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Wind Energy

by | Mar 10, 2022 | Renewable Energy

Introduction

Wind energy is a renewable energy resource, an indirect solar energy source. The wind is generated by the difference in pressure, which occurs due to uneven heating of the earth’s surface. That uneven heating causes temperature difference, then energy is moving from the earth surface to the air molecule and move by the convective effect and leads to the formation of wind. The upward movement of air is called air current, and the horizontal movement of air is called wind. Generally, wind moves from a high-pressure area to a low-pressure area. Around 0.5% of the incident solar radiation is changed into the wind. Moving wind’s kinetic energy is used to generate electricity or used for mechanical work is referred to as wind power.

The generation of wind currents by the convective effects resultingfrom solar heating

Various factors are responsible for wind energy distribution like:

The mountain chain channelization of air current, the trees, buildings, and hills create obstruction and divert the direction of air.  The surface friction effect defines the wind speed. That is why wind speed over the sea is high while over the land is low. The topography of the area affects the wind speed.

The power available in the wind is calculated by the concept of kinetics. The principle used to work by the windmill is to transform the wind kinetic energy into mechanical energy. The maximum efficiency in obtaining energy from wind is 59% or 16/27.

 

Power = Energy/unit time

The energy available = Kinetic energy of the wind

The kinetic energy of any particle = ½ mV2 ………………. (1)

Amount of air passing in unit time through an area A, with velocity V = A.                                 V Its mass is equal to its volume multiple by its density ρ of air,

m= ρ A.V…………….. (2)

m is the mass of traversing area A swept by the rotating blades of a windmill-type generator.

Substituting this value of mass (2) in kinetic energy equation (1)

Kinetic energy = 1/2 ρ A.V.V2………………(3)

Kinetic energy = 1/2 ρ A.V3 watts………………(4).

The available power of wind is proportional to the air density and the density of air is 1.225kg/m2

Since the area is normally circular of diameter D in horizontal axis aero turbines,

? = ?D2 4 ?q.m …………………. (5)

Substitute (5) in (4), it becomes

Available wind power = ½ ρ?D2 4 .V3 watts………….. (6)

= 1/8ρ.?? 2V 3………………… (7)

History Of Wind Energy

The early use of wind energy for producing work occurred in ancient Egypt. By forming a sailboat, which uses wind kinetic energy and converts it into the boat’s kinetic energy. The first windmill was invented in the Persia 500-900AD era and was used for granary work. During the late 1800’s U.S. settlements expanded. During that time, the Halladay windmill was introduced and was used for farming and irrigation purposes. During the late 19th century, windmill tech advanced with electrical technology, and the first electricity-generating windmill was introduced in 1888.

history of wind advancement

With advancements in technology, the advancement in a wind turbine increases the power generation by 1MW. Continuous technological advancement, R&D changed the windmill for electricity power generation and reduced the wind turbine cost. In 2010,  11% of energy was shared by the wind in the U.S. and increased by 15% in 2016. In India, the production of electricity from wind was 31GW in 2017. It shares 6.6% of the global market.

history of wind advancement

                                                                                    History of Wind Advancement

Wind Energy Scenario Of World

18% of the world’s energy consumption comes from renewable energy resources, such as large hydropower, traditional biomass, solar, geothermal, and biofuel. Wind energy is leading the renewable energy resources worldwide, and it is more affordable than fossil fuel use. Its installation increases exponentially in China, which produces 486GW of electricity from wind power and has become the top country in wind power. Engineers constantly improved the windmills designed to increase power generation. With the biggest blade 80 meter span, and the tower height with 178meter. India is the fourth-largest wind energy harvesting country that installed 31GW wind power in 2017. That accounts for a 6.6% global market share. China is the world leader and followed by the USA and then Germany.

map of world superposed with the electricityg generation from wind energy

The wind power potential of India is 2.5 x 104MW with 1870MW installed capacity. The largest power rating in India was installed in Suzlon (Tamil Nadu), with a 2 MW capacity. Gujarat has the maximum gross wind energy potential with 9675MW. There is immense wind energy potential in offshore and onshore areas of India.

Wind resource in different states of India (Source: MNRE)

The wind resource in different states of India (Source: MNRE)

Basic Principles Of Wind Energy Conversion Systems (WECS)

The generation of wind due to receiving uneven solar radiation causes the movement of the wind. The wind energy is harnessed by the wind turbine placed over the tower. The wind speed is directly proportional to the height. The tower’s height is 100 feet, which is good due to faster and less turbulent wind. The speed of wind at 10m is 20-25% higher than compared to the surface because of less drag force at the height. The average wind speed needed to produce electricity must exceed at least 6-8 meters per second for a small turbine.

Basic element of wind energy conversion system

Basic element of wind energy conversion system

 

The Basic Element of Wind Energy Conversion System

The principle of harnessing wind energy is to convert the wind kinetic energy into mechanical energy, and that mechanical energy is used to produce electrical energy, wind strike on the turbine or blade of the windmill that causes the blades to rotate. These blades are connected with a shaft connected to the generator, producing electricity. Wind turbines are not 100% efficient, and windmills can generate 1/3 of maximum output. Wind power depends on wind speed, air density, and the cross-section of windswept areas. The maximum energy from available wind is directly proportional to the cube of wind speed if a slight rise in the wind speed will increase the wind power.

The efficiency is determined in terms of the coefficient of power (Cp). The coefficient of power of the rotor is defined by the ratio of actual power produced by the rotor to the available theoretical power in the wind.

Power coefficient = power of wind rotor/ power available in the wind

According to the Betz law, only the 16/27 of wind power is able to be converted into mechanical power for a windmill. P max=0.593 * P total.

Types of wind energy systems  

Wind energy is converted into electrical energy with the help of a wind energy conversion system (WECS). The important component of this system is a wind turbine that harnesses wind energy.

The essential component of a wind energy conversion system for electricity:

Aero-turbine, Gearing, Coupling, Electrical generator, Controller

The turbine is the main component that harnesses the energy, and it is classified into two categories as

Horizontal axis Wind turbine (HAWT): It is the most common type of turbine. The rotation axis of the wind turbine is parallel to the ground in this type of turbine, and the blade’s axis rotation is parallel to the flow of wind. This type of turbine in a windmill is an aero turbine with 35% efficiency and 15% farm mill efficiency. The common component of this type of turbine is a rotor with a blade that converts the wind into rotational energy, with a generator, control system, and gearbox. That converts rotational energy into electrical energy.

Vertical axis Wind turbine (VAWT): This type of the axis is also parallel to the ground. It cannot take advantage of high wind speed, making it less common than HAWT. Their design has several types: various wind turbines with 35% efficiency, girosmill wind turbines with 35% efficiency, and savouries wind turbines with 30% efficiency. The advantage of this type of wind turbine is no need for orientation of the wind turbine concerning the direction of the wind, low cost, and easy maintenance. However, the disadvantage is that it is not as efficient as HAWT.

types of vertical axis wind turbine

 Types of  vertical axis wind turbine

Economics of Wind Energy Utilization

Wind energy is renewable energy, which is a clean and never-ending energy resource that contributes to the environment and economy of the country. Wind energy reduces the dependability of energy produced from fossil fuel and some renewable energy. The economic factors of the wind farm and windmill installation include capital cost, land cost, operational management cost. The production cost of wind power is high as compared to conventional fuel.

The capital cost is very high for the wind farm, and it is necessary to consider substantial financial capital in the long duration of the wind farm project. The capital cost of wind farms is constituted by construction, grid-connection, electrical connection, wind turbine, planning, approval, and management. Capital cost of such a component may vary with the location of a wind farm. The capital cost of an average wind farm can range from euro 60,000 to 1,000,000 per M.W. per annum. The turbine’s cost is 65%, construction 13%, and the 8% in electrical infrastructure are significant capital expenditures. The operational and management cost can be around 8000-10000 euro per M.W. per annum. Incentives in wind energy installation are an economic tool to encourage more wind farm installation by investors to support socially beneficial projects.

Wind Energy Potential and Site Selection

The potential of wind energy depends on several factors that are located onshore or offshore, topography, hilly region, wind speed. The maximum output a wind turbine can give is 59%, with average efficiency ranging from 35-40 % depending on location, type of turbine, and wind speed. Wind energy potential in India with installed capacity is 28419.40MW, and the target is 60,000MW for 2022. The selection of a site for installation of a windmill or wind farm requires several features like

  • Ideal wind speed.
  • Good roadway access to sites
  • Appropriate terrain and geology for the onsite permit
  • Low population density
  • Minimum risk of agroforestry operations
  • Close to the suitable electrical grid
  • Supportive landholders
  • Significant tourism infrastructure in place
  • Privately owned freehold land
  • Good industrial support for construction and ongoing operations
  • Land use is primarily for grazing and cropping
  • Significant potential for revalidation

Basics Of A Wind Farm

The wind farm is the electricity production from the wind that consists of a group of wind generators that range from 600KW to 5MW spreading across the land to produce maximum power from wind. Three types of the wind farm as onshore

A wind farm that is at least 3Km inland from the coast, near-shore wind far <3Km from the coast, and offshore in lakes or open sea many miles from the shore. The wind farm is located in the region where the wind is available at high speed to gain maximum output without infringing the pre-existing settings, economy, business, and sailing routes. The energy produced by each windmill is channelled downward in electrical ground cable, and the segment which controls the wind turbine is also coming from the ground cables. Each of the wind farms carries a delivery to the main station. The produced energy is channelized into the electric grid to meet the electricity demand commercially.

 

 

 

Author

  • The author has done a master's in Environmental science and is currently working as chief Environmental Advisor with New Delhi State Government.

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