Lightweight, Collapsible Wind Turbine

Transcription

1 Lightweight, Collapsible Wind Turbine Design Team Dan Faulkner, Leanne Fortune, Alex Schaps, Kevin Zephir Design Advisor Prof. Mohammad Taslim Abstract The goal of this project is to create a more cost effective solution for powering electronics in remote locations by utilizing a renewable energy source, such as wind. This was done by designing a collapsible helical turbine that is vehicle mounted. This design was selected because it is the most efficient and the least complex out of all other wind turbine designs. The helical turbine design also has a base mounted generator which reduces the overall weight at the top of the turbine. In order to make the turbine collapse to less than a quarter of its full size, it completely dissembles so that the blades (40 inches in length) are the largest piece stored. The blades disconnect from the spokes utilizing a snap-on mechanism that is quick and efficient. The spokes then disconnect from the central hubs with latches similar to those found on a typical toolbox. Lastly, the supporting shaft breaks down into smaller, 40 inch sections. These sections connect to each other using a male-to-female concept and are secured with through pins that can easily be removed. The three blades, disassembled shaft, spokes, and pins all fit into the storage box. This box also includes a compartment for the electronic system and for the gearbox. This system includes a generator to transfer the energy obtained from the turbine through a charge controller to two 12V batteries. The collapsibility concept was proven so it could easily be implemented in to the defense or commercial sector. Figure 1: Turbine Attached to Military Humvee

2 The Need for Project To create a more cost effective solution for powering electronics in remote locations by utilizing a renewable energy source. Over the past several decades fossil fuel consumption has risen considerably throughout the world. Currently, US military vehicles in hostile areas are required to idle so that all necessary electronics are kept running. With vehicles such as the Humvees idling at 6.4 gallons per hour, where an hour of idling on a typical mission includes 10 vehicles, the total consumption would be 64 gallons per hour for an entire mission. This situation is not an uncommon occurrence for the military, and it can increase rapidly when the United States is at war. Creating a reliable alternative that would allow a vehicle to stop and shut off its engine yet still receive power for electronics through a wind scavenging system is necessary to decrease these costs. The Design Project Objectives and Requirements The objective of this project is to Design Objectives design and test a lightweight, The objective of this project is to accomplish a proof of concept collapsible wind turbine that can for a collapsible wind turbine. It is essential for the design to be be mounted on a military or lightweight so that it can be mounted on the side of the vehicle and recreational vehicle. assembled by two people. It must also be extremely efficient at lower than normal heights. Design Requirements Several requirements must be met in order for the prototype to be considered successful. The most critical requirements are that it must provide 50W of power in 12 mph winds and be able to collapse to 1/8 of its deployed size, quickly and efficiently. The wind turbine assembly should also be vehicle mounted and output 24 VDC along with the other specifications. Design Concepts Considered A horizontal axis turbine, a Three wind turbine design concepts were considered and evaluated vertical axis turbine, and a during this project before the final design was chosen. These three helical axis turbine were designs were a three blade horizontal axis turbine, a vertical axis considered. turbine, and a helical axis turbine based on the Gorlov design. Horizontal Axis Turbine This traditional wind turbine is most commonly used to provide power on a large utility scale. In this design the tower would be telescoping and the blades would then collapse by folding onto

3 Figure 2: Horizontal Axis Turbine Figure 3: Gorlov Turbine themselves whether rotating around the center point or folding back over the main power train. This design would have three blades to optimize the efficiency of the turbine and to minimize drag. One of the advantages of this design is the adjustable blade pitch, which would allow the turbine to collect the most wind energy available at a given time. Vertical Axis Turbine The Darrius vertical axis wind turbine was analyzed for initial brainstorming of collapsibility. This turbine would collapse by utilizing a telescoping central column and the rotors would be made out of a pliable material so that they could fold in half lying horizontal to the ground. An advantage to this design is the ease of collapsibility. However, it may be difficult to obtain the desired efficiency due to vertical axis wind turbines inefficiency compared to horizontal axis turbines. Helical (Gorlov) Turbine The Gorlov turbine is currently designed to function in water and air. The helical turbine is unique to other turbines because the rotational direction is independent of the wind direction, which eliminates the complexity of a yawing mechanism. Final Design Concept The Gorlov turbine design was chosen because of its increased efficiency and decreased complexity. Figure 4: Collapsed Turbine in Storage Box A Gorlov Turbine design was pursued in order to meet the project specifications. This design was selected because it is more efficient and has decreased complexity. Design Description The design is comprised of three blades which rotate across 30 of the total circumference of the turbine. The blades are 40 inches long and disconnect from the spokes using a set of tabs. This allows the spokes to hinge down along the sides of the supporting shafts. These shafts disassemble into three shafts, each a length of 40 inches. This allows for the turbine to be placed at an optimal height. The shafts connect to each other and are secured with through pins that can easily be inserted and removed. The blades, shafts, two of which include the spokes, and pins all fit into their designated compartment in the storage box.

4 Figure 5: ANSYS Analysis of Turbine Figure 6: Airfoil Profile for Hotwire Figure 7: Airfoil Cutting Jig Analytical Investigation A permanent magnet generator will be used because it is designed for use with wind turbines. A gearbox was designed in order to give the generator a higher rpm for operation. This gearbox is designed to give a 1:12 gear ratio with the use of four gears. It is connected via ½ diameter stainless steel shaft. The shaft will then be supported by six bearings of various types. In order to protect the turbine from spinning wildly out of control a continuous load must be maintained on the generator. This also gives it the ability to charge the battery effectively. A smart charge controller is used to charge the battery in stages which reduces electrical losses. This controller provides us with not only the ability to keep a constant load on the turbine and a smart charge, but it also protects the system from back flow of current and over charging. Experimental Investigation The material and the manufacturing of a lightweight rigid set of blades, or airfoils, was investigated and engineered based on other experiments done within the field. The blades consist of an Expanded Polystyrene foam core laminated with a fiberglass shell to give it more strength and resistance to wear. The foam was cut using a hotwire made up of a bare 21 AWG stainless steel wire shaped into the NACA0018 airfoil profile. This profile receives a low voltage and high current when it was connected to a variable transformer. This hotwire was attached to the end of a jig that was designed and constructed in order to give the blades the helical curve that is desired. This process yields 20 inch cores that were then trimmed in order to use the optimal pieces. These pieces were then joined using a dovetail type connection and an adhesive to give the blades their total length. The blades were then covered with a fiberglass sleeve, resin, and then vacuum bagged in order to let the resin set and to keep the fiberglass from being damaged. This process created a lighter yet stronger fiberglass airfoil. Key Advantages of Recommend Concept The advantages to this design are that it can be disassembled for easier storage which provides shelter for the blades and components when the turbine is not in use. This design is easy to transition into a

5 large scale manufacturing facility because it is made up of minimal custom parts. It is also lightweight so it can be assembled and disassembled without the use of any added tools. It also has the potential to be used outside the military sector, for example mounted on a recreational camping vehicle or for disaster relief. Financial Issues The use of fiberglass coated foam airfoils for mass production, along with the overall prototype cost, was the main financial concerns. It is important to manufacture these units at a high volume and at small cost in order to provide a cost effective solution for consumers. A small wind turbine can be used to replace small generators that are often times used in power outages and disaster areas. They create a more cost effective way to get electricity, especially if transportation is limited or there are no gas stations available due to natural disasters or remote locations. The manufacturing of the airfoils is the most expensive piece of the prototype but with mass manufacturing the cost would drastically decreased if the process was automated. A larger jig would also be constructed to accommodate a full blade. If a larger reusable vacuum bagging process was used the blades could be fiber glassed and vacuumed bagged in larger numbers. Recommended Improvements Further development of the This design is a proof of concept for collapsibility. A possible overall durability for use in harsh stage two of this project would be to investigate materials that can conditions would make the design withstand harsh conditions which can be found in remote locations idle for military applications. like deserts or arctic regions. Also, the turbine should have the ability to maintain performance if it is exposed to petroleum products which often times can be found on military vehicles and bases. These specifications would be essential to make the turbine idle for military applications.