WIND Energy

Wind is the natural movement of air across the land or sea. Wind is caused by uneven heating and cooling of the earth's surface and by the earth's rotation. Land and water areas absorb and release the different amount of heat received from the sun. As warm air rises, cooler air rushes in to take its place, causing local winds. The rotation of the earth changes the direction of the flow of air.

Wind is simple air in motion. It is caused by the uneven heating of the earth's surface by the sun. Since the earth's surface is made of very  different types of land and water, it absorbs the sun"s heat at different rates.

During the day, the air above the land heats up more quickly than the air over water. The warm air over the land expands and rises and the heavier, cooler air rushes in to take its place, creating winds. At night, the winds are reversed because the air cools more rapidly over land than over water.

Today, wind energy is mainly used to generate electricity. Wind is called a renewable energy source because the wind will blow as long as the sun shines.

How wind machines work:-

Basic Technology

Wind electric generator converts Kinetic energy available in wind to electrical energy by using rotor, gearbox and generator.

The Basic Process

The wind turns the blades of a windmill like a machine. The rotating blades turn the shaft to which they are attached. The turning shaft typically can either power a pump or turn a generator, which produces electricity.

Most wind machines have blades attached to a horizontal shaft. This shaft transmits power through a series of gears, which provide power to a water pump or electric generator. These are called horizontal axis wind turbines.

There are also vertical axis machines, such as the darrieus wind machine, which has two, three or four long curved blades on a vertical shaft and resembles a giant eggbeater in shape.

The amount of energy produced by a wind machine depends upon the wind speed and the size of the blades in the machine. In general, when the wind speed doubles, the power produced increases eight times. Larger blades capture more wind. As the diameter of the circle formed by the blades doubles, the power increases four times.

Types of Wind Machines:-

Wind energy is the Kinetic energy associated with the movement of atmospheric air. It has been used for hundreds of years for sailing, grinding grain and for irrigation. Wind energy systems convert this kinetic energy into more useful forms of power. Wind energy systems for irrigation and milling have been in use since ancient times and since the beginning of the 20th century it has been used to generate electric power. Windmills for water pumping have been installed in many countries, particularly in the rural areas.

Wind turbines transform the energy in the wind into mechanical power, which can then be used directly for grinding etc. or further converting to electric power to generate electricity. Wind turbines can be used singly or in clusters called "wind farms". Small wind turbines called aero-generators can be used to charge large batteries.

Five Nations:- GERMANY, USA, DENMARK, SPAIN and INDIA- account for 80 % of the world's installed wind energy capacity.

***INDIA ranks 5th in the world with a total wind power capacity.

There are two different types of wind machines namely:-

• Horizontal-axis wind machines
• Vertical-axis wind machines

Video about:- Enercon E126 - The most powerful wind turbine in the world

1). Horizontal-axis wind machines:- 

Most wind machines being used today are the horizontal axis type. Horizontal axis wind machines have blades like airplane propellers. A typical horizontal wind machines stands as tall as a 20 story building and has three blades that span 200 feet across. The largest wind machines in the world have blades longer than a football field.

2). Vertical-axis:- 

Vertical-axis wind machines have blades that go from top to bottom and the most common type (Darrieus Wind Turbines) looks like a giant two-bladed egg beaters. The type of vertical wind machines typically stands 100 feet tall and 50 feet wide. Vertical -axis wind machines make up only a very small percent of the wind machines used today.

The Wind Amplified Rotor Platform (WARP) is a different kind of wind system that is designed to be more efficient and  use less land than wind machines in use today. The WARP does not use large blades, instead it looks like a stack of wheel rims.

Each module has a pair of small, high capacity turbines mounted to both of its concave wind amplifier module channel surfaces. The concave surface channel wind toward the turbines, amplifier module channel surfaces. The concave surface channel wind towards the turbines, amplifying wind speeds by 50% or more.

Wind and The Environment:-

In 1970s, oil shortage pushed the development of alternative energy sources. In the 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 fossil fuels continues to increase.

Wind Energy is an economical power resource in many areas of the country. Wind is a clean fuel, wind farms produce no air or water pollution because no fuel is burned. Growing concern about emissions from fossil fuel generation, increased government support and higher costs for fossil fuels have helped wind power capacity in the US grow substantially over the last 10 years.

The most serious environmental drawbacks to wind machines may be their negative effect on wild bird populations and the visual impact on the landscape.

Application of the Wind Energy:-

Water-pumping windmills, aerogenerators (small wind electric generators) and wind-solar hybrid systems have been found to be useful for meeting water-pumping and small-power requirements in a decentralized mode in rural and remote windy areas of the country.

The MNRE is implementing a programme on "Small Wind Energy and Hybrid Systems" to promote utilization of water-pumping windmills, aerogenerators and wind solar hybrid systems for water pumping and power generation.

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 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 to a reciprocating pump of 50-150 mm diameter through a connecting rod.

Such windmills start lifting water when wind speed approaches 8-10 km/HR. 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 depth of 60m. Water - pumping windmills have an advantage that no fuel is required for their operation and thus they can be installed in a remote windy area 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/hr). Further, special care is needed at the time of the site selected as the sites should be free from obstacles such as building and trees in the surrounding areas.

The cost of the system being high, many individual users do not find them affordable. It varies from Rs 45000 to 150000, depending on the type. In addition, Rs 10000 - Rs 20000 is required for the foundation, Storage tank and the installation of the windmill. As the system involves moving parts, it requires frequent maintenance, the repair and maintenance cost of a windmill is about Rs 2000 per year.

The MNRE provides a subsidy of up to 50 % of the ex-words cost of water-pumping windmills, subject to a ceiling of Rs 20000, Rs 30000 and Rs 45000 Rs in the case of direct drive, gear type and AV-55 Auroville models, respectively. For non-electrified islands, subsidy of up to 90% of the ex-works cost is provided for the above types of windmills, subject to a ceiling of Rs 30000, Rs 45000 and Rs 80000 respectively.

Aerogenerator:-

An aerogenerator is a small wind electric generator having a capacity of up to 30 KW, Aerogenerator is installed either in stand-alone mode or along with solar photovoltaic (SPV) systems to form a wind solar hybrid system to form a wind-solar hybrid system for decentralized power generation.

The aerogenerator is suitable for power generation in un-electrified areas having adequate wind speeds. It consists of a rotor of 1-10 diameter having 2-3 blades, permanent magnet generator, control devices, yaw mechanism, tower, storage battery etc.

The aerogenerator rotor starts moving at a wind speed of 9-12 km/hr. However, it produces optimum power at the rated wind speed of 40-45 km/hr. The limitation of not being able to provide power as and when it is required is overcome by storing it in a battery bank.

The aerogenerator cost about Rs 2.00-2.50 lakhs per KW. In addition, the cost of installation including civil works is estimated at Rs. 5000/KW. The repair and maintenance cost is about Rs. 2000/ KW per annum.

Wind-Solar Hybrid Systems:-

When an aerogenerator and an SPV system are interfaced, the power generations from these is mutually supplemented and the resultant hybrid system offers a reliable and cost-effective electricity 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.

The approximate cost of installation, including civil works, is about Rs. 10000 per KW. Maintenance and repair cost is about Rs 3000 per KW per annum. Subsidy of up to 50% of ex-works cost of the system is provided, subject to a maximum of Rs. 1.25 lakhs per KW to individuals, industries and R&D and academic institutions.

The MNRE provides a subsidy for community use and direct use of central/state government departments and defense and para-military forces of up to 75% of the ex-works cost of the system subject to a maximum of Rs. 2.4 lakhs per KW is available.

System Availability and Repair/Servicing Facility:-

Water-pumping windmills, aerogenerators and wind-solar hybrid systems are installed through state nodal  using central subsidy.

The state nodal agencies are responsible for providing repair/service facilities through the respective manufacturers.

Potential and Achievement:-

Water-pumping windmills require only medium wind regimes. Considering the availability if required wind speeds and the level of the prevailing water table, potential exists for installing water-pumping windmills in almost all states except in hilly and rocky regions.

Aerogenerators and wind-solar hybrid systems require high wind speeds and good solar radiation. Potential exists for their installation in almost every major states of India.

So far, about 1000 water-pumping windmills and 380 KW aggregate capacity of aerogenerators/wind-solar hybrid systems have been installed in the country.

GAURAV SARASWAT