May 24, 2021
The purpose of the wave energy converter project is to demonstrate the wide range of applications which wave energy can hold for the modern world and future energy projects. In order to model this energy conversion concept, a scaled bridge will be constructed that has wired LED lamp posts, and a display registering the output energy from the system.
The first stage of developing the design for the wave generator was to find the most effective form for the tank. The size of the tank specifically is a direct factor, as the linear forces shaping the waves are dictated by the shape of the tank. The size was determined to be optimal with the dimensions of 6ftx2ftx3ft, as calculated with the scale factor of 1:40 in consideration. The tank, while having the capacity for 3 ft of depth, will only have 2 ft of water during testing, in order to account for splashing and change in water height during wave generation. Additionally, due to the reflective nature of waves, the back end of the tank will have a textured slant at a 45˚ angle to allow the waves to break and not cause turbulent water. In order to further let the energy carried in the waves to dissipate evenly across the tank, a mesh panel will be lined in front of the slanted area, allowing the water to flow through and across the back of the tank.
The mechanical structure of the tank needed to be considered heavily given the extreme weight of the water. From the measurements, the amount of water will equal 680 liters, or 1500 lbs of weight. For the integrity of the visual components of the project, the internal structure of the tank will be made primarily of plexiglass, allowing for a clear window for viewers. The sheets of plexiglass will be joined and waterproofed with acrylic glue and aquarium silicone. However, with this amount of weight and pressure, plexiglass has the tendency to bow outwards, regardless of any sealing methods. Thusly, this requires a reinforcement of aluminum to keep the shape of the tank. The aluminum will cage the sides of the tank with 0.5 in bars, 0.75 in apart – keeping multiple viewing areas with maintained structural integrity.
The wave generator system will include 2 linear actuators which are submerged into the water and create the wave defining motion. These actuators will be powered by 2 high torque, high voltage servos motors outside of the tank along with the rest of the electronic system. The servos are wired into a Teensy 4.0 microcontroller, which will allow the system to be programmed to a specific wave motion and adjustable. Additionally, the microcontroller will be connected to a liquid crystal display (LCD), allowing the system to be monitored and responsive. A power supply of 24V will give the electronics the necessary distributed power.
The energy converting system is suspended above the middle of the tank, via a model bridge constructed for the project. The system will be contained inside a clear acrylic box for viewing purposes. The method of energy conversion is controlled via one dimensional ball bearings and pistons that use the buoyant force of the waves to create rotational motion and generate electricity. The pistons respond to the circular motion of waves which correspond to the known up and down motion, and thusly rotate the shaft of the system which will be connected to a geared generator.
Figure 1: Example crankshaft diagram GIF, showing rotational motion
Attached to the generator will be an amperage sensor, that registers the power flow and displays the current energy going into the LED lamp posts. This energy likely will be fractional of the original power supply current input, however, the project demonstrates potential for energy optimization and efficiency in future developments.
Figure 2: Flowchart showing an electrical efficiency diagram of the system
This flowchart included demonstrates the electrical flow of the system, and where losses in energy are found. The largest loss in the energy of the system occurs in between the power supply and the servos, and additionally between the linear actuators and the wave. In looking at the considered parts, the calculated output would be roughly 0.1 amps of power, which calculates to be around 11% efficiency on the untested system. Additionally, this output would be completely sufficient to power the LED’s and demonstrate the system’s energy conversion, as the LED lamp posts require only 0.02 amps of power to run continuously. This is considered a highly optimal system, given the large area of power loss across the system. Future models of the project may be focused on increasing the efficiency or determining alternate energy conversion systems to optimize this energy loss.