-: IMPORTANT NOTICE :-
Your answer is given in the explanation section, so please read carefully the explanation section for getting 100% in on the nptel assignment.
From 2005 to 2019, wind energy electricity production has grown by 5 times its 2005 value.
True
False
True. Wind energy electricity production has indeed grown significantly from 2005 to 2019. It's important to note that the exact growth rate may vary depending on the specific region or country being considered, but on a global scale, wind energy production has generally experienced substantial growth during this period.
Onshore wind energy generated electricity is cheaper than offshore wind energy generated electricity.
True
False
True, generally speaking, onshore wind energy generated electricity is typically cheaper than offshore wind energy generated electricity. This is due to several factors, including lower construction and maintenance costs for onshore wind farms, as well as easier access to infrastructure and less complex installation procedures. Offshore wind farms require more expensive installation and maintenance due to the challenges of building and operating in marine environments, which can increase overall costs. However, it's important to note that the cost gap between onshore and offshore wind energy has been decreasing over time as technology improves and economies of scale are achieved in the offshore wind sector.
Most of the wind energy available on Earth is technologically inaccessible.
True
False
That statement is **true** to some extent. While there is a significant amount of wind energy available on Earth, not all of it is easily accessible or technologically feasible to harness. Some regions with strong and consistent winds, such as high-altitude areas or extremely remote locations, might present challenges for installing and maintaining wind turbines. Additionally, there could be environmental, regulatory, or logistical constraints that make certain areas less suitable for wind energy development.
However, it's also worth noting that advances in technology, such as the development of more efficient and versatile wind turbine designs, along with improvements in energy storage and transmission systems, could potentially increase the accessibility of wind energy resources over time. As technology continues to evolve, the ability to tap into previously inaccessible wind resources may improve.
In general, equatorial regions have higher wind energy resource than high latitudes.
True
False
False. In general, high latitudes (closer to the poles) tend to have higher wind energy resources compared to equatorial regions. This is because the temperature differences between the equator and the poles create atmospheric pressure gradients, which drive stronger and more consistent winds at higher latitudes. These strong winds are favorable for wind energy generation.
Equatorial regions, on the other hand, often experience more stable and uniform weather patterns, which can lead to less variation in wind speeds and lower overall wind energy potential. While equatorial regions may still have sufficient wind resources for wind energy generation, they tend to have lower average wind speeds compared to certain high latitude areas.
It's important to note that wind patterns and energy potential can vary widely depending on local geographical features and climatic conditions. This general trend may not hold true for every specific location.
In general, coastal offshore regions have higher wind resource than interior land regions.
True
False
True. In general, coastal offshore regions tend to have higher wind resources compared to interior land regions. Coastal areas are more exposed to open ocean winds and typically experience stronger and more consistent wind speeds. This is due to the unobstructed flow of air over the water's surface and the absence of significant land features that can disrupt wind patterns.
Offshore wind farms located in coastal areas can take advantage of these higher and more consistent wind speeds, leading to increased energy production and efficiency. On the other hand, interior land regions may have lower and less predictable wind speeds due to various factors such as terrain features, buildings, and vegetation that can cause wind turbulence and reduce the overall wind resource.
However, it's important to consider site-specific factors, as well as advances in wind turbine technology and energy transmission, which can make certain interior land regions viable for wind energy development as well.
Crests of hills and mountains are considered good locations for turbine placement.
True
False
True, the crests of hills and mountains can be considered good locations for wind turbine placement, especially in areas with sufficient wind resources. This is because elevated terrain features like hills and ridges can channel and accelerate wind, resulting in higher wind speeds at those locations. When wind flows up the slope of a hill or mountain, it can create a phenomenon known as "orographic lift," which increases wind velocity and makes these areas potentially favorable for wind energy generation.
However, there are several factors to consider when determining the suitability of hill and mountain locations for wind turbines, including wind speed, wind direction, accessibility, environmental impact assessments, and local regulations. Additionally, the complex terrain can influence the aerodynamics of wind turbine operation, and careful engineering and design considerations are necessary to optimize energy production and turbine performance.
It's important to conduct thorough site assessments and studies before installing wind turbines on hills or mountains to ensure safety, efficiency, and minimal environmental impact.
At maximum efficiency condition, the velocity of wind downstream of the turbine is 50 % of the velocity of wind upstream of the turbine.
True
False
At maximum efficiency conditions, the velocity of wind downstream of the turbine is generally **not** 50% of the velocity of the wind upstream of the turbine. In fact, the efficiency of a wind turbine is usually defined by its power coefficient, which represents the proportion of the available kinetic energy of the wind that the turbine is able to convert into mechanical power.
The Betz limit, which is a theoretical limit for wind turbine efficiency, states that the maximum possible kinetic energy that can be extracted from the wind by a wind turbine is around 59.3% of the total kinetic energy in the wind stream. This implies that the theoretical maximum efficiency is achieved when the velocity of the wind downstream of the turbine is reduced to about 59.3% of the upstream wind velocity.
In practical terms, real-world wind turbines achieve efficiencies that are lower than the Betz limit due to factors such as aerodynamic losses, mechanical losses, and wake effects. The velocity of the wind downstream of a wind turbine will be influenced by these factors, but it will not typically be as low as 50% of the upstream velocity. The actual downstream wind velocity will vary depending on the specific design and operating conditions of the wind turbine.
The lift force generated by the wind on the blade cross-section is responsible for the rotational motion imparted on the wind turbine blades.
True
False
Yes, that's correct. The lift force generated by the wind on the blade cross-section is indeed responsible for the rotational motion imparted to the wind turbine blades. Wind turbine blades are designed with an airfoil shape similar to that of an airplane wing. When the wind flows over the curved surface of the blade, it creates a pressure difference between the upper and lower sides of the airfoil.
This pressure difference, along with the shape of the airfoil, generates lift force perpendicular to the wind direction. The lift force, in turn, causes the wind turbine blades to rotate around their central axis. This rotational motion is then transferred to the generator, which converts the mechanical energy into electrical energy.
The combination of lift and drag forces acting on the wind turbine blades allows for the efficient conversion of wind energy into usable electricity. The aerodynamic design of the blades plays a crucial role in optimizing the capture and conversion of wind energy.
The power delivered by a wind turbine increases linearly with increasing wind speed.
True
False
False. The power delivered by a wind turbine does not increase linearly with increasing wind speed; it actually increases with the cube of the wind speed. This relationship is described by the power curve equation for a wind turbine:
P = 0.5 * ρ * A * Cp * V^3
Where:
P = Power output
ρ = Air density
A = Swept area of the rotor blades
Cp = Coefficient of performance (efficiency)
V = Wind speed
As you can see from the equation, the power output (P) is proportional to the cube of the wind speed (V^3). This means that even a small increase in wind speed can lead to a significant increase in the power output of the wind turbine. However, there is an upper limit to this relationship, as wind turbines have cut-out wind speeds beyond which they shut down to avoid damage.
It's important to note that while the power output increases with wind speed, the efficiency of the wind turbine may vary at different wind speeds, and the turbine may have an optimal operating range for maximum efficiency and power output.
Net power generated by a set of wind turbines in a wind farm is independent of blade diameter.
True
False
False. The net power generated by a set of wind turbines in a wind farm is not independent of blade diameter. Blade diameter is a crucial factor that directly impacts the overall power generation capacity of a wind turbine and, consequently, the net power generated by a wind farm.
Larger blade diameters typically allow wind turbines to capture more energy from the wind, as they have a larger swept area and can intercept a greater volume of air. This increased capture of wind energy leads to higher power output. Wind turbine design, including blade diameter, is optimized to achieve the best balance between capturing wind energy and other considerations such as structural integrity, aerodynamics, and operational efficiency.
In essence, larger blade diameters often result in higher power output and increased energy production for a wind farm, given that other factors such as wind speed, turbine efficiency, and operational conditions remain constant.
At location A, the average wind speed is 12 m/s while at location B, the average wind speed is 10 m/s. The ratio of available wind power for these two locations is W˙A/W˙B
=?
1.2
1.44
1.728
2.074
The available wind power at a location is proportional to the cube of the wind speed. Therefore, the ratio of available wind power (Wa) at location A to available wind power (Wb) at location B can be calculated using the wind speed ratios:
\[ \frac{Wa}{Wb} = \left(\frac{Va}{Vb}\right)^3 \]
Where:
- Wa is the available wind power at location A
- Wb is the available wind power at location B
- Va is the wind speed at location A (12 m/s)
- Vb is the wind speed at location B (10 m/s)
Plugging in the values:
\[ \frac{Wa}{Wb} = \left(\frac{12}{10}\right)^3 = \frac{1728}{1000} = 1.728 \]
So, the ratio of available wind power at location A to location B is approximately 1.728.
For a location, it is found that Rayleigh distribution (of wind speed) has a scale parameter value of 13.5. What is the most probable wind speed at that location? (Choose the closest value)
12 m/s
10.5 m/s
9.5 m/s
8 m/s
In a Rayleigh distribution, the most probable wind speed (mode) is given by the formula:
\[ \text{Mode} = \text{Scale Parameter} \times \sqrt{\frac{2}{\pi}} \]
Given a scale parameter value of 13.5, we can calculate the most probable wind speed:
\[ \text{Mode} = 13.5 \times \sqrt{\frac{2}{\pi}} \approx 10.15 \]
Rounded to the closest value, the most probable wind speed at that location is approximately **10 m/s**.
The average velocity in a location is 10 m/s. The velocity value of wind at which that location will have maximum power assuming Rayleigh distribution of wind speed is
10 m/s
12 m/s
14 m/s
16 m/s
In a Rayleigh distribution of wind speed, the wind speed value at which a location will have maximum power is related to the scale parameter of the distribution. The relationship between the scale parameter (σ) and the wind speed value (V_max) at which the distribution has its maximum is given by:
\[ V_{\text{max}} = \sqrt{\frac{2}{3}} \cdot \sigma \]
Given that the average velocity at the location is 10 m/s, we can assume that the scale parameter (σ) of the Rayleigh distribution is related to the average velocity. The relationship between the scale parameter and the average velocity for a Rayleigh distribution is:
\[ \sigma = \frac{\text{Average Velocity}}{\sqrt{\frac{\pi}{2}}} \]
Substituting the average velocity (10 m/s) into the equation:
\[ \sigma = \frac{10}{\sqrt{\frac{\pi}{2}}} \]
Now we can plug the calculated value of the scale parameter into the equation for the wind speed value (V_max):
\[ V_{\text{max}} = \sqrt{\frac{2}{3}} \cdot \left(\frac{10}{\sqrt{\frac{\pi}{2}}}\right) \]
Calculating the value:
\[ V_{\text{max}} \approx 10.75 \, \text{m/s} \]
Therefore, at the location with an average velocity of 10 m/s and assuming a Rayleigh distribution of wind speed, the wind speed value at which the location will have maximum power is approximately **10.75 m/s**.
Identify which of these instruments is not present in a Nacelle
A vane
A pitch controller
A brake
A temperature sensor
A **temperature sensor** is typically not present in a nacelle. While the other instruments listed – a vane, a pitch controller, and a brake – are commonly found in a wind turbine nacelle, a temperature sensor is not a standard component of the nacelle's instrumentation. Temperature sensors might be located in various parts of a wind turbine for monitoring purposes, but they are not typically part of the nacelle's internal instruments.
A 3 bladed turbine has a tip speed ratio of 12. The rated wind speed is 12 m/s and the blade radius is 60 m. At rated conditions, what is the rpm of the wind turbine shaft? (Select closest value)
23 rpm
2.3 rpm
230 rpm
0.23 rpm
The correct answer is **2.3 rpm**.
The tip speed ratio (TSR) is defined as the ratio of the tangential speed of the blade tips to the wind speed. Mathematically, TSR is given by:
\[ \text{TSR} = \frac{\text{Blade Tip Speed}}{\text{Wind Speed}} \]
For a 3-bladed wind turbine, the blade tip speed is related to the rotational speed (rpm) and the blade radius (R) by the formula:
\[ \text{Blade Tip Speed} = \text{rpm} \times 2 \pi R \]
Given the TSR value of 12 and the wind speed of 12 m/s, we can set up the equation:
\[ 12 = \frac{\text{rpm} \times 2 \pi R}{12} \]
Given the blade radius (R) of 60 m:
\[ 12 = \frac{\text{rpm} \times 2 \pi \times 60}{12} \]
Solving for rpm:
\[ \text{rpm} = \frac{12 \times 12}{2 \pi \times 60} \approx 2.27 \]
Rounded to the closest value, the rpm of the wind turbine shaft at rated conditions is approximately **2.3 rpm**.