Wind power is the conversion of wind energy into a useful form of energy, such as electricity, using wind turbines. Wind energy is a form of solar energy. About 1% to 2% of the energy coming from the sun is converted into wind energy. Generation of air currents is a direct effect of the combination of two phenomena: circulation of hot air and Earth rotation.
Wind power comes under the heading of Renewable energy. Other renewable sources of energy include Biofuel, Biomass, Geothermal, Hydropower, Solar Energy, Tidal power and Wave power.
Analysis
The energy consumed to manufacture and transport the materials used to build a wind power plant is equal to the new energy produced by the plant within a few months of operation.
The five countries with the highest installed wind power capacity in Megawatts are (2008):
1. USA 25000 +
2. Germany 24000 +
3. Spain 16500 +
4. China 12000 +
5. India 9600 +
But if we look at how much a country’s electrical energy needs are met by Wind Power, it shows a different picture (2008):
1. Denmark 19.1%
2. Portugal 11.3%
3. Spain 11.1%
4. Germany 7.0%
5. Rep of Ireland 7.0%
To put it in perspective, Wind Power only meets 1.3% of USA electrical needs. The potential of wind power on land and near-shore is calculated to be 72 Terawatts, equivalent to 54 billion tons of oil equivalent per year, or over five times the world’s current energy use in all forms.
1. Manufacturers of Large Wind Turbines
General Electrics and Clipper Windpower of USA; Enercon, Siemens, Nordex, REpower and Fuhrlaender of Germany; Darwind, Lagerwey of Netherlands; Gamesa of Spain; Vestas of Denmark; Mitsubishi of Japan and Suzlon of India are some of the leading manufacturers in the world.
2. Largest Wind Turbines
Clipper Windpower of USA just clipped the record held by Enercon of Germany by building the largest wind turbine that can generate 7.5 megawatts. It stands at 100m (328 ft) tall and has a rotor diameter of 150 m (492 ft).
Enercon E-126 which is already up and running has a 7 megawatts capacity. Just one E-126 turbine is generating enough to power 5000 households of four in Europe.
The race continues and wind turbines with generating capacity of 10+ megawatts are already on the drawing boards.
3. Technicals
WIND POWER can be divided into three parts:
A. Wind
B. Wind turbine
C. Transmission
A. Wind
Measurement of wind is the most important aspect of wind energy. Wind measurements are made by an instrument called anemometer. Wind measurements are made over months and a sometimes year before a site is chosen for a wind farm. Meteorological department is usually in charge of collecting the data. Typical sensors include, but are not limited to: sonic anemometers, 3-cup and propeller anemometers, wind vanes, temperature sensors (air, water, equipment, and product), solar radiation, electrical current, resistance, power, and voltage.
Because so much power is generated by higher wind speed, much of the energy comes in short bursts. The consequence is that wind energy from a particular turbine or wind farm does not have as consistent an output as fuel-fired power plants; utilities that use wind power rely on other sources of energy generation for times when the wind is weak: thus wind power is primarily a fuel saver rather than a capacity saver.
For a wind farm, an average yearly minimum wind speed of 17-21 km/hr (11-13 mph) is a must. Wind speed between 7.8 – 8.6 meter/second is considered outstanding and above 8.6 m/s is considered superb.
B. Wind Turbine
The main components of wind turbine consist of the Tower, the rotor blades, Nacelle (cover housing) which in turn carries the rotor shafts, gears, electrical generator, heat exchanger and electrical instrume
i. Tower
The wind is more erratic close to the ground and it blows faster at altitudes. At night, surface winds usually subside while at higher altitudes, they remain more or less the same or even increase. By doubling the height of the tower increases the expected wind speed by 10% and the expected power by 34%. But doubling the height requires doubling the diameter of the tower, which leads to increased costs. Modern towers are made of pre-stressed concrete and or tubular steel segment. Lattice towers of welded steel are cheap but for aesthetic reasons have been replaced by tubular structures. The price of a tower is generally around 20% of the total cost. Tower heights have moved beyond 100m in the large turbines
ii. Turbine Rotor Blades
Wind turbine blades are most often fabricated by hand using multiple layers of fiberglass cloth. The traditional method is for the sheets to be cut to shape, laid down in a mold by hand, sprayed or rolled with resins, and finally cured.
The maximum blade-length of a turbine is limited by both the strength & stiffness of its material and labor cost. Most modern rotor blades on large wind turbines are made of glass fiber reinforced plastics, (GRP), i.e. glass fiber reinforced polyester or epoxy. Using carbon fiber or Kevlar as reinforcing material is being introduced, which will reduce the weight of the blade by 30% of more. Steel and aluminum alloys have problems of weight and metal fatigue respectively. They are currently only used for very small wind turbines.
The size of the turbine blade is very important. Tip speed ratio of wind turbines is the ratio between rotational speed of the tip of the blade and the actual velocity of the wind. If both the tip speed and wind speed is the same, the ratio is 1. The current big wind turbines are achieving ratios of 6 or 7. The largest blade size is approaching 200 ft in length.
4. Transmission
One of the challenges of wind power is connecting the erratic power production of wind turbine to the national grid. A wind farm can be up and running within a year while transmission lines can take 4-5 years to construct. Managing over production times with under production times is a challenge. Grid stability is very important and it raises challenges when a system has huge fluctuations in production.
5. Advantages of Wind Energy
Wind energy is one of the cleanest sources of renewable energy. No hazardous waste, no vapor/emissions and minimal environmental impact. Furthermore, the ground underneath the wind turbine can be used for agriculture, grazing and other uses.
Wind is available all across the globe and every country has the potential to produce wind energy. Its technology is readily available and multiple countries are constructing them under license which lessens reliance on a select few providers. It is also not a protected technology like Nuclear.
6. Disadvantages
Wind power is intermittent power source. It is a non-dispatchable source of energy which means that it cannot be turned on or off on demand because wind cannot be controlled by operators like gas, oil or hydropower can be. Grids must be able to quickly compensate for sudden loss of power production by either creating large scale storage capacity or depending on widely dispersed (geographically) wind farms.
Usually electrical needs are highest during working hours, is also the time the winds are usually at their lowest speeds. Similarly the wind is slower during summers when electricity needs are highest for the year. So there can be discrepancy between need and availability.
Some of the highest quality wind resources are located in far off & inhospitable areas. The cost of construction and maintenance of large wind turbines in those areas, and the distance of transmission to the central grid can become costly.
Wind turbines in inhabited areas can be noisy but newer technology is minimizing the noise production and many new turbines are less noisy than many ordinary vehicles or machines at work.
The impact on birds was a concern but studies show that wind turbines kill 20 times fewer birds per unit of energy compared to fossil fuel power plants.
7. Cost of Wind Turbine
There are many factors contributing to the cost and productivity of a wind plant. For instance, the power a wind turbine can generate is a function of the cube of the average wind speed at its site, which means that small differences in wind speed mean large differences in productivity and electricity cost. Additionally, the swept area of a turbine rotor is a function of the square of the blade length (the radius of the rotor’s swept area). A modest increase in blade length boosts energy capture and cost-effectiveness. Financing methods can make a major difference in project economics as well. Securing significant investment capital or joint ownership of a project can cut costs significantly.
On average, wind power development costs around $1 million per megawatt (MW) of generating capacity installed but coming down fast. To take advantage of economies of scale, wind power facilities should be in excess of 20 MW.
To date, wind energy is the most cost competitive renewable energy option on the market. In fact, wind energy’s cost has declined so much that it rivals many traditional power generation technologies. However, utilities will tend to purchase power from what they consider to be the cheapest and most reliable technology. In most cases today, that is natural gas.
8. Wind Energy in Pakistan
Pakistan government set up The Alternative Energy Development Board (AEDB) in 2003 to act as the central national body on the subject of renewable energy in Pakistan.
In addition, United Nations through their Development Program UNDP created Sustainable Development of Commercial Scale Wind Power Generation Project referred to as Wind Energy Project (WEP). They implemented this program in Pakistan in 2004 through AEDB and it was funded by Global Environment Facility (GEF). It is called UNDP/GEF WEP Pakistan. The main goal was to create awareness in the government, business and academic circles, strengthen existing renewable energy policies and create new opportunities for wind power in Pakistan.
For wind farming, feasibility studies were carried out by the meteorological department of Pakistan with help from the firm National Renewable Energy Laboratories (USA) under USAID assistance program. The data has been analyzed by AEDB.
A large corridor of wind-swept area was identified in district Thatta, the southernmost district of Sindh. The wind corridor is 60 km wide between the cities of Gharo (north east of Karachi, on N5 highway) and old port of Keti Bandar close to where Indus River joins the Arabian Sea. And the corridor extends 180 km upwards to Hyderabad. AEDB believes that this corridor has the exploitable potential of 50,000 MW of electricity generation through wind energy alone. The whole coaster belt of Pakistan is considered very feasible for wind energy. Other very promising area of wind source is the district of Swat. Due to the current political turmoil, the development of wind farms has been put on hold in that area. AEDB also estimates that more than 5000 villages can be electrified through wind energy in Sindh, Balochistan and Northern areas.
Major wind resource areas in Pakistan [1]
Southeastern Pakistan especially
- Hyderabad to Gharo region in southern Indus Valley
- Coastal areas south of Karachi
- Hills and ridges between Karachi and Hyderabad
Northern Indus Valley especially
- Hills and ridges in northern Punjab
- Ridges and wind corridors near Mardan and Islamabad
Southwestern Pakistan especially
- Near Nokkundi and hills and ridges in the Chagai area
- Makran area hills and ridges
Central Pakistan especially
- Wind corridors and ridges near Quetta
- Hills near Gendari
Elevated mountain summits and ridge crests especially in northern Pakistan
German company Fuhrlaender, Access Energy of USA and AEDB of Pakistan signed an agreement to manufacture wind turbines in Pakistan and produce 1000 MW of electricity at the Gharo Wind Power Plant. It was the first such commercially viable project in Pakistan. The project is under way.
A wind farm of 300 MW being established by Turkish firm Zorlu Enerji Group is situated in the city of Jhimpir (situated by Lake Kalri – between Hyderabad in the north and Thatta in the south). Its first phase of 6 MW was officially inaugurated by the Prime Minister on April 19th, 2009. The next phase will increase the capacity to 50 MW in 2010 and finally 300 MW in the future.
Another Wind Power project is the New Park Energy located near Port Qasim. AEDB selected General Electric to provide its 1.5 MW wind turbines for its phase I construction. Phase I was completed in 2007. Planned total power is in the region of 1000 MW.
More land has been allocated to investors in the areas of Bhanbore and Kuttikun (Sindh). Pakistan government has a short term goal of developing 700 MW of wind energy by 2010. And by 2020 reach a target of 3730 MW through wind energy. Given the population explosion and demand by people and industry, this projected development is falling far short of the available potential.
To deal with the current and future energy requirements of Pakistan, the government will need to give strong backing to renewable energy sources and invests heavily in acquiring the technology, development of wind turbine industry and construction of large scale wind farms to overcome the shortage of energy. When infrastructure is in place, wind farms can be constructed within a few months to less than two years compared to other renewable and non-renewable plants that can take number of years or decades to build.
[1] NREL: National Renewable Energy Laboratory- USA
http://www.nrel.gov/applying_technologies/pakistan/wind/pdfs/afg_pak_wind_june07.pdf
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