Mechanical Design of Turbine Blades
Milestone 1
For this milestone we were required to write a pre-project research memos which talks about the current state of wind turbine technology and some design factors for it.
We have been harnessing wind energy for hundreds of years. It was first used to grind grains and pump water, but now it is used as a renewable energy source. Some key components of a wind turbine are the rotor blades, shaft, and the generator. “When the turbine blades capture wind energy and start moving, they spin a shaft that leads from the hub of the rotor to a generator. The generator turns that rotational energy into electricity. At its essence, generating electricity from the wind is all about transferring energy from one medium to another” [1]. With the demand for clean and renewable energy continuing to increase, designers take into account of multiple factors when designing wind turbines in order to efficiently turn wind into usable energy. Design factors: There are multiple factors to consider when designing a wind turbine. One of them being the rotors, which “is the main part of a modern wind turbine design that collects the winds energy and transforms it into mechanical power in the form of rotation” [2]. The number of blades a turbine has is a factor, it affects cost because the more blade one has the more expensive it will be and affects stability because even-numbered designs are less stable while odd-numbered is smoother and “rotates smoother because the gyroscopic and flexing forces are more evenly balanced across the blades increasing the stability of the turbine”[2]. Furthermore, the design of the rotor blades is important. They determine if they will use the 3 Project-1 lift or drag method to extract energy from the wind. To add, the length of the blades is another factor when designing a wind turbine. The length affects 3 Project-1 how much area it covers 3 Project-1 when going in circles, “ as the swept area of the rotor increases, the area it covers also increases with the square of the radius” [2], will also increase the amount of energy received, weight and cost of the turbine. Another factor is the angle of the blades. The right angle will make it the most efficient because the wind will not always hit a turbine straight on, they might come from a different angle. Choosing the right angle of the blade will increase efficiency. The last factor is construction, the type of material used to create the blades. The material needs to “combine the necessary structural properties of high strength to weight ratio, high fatigue life, stiffness, its natural vibration frequency and resistance to fatigue along with low cost” [2]
[1] Julia Layton, How Wind Power Works, howstuffworks. Available: https://science.howstuffworks.com/environmental/green-science/wind-power.htm#pt2. [Accessed: September 27, 2020]
“Wind Turbine Design”, Alternative Energy Tutorials. Available: https://www.alternativeenergytutorials.com/wind-energy/wind-turbine-design.html. [Accessed: September 27, 2020]
Milestone 2
The objectives for this milestone were to create an objective tree and problem statement for our assigned scenario.
Objective Tree
Problem Statement
The country of Sweden needs an effective and light wind turbine to reduce the effects of harmful green house gases in the environment. The wind blade should have low impacts on the environment and should contain 3 blades per windmill.
Top Three Objectives
Cost
Rationale: The cost of the wind turbines is important because many wind turbines will need to be built in order to power multiple cities. Although it is difficult to avoid using certain materials like carbon fiber in the design of the wind turbine blades, we want to minimize the cost of such materials to ensure the efficiency and the longevity of the blades.
Efficiency
Rationale: The wind turbine should be able to produce electricity at maximum efficiency because the turbines will be required to power multiple cities. During different wind speed conditions, the blades should adjust themselves in order to generate electricity accordingly. Lesser overall wind turbines should be required to lower the cost of production.
Rationale: The blades need to last a long time so it can continuously produce energy for Sweden. If wind turbines blades need to be replaced constantly, it will be expensive and not worth the price. Moreover, it needs to be durable, able withstands all sorts of weather so it can have a long-life span. People need a reliable source of energy, if the blades needs to be replaced constantly that will affect the amount of energy produces which will affect the public.
Longevity
Objectives Metrics
Swedish Krona (kr), USD ($)
1-4 million per wind turbine is ideal. We are aiming for the range $2-3 million.
Cost
Efficiency
Percentage (%)
Our aim is to have an efficiency greater than or equal to of 50%. Anything less is not ideal.
Output Energy (Converted Electrical Energy)/ Input energy (Wind received) * 100%
Longevity
Units: Number of years until they need to be replaced.
Metric: Rating of how long the wind turbine blades last (bad, good, satisfactory)
More than 20 years = Good
Equal to 20 years = satisfactory/ideal
Less than 20 years= Not wanted/bad
Milestone 3A
In this milestone, my team mates and I determined our primary and secondary objectives for our assigned scenario. From that we generated 4 material property chart with our given MPI, to find the most suitable material to use for our wind turbine. I was tasked to find suitables materials based on CO2 emissions and Youngs Modulus.
Scenario: Pioneer in Clean Energy
My Property Chart
Team Member #1 Property Chart
Team Member #2 Property Chart
Team Member #3 Property Chart
We pool our property charts together to determine the best material based on our objectives.
We rank each factor based on importance then evaluate each material based on our criteria.
Steel (low alloy) showed that it had a high MPI, therefore it was chosen to be one of our 3 finalists. Based on the decision matrix, it proves the most favorable as it has lowest cost and highest durability. This makes it a better choice than the other 2 materials as it is more well-rounded, the other 2 materials only have low CO2 emissions.
Milestone 3B
For the second half of this milestone, we calculate for the maximum deflection using geometric and deflection equations. After we get our values we develop a CAD model of the wind turbine blade on which we perform a deflection simulation using Inventor. For this we used Brass, not low alloy steel which is our chosen material.
CAD Model
Deflection Simulation
Milestone 4
For our last milestone we determined the geometric requirements of our wind turbine blade using our chosen material. Moreover, we will perform an Inventor simulation to determine the thickness of our blade that will staidly our deflection constraint. Each member is given a thickness, which they use to calculate for a deflection value. We used the formulas below to calculate 4 deflection values.
We followed Design A- Stiff material because out material property for Low Alloy Steel matched it.
Our deflection calculations:
We got a range of deflection values from out calculations. We knew that we needed a deflection within the range of 8.5mm and 10 mm. To determine our thickness, we used Inventors built in deflection simulation to find the thickness. Through a series of trial and error, we determined our thickness to be 25mm.
Final Deliverable
Finalized Problem Statement
To fulfill the needs of the Sweden wind farm, an environment efficient wind turbine needs to be created in order to reduce the greenhouse effect gases. The material for the turbine blade needs to be strong, long-lasting and most importantly have a low impact and cause low CO2 emissions since our goal is to reduce CO2 emissions to zero
Conceptual Design
According to the material performance indices (MPI’s) it was determined that the most optimal material to complete the objectives of this scenario would maximize yield strength and Young’s modulus, while minimizing cost of production and CO2 emission. Using each of the previously mentioned MPI’s a material property chart, was created in order to determine a top 5 materials list for each of the MPI equations. The final selection was narrowed down to 3 options by comparing the list of top 5 materials and taking the 3 most common, those being wood (typical and along grain), bamboo, and steel (low alloy). The 3 material finalists were then inputted into the decision matrix in order to determine which one of the 3 best fit our design factors that were previously stated. From the decision matrix wood and bamboo received a score of 20 points while the steel received 21 points meaning that out of the 3 materials steel was the best material for our given scenario. However, these results are based off only the main design factors, when working on a project such as this many more factors must also be considered. An example of an additional material consideration is, how weather resistant the material is. If the material cannot withstand a variety of environmental conditions, then it most likely is not reliable enough for a country to depend on that source of energy. Another material consideration is the ease of access Switzerland has to the desired material, if Switzerland can domestically produce the required material, they will be able to save on import costs.
Design Embodiment
The deflection constraint was calculated to be between 8.5mm and 10 mm. A variety of thicknesses ranging from 15mm - 150 mm were used to calculate an estimated deflection. Through a process of trial and error, a thickness of 24.5mm was discovered to be the thickness to get a deflection of 9.66mm, which is within the calculated range.
Concluding Remarks
The task is to develop a wind turbine for Switzerland that will reduce CO2 emissions to 0 by 2045. In order to accomplish that, GRANTA was used to determine the best suited material based on important factors listed on the decision matrix shown above. Multiple calculations were carried out to determine a range of thickness that yielded a deflection between 8.5mm and 10mm, from there multiple simulations were ran in order to test the range of thicknesses. Additional factors to consider are lifespan, durability and economy. The turbine farm cannot be a burden to the economy, it needs to make money for it to run. It can achieve that by having a longlife span and be able withstand all sort of weather, so it doesn't need to be replaced often. Moreover, it can be more cost effective if Switzerland can domestically produce the required material. In all, the design process in large scale projects such as this, is especially important as it identifies key factors, constraints, and objectives of a project. This allows for the problem to be broken down and be handled and smaller and more manageable steps.