Wave energy design

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Student Report (National Research Council of Canada. Institute for Ocean

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Wave energy design

DOCUMENTATION PAGE

SR-2007-15

NRC REPORT NUMBER DATE

August 2007

REPORT SECURITY CLASSIFICATION

Unclassified

DISTRIBUTION

Unlimited

TITLE

Wave Energy Pump Design AUTHOR(S)

Ron Ryan

CORPORATE AUTHOR(S)/PERFORMING AGENCY(S)

Institute for Ocean Technology, National Research Council, St. John’s, NL

PUBLICATION

N/A

SPONSORING AGENCY(S)

IOT

IMD PROJECT NUMBER

42_2265_10

NRC FILE NUMBER KEY WORDS

Wave Energy, 42_2265_10, Energy, Ocean Energy

PAGES FIGS. TABLES SUMMARY

This project concerns the design of a dual acting water pump that is powered by wave energy. The design is flexible to allow testing of different scenarios to see what would be the best course of action for future designs at IOT.

ADDRESS National Research Council

Institute for Ocean Technology Arctic Avenue, P. O. Box 12093 St. John's, NL A1B 3T5

National Research Council Conseil national de recherches Canada Canada Institute for Ocean Institut des technologies

Technology océaniques

WAVE ENERGY PUMP DESIGN

SR-2007-15

Ron Ryan

Table of Contents 

Introduction ...2

Design Criteria...2

The Concept ...2

The Design ...3

Bottom Universal Joint...3

Support Frame...3

Double Acting Pump ...4

Top Universal Joint ...5

Float Support Assembly ...6

Design Analysis Description and Results ...7

Final Design Description ...7

Conclusion/Recommendations...7

Appendix A: Calculations...8

Appendix B: Fabrication Drawings...20

Appendix C: Other Parts/ Information...41

Table of Figures 

Figure 2: Support Frame and Bearings... 4

Figure 3: Double acting pump... 5

Figure 4: Top Pivot Joint Assembly... 6

Figure 5: Float Support... 6

Introduction 

This design was undertaken as part of project 42_2265_10, “Wave Energy Pump”. The purpose of this project is to get the National Research Council – Institute for Ocean Technology (NRC-IOT) more involved in wave energy and develop a wave energy program. Wave energy is becoming a popular form of energy, with some different types already producing usable energy. The concept for this design is a water pump, which is to be powered by wave energy. This is the first design out of many to be completed by NRC-IOT. The goal is to design, fabricate, and test three models at

different scales to get a scaling affect to help predicted how a full-scaled model would react. This first model will be a flexible design so that different scenarios and

configuration can be performed in order to determine which configuration the pump performs the best. This information will assist in the development of future models.

Design Criteria 

Before the design process could begin, a list of design criteria was needed. These criteria were obtained through some preliminary meetings. The first limitation was a $5000 budget to cover design, fabrication, and testing. So the model had to be

designed and fabricated inexpensively. In house materials should also be used to help keep cost down. However there are always same cases where you would need to order in special materials. The pump also needs to be a double acting pump to better test the model. This model is to be first tested un-instrumented however the possibility that instruments may be added later has to be taken in to consideration and can be added with some small modifications. Different sizes and shapes of float need to be tested. A restoring force such as springs or bungee cords needs to be connected. There was also the need for the pivot joints to be fixed or free to rotate. The force acting on the float that is to be used for the design is 533.25N (119.88lbf), which was

calculated by an in house IOT program that is based on Morrison’s equation formulation to compute the forces along a vertical cylinder up to the free surface. Some input parameters for the program consist of the height, length, and period of the wave as well as the cylinder diameter and the water depth.

The Concept 

The model is based on a buoy type design to extract wave energy. The buoy will rise and fall (usually in an elliptical motion) with the wave and is connected to a double acting pump that will draw water in and then pump it out. The incoming and outgoing water could possible turn a turbine to create energy. In our case we will be measuring the pressure and volume of water that is being drawn in and pumped out.

The Design 

Bottom Universal Joint 

The bottom pivot joint only rotates around one axis since the model is only going to be tested in Uni-directional waves and not multi-directional waves so there is no need for a universal joint. The joint is bolted together and is also bolted to the mooring plate. This helps keep the strength of the Aluminium 6061-T6 where welding would decrease the strength by 1/3. The plates are 0.5-inch thick, which is to accommodate the size of the bolts needed. It can be fixed at 15, 30, 45, or 60 degrees from the vertical position in both directions. By removing the two locking bolts the joint is free to rotate about the bottom bolt so that the pump can rotate with the wave. See figure 1 for an image of the bottom pivot joint and mooring plate.

Figure 1: Bottom Universal Joint and Mooring Plate

Support Frame 

The support frame consists of 4 Aluminium 6061-T6 1.5inch angles being 0.125 inches thick. One for each corner of the double acting pump and they connect though stainless steel bolts to a 0.5 inch thick 5 by 5 inch sheet, two on top and one on the bottom. The support frame will reinforce the double acting pump so the pump will see only small forces and deflections. Based on a horizontal force of 120lb acting on the float, a moment of approximately 6600 lb-in is being resisted by the Support frame with a factor of safety of 9.8 when the piston shaft is fully extended; see Appendix A for full calculations. The support frame also supports the returning force connector and can also be used to support other testing equipment. The returning force connector can be adjusted to fit different size springs to provide for variation in restoring force. The support 3 | P a g e

frame consists of two bearings at the top to transfer the force from the piston shaft to the support frame so that there is little to no forces acting on the inside of the pump from the piston. See Figure 2 for an image of the support frame and bearings.

Figure 2: Support Frame and Bearings

Double Acting Pump 

To keep costs down we had inherited an Acrylic pipe from another project and it set the scale for the design. The double acting pump consists of a 3-inch OD and 2.5-inch ID pipe, with a 5 x 5 inch plate that is 0.5 inches thick on the top and the bottom. The top plate will have a hole to allow the piston shaft to enter into the pump with a seal at the top to prevent access water from entering or exiting the pump. The pipe itself will see very little loads and deflections, however, the pipe rod will see a bending moment of approximately 4320 lb-in and have a safety factor of 1.6; see Appendix A for full calculations. The pipe will have 4 holes drilled into it, two at the top and two at the bottom; this is where the inlet and outlet valves will be connected. The pipe is also transparent so that we may observe the piston during operation. See Figure 3 for an image of the double acting pump. The piston shaft is made of aluminium 6061-T6 as is

the piston. There is also rubber stops at both ends inside the pipe to take some of the impact forces when piston reaches its travel limits.

Figure 3: Double acting pump

Top Universal Joint 

The top pivot joint is similar to the bottom pivot joint, where it also rotates about one axis. It can only be fixed perpendicular to the pump or free to rotate around one of the two bolts by the removal of the other bolt. In the free position the float would align itself with the wave so the force would be distributed along the bottom. This would cause a portion of the 120 lb force to act horizontally and vertically on the top pinned

connection depending on the angle of the float. The top restoring force connection is also connected to the top pivot assemble as well. Springs or bungee cords could be connected. See figure 4 for an image of the top pivot joint assembly.

Figure 4: Top Pivot Joint Assembly

Float Support Assembly 

Below in figure 5 we see the float support assembly that allows for different sizes and shapes of floats to be connected to the pump. The two 0.5 inch threaded rods would apply a compressive force that helps hold the float securely and also prevents the float from rotating about the axis along the rod. The length of the two threaded rods would determine on the thickness of the float.

Figure 5: Float Support

Design Analysis Description and Results 

All the design calculations were completed by hand and are provided in Appendix A. There was also no Finite Element Analyses (FEA) preformed to confirm these

calculations, so a design check would need to be considered. The worst condition that the wave energy pump would be faced with is to have the 120 lb force acting on the float while the two pivot connections were fixed in there vertical position and while the piston shaft is fully extended. There is also a factor of safety on all parts of greater than 1.5.

Final Design Description 

This design is to be tested to determine what conditions work the best. There are

approximately 12 possible configurations not including different floats or restoring force such as spring or bungee cords. To keep the cost down all the parts are to be bolted together with no welding requirements. The wave pump would need to be in a water depth of approximately 4.5 ft (1.37m) with amplitude of approximately 0.8 ft (0.25m).

Conclusion/Recommendations 

Before fabrication begins there are a few recommendations that need to be considered. When the float is in the free position it only has a 45 degrees angle of freedom before interference from the top restoring force connector take place. A possible correction is to increase the length of the restoring force bar and bending it (curvature to be determined); allowing a wider angel of freedom so that when the wave pump is fixed at 45 degrees the float (in calm seas) would not have any

interference with the restoring force connector. A recommended angle of at least 70 degrees of freedom for the float should be considered. If the bending of this bar is preformed then the height of the Top Pivot Joint M Connector can be shortened. Also in order to protect the pump and its major components, failure should occur at the top pivot joint bolts. The bolt size should be changed so that the factor of safety is the lowest at that point. Other than those recommendations the design conforms to all design criteria and is ready for fabrication pending a design check.

Appendix A: Calculations 

Appendix B: Fabrication Drawings 

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Appendix C: Other Parts/ Information

Part List

Valve to Piston Housing Connector (x4) Top Pivot M Connector (x1)

Top Pivot F Connector (x2)

Top Support Plate (x1) ...CHECK DESIGN IF BEARING IS CHANGED Top Support Plate Secondary (x1) ...CHECK DESIGN IF BEARING IS CHANGED Top Spring Connector (x1)

Top Rod Connecting Plate (x1) Top Piston Housing Cap (x1) Top Float Plate (x1)

Rubber Stops (x4) ...NOT DESIGNED Seal (x1) TO BE CHECKED

Swing Check Valve (x4) ...BORROWED FROM ANOTHER PROJECT Support Frame Member (x4)

Piston (x1) ...BORROWED FOR ANOTHER PROJECT Piston Shaft (x1)

Piston Housing (x1) Mooring Plate (x1) Threaded Rod (x2)

Bottom Pivot Joint M Connector (x1) Bottom Pivot Joint F Connector (x2) Bottom Support Plate (x1)

Bottom Restoring Force Connector (x2) Bottom Piston Housing Cap (x1)

Bottom Float Plate (x1)

UHMW Bearings (x1) ...TO BE CHECKED

Threaded Rod (x2) ...TO BE DESIGNED WITH FLOAT Hardware

http://www.kbico.com/products.asp?prodID=61

There are four swing check valves to be borrowed from another project.

http://www.mcmaster.com/

The bearing design needs to be checked. If any changes are made, make sure you check the appropriate part for compatibility or re-design.

http://www.skfextranet.com/catalogs/457010/sealdetail.asp?s=12337

The Seal need to be checked. If any changes are made, make sure you check the appropriate part for compatibility or re-design.

This is a model of the piston to be used that is being borrowed from another project.

**NOTE: The original 120 lb force was based on a water depth of 0.6m. The model needs at least 1.37m so the force is increased by 10% and should not affect the design.