Wind Energy: An Overview
Renewable energy is the key to create a carbon-neutral society in the future. The wind has been blowing on the face of Earth for more than millions of years. The energy potential of the wind has been used to produce electricity. During the early days, wind energy was used for irrigation purpose. Wind energy is quite an interesting topic to discuss. In the blog, I would be explaining wind energy in detail.
What Is Wind? What Causes Wind?
Before understanding the meaning of wind energy, one must understand the meaning of wind and its cause. The wind is defined as the horizontal movement of air past a given point. It is a great equalizer of the atmosphere, transporting heat, moisture, pollutants, and dust great distances around the globe.
The displacement of wind is caused by the difference in pressure caused by the variation of temperature. The air displaces from a region of high pressure to a region of low pressure.
What Are The Factors That Affect The Kinetic Energy Generated And Power Delivered From Wind?
The kinetic energy associated with wind depends on the two main parameters. They are as follows:
- The Mass Of Air
- The Velocity Of Wind
From the above mathematical formula, it's clear that kinetic energy associated with the wind is directly proportional to the mass of wind flow. It is also directly proportional to the square of the wind velocity.
The maximum power that could be delivered to a wind turbine by a flow of moving air depends on the following parameters. They are as follows:
- The Density Of Air
- The Area Of The Rotor
- The Wind Velocity
From the above mathematical formula, it's clear that maximum power that could be delivered to a wind turbine by a flow of moving air directly proportional to the density of air, area of the rotor and cube of the velocity of wind speed.
What Is The Difference Between A Wind Farm And A Wind Turbine?
The term wind turbine and wind farm are the most commonly used words in the wind energy sector. In this part of the blog, I would be explaining the above two terms in a very simple manner. Wind turbine operates by converting the kinetic energy in the wind into mechanical power which is used to generate electricity by spinning a generator.
On the other hand, a wind farm is a collection of wind turbines within a large area to generate electricity. These wind farms can be span over an area ranging from a few square miles to hundreds of square miles based. The wind farm can either be an on-shore type or an off-shore type.
What Are The Parameters Involved In Selecting An Area For Setting Up The Wind Farm?
The basic requirement of a wind farm is consistent wind travelling at moderate speed (neither too fast nor too slow). Ideal spots need to be chosen based on the required wind speed for establishing the wind farm. Factors like relative proximity to structures like buildings and houses and possible environmental impacts of building the farm are considered while setting up the wind farm.
Once the location is selected, the turbines are placed in such a way that maximum power can be obtained from the wind farm. The turbines must be placed approximately about 3 to 10 rotor diameters apart. For example, if a 60-meter diameter wind turbine is used in a wind farm then the distance between the wind turbines must be approximately 180–600 metres.
This spacing is made as a compromise to ensure the compactness of the wind farm. The other main goal of the spacing is to prevent the turbines from hindering each other when they are working. This is called shadowing.
History Of Wind Energy
The history of generating energy from wind dates way back to 3,500 BCE. The Egyptians invented sailboats which were propelled using the wind. According to leading historians, the Chinese used windmills to pump water. During the 500 AD to 900 AD, the Persians innovated the windmills to crush grains and pump water.
In the 1st Century AD, a greek engineer Heron Of Alexandria invented the wind wheel. This was considered to be the first wind turbine to have been invented. Heron of Alexandria is well known for his contribution to the world of mathematics and science. He is popularly known for the “Heron’s Formula” which is used to calculate the area of any type of triangle. He has invented incredible machines that continue to inspire the present generation.
Yet there was always the debate on who invented the first wind turbine for nearly 1800 years. In the year 1887, the first wind turbine to produce electricity was invented by a Scottish engineer and academician, Professor James Blyth. In July 1887, Blyth built a cloth-sailed wind turbine or “mill” in the garden of his holiday cottage in Marykirk. He used the electricity from the wind turbine to charge the batteries to store the electricity used to power the lights in his cottage, which thus became the worlds first house powered by wind-generated electricity.
The article was raised at the Philosophical Society of Glasgow on 2 May 1888. Blyth described the wind turbine as a “tripod design, with a 33-foot wind shaft, four arms of 13 feet with canvas sails, and a Burgin Dynamo is driven from the flywheel using a rope”. The turbines produce enough energy to light ten 25-volt bulbs in a “moderate breeze” and could even be used to power a small lathe.
Charles F Brush is one of the founders of the American electrical industry. He invented a very efficient DC dynamo used in the public electrical grid, the first commercial electrical arc light and an efficient method for manufacturing lead-acid batteries. His company Brush Electric in Cleveland, Ohio, was sold in 1889 and in 1892 it was merged with Edison General Electric Company under the name General Electric Company (GE).
During the winter of 1887–88, Brush built what is today believed to be the first automatically operating wind turbine for electricity generation. It had a rotor diameter of 17 m (50 ft). The turbine consisted of 144 rotor blades made up of cedarwood. This wind turbine ran for a period of 20 years. Despite the large size of the turbine, the generator was only a 12 kW model. This is because the slowly rotating wind turbines of the American wind rose type do not have a particularly high average efficiency.
By the year 1900, nearly 2500 windmills were built in Denmark to generate nearly 30 MW. Poul la Cour (1846–1908) was originally trained as a meteorologist. He is considered the pioneer of modern electricity-generating wind turbines. He is also considered one of the pioneers of modern aerodynamics and built his own wind tunnel for experiments. He discovered that fast-rotating wind turbines with few rotor blades are more efficient for electricity production than slow-moving ones. In the year 1905, he established the Society of Wind Electricians.
We have come a long way from generating electricity from wind energy to charge the batteries to store the electricity used to power the lights in his cottage in 1887 to produce 743 GW of electricity from wind energy globally in 2021.
Types Of Wind Turbines Based On The Axis Of Rotation Of The Blades
Predominantly there are two basic types of wind turbines. They are as follows:
- Horizontal Axis Wind Turbine (HAWT)
The rotating axis of the blades is parallel to the direction of wind blowing. The main rotor shaft runs horizontally. The HAWT is used in wind farms where the wind flow conditions are moderate. The rotor faces the wind steam to capture maximum wind energy. The HAWT are classified into two types. They are upwind turbine and downwind turbine.
2. Vertical Axis Wind Turbine (VAWT)
The rotating axis of the blades is perpendicular to the direction of the wind. The main rotor shaft runs vertically. This type of turbine can work in turbulent wind flow conditions. The VAWT has the ability to accept the wind steam in any direction. The various types of VAWT are Darrieus Wind Turbine, Savonius Wind Turbine and Quiet revolution VAWTs.
Comparing The Horizontal Axis Wind Turbine (HAWT) & Vertical Axis Wind Turbine (VAWT)
The maintenance and inspection are quite difficult for a Horizontal Axis Wind Turbine as compared to the Vertical Axis Wind Turbine. A HAWT can produce more power as compared to that of a VAWT. A HAWT has better efficiency as compared to that of a VAWT.
Types Of Wind Turbines Based On Their Location And Their Connection To The Grid
The wind turbines are also classified into three more types based on where they are installed and their connection to the grid. They are as follows:
- Land-Based Wind Turbines
These wind turbines have a power rating ranging from 100 kilowatts to as large as several megawatts. Larger wind turbines are more cost-effective and are coupled together to produce electricity. They are also called on-shore wind turbines.
2. Off-Shore Wind Turbines
These wind turbines are built in the oceans away from the seashore. They are quite massive in height and size(sometimes even taller than the statue of liberty). The components to build the offshore wind turbines are transported using the ships. These turbines are designed to capture powerful ocean winds and generate vast amounts of energy.
3. Distributed Wind Turbines
Wind turbines are installed near the place where the energy produced will be consumed. Small wind turbines with a power rating of almost 100 kW are generally used for residential, agricultural, and small commercial and industrial applications.
Parts Of A Wind Turbine
With the reference to the above diagram, I would be explaining the various parts of a wind turbine. The important parts are the gearbox, rotor, generator, control and protection system, tower and foundation.
- Rotor: They are aerofoil shaped blades that encounter the wind. They are aerodynamically designed to convert kinetic energy from the wind into mechanical energy through a connected shaft.
- Gearbox: It plays an important role in altering the rotational velocity of the shaft to suit the generator for power generation. The gearbox is arguably the most expensive and heavy part of the turbine.
- Generator: It is a device used to convert mechanical energy into electricity.
- Control and Protection System: It is a safety system that prevents the turbine from working under dangerous conditions. For example, extremely high speeds of wind can damage the bearings of the turbine. In such adverse conditions, the brake systems are activated to protect the wind turbine.
- Tower: The tower connects the rotor and the foundation. The tower height is chosen in such a way that the rotor can find strong winds.
- Foundation: The foundation is designed to hold the entire wind turbine firmly on the ground. It usually consists of a solid concrete assembly around the tower to maintain its structural integrity.
How Does Wind Energy Work?
Ideally, wind turbines are situated in a place with regular and consistent winds. The wind pushes the aerodynamically designed blades. These blades are designed in such a way that they can be pushed upwind or downwind of their location.
The kinetic energy from the wind is transformed into mechanical energy when the wind meets the windmill blades and pushes them. The movement of the blades then turns a drive shaft. The spinning drive shaft is connected to a gearbox with a suitable gear ratio that increases the speed of rotation. Once these gears reach a required speed, they can power a generator that produces electricity. The generator produces 60-cycle AC (alternating current) electricity. A transformer may be used to convert the AC to other forms based on the requirements. The electricity produced from the wind turbine can be either stored in a battery or it can be sent through transmission lines to residential or industrial areas.
Advantages And Disadvantages Of Wind Energy
Wind energy has its own set of pros and cons. In this section of the blog, I would be explaining the advantages and disadvantages of wind energy.
Advantages Of Wind Energy
- Wind Energy Is Cost-Effective: The global weighted average cost of electricity from onshore wind farms in 2019 was USD 0.053/kWh with region-based values ranging from USD 0.051 to USD 0.099/kWh. A wind turbine is designed to work for a period of at least 20 years.
- Creating New Employment Opportunities: According to the latest analysis by the Global Wind Energy Council (GWEC), 3.3 million new wind power jobs can be created globally by 2025. The above-cited figure includes direct jobs in both onshore and offshore wind. It also includes job creation in project planning and development, manufacturing, installation, operation and maintenance (O&M) and decommissioning.
- Wind Is A Clean Source Of Energy: There is zero greenhouse gas emission from a wind farm. This simply tells us that wind is truly a clean source of energy.
- Wind Energy Is Renewable: Wind would continue to blow for immortal centuries. It is not going to exhaust like fossil fuels within a century. the wind is freely available and inexhaustible in our atmosphere.
- Wind Energy Is A Sustainable Source Of Energy
Disadvantages Of Wind Energy
- The Wind Is Inconsistent: The wind speed is quite inconsistent and unpredictable like solar energy. Despite being a renewable source of energy, wind speeds fluctuate daily. The site for setting up the wind farm requires a lot of research on wind speed analysis.
- Wind Turbines Involve High Upfront Capital Investment: The cost of a turbine is worth millions of dollars. The survey for establishing a wind farm is quite expensive. The manufacturing cost and setting up a turbine at the wind farm adds to the upfront cost. On the other hand, setting up an off-shore wind turbine is more expensive as compared to the on-shore wind turbine.
- Installation Can Take Up A Significant Portion Of Land: Installing a wind turbine would take away land which was once the bedrock of agricultural activities for many years.
- Wind Turbines Are Suited To A Particular Region: Wind turbines are suited to the coastal regions which receive wind throughout the year to generate power. Countries without any coastal or hilly areas may not be able to harness the power of wind energy.
- Wind Turbines Can Be A Safety Hazard: The frequency of tornadoes, hurricanes, and cyclones has been increasing annually. The wind turbines are susceptible to being damaged by natural calamities like tornadoes, hurricanes, and cyclones.
Understanding The Environmental Impact Of Wind Energy
In this section of the blog, I will be highlighting the positive and negative impact of the wind energy environment. Putting aside the inconsistency of the wind and the high upfront cost of setting up the wind turbines, the wind is a renewable source of energy. It is freely available and inexhaustible in our atmosphere.
Generating energy from wind does not produce any greenhouse gas as compared to the conventional sources of energy (ie Fossil Fuels). According to the Global Wind Energy Council, presently 743 GW of wind power is generated globally. This has prevented over 1.1 billion tonnes of Carbon Dioxide emissions globally which is equivalent to the annual carbon emissions of South America.
On the other hand, the negative impact of wind turbines on birds and bats are widely studied by researchers. When the blades of wind turbines rotate at high speeds, the air pressure around the blades shifts and increase the chances of birds and bats colliding with the blades. The exact impact on local bird and bat life can vary dramatically from one wind farm to another. Wind turbines are a bit noisy during their operation. When many wind turbines work together in a wind farm, the noise produced is unbearable.
Conclusion
Wind energy can play a vital role in creating a carbon-neutral world by 2030. According to the Global Wind Report 2021 published by the Global Wind Energy Council, the year 2020 was the best year in the history of the global wind industry despite the COVID-19 pandemic. In the year 2020, 93 GW of new capacity was installed which accounts for a 53 per cent year-on-year increase. The report also states that the world needs to be installing wind power three times faster over the next decade in order to stay on a net-zero pathway and avoid the worst impacts of climate change.
As a concluding remark, I would like to say
Wind energy is a renewable source of energy. They are a sustainable source of energy but it has some environmental downsides. Proper research work is needed while establishing the wind farms. The research work must aim to abate the unsustainable land use and habitat destruction on wind farms.Further more, the wind turbines must be placed in a stratergic manner to prevent the migratory birds and bats from being killed due to the collision with the wind turbines. Technological advancemnets can make wind turbines more bat and bird friendly. Implementing sensor in the wind farms can anticipate birds and bats flying close by, allowing the turbines to shut down entirely.
