Wind Farms – Hot Air or Legitimate Alternative Energy?

The use of wind, or wind power is not a new concept. For many years people around the world have harnessed the wind in order to pump water from the ground, generating electricity or to power their mills. In recent years there has been a substantial shift towards renewable or natural energy, with the advent of solar, wind, geothermal, wave or tidal power, among many others. Many countries have seen 'wind farms' which are quite substantial in size get developed. Whilst many claim that the harnessing of wind power is a significant step towards an efficient and clean means of producing energy, the people who oppose wind farms, or more specifically the modern wind turbines have claimed that these turbines can have adverse health effects, do not produce enough power to justify the cost, or consume more energy in their production than they will ever save in their lifetime. This article will discuss issues such as the history of wind power generation, how they work, and also try and perform a balanced cost/benefit analysis against common energy production methods such as coal power.

History of Wind Power

The utilisation of wind power is not a new concept. For hundreds of years farmers have used windmills to pump and drill for water and also to run their mills for the crushing of grain. The first known use of wind to produce electricity however dates back to the year 1887, where Scottish professor James Blyth produced wind turbines which he claimed he used to power his home. Remarkably, in the same year, Professor Charles Brush built a turbine which could produce 25 kilowatts of power which powered batteries in his cellar. In the same period of time, scientist Paul la Cour started to design and build wind turbines which would bring power to a rural area in Denmark, and this is thought to have been the first large scale project of it's kind 1). These gentleman lay the foundation for what would be an incredibly competitive and innovative means to produce energy.

The 1920's and 1930's saw the real increase in production of wind turbines from a volume perspective. Large manufacturing companies in Europe, The USSR and the United States all started producing large scale turbines, with Russian developers producing a turbine which stood 30 metres tall and could produce 100 kilowatts at 32% output, which is not much lower than what turbines can produce today. Whilst these were impressive figures, the projects were limited to rural areas due to the electricity grid being limited, so the turbines would need to be in close proximity to the areas to which they were directing their power 2).

The ensuing decades saw significant improvements in wind turbine technology, with scientists developing bigger and more powerful models, including the vertical turbine, which is the base for many designs today. In the early 1990's large scale wind farms started to become established in Europe and the United States, with improvements in the electricity grid and carrying capacities being increased making such projects financially viable. At the end of 2012, it is estimated that there were 225,000 wind turbines operating in 79 countries, with Germany and Denmark being the most prolific users 3).

Physics of Wind Turbines

wind_farm.jpg

Wind Farm, Washington State 4)

The first pre requisite for the use of wind turbines is wind, and the prevalence of wind. It is critical that wind turbines and wind farms are located in positions and oriented in ways in which they can gain the maximum efficiency from the wind. Wind is created by two factors; solar radiation and the spinning of the earth on it's axis. The seasonal tilt of the earth can also determine the amounts and direction of wind which will generally travel in a longitudinal direction. Generally these winds are on the upper levels of the atmosphere, however these directions of wind have a direct impact on local or surface wind speeds and directions 5).

Once the direction of the prevailing winds have been calculated, local factors then come into consideration. Local winds can be influenced by mountains, valleys, bodies of water and other geographical factors and also air temperatures. There are certain parameters which project developers usually go by when deciding where wind farms should be located. Data will be collected and compiled for several years before deciding on an exact location, with data needing to be correct within 5% accuracy in order to make the best choice. In small to medium wind farms, such as farms that occupy between 5 to 20 kilometres square, the usual minimum is 4 metres per second on average yearly at turbine heights between 10 and 35 metres 6).

With larger turbines, a minimum average wind speed of at least 5 metres per second is desired at heights of around 50 metres. The amount of wind energy created at 5 metres per second compared to 4 metres per second is almost double. Most larger wind farms will be located in flat areas, generally away from hills and large trees, and can be up to 100 metres in height. With the height od the blades included, this can sometimes be as high as 160 metres.

There are generally two types of wind turbines, horizontal axis turbines, which are the common type that you will see on things such as windmills, and vertical axis turbines, which are also known as the eggbeater style. Most commercial wind farms will tend to use a horizontal axis turbine due to better overall results and reduced maintenance periods.

The turbine consists of many components. They are as follows:

__Blade or Rotor__

This is the most visible part of the wind turbine, and most commercial wind farms will use the 3-blade rotor. These blades are designed so that they are aerodynamically efficient, reducing the amount of drag or wind shear whilst getting the maximum amount of thrust. These blades will vary depending on the location, wind speeds, turbine type or other geographic factors.

__Drive Train__

When the rotor spins, it sets the drive train into motion. The drive train is similar to the gear box in a car, with the rotor connected to the shaft which in turn drives a series of cogs which are connected to the generator.

__Generator__

This drive trains spinning motion transfers to the generator, where the coil generates the an electrical current. This current is then sent to the main power grid, or storage batteries, or a combination of both.

__Tower__

This is the structure which supports all of these components, and can range in height from 10 metres to over 100 metres. The larger commercial wind farms tend to use the 100 metre towers.

Wind Turbine Components

Performance

Whilst all the predictions can estimate what a wind turbine may produce in regards to power output, the proof is in the actual performance. There are different ways in which to measure the performance of the turbine, such as:

__Capacity Factor__

The capacity factor is calculated by the amount of kilowatt hours produced by the turbine. This is done by dividing the amount of energy generated by the amount of time, for example over a year. So in essence the capacity factor is -

CF = average power/rated power

In order for a wind farm or individual turbine to be efficient, values of > 0.3 are desired.

__Availability__

This performance measure depends on the amount of time within that say one year period that the turbine was in production, and not stopped for maintenance or other problems. In early projects, this number could sometimes be as low as 0.5, ie operational only 50% of the time. Most modern systems run at the availability rate of 0.95 to 0.98.

__Connect Time__

This is the amount of time that the turbine is actually spinning fast enough to be able to generate electricity. There are very few places on the planet where the wind will blow at 5 metres per second 24 hours a day, so the connect time is critical when measuring performance. This connect time is more dependent on site planning and the correct engineering of the turbines. In order for a turbine to be efficient, the target number for connect time should be at least 0.6.

__Lifespan__

Most wind turbine units have a lifespan of 25-30 years. This is a critical aspect as the cost of one of these units is quite considerable, and the turbine will only start going into positive energy output (for example cost, production costs, amount of energy in production used versus amount of energy produced) in the latter years of it's energy production. It is key that the component used in the turbine can fit into these time frames 7).

Production Costs

Like all other industries, Wind Farms must be able to compete with other sources of energy. When determining the viability of a project, factors such as construction costs, land costs, maintenance costs and the price of competing energy sources must be taken into consideration. There are also other indirect costs which can be factored, such as the economic situation of the country where the project is being built, inflation and legal fees.

It is hard to put an exact price tag on a turbine due to the several individual factors that may be involved, such as:

__Assessment__

Depending on the location of the project, there may be several years of environmental assessment, site assessment and wind speed measurements required. Such studies can be very costly depending on the country and the terrain.

__Construction__

The costs for construction can vary greatly not only from country to country but also from region to region. There are many variables to this component, such as access, availability of materials, costs of labour, weather factors and also cost of maintenance labour.

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Wind Turbine Construction 8)

__Cost of Turbines__

The individual cost of a wind turbine can also vary depending on the amount of turbines built in one batch, the quality of the materials, the specifications of the blades and the energy outputs. Speaking generally, the overall costs of a large wind turbine project will be between 1.5 and 2.5 million dollars per megawatt produced. Most large scale wind turbines produce 2 megawatts 9).

Benefits vs Costs vs Coal

Whilst large scale wind farm projects can be quite costly during the set up and construction phases, advances in technology have narrowed the gap between coal energy production and renewable and natural energies such as wind power. The return on investment for wind farms can be calculated using a variety of methods, however the simplest way is by using the Simple Payback Period Method. This method calculates the original cost of the project divided by the average annual electricity return such as this simple formula:

SP (Simple Payback) = Cc (Capital cost) / AAR (Average Annual Return = E (Energy produced) x R (Rate of electricity))

Hence SP = Cc / AAR

There are also more complex methods to measure the costs and benefits of these projects, such as the Cost OF Energy method, where the costs of producing the energy from the wind farm is projected against varying rates of electricity costs and the Discounted Cash Flow method which is a mechanism for trying to obtain more cash flow early in the project and less later, however for the sake of this article we do not need to go into the specifics of these 10).

It is extremely difficult to measure the costs and benefits of a natural energy source such as wind power and a conventional power source, coal fired electricity plants. A standard coal powered electricity plants can cost anywhere between 700 million and one billion dollars. Once this plant is established, it has running costs which far outweigh wind farms as it needs to continually purchase coal and requires more staff in order for it to operate. The current price of thermal coal, at the date of this article being written, is at $88US. Please see comparison below, which will use the production per megawatt produced as the baseline figure, with the maintenance and staff costs being based on one calender year. Please note that these prices are approximate only, these may vary according to timing, location or other factors. Price is in USD.

__Wind Power__

Construction Costs: $2,000,000

Operations and Maintenance Costs: $1,000 11)

__Coal Power__

Construction Costs: $3,500,000 12).

Operations and Maintenance Costs: $1,500 13)

coal_power_plant.jpg

Coal Fired Power Station 14)

Whilst the construction and maintenance costs of a coal fired power plant is more expensive, there are still some areas where coal is superior to wind or other renewable and natural energy sauces. Wind or solar power does not have the capability to ramp up production during times of peak usage, and in times of low usage and high production, there are little options for the storage of this extra energy. On the flip side however, coal fired power plants have high rates of carbon dioxide emissions into the atmosphere, compared to wind farms which have little to no emissions.

There have also been claims that the amount of energy used to build a wind turbine outweighs the amount of energy it may produce or save in it's lifetime. Studies have shown that wind turbines pay back their energy 'debt' in approximately 6 months and produce up to 25 times of the energy that was used to build and maintain them, making these claims a myth at best. This study was conducted over a time span of 30 years with 119 different turbines tested with 50 types of analysis performed 15).

Health Impacts

In recent times there have been various claims about the potential negative health impacts that may be caused by large wind turbines. In 2013, a report was published in the Canadian Family Physician, a medical journal. The author, Dr Roy D. Jeffery, claimed that people who live near large wind turbines were likely to suffer from adverse health effects. Most of these ill effects were reported to have come from stress, insomnia, headaches, anxiety and depression. The author linked the construction of wind farms in the general vicinity of the victims as the cause of the ill effects, and also cited several other similar studies. He concluded that where possible these wind farms should be kept separate from residential areas 16). The author of this article and the journal made some corrections to their original publication here http://www.cfp.ca/content/59/9/921 in order to clarify some inconsistencies.

There have also been several studies that refute these claims. In 2011 a study was conducted by the National Health and Medical Research Council, which is a department of the Australian Government, and this study concluded that there was no scientific link between industrial wind turbines and adverse health in people who live nearby. The study tested various the potential health impacts that could come from noise, infrasound, electromagnetic interference, shadow flicker or glints from the blades and found that there was no evidence of any of these factors possibly causing any negative health impacts 17).

Even though the arguments made that link industrial wind turbines and adverse health effects are tentative at best, most projects are now using minimum setbacks between the turbines and human habitations in order to alleviate any possible concerns by individuals and communities 18).

Conclusion

This article has discussed the history of wind energy, how its works, the costs of production, comparisons to other electricity producers and perceived health effects. Wind power technology has come a long way since it's early days, and there are now some impressive structures which can produce high levels of electricity. Significant amounts of research is required in order to determine whether certain areas are suitable to wind farms, also with the potential costs of the project due to location, access, topography and other construction and legal costs. When these conditions are met, there is little doubt that wind power is a preferable to coal fired electricity, however there can be drawbacks.

Wind power can struggle during peak usage periods due to being unable to increase its output, and power can sometimes be wasted when production outweighs demand. The best solution to these problems would be to have a multi-faceted approach. Coal fired power stations can increase and decrease energy production at will, but there are several negatives to coal power, such as carbon dioxide emissions and other air pollutants.

The energy grid would be best suited to have both wind and coal power, with wind being the primary producer, and the coal fired power plant used at it's lower limits with the potential to increase output during peak times. This would contribute to energy usage being cleaner, with no concerns of power cuts during peak periods.

The negative health impacts of wind turbines appear to be negligible. With the advent of setbacks and minimum distances from human habitation, there should be no adverse health effects suffered by any residents near these wind farms. The study that was conducted by the Canadian Family Physician journal links wind turbines to a host of perceived illnesses, however the reported symptoms could be caused by a host of other factors, which not taken into consideration by this study.

Alternative Energy | Environment

1)
The Guardian, 2008, 'Timeline: History of Wind Power', Available: http://www.theguardian.com/environment/2008/oct/17/wind-power-renewable-energy
2)
Nelson, V., 2009, 'Wind Energy: Renewable Energy and the Environment', Chapter 1, CRC Press, ISBN: 978-1-4200-7568-7
3)
World Wind Energy Association, 2013, '2013 Half Year Report', Available: http://www.wwindea.org/home/index.php
4)
Wind Farm in Washington State by Walter Siegmund licence CC 3.0, Available: http://commons.wikimedia.org/wiki/File:Wind_farm_7966.JPG
5)
Nelson, V., 2009, 'Wind Energy: Renewable Energy and the Environment', Chapter 3, CRC Press, ISBN: 978-1-4200-7568-7
6)
Nelson, V., 2009, 'Wind Energy: Renewable Energy and the Environment', Chapter 9, CRC Press, ISBN: 978-1-4200-7568-7
7)
Nelson, V., 2009, 'Wind Energy: Renewable Energy and the Environment', Chapter 8, CRC Press, ISBN: 978-1-4200-7568-7
9)
Windustry.org, 2014, 'How Much Do Wind Turbines Coast', Available: http://www.windustry.org/resources/how-much-do-wind-turbines-cost
10)
Wang et al, 2008, 'Benefit Evaluation of Wind Turbine Generators', IEEE Transactions on Power Systems, vol.24, no.2, pp 694-695
11)
NREL, 2011, 'Economic Development Impact of 1000mw of Wind Energy in Texas', Available: http://www.nrel.gov/docs/fy11osti/50400.pdf
12)
Schlissel, D, Smith ,A & Wilson, R, 2008, 'Coal-Fired Power Plant Construction Costs', Available: http://schlissel-technical.com/docs/reports_35.pdf
14)
Coal Fired Power Station by Rennett Stowe licence CC 2.0, Available: http://commons.wikimedia.org/wiki/File:Coal-fired_Power_Plant_(3518071026).jpg
15)
Kubiszewski, I, Cleveland, C, Endres, P.K, 2010, 'Meta-analysis of Net Energy Return for Wind Power Systems', Renewable Energy, vol. 35, no.1, pp.218-235
16)
Jefferys, R.D, 2013, 'Adverse Health Effects of Industrial Wind Turbines', Canadian Family Physician, vol. 59, no.5, pp. 473-475, Available: http://www.cfp.ca/content/59/5/473.full
17)
Nhmrc, Australian Government, 2011, 'Wind Farms and Human Health', Available: http://www.nhmrc.gov.au/your-health/wind-farms-and-human-health
18)
Knopper, L. D., & Ollson, C. A, 2011, 'Health Effects and Wind Turbines: A Review of the Literature', Environmental Health : A Global Access Science Source, vol.10, no.1, p.78

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