.D.L Freeman, D.L Elliott and RL George WindEnergy Atlas Pacific Norwest Laboratory, Richland Washington 1981.
- Anderson S.P.D, Pacific Norwest
- Baker R.W and E.W Hewson Network Wind Power Over thePacific Norwest Bonneville Power Administration, Portland 1981.
- Baker R.N andW. Hewson Network Wind Power Over the Pacific Norwest.
- Black and Veatch Power Plant EngineeringChapman and Hall New Yoke 1996.
- Black and Veatch, Power Plant
- Eldridge F. Wind Machines Van Nostrand Reinhold
- Eldridge F. Wine