In the last few decades, renewable energy has proved to be transformative for many countries globally. For instance, wind energy is deemed the second largest contributor to renewable energy in regions such as Australia as it contributed to an estimated 5.7% of the overall power in 2017. However, numerous concerns still exist with regards to the investment feasibility and cost-effectiveness of renewable power sources such as wind and solar. The unique thing is that with new designs and technological innovations, energy sources such as wind are increasingly being diversified to meet the global energy demands. Moreover, the rising demand for alternative energy sources tends to propel the renewable energy sector to the mainstream.
In this article, all the aspects necessary to keep you up to speed with regards to wind energy will be covered in detail.
Wind as a source of energy
Wind energy is a type of energy whose process ends up creating electricity through the use of the naturally occurring airflows within the atmosphere. The wind gets facilitated by the uneven heating of the atmosphere combined with the varying surfaces of the earth as well as its rotation. As such, modern turbines get utilized in the capturing of kinetic energy from this wind hence generating electricity. By definition, a wind turbine or windmill is a tool that turns wind’s kinetic energy into renewable electricity. It is critical to note that unlike fans, wind turbines do not utilize electricity to make wind. Instead, their principle involves using wind to make electricity. The turbines make use of aerodynamic force that emanates from the rotor blades. The rotor blades function as the typical helicopter rotor blade. The mechanism is in such a way that whenever air flows across the blade, air pressure on one end decreases. This difference in the air pressure on the two sides of the rotor blades ends up creating lift and drag. It translates to the force of the lift being stronger than the drag on the rotor leading to constant spinning. Modern turbines have the rotors connected to a generator directly or indirectly. The conversion of the aerodynamic force to the rotation of a generator produces electricity.
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It is evident that wind is a solar energy form that is caused by the concurring of the rotation of the earth, irregularities of the earth’s surface and the uneven heating of the atmosphere. In this, wind flow speeds and patterns tend to vary globally as they are largely influenced by vegetation, topography and water bodies. Humans have since time immemorial utilized the wind flow’s mechanical energy for numerous purposes such as sailing. However, the mechanical energy gets converted into electricity with the help of a generator hence assisting with tasks such as pumping water and grinding grain. The unique thing is that with increased research and development, the blades of the current wind turbines are made in such a way that they are as aerodynamic as possible. This way, they end up making the most of the wind’s energy. The next section expounds on the different types of wind turbines you are bound to come across.
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Types of Wind Turbines
While there exist different types of turbines, most modern types have typically 3 blades that rotate clockwise. In this, the wind turbines tend to run either at fixed or variable speeds. The fixed speed turbines have a constant speed of rotation irrespective of the wind power. To facilitate this, they possess a gearbox that generates electricity at the right frequency. On the other hand, variable speed machines typically speed up and down concerning the wind power available. Hence, the correct grid frequency ends up being generated electronically.
Modern turbines largely fall into two types:
These are the general structures that many picture in their minds when thinking about turbines. These have three blades at the top of a shaft. The blades point towards the direction of the wind through the help of a pivot at the top of the shaft. Since their working mechanism involves the rotor blades being pointed to the wind, some of these structures have smaller turbines that are directed by wind vanes on the shaft. However, larger turbines possess wind sensors whose role is to turn the turbines towards the direction of the wind. For instance, you are bound to come across a horizontal-axis turbine that has a tail fin to keep the rotor blades facing the wind. Such also helps with issues of mast turbulence. Worth noting is the fact that horizontal-axis turbines these days are fitted with gearboxes. These help in accelerating the slow rotation so that it is rigid enough for the generator turbines.
Vertical-axis wind turbines are ideally useful in urban contexts or even areas where the direction of the wind is uncertain. This type of turbine has a main root that gets mounted on a vertical shaft. The blades present in this type of turbine, therefore, end up spinning like a carousel that sits on a vertical axis. The vertical-axis turbines are unique from the horizontal-axis ones as the former do not need to face towards the wind since the blades spin regardless. Moreover, they tend to have minimal maintenance practices as the rotor housing does not necessarily have to be hosted in the air. However, the additional torque on the vertical axis makes these less efficient than the horizontal ones. Vertical-axis turbines come in varieties such as darrieus, giro mill, savonius, and the twisted savonius.
How Much Does a Wind Turbine Cost?
When looking at the cost of a wind turbine, it is essential to identify whether it is being used commercially or residentially. During the installation of a wind turbine, many factors influence the total project cost. For instance, you have to consider the cost of the turbine itself, the cost of any electrical distribution network upgrades or even the cost of site works. However, for a typical home or farm turbine of less than 100 kilowatts, the cost is approximately $3000 to $8000 per kilowatt. As such, a 10-kilowatt turbine that can power a large home ends up having an installation cost of $50000-$80000. A point worth mentioning is that turbines tend to have remarkable economies of scale. This means that while smaller residential or farm turbines might be costing less generally, they end up being expensive based on each kilowatt of energy-producing capacity.
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On the other hand, a utility-scale wind turbine costs approximately $1.3 million to $2.2 million per Megawatt of nameplate capacity that is installed. Currently, the commercial-scale turbines that are installed have a 2MW size. Therefore, the rough estimate of installing such a turbine would translate to $3 to $4 million. However, just as indicated above, the price may fluctuate with respect to individual components such as the blades, the rotor hub, gearbox, controller, generator, transformer or tower. The reason behind this is that wind turbines of the modern-day are customized products. A customer hence ought to pick a turbine that adequately meets their needs or even budget.
How Much Energy Does a Wind Turbine Produce
Essentially, the amount of wind energy that can be generated by a turbine depends on the annual average wind speed, the installation site, and its size. However, it is also prudent that you look at a wind turbine’s power rating. The power rating gets measured in kilowatts (kW). This rating helps you get a clue about the size of the turbine with respect to the wind energy it can produce. An important aspect to note is that the kW rating is not a clear reflection of the total output capacity. To comprehend this, it would be ideal to consider the following analogy.
An individual could be having a 100-watt bulb in their bedroom. Leaving this bulb switched on for approximately 10 hours would result in 1 kWh being used on average. With these figures, turbine industry experts project that a 10kW wind turbine possesses the potential to give 10000 kWh annually.
Note that this estimation is on the assumption that the turbine operates under favorable conditions. This is not always the case as there will be periods where the wind to produce this energy lacks. In this case, the most ideal strategy to calculate the energy a turbine produces would be to multiply the mechanical efficiency of the turbine with the air density. The result should then be multiplied by the blade length and the wind speed. Debunking aspects like the wind speed, the United States Department of Energy indicates the annual average wind speed at 50 meters above the ground.
As such, the recommended wind speeds should be above 10 miles per hour mark. With the estimation that each United States home consumes 10656 kWh per year, 332 homes would be served as it would translate to 888 kWh monthly.
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Therefore, it is clear that the energy a turbine produces is a function of the turbine size, the wind speed, and the location. With these guidelines, a consumer will always be keen on the size or materials used to assemble the tool, the location of the turbine and the wind speed.
How tall are wind turbines?
In regions like the United States of America, wind turbines have been growing with regards to both the capacity and height in the last few years. In this, taller turbines are being preferred due to their unique ability to utilize the wind resources available optimally. A perfect example is the GE 1.5 megawatt model that has 116-ft blades on a 212-ft tower leading to a total height of 328 feet. With such a turbine, the blades are projected to sweep through a vertical airspace of almost an acre. Another epitome would be the 1.8 megawatt Vestas V90 in the country of Denmark. It possesses 148-ft blades and a 262-ft tower. This totals to 410 feet. While turbines with the height of 280 and above were few in the United States before 2006, this figure became the average height for many wind turbines as at 2012. Currently, there are numerous models as well as new once being introduced that comfortably reach 600 feet in total height. The transportation of some of the parts of the large cranes often presents challenges. This is the case as a typical wind turbines farm is bound to be located in remote areas. Therefore, curves have to be straightened while existing roads have to be widened. During the setting in of turbines of varying lengths, the steel tower gets anchored in a platform that many tons of steel rebar and concrete. Experts indicate that this is between 30 to 50 feet across and 6 to 30 feet in depth. At other times, longer turbines have their shafts driven deeper to help with the anchoring.
How Much Spacing is Ideal in a Wind Turbines Farm?
For residential turbines, the question normally narrows down to the distance obliged between a wind turbine and other obstructions. However, the rule of thumb is that a residential turbine should be installed 492.1 feet (150 meters) away from the nearest obstruction. The height should be in such a way that the bottom of the rotor blades sit 9 meters (29.5 feet) above any obstruction such as trees or buildings. On the other hand, wind farms tend to generate utility-scale energy. The unique thing is that the turbines in these farms resemble those in residential settings.
This means that to be efficient they should be installed in an area where the wind is smooth flowing. Therefore, turbines in a farm need to be well spaced from each other. An ideal recommendation is that the turbines should be 7 rotor diameters away from one another. Practically, a 262-foot rotor should be approximately 560 meters from an adjacent turbine. Moreover, doubling this space would contribute significantly to the efficiency of your farm.
Key Factors Affecting Wind Farm Bankability
Many developers or even individuals that are on the quest for renewable energy for utilities ought to consider the leveled cost of energy (LCOE). In this, the LCOE of wind energy has been gaining momentum rapidly hence making it an attractive option. However, it is critical to state that the LCOE of wind could vary from one project or even from one wind farm to another. Some of the factors that a developer ought to keep tabs on and consequently impact the project profitability include deliverability, risk, efficiency, reliability and the safety.
These are discussed below:
This is a significant issue as it faces an individual or even developer from the site selection to the operations. Wind turbines professionals indicate that controlling the risk is essential as it comes in handy when one is looking for financing. While the financial models might point out that the wind farm project will be profitable, you also have to show that it is bankable by mitigating risks. Therefore, it is good to understand aspects such as the grid connectivity. A grid integration analysis, in this case, can help in understanding whether challenges might occur later on in the project.
Conversely, a transmission and distribution root-cause analysis can help in locating trouble spots related to power quality or stability.
When a wind farm or turbine site has been selected, environmental permits in place and even the funding granted, it is time to strive to put up the project within the stipulated schedules. This is an ideal factor to consider especially since most developers end up dwelling on pre-negotiated power purchase agreements (PPAs) in their securing of funding. In such an agreement, there are milestones that should be met so that the PPA remains effective. As such, it is ideal to go for the right supplier so that the project ends up being commissioned and completed within the schedule.
The United States Energy Information administration cites that approximately 7% of energy gets lost during transmission and distribution. While this number may not seem large, it is ideal to reduce it with your turbines or farm. The unique thing is that a 1.67 MW turbine has the ability to reduce carbon emissions by over 3000 tons. Moreover, it would be ideal to consider offshore development due to the high strength and reliability of the offshore winds. While onshore could have a lower LCOE, it could lead to collisions with individual parties over issues like noise or a potential environmental impact. Since the greatest losses come from the energy transmitted over long distances investing in technology can help in boosting the efficiency of your project or even addressing potential environmental concerns. For instance, high-voltage direct-current (HVDC) cables can be utilized.
The renewable energy industry can be dangerous. Considering that there is an active shortage of skilled workers in the industry due to a few youth choosing the technical careers, companies have to be cautious about unusual working conditions like the installation of a turbine. An ideal strategy to boost safety is to have minimal maintenance by utilizing self-healing solutions or even turbines with few components.
The quality of energy is a significant concern in wind farms. The reason behind this is that the variable nature of this energy can lead to an unstable output on the grid voltage or frequency. Luckily, grid operators in the recent past have put in place grid-codes that ensure that the uncertain fluctuations do not end up disrupting the grid. Wind farm developers can compensate for the variability by implementing energy storage innovations or even the use of back up sources of power.
Wind Energy Pros and Cons
In any type of energy source, there exists both advantages and disadvantages. Irrespective of the fact that wind energy is the fastest-growing source of energy globally, it also has its pros and cons. These are expounded on below in the following section.
Clean and Renewable Energy Source
The production of wind energy is termed as ‘clean’. This is because unlike oil, coal or natural gas, the wind energy production does not result to the emission of greenhouse gases such as carbon iv oxide. While some considerations have to be taken into account with regards to the environment especially in large wind turbine farms, the turbines do not rely on fossil fuels to be operational. Besides, this energy is renewable meaning it never runs out. Economically, this is helpful as nations with such farms do not have to rely on fossil fuels from other regions. A country can, therefore, harness this energy as long as the wind blows.
When upfront installation costs are considered, residential and wind farm turbines can seem expensive. However, once these are up and running, the costs are extremely low. The reason is that the fuel (wind) is free and at the same time these turbines are not hard to maintain throughout their lifetime.
Savings for land owners
Landholders that rent their spaces to wind farms can end up making lots of additional cash. The government can end up installing turbines on your land and you end up being on a payroll. As a developer, producing more energy than you actually oblige from the wind farm can prompt the general grid to collaborate with you hence adding extra cash.
On the other hand, some of the cons of wind energy include:
Intermittency of Wind
Sometimes the wind does not blow reliably. Despite that most turbines run at 30% capacity on average, this energy source can be unavailable especially during periods of peak electricity demand. To circumnavigate this, wind energy needs to be accompanied by some storage technology devices. Moreover, it would be ideal to have the location of turbines in high altitudes.
Noise and Visual Pollution
Another con roots from the fact that wind farms result in visual and noise pollutions. This is because turbines can result to much noise. Besides, these turbines can end up interrupting scenic landscapes such as oceans, mountain ranges or even lakes.
Threat to Wildlife
Turbine blades can be quite large. Since these rotate at fast speeds, they can end up harming species that pass through them such as bats or birds. While currently this cannot be prevented, it is ideal to understand consequences that may arise.
The information given above gives a comprehensive overview of the wind energy. In this, aspects such as how wind turbines work were elucidated on and the different types of turbines discussed. Critical aspects such as the cost of turbines, the length, spacing and even the amount of energy that can be reaped from this energy source were covered. For developers, the factors that affect wind farm bankability were discussed so that they end up having viable and achievable projects. Finally, the pros and cons of wind energy were highlighted. Overall, wind energy continues to show great potential as it is environment friendly, renewable, and is considerably cheaper than the mainstream energy sources.