This page contains the fabrication process of the prototype, the testing of the prototype and design optimization. Relevant pictures are supplemented for each section.

Prototype Fabrication

Buoy Assembly

After finalizing the calculations to determine the dimensions of the various device components including the buoy, the team was able to utilize one of the buoys from the maritime center due to the similarities in such dimensions. This float is made by four foam layers, sandwiched together by two 2” by 2” plywood boards with eight evenly distributed holes so that threaded rods can be utilized along with their respective washers and nuts to fasten the components together. The buoy was painted and four additional threaded rods were installed in order to provide support to the mounting plate, which is easily put in place by simply sliding it through the rods and serves as a “quick connect” to the piston – shaft assembly.

Piston-Cylinder Assembly

This sub assembly consists of the cylinder which contains the piston (shaft and head), and the covers that will ensure the piston stays inside of the cylinder while it is pumping water into pipeline. The top cover has two check valves that control the inlet of the water on the down stroke, and the outlet of the water during the upstroke. The piston rod is attached to the cover by utilizing water tight cup seals and a two stainless steel flanges that hold the seals in place. All of these assembly components were machined at the Stevens Machine Shop except for the actual cylinder which was provided by John Pearlman’s father from Ridgefield Public Works; the covers were machined out of polypropylene and the inner cylinder for the piston as well as the outer cylinder was made out of PVC. Once all the parts were machined and put together in the wave generator tank, the team was able to make some slight changes to the length of the rod as well as the quick connect mechanism between the buoy and the piston. Ultimately, the parts were spray painted with exterior acrylic paint.

Prototype Testing

The prototype was tested at the wave generator tank located at the Davidson Laboratory which can produce waves of up to 12 inches. The team tested the pumping device at different wave heights and periods to analyze the effects such have on wave energy extraction in terms of Head; the greater the head the more power generated from the waves. Please see attached videos for testing details, which include the set up and actual test time. The following table shows the summary of the test results and observations.

Note: Actual wave height is 65% from theoretical value.

Design Optimization

Having finalized the testing phase or the project, the team met with Dr. Pochiraju to discuss the observations and results from the experience and several suggestions that pertain to the design arose; it was concluded that it would be necessary to replace the aluminum rod-shaft by a steel rod which will provide more stiffness to the buoy preventing it from swaying back and forth. In addition to this a key point was deducted from the meeting, the device was not performing as expected due to the fact that the piston was grounded to the bottom of the tank, which results in a loss of head, therefore, a structure needs to be built to elevate the device by at least a foot which will increase the overall device efficiency, such structure will be built in such a way that it will serve as a guide for the buoy thus constraining its movement and rod excessive deflection which directly affects the pumping stroke. One last change required to optimize the design was the pipeline design, for the first test, the team utilized flexible PVC hose, which actually worked against the pumping due to its many kinks and overall length; such hose was replaced by a greater diameter rigid PVC pipe which finalizes in a 1.5” check valve that acts as a nozzle which ideally will gives place to a greater head.