Wind Power

Wind energy has been utilized by mankind for sailing, grinding, and other mechanical applications for centuries. In the recent past, wind energy has emerged as a viable renewable energy option wit increased application in water pumping, battery charging, and large power generation. It is environmentally benign and does not emit greenhouse gases (GHG).
Wind energy, the world's fastest growing energy source, is a clean and renewable source of energy that has been in use for centuries in Europe and more recently in the United States and other nations. Wind turbines, both large and small, produce electricity for utilities and homeowners and remote villages. In addition to the cleanliness of this energy source it is also perpetual. Unfortunately, wind power is very unreliable and its strength depends on local weather patters, temperature, time of year, and location. In addition to its unreliability, wind power equipment is also very expensive compared to other energy sources.

History

The first use of wind power was to sail ships in the Nile some 5000 years ago. The Europeans used it to grind grains and pump water in the 1700s and 1800s. The first windmill to generate electricity in the rural U.S.A. was installed in 1890. Today, large wind-power plants are competing with electric utilities in supplying economical clean power in many parts of the world.

Wind Power Generation

Generation of electricity has emerged as the most important application of wind energy world-wide. The concept is simple: flowing wind rotates the blades of a turbine, and causes electricity to be produced in generator unit. The blades and generator (housed in a unit called ‘nacelle’) are mounted at the top of a tower.

Technology
Wind turbines generally have three rotor blades, which rotate with wind flow and are coupled to a generator either directly or through a gear box. The rotor blades rotate around a horizontal hub connected to a generator, which is located inside the nacelle. The nacelle also houses other electrical components and the yaw mechanism, which turns the turbine so that it faces the wind. Sensors are used to monitor wind direction and the tower head is turned to line up with the wind. The power produced by the generator is controlled automatically as wind speeds vary. The rotor diameters vary from 30 metres (m) to about 90 m, whereas the towers on which the wind electric generators (WEGs) are mounted, range in height from 25 to 80 m. The power generated by wind turbines is conditioned properly so as to feed the local grid. The unit capacities of WEGs presently range from 225 kilowatt (kW) to 2 megawatt (MW), and they can operate in wind speeds ranging between 2.5 m/s (metres per second) and 25 m/s.
Wind speed data of potential locations is compiled for a period of one to two years, to identify suitable sites for the installation of WEGs. Thereafter, WEGs are installed on the sites with appropriate distances between them to ensure minimum disturbance to one another. After the identification of sites, wind turbines generally take two to three months for installation. The equipment is tested and certified by agencies to ensure that it conforms to the laid-down standards, specifications, and performance parameters. The machines are maintained by the respective manufacturers after installation.

Water-pumping windmill

A water-pumping windmill pumps water from wells, ponds, and bore wells for drinking, minor irrigation, salt farming, fish farming, etc. Available windmills are of two types, namely direct drive and gear type.
The most commonly used windmill has a horizontal axis rotor of 3–5.5 m diameter, with 12–24 blades mounted on the top of a 10–20 m high mild steel tower. The rotor is coupled with a reciprocating pump of 50–150 mm diameter through a connecting rod. Such windmills start lifting water when wind speed approaches 8–10 kilometres (km) per hour. Normally, a windmill is capable of pumping water in the range of 1000 to 8000 litres per hour, depending on the wind speed, the depth of water table, and the type of windmill. Windmills are capable of pumping water from depths of 60 m. Water-pumping windmills have an advantage in that no fuel is required for their operation, and thus they can be installed in remote windy areas where other conventional means of water pumping are not feasible.
However, water-pumping windmills have limitations too. They can be operated satisfactorily only in medium wind regimes (12–18 km per hour). Further, special care is needed at the time of site selection as the sites should be free from obstacles such as buildings and trees in the surrounding areas. The cost of the system being high, many individual users do not find them affordable.

Wind–solar hybrid systems

When an aerogenerator and an SPV system are interfaced, the power generation from these is mutually supplemented, and the resultant hybrid system offers a reliable and cost-effective electric supply in a decentralized mode. The wind–solar hybrid system mainly consists of one or two aerogenerators along with SPV panels of suitable capacity, connected with charge controller, inverter, battery bank, etc. to supply AC power. The major advantage of the system is that it meets the basic power requirements of non-electrified remote areas, where grid power has not yet reached. The power generated from both wind and solar components is stored in a battery bank for use whenever required.

Wind Energy in India

India has 9 million square kilometers land area with a population over 900 million, of which 75 percent live in agrarian rural areas. The total power generating capacity has grown from 1,300 MW in 1950 to about 100,000 MW in 1998 at an annual growth rate of about nine percent. At this rate, India needs to add 10,000 MW capacity every year. The electricity network reaches over 500,000 villages and powers 11 million agricultural water-pumping stations. Coal is the primary source of energy. However, coal mines are concentrated in certain areas, and transporting coal to other parts of the country is not easy. One-third of the total electricity is used in the rural areas, where three-fourths of the population lives. The transmission and distribution loss in the electrical network is relatively high at 25 percent. The environment in a heavily-populated area is more of a concern in India than in other countries. For these reasons, the distributed power system, such as wind plants near the load centers, are of great interest to the state-owned electricity boards. The country has adopted aggressive plans for developing these renewables. As a result, India today has the largest growth rate of the wind capacity and is one of the largest producers of wind energy in the world.
In 1995, it had 565 MW of wind capacity, and some 1,800 MW additional capacity is in various stages of planning. The government has identified 77 sites for economically feasible wind-power generation, with a generating capacity of 4,000 MW of grid-quality power. It is estimated that India has about 20,000 MW of wind power potential, out of which 1,000 MW has been installed as of 1997. With this, India now ranks in the first five countries in the world in wind-power generation, and provides attractive incentives to local and foreign investors. The Tata Energy
Research Institute’s office in Washington, D.C., provides a link between the investors in India and in the U.S.A.