Wind Turbines And Wind Energy

Published Date: 02 Nov 2017

Table of Contents

Abstract 3

Introduction 4

A Brief History of Wind Energy Technology 4

Current Wind Turbine Technology 6

Wind Power Utilization in the United States 6

Description of Wind Turbine Technology 7

Factors to Consider When Putting Up a Turbine 7

How Residential Wind Turbines Work 9

Advantages and Disadvantages of Wind Turbine Technology 13

Impact on the Economy 14

Impact on Society 15

Impact on the Environment 15

Conclusion 15

References 17

List of Figures

Figure 1: The working components of a typical modern wind generator 10

Figure 2: Photo of a horizontally mounted wind turbine (x-axis): 11

Figure 3: Photo of a Vertically mounted wind turbine (y axis) 12

Abstract

The conversion of wind energy into a more useful type of energy is known as wind power production. It may be in the form of using windmills to produce mechanical power, pumping water using wind pumps or generation of electrical power using wind turbines. Wind provides a clean and renewable source of energy and has no significant negative environmental impacts. Because wind utilized by this technology is free, there are no additional operating costs once the turbines are installed. The wind power industry is booming, technological advances and mass production are making wind turbines cheaper while many governments are offering tax incentives to spur the development of wind energy.

With a main focus on the importance of using alternative energy resources, the purpose of this research is to examine and document data and finding related to the fiels of wind energy and related technologies such as wind turbine systems in particular. The paper will initially provide some background and historical facts about wind turbines and wind energy as it will also present information about their impact on the economy, society, and the environment. The paper also includes a discussion about, the mechanics of wind turbines and how they work, as well as related advantages, disadvantages, trends and statistical data. Though electric generating wind turbines have been in use for over 120 years, their popularity is growing more than ever due to the constantly increasing energy demands throughout the world. Wind energy systems are quickly becoming mainstream in many applications around the world. On the other hand, current forms of non-renewable energy, such as fossil fuels, are depleteing more quickly with an increasing population while the unclean and polluting nature of most of these forms of energy is causing undeniable harm to the environment and the people of the planet.

Introduction

Wind energy remains the fastest growing source of energy in the world and would be used to sustainably power homes, businesses and industries with clean and renewable electricity in future. The environment and its cleanliness are highly important for the survival and continuity of the human race (McGowan & Connors, 2000). According to Ziv & Media, (2013), by 2050, renewable energy sources such as wind and solar will generate a third of energy needed in the world. This is due to population growth, climate and change and increasing depletion of fossil fuels. Sustainable energy comes in many forms and it is more important now because of unpredictable and erratic climatic factors. Without new and better forms of sustainable energy, catastrophic natural occurrences might persist. Among the available renewable energy sources, wind power presents viable solutions to global warming problems, the energy crisis and sustainability of the human race (Taylor, 2013). By the end of 2011, use of wind power had been commercialized by 83 countries worldwide.

A Brief History of Wind Energy Technology

Wind turbines are machines that are engineered and designed to convert the turbine’s kinetic energy, that is the spinning movement of the turbine blades due to the wind, into mechanical energy so that it can be used to produce electricity that ultimately powers something else. While wind turbines are mostly used to generate electricity and power, their earlier form known as the windmills, is used for other activities such milling grains, pumping water, and other uses. Because the principle behind the operation of windmills and wind turbines is very similar, the bypof each of these machines become one of the few defnig factors (Sterzinger & Svrcek, 2004). These machines have been used in various ways for hundreds of years, but their use slowly degenerated as new and faster technologies came along to replace them. The concern now, however, is that wind turbine technology should have greatly continued to develop along with other energy sources such as oil, gas and hydroelectricity. If that were the case, perhaps the energy needs and energy usage in the world would be much different at present.

It is not clear where the first windmill originated from. It is theorized that small scale wind turbines propelled boats up and down the Nile river as early as 5000 BC. In 2000 BC china used crude wind turbine to pump water in rural areas. The oldest known windmills that were actually uncovered were the merry-go-round styled windmills with woven reed sails, which ancient Persia used to grind grain. By the 11th century the Middle East had improved its turbine technology and the bulk of its food production was powered solely by these turbines (Darvill, 2012). The styles of windmills slowly evolved to match the climate that they were needed to endure. The famous pinwheel style windmill that many people are accustomed to was invented in the U. S in the 1860’s. It was used by the railroads for filling water tanks, and also by rich land owners who wanted running water pumped to their property (McGowan & Connors, 2000).

With the industrialization of Europe and the US, the popularity of the wind mills faltered even though its power output had increased significantly as illustrated by the U.S Department of Energy (2011). For instance, in 1940 the largest wind turbine of the time was constructed in Vermont and fed utilities to the local communities during World War II. People’s interest in wind turbines remained fickle and fluctuated with the price of fossil fuels. In 1920’s, Marcellus Jacobs had completed and patented nearly twelve different versions of three-bladed turbines and widely produced them until the 1950’s when he had to close down his business due to loss of customers. This loss in business was attributed to the fact that by the 1950’s most people could get electricity from the large local utilities and preferred other more dependable energy sources like hydropower and fossil fuel to wind energy which tended to fluctuate (U.S Department of Energy, 2011). Turbine technology did not receive a second thought until the 1970s when fossil fuel prices soared and the nation experienced a devastating fuel crunch. During this time many advances in the efficiency of wind turbines had been made which culminated into the current wind farms.

Current Wind Turbine Technology

Due to the rising cost of fossil fuels and wide concern over the state of the environment, there is an increasing interest in the renewable power sources that are now being offered. Among these resources the wind turbine has certainly advanced from its early beginnings. Through centuries of redesign and fine tuning, today’s wind turbines run more efficiently and produce more electricity with less wind current than the old windmills. From the works of Energy Matters (2013), larger wind turbines that operate above 100 kilowatts are often termed as industrial turbines. These turbines are often grouped together in areas that are called wind farms and supply power to electricity generating companies. Smaller turbines that run under 100 kilowatts are mostly used by private homes. Some that are used together with diesel or other fuel are often referred to as hybrid units.

Wind Power Utilization in the United States

The United States alone generated in excess of 26.6 billion kilowatt hours per year of wind generated electricity in 2008. In the year 2012, China and US passed 50,000 MW production while the European Union surpassed 100,000 MW (U.S Department of Energy, 2013). This amount of energy is enough to power nearly 2.5 million homes, or a city roughly the size as Los Angeles. This only amounts to 0.4 percent of the Nation’s total electricity production. However, wind generated electricity has been on the rise. From 2002-2008, wind generated power has quadrupled, doubling after approximately three years (U.S Department of Energy, 2013). There are currently 28 states that produce wind generated electricity. The states with the most wind production are Oklahoma, Iowa, Minnesota, Texas and California. The US pioneered wind generating farms and was a world leader in installed capacity until 1997 when German surpassed it and in 2010 when China took over (Darvill, 2012). Germany, Spain and India follow in that order.

The arsenal of new technology has facilitated for the cost of producing electricity generated from wind. Special pricing for green programs and projects as well as tax incentives for renewable clean energy has contributed to the increasing growth of wind turbine sites. Throughout the United States, there are energy untility providers that offer a special pricing for customers who want to replace their consumption of fossil fuels with other forms of alternative green energy sources like as solar energy and wind energy. Unfortunately, customers opting out of the use of fossil fuels are usually faced with more expensive fees. The option is still available nonetheless. (DOE, 2009).

Description of Wind Turbine Technology

Wind turbine technology has significantly evolved from the 1970’s and new methods of turning wind into useful power have been demonstrated in Europe and the United States. To give a light on the wind turbine technology, factors to consider when putting it up, how it works and its merits and demerits have been illustrated below.

Factors to Consider When Putting Up a Turbine

Among the many factors involved, location is the most important when considering the construction of a wind turbine. A clear area where wind reaches minimum speeds of nine miles per hour is ideal for the building of a wind turbine. Coastal areas and plains are typically ideal locations due to the large amount of available wind (Taylor, 2013). In order to determine if a site is suitable for a wind energy project, calculating the mean wind speed is important. The factors that affect th mean are wind speeds that must be at certain minimum, and the distribution of the tubines on site so that the outputs of the turbines are very similar. The variation between wind speed and wind direction, gusty winds, and seasonal air density are other factors that must also be taken into consideration. Strong, gusty, and unstable winds have a substantial negative effect on the amount of power the wind turbines outputs. Because these strong winds and are usually harmful to the operation of turbines, stable winds that blow in the same direction are considered more ideal. It is worth noting that the denser the air the harder the wind turbine must work. Dense air essentially acts as a source of friction that the blades must overcome, thus allowing for less efficiency. Higher altitudes are ideal because the air there is thinner. The terrain upon which the wind turbines are built must be relatively flat (Sterzinger & Svrcek, 2004).

Apart from the physical requirements, legal factors should also be considered. City ordinances should be checked because some laws prohibit erecting tall structures in some areas. Another consideration should be consulting with the insurance agency that covers the property. Some insurance companies may have regulations that dictate where the tower can be erected, and some premiums on the homeowners may be negatively affected due to the liability of owning a wind turbine. Cost factors should be looked into as well as it varies depending on the type (Danish Wind Industry Association, 2003). Single turbines often cost more on average than groups of them, and there can be very definite and pronounced differences in the price of these items depending on how many are purchased, how large they are, and how much power they are capable of producing. For smaller household-sized turbines, the cost to install can be from around $6000 to a high of $20,000.

How Residential Wind Turbines Work

Wind turbines have a vertical shaft and large rotating blades that spin when the wind blows. What happens to the power that is generated from the spinning of the blades depends on the design of the wind turbine and what it is used for. How much power is transferred when a wind turbine spins depends on the density of the air, the area that the rotor reaches, and the wind speed (Sterzinger & Svrcek, 2004). Not all of the air that goes through the wind turbine can be turned into energy.

The invention of the aerofoil style rotor as shown in figure 1 below brought about a more efficient turbine with an increased electrical output. An aerofoil styled blade lifts with the air currents in the same manner as an airplane wing, giving it far less drag than the older style blades which relied solely on the wind to push them up and around. These new aerofoil styled turbines are made up of a three bladed rotor which is mounted to a central hub that runs to a shaft and gearbox which in turn mounts to a generator. As the blades turn and pick up kinetic energy, it causes the shaft and gears to turn, carrying the kinetic energy to the generator and thus converting it into direct current. Most wind turbines have a tail to keep the rotor aligned (Energy Matters, 2013). The size of the rotor blades or "sweep area" determines the amount of power that the turbine can generate. The larger the sweep area the more power is harnessed. An effective turbine should be equipped with a speed governor to slow the rotor in times of excessive wind and keep the blades from becoming damaged. A cooling and lubricating unit can also be attached in the housing unit to save wear and tear on the gearbox and shaft. Air brakes are efficient for installation as a braking system in the unit to stop the blades from turning in times of extreme wind or routine maintenance.

Figure 1: The working components of a typical modern wind generator

Source: American Wind Energy Association (AWEA), 2013

The turbine is mounted on a tower by following a general rule of thumb that the higher the tower is the more wind the turbine will intercept. A taller tower better overcomes the air turbulences that more frequently occur closer to the ground. It is ideal to have the rotor mounted so that the blades are at minimum 30 feet above any obstacles that lay close by. Towers can either be free standing units or guyed to the ground with cables. Guyed towers are more cost efficient to erect but require more ground space due to the fact that the guyed cables need to be at least three quarters the length of the tower and extend out in several different directions (Putnam, 1998). According to the U.S Department of Energy (2013), there are two basic types of wind turbines, the Horizontal Axis Wind Turbine (HAWT) and Vertical Axis Wind Turbine (VAWT). Figure 2 below shows the HAWT.

Figure 2: Photo of a horizontally mounted wind turbine (x-axis):

Source: American Wind Energy Association (AWEA), 2013

Vertical axis turbines as shown in figure 3 incorporate a different approach in blade design. Vertical turbines are ideal for locations that have a high variance in wind direction because the blades do not have to face directly into the wind. They are commonly placed on top of buildings instead of being grouped together as wind farms because they are 50% efficient as horizontal turbines. This is due to additional drag as the blades rotate (Putnam, 1998).

Figure 3: Photo of a Vertically mounted wind turbine (y axis)

Source: American Wind Energy Association (AWEA), 2013

Wind turbines produce power in direct current so a synchronous inverter box is required to convert this energy into alternating current for use in the home. Battery banks may be used to store excess energy produced by the unit for people who choose to live without being tied to the electric utilities provider, commonly termed as "off the grid" (U.S Department of Energy, 2013). Another option for people whose homes are tied to the grid is purchasing a dual meter which will roll backwards when the turbine is putting excess electricity into the grid, or forward when there is no wind and the energy being consumed by the home owner is being supplied by the utilities provider. This option of a grid tied system is ideal for most people especially in states where the electric companies offer buy back program for energy produced from renewable resources such as solar panels and wind turbines, commonly referred to as "net metering" (Putnam, 1998).

Advantages and Disadvantages of Wind Turbine Technology

There are merits and demerits accruing from the wind turbine technology. Some benefits of owning a wind turbine system include considerable decrease on people’s dependency on local utility providers as a source of electricity. According to Taylor (2013) Some states offer tax incentives to people who invest in renewable energy resources. They also offer buy back program for the excess energy that is pumped into their grid, giving homeowners a monthly source of income for producing renewable energy from the wind turbine. Some wind farms can be used as a tourist attraction and is a good means of satisfying energy demand in remote areas. Turbines are also cost efficient and easy to maintain. The most significant advantage of the technology is its negligible impact on the environment. Wind turbines emit no greenhouse gases and are a low cost source of 100 percent renewable energy (Danish Wind Industry Association, 2003). Wind farms are often found in rural areas, offering the land owners a chance to earn extra income by leasing their land to companies that own the turbine, yet still letting the landowner use the land for their agricultural needs since the turbine do not actually cover much ground space.

One of the main disadvantages that most companies and individuals face when deciding to venture into wind turbine technology is the initial cost of equipment and installation. Most suitable wind sites are often in remote areas far away from the bigger cities where the bulk of the electricity is actually needed. The land areas may also have other valuable resources or uses which highly compete with or outweigh the need for electrical production. With no way other than batteries to store energy generated from the wind, producing companies find it inconvenient due to the fact that wind generated electricity does not always meet public demand for electricity. Availability of wind is not always reliable. According to Darvill (2012), another concern with the larger wind farms and home owners is the amount of noise that turbines and generators can create as well as the effects they may have on local wildlife especially birds. Wind turbines can also interfere with satellite, radio, and television transmissions and interfere with the aesthetics of a place.

Impact on the Economy

According to the Noble Environmental Power (2013), wind farms bring economic empowerment to communities in which they are hosted. Jobs are created during installation, operation and maintenance. Tax revenues from wind farms in turn flow to public facilities while financial easements to landowners provide a significant amount of extra income as they continue with their existing land use. It also develops a country’s manufacturing sector as demand for turbines and its equipment increases and helps stabilize electricity costs for users. Revenues from wind farms used as tourist sites contribute an income to the economy as well.

Impact on Society

Major social concerns on wind turbines are safety, aesthetics and noise pollution. A turbine break may fail and present a safety hazard as it can disintegrate or catch fire. Large turbines interfere with the aesthetics of a place. They may also create a shadow flicker, interfering with light penetration during the day. It also causes noise annoyance but modern turbines have been constructed in a way that the noise produced is minimal. The blades may cut into the path of communication channels and interfere with transmissions (IUCN, 2012). Undesirable social issues can be solved through community consultations, correct siting, size and design of the turbines.

Impact on the Environment

Environmental impacts of wind turbine technology are relatively minor with regard to pollution. It consumes no fuel and does not pollute the air or water resources unlike fossil fuels. Even though wind farms require a large land area for installation, other compatible land uses such as agriculture may still be carried out on the same land. Reports of bat and bird mortality have been noted as it is the case with other artificial structures and the extent of the ecological effect may be insignificant. Although its impact on other birds is negligible, it can have disproportionate impacts on endangered bird species such as raptor and golden eagle which prefer corridors with high wind speed where most turbines are located yet the birds have a very slow reproduction rate (IUCN, 2012).

Conclusion

From the foregoing, it is evident that although wind turbines have been producing electricity for over 120 years, until recently has wind energy been considered a viable and sustainable energy source. A combination of advancing technology, concern over environmental sustainability and a growing population with growing energy demands has helped set the stage for this to happen. Wind energy emits no harmful pollutants, is inexpensive, moderately efficient and is 100% renewable. Once wind energy technology, along with other forms of alternative renewable energy sources become fully integrated as the main power producing sources in the United States and the world at large, energy independence will be gained and human environmental footprint will be tamed.

Even though windmills were used throughout history for a lot of applications, using them to produce energy is something different. The wind speeds have to be high enough on a consistent basis, and there are other issues such as costs, noise and location to deal with. A major concern why the uptake of wind energy technology has been slow is the fact that they often do not produce enough energy to completely take over the electricity needs for a home or business yet it is a capital intensive technology. With that being the case, a person who installs one still has to pay an electricity bill, only that it is reduced. The main advantage of the wind turbine is likely an environmental one because it is non polluting. However still, there is not sufficient amount of data to prove that on a long trem basis, the wind turbine technology woul be the best energy producing alternative in order to minimize the carbon footprint of household in countries around the globe.

If wind turbines were financed in the same level as other energy sources such as gas plants, the costs involved would greatly reduce and ensure that this clean energy source will guarantee man’s survival beyond the 21st century.