ASME ECTC 2011 OceanWaveEnergyGenerator

7
ASME Early Career Technical Journal 2011 ASME Early Career Technical Conference, ASME ECTC November 4 – 5, Atlanta, Georgia USA OCEAN WAVE ENERGY GENERATOR Francis S. Fernandez Florida International University Miami, Florida, USA Bader Ale Florida International University Miami, Florida, USA Alfonso Parra Florida International University Miami, Florida, USA Sabri Tosunoglu Florida International University Miami, Florida, USA ABSTRACT Fossil fuels have been a popular source of energy for a long time. Some of the more prominent drawbacks are its finite life and toxic byproducts. Newer technologies have risen to solve this problem. Currently, technologies being researched include devices to harness solar and wind energy. Existing wave-generating units are usually around 12 feet high and are designed with the intent of operating in active wave-rich waters with average wave heights of 8 to 10 ft. These units can produce as much as 10 kW of power. Along with a smaller- scale design this team explores cost-effective alternatives which could potentially allow smaller buoys to produce less power in coasts averaging 2-to-6-foot-high waves. The project also puts to use basic laws of electromagnetism, such as Faraday’s Law of Induction and Ampere’s Law. INTRODUCTION The harnessing of energy is one of the most critical challenges at the forefront of all of humanity’s concerns. It affects societies in almost all aspects including economic, political, military, and technological venues. In recent years renewable energy has become a pressing matter for the latest generation of engineers and researchers. They are confronted with the responsibility of designing environmentally safe products which require less conventional energy or that run on cleaner renewable fuel. This team’s design project is a commitment to further realize these efforts by researching and developing current ocean wave energy technology for the benefit of all humanity. One of the goals is to achieve the development of small buoy units that are capable of harnessing energy from ocean waves specific to low-wave-height coastal areas such as Florida and Georgia. Among other alternatives there have been advancements promoting the use of solar, electrical, bio-fuel, and wind energy. But in order to keep up with the demands of today more progress is needed. Fossil fuels will not last indefinitely and it quickly becomes imperative that alternatives be developed to the point that they become viable and readily available for all people and societies to use. The team considers harnessing and using ocean wave energy which can potentially and in the long run alleviate the current dependence on conventional fuels. LITERATURE SURVEY Traditional sources of energy have helped propel the world’s economy and technology in insurmountable ways. Some of the greatest advancements are not only due to fossil fuels, but also greatly depend on them. Additionally, there are serious challenges and consequences associated with their use such as pollution, ecological disasters, and addicting economic, political and social dependences. Research and development is being made on fields related to the advancement of alternative fuel options. These fields extend to solar, wind, electric, bio- fuel, and most recently, ocean wave energy [3]. Figure 1 - Components of a Water Wave [6] Figure 1 shows the components that make up a standard ocean wave. The approaches used in the development of wave technology are float or pitching devices, oscillating water columns, and wave surge or focusing devices. Additional considerations need to be made, such as how far off-shore should actual structures stand. The closer to land, the easier it becomes to maintain and service these devices. While the further away these structures can provide a greater potential for ASME 2011 Early Career Technical Journal - Vol. 10 142

description

ASME ECTC 2011 OceanWaveEnergyGenerator

Transcript of ASME ECTC 2011 OceanWaveEnergyGenerator

ASME Early Career Technical Journal 2011 ASME Early Career Technical Conference, ASME ECTC

November 4 – 5, Atlanta, Georgia USA

OCEAN WAVE ENERGY GENERATOR

Francis S. Fernandez

Florida International University Miami, Florida, USA

Bader Ale Florida International University

Miami, Florida, USA

Alfonso Parra Florida International University

Miami, Florida, USA

Sabri Tosunoglu Florida International University

Miami, Florida, USA

ABSTRACT

Fossil fuels have been a popular source of energy for a long time. Some of the more prominent drawbacks are its finite life and toxic byproducts. Newer technologies have risen to solve this problem. Currently, technologies being researched include devices to harness solar and wind energy. Existing wave-generating units are usually around 12 feet high and are designed with the intent of operating in active wave-rich waters with average wave heights of 8 to 10 ft. These units can produce as much as 10 kW of power. Along with a smaller-scale design this team explores cost-effective alternatives which could potentially allow smaller buoys to produce less power in coasts averaging 2-to-6-foot-high waves. The project also puts to use basic laws of electromagnetism, such as Faraday’s Law of Induction and Ampere’s Law. INTRODUCTION

The harnessing of energy is one of the most critical

challenges at the forefront of all of humanity’s concerns. It affects societies in almost all aspects including economic, political, military, and technological venues. In recent years renewable energy has become a pressing matter for the latest generation of engineers and researchers. They are confronted with the responsibility of designing environmentally safe products which require less conventional energy or that run on cleaner renewable fuel. This team’s design project is a commitment to further realize these efforts by researching and developing current ocean wave energy technology for the benefit of all humanity. One of the goals is to achieve the development of small buoy units that are capable of harnessing energy from ocean waves specific to low-wave-height coastal areas such as Florida and Georgia.

Among other alternatives there have been advancements

promoting the use of solar, electrical, bio-fuel, and wind energy. But in order to keep up with the demands of today more progress is needed. Fossil fuels will not last indefinitely and it

quickly becomes imperative that alternatives be developed to the point that they become viable and readily available for all people and societies to use. The team considers harnessing and using ocean wave energy which can potentially and in the long run alleviate the current dependence on conventional fuels.

LITERATURE SURVEY

Traditional sources of energy have helped propel the

world’s economy and technology in insurmountable ways. Some of the greatest advancements are not only due to fossil fuels, but also greatly depend on them. Additionally, there are serious challenges and consequences associated with their use such as pollution, ecological disasters, and addicting economic, political and social dependences. Research and development is being made on fields related to the advancement of alternative fuel options. These fields extend to solar, wind, electric, bio-fuel, and most recently, ocean wave energy [3].

Figure 1 - Components of a Water Wave [6]

Figure 1 shows the components that make up a standard ocean wave. The approaches used in the development of wave technology are float or pitching devices, oscillating water columns, and wave surge or focusing devices. Additional considerations need to be made, such as how far off-shore should actual structures stand. The closer to land, the easier it becomes to maintain and service these devices. While the further away these structures can provide a greater potential for

ASME 2011 Early Career Technical Journal - Vol. 10 142

energy collection. Near-shore devices are generally situated between 30 and 75 feet away from land.

A long-standing benefit of wave energy generation includes the ability to produce essentially free energy and requires no additional fuel to operate. Additionally, the costs to maintain energy-generating buoys are on the low end. Also, depending on the location, it can be a major contributor of renewable energy. There are also disadvantages which include the cost it takes to develop worthwhile technology. The variable nature of wave frequency and height also makes the energy-transfer rates unpredictable. It can also disrupt or alter marine life in the vicinity. Deciding how and where these structures will be most beneficial becomes a critical part of the decision-making process.

Figure 2 - U.S. and FL Coastline Wave Heights (7/24/11) [7]

The main challenge when making considerations pertaining to wave-harnessing is how these waves affect and interact with the local environment. In this case, there is the incorporation of unique features added which would allow an existing working design to become more efficient in harnessing less-powerful waves in states such as Florida. The east coast of the United States is the weaker of the coasts when it comes to wave height and strengths, thus smaller and more energy-sensitive design alternatives are preferred. Figure 2 provides a recent snapshot of the wave heights (in feet) for the United States and Florida coastlines, respectively.

EXISTING TECHNOLOGY

There are many designs which prove to be very promising

for a research project of this scope. One popular design alternative initially developed in Oregon State University (OSU) primarily involves the use of Faraday’s Law of Induction. The end design is large, bulky, and efficient which enables it to fully take advantage of the wave heights readily available in the western coast of the U.S. Figure 3 shows a conceptual schematic outlining the main features of a wave park. OSU’s project is comprised of a multidisciplinary research team that works closely with the Oregon Department of Energy [2].

Figure 3 - Magnetic Induction Wave Energy Design [2]

Another technological concept is developed by SIE-CAT which employs a system of buoys configured in a linear fashion to compress air and eventually lead it to a main reservoir tank at the bottom of the ocean. Each buoy is attached to a cylinder and is used to pressurize the air that is being sucked in through an intake valve at the surface. With the help of the undulating behavior of waves the buoy rises to the crest of the wave, creating a partial vacuum in the cylinder. The wave eventually lowers the buoy once it reaches the trough. This is similar to the behavior of an internal combustion engine. Each consecutive buoy, compressing the air ever so slightly is further compressed by successive buoys. The final pressure buildup in the reservoir tank can then be used to power a turbine to generate electricity. Figure 4 below illustrates a simplified representation on how the technology works [4].

Figure 4 - SIECAT Compressed Air Energy Design [4]

There are other devices known as Pelamis Wave Energy Converters which work by making use of cylindrical pontoons that are able to float and move about hinge joints such as those illustrated in Figure 5. The Pelamis converters have an energy output rating of approximately 15 kW/m per year. They have also been noted for their performance, cost, design, and overall

ASME 2011 Early Career Technical Journal - Vol. 10 143

efficiency [1]. The Pelamis generators are currently located in Edinburgh, Scotland and Povoa de Varzim, Portugal.

Figure 5 - Pelamis Wave Energy Converter [8]

PROPOSED DESIGN Two prototypes are considered for the final design. Mass-

producing a product facilitates and in most cases, justifies the high cost of the development and design of molds. In the case of this project, purchasing a mold at a high cost for the production of a single prototype does not justify its price. However, it must be noted that if this team’s product were put into high volume production the thought process would be different. Therefore a distinction must be made between the conceptual prototype, the prototype that would be designed with the intention of mass-production and high durability in mind, and the modified prototype, or the low-cost alternative designed to survive project testing and experimental analysis. A comparison between both prototypes is shown in Figure 6. As can be noted there are visual differences that set both models apart. However, in terms of actual components they remain very closely related.

Figure 6 - Proposed Conceptual and Modified Prototypes

The designs mainly differ in areas where it becomes extremely expensive and difficult to manufacture parts. The conceptual prototype is the ideology and thought process used in developing a quality product able to withstand long-term environmental hostilities of the ocean. Its parts and functionalities are analyzed without experimental testing. The modified prototype is built based on readily available alternatives which jeopardize the life and durability of the buoy.

However, it allows the engineering team to construct and evaluate parameters critical to the success of the project.

The primary components of the wave power buoy are

solenoid, neodymium magnet, and float. The solenoid is designed approximately 1 ft in length and 5 inches in diameter. Two magnets are mated to form one magnet 4 inches in diameter and 4 inches in length. The industry field strength is rated in terms of a hybrid N42-N52. At the surface (2 inches from the center) the magnetic field strength is rated at approximately 2,500 Gauss. At 4 inches from the center the magnetic field rating is approximately 700 Gauss. Magnetic field ratings are usually obtained empirically (through experimentation). However, the mathematical model is based on the equation

∙ = 0 (1)

In this equation B is the magnetic field and s represents the

closed surface area of the system. Using empirical methods the strengths are determined by extrapolation using the results from Figure 7.

Figure 7 - N42 Magnetic Field Strength at Surface Area

It should be noted that at the surface the magnetic field strength decreases with increasing length of the magnet while at a distance outside of the magnetic surface the field actually increases with increasing length of the magnet. Figure 8 shows the relationship between magnetic field strength and increasing magnet length 2” away from the surface of the 4” diameter magnet.

For the conceptual design the float is approximately 2 feet

in diameter and constructed from industrial insulation Styrofoam and nylon. The surface finish is protected with fiberglass resin in order to increase its durability. The case containing the magnetic core is anchored from the bottom to the sea floor and thus, remains relatively stationary. The solenoid is attached to the float and as waves produce a difference in height relative to the core it is free to move in a vertical fashion. The change in magnetic field relative to the solenoid is what causes a flow of current in the solenoid. This

0

1000

2000

3000

4000

5000

6000

0 1 2 3 4

Mag

neti

c Fi

eld

(Gau

ss)

Length of Magnet (in)

Field Strength vs Length

At Surface (4-in Diameter)

ASME 2011 Early Career Technical Journal - Vol. 10 144

current will then travel outside the solenoid through a secured water-proof outlet and into a battery located nearby.

Figure 8 - N42 Magnetic Field Strength 2” from Surface

PROPOSED DESIGN Ideally the capture of wave energy is desired in offshore

locations, where it is not only more productive, but can also be technologically feasible. Even though wave energy can be considered a form of continuous source since it is constantly being generated it is also highly variable. This is not to say that the output cannot be accurately predicted, as with the help of meteorological advances it has become scientifically and reliably possible to determine the size and intensity of ocean waves within monitored coasts [5].

The equation most often employed to determine the amount of power generated by coastal waves is given by

= 64 (2)

In this equation, P is the generated power. The variable ρ is the density of seawater, 1,025 kg/m3. The variable H represents the wave height, in meters. Variable T is the length period of the wave, in seconds. Finally, g is the gravitational acceleration, 9.8 m/s2. Equation (2) can be reduced to the following.

≈ 0.5 (3)

Knowing that a few miles off the coast of Florida the

waves reach an average of approximately 3 ft. (~1 m) with a period of approximately 8 seconds, equation (3) yields 4 kW per meter or 1.79 hp per foot of Florida coastline. It should be noted that this is the potential power and that the amount harnessed, depending on the method used, can be substantially less. Additionally, in coasts where the wave heights are much higher, such as in the western coast of the United States, the power potential can be as high as 16 hp per foot of coastline.

Table 1 shows a comparison between the wave heights in

both, meters and feet, and the potential power generated in

kilowatts per meter and horsepower per ft. As noted earlier, these values represent only the amount of power that could potentially be harnessed by technologically feasible means. As science advances the efficiency with which this power can be harnessed is improved.

Table 1 - Power Potential per Wave Height

Wave Height (m)

Wave Height (ft)

Power (kW/m)

Power (hp/ft)

1 0 0 0 0.0 2 0.5 1.5 1 0.4 3 1 3 4 1.8 4 1.5 4.5 9 4.0 5 2 6 16 7.1 6 2.5 7.5 25 11.2 7 3 9 36 16.1 8 3.5 10.5 49 21.9 9 4 12 64 28.6

Additionally, by using equation (2) it is possible to develop

a graphic interpretation illustrating the amount of power that is potentially generated versus the wave height. In the graph shown in Figure 9 periods of 7, 8, and 9 seconds are used in order to draw a comparison between the power generation and wave height differentiated by the length of time it takes between wave crests. However, it should be noted that the period can be adjusted depending on the location of the wave energy-generating device. As previously mentioned, the intensity and frequency of waves in the western coast are much more pronounced.

Figure 9 - Power Potential vs. Wave Height

0

100

200

300

400

500

600

700

0 1 2 3 4Mag

neti

c Fi

eld

(Gau

ss)

Length of Magnet (in)

Field Strength vs Length

4"-Diameter, 2Inches FromSurface

0

10

20

30

40

50

60

70

80

0 2 4 6

Pow

er P

oten

tial

per

Met

er C

oast

line

(kW

/m)

Wave Height (m)

At 8 s Period

At 7 s Period

At 9 s Period

ASME 2011 Early Career Technical Journal - Vol. 10 145

BUOY DESIGN AND ANALYSIS Engineering evaluations are performed before the

construction and testing of the modified prototype. These analyses entail the relevant mechanical engineering theories that help drive the overall success of the research and design project. For all finite element tests a mesh size of approximately 0.5 inches is used. Figure 10 contains additional details and properties specific to the mesh size.

Figure 10 - System Element Properties

The engineering analyses were mostly performed using SolidWorks and ANSYS software and included the following:

• Thermal • Kinematic • Dynamic

• Electromagnetic • Buoyancy • Force and Stress

• Fluid Mechanics • Fatigue • Coastal

Some of these evaluations are outlined in the following

sections of this report. To see a complete report of all these studies contact Florida International University, Mechanical and Materials Engineering Department, or Francis S. Fernandez at [email protected].

THERMAL ANALYSIS

In terms of thermal properties PVC is a poor conductor of

heat and thus, the analysis and results are consistently monotonous. The results for the magnet and solenoid case temperature gradient distributions are shown in Figure 11.

Figure 11 - Magnet and Solenoid Case Temperature Gradient

Distribution (1 BTU)

The deflection temperatures of schedule-40 PVC are illustrated in Table 2. The average oceanic temperature near the coast of Miami Beach, Florida is 78 °F, with the yearly temperatures fluctuating between 71 and 86 °F. Considering the heat factor alone, PVC is able to withstand these temperatures all year round since the load on the buoy due to the buoyancy effect does not exceed 40 lbs. These values do not take into consideration the tidal and rip current effects that add to the buoy load.

Table 2 - Deflection Temperatures of Schedule-40 PVC

Pressure (psi) Deflection

Temperature (°F)

66 167

246 125

ELECTROMAGNETIC ANALYSIS

The current produced in an environment such as the ocean

and with the equipment being used is of the alternating type (AC). This is important because in order to produce useful energy the buoy requires that the AC current is converted into DC with one of the many available market products. Since the team’s goal is to generate 12 volts, the current quantity has not been set as one of the primary objectives.

The calculations for the magnetic field analysis are managed by using Ampere’s Law, equation (4):

= (4)

Since testing magnetic fields require experimental analyses

application software aids in determining the values of magnetic fields at different distances from a given magnet. In this case a magnetic calculator is used provided by the manufacturer of the magnet. Imported magnets are rigorously tested to match the results predicted by field-calculating software. For example, a magnetic field strength of 2743 Gauss is recorded at the surface for a magnet of grade N42 and dimensions 4” (diameter) and 3” (length).

ASME 2011 Early Career Technical Journal - Vol. 10 146

As shown in Figure 12, the magnetic strength decreases

from 2743 Gauss to 613.3 Gauss when the distance is increased from 0 (at the surface) to 2 inches from the surface (4 inches from the center of the magnet). This is a significant decrease that would have a tremendous impact on results when designing a buoy that must allow for a medium (water) to flow through it.

Figure 12 - Magnetic Strength 2 Inches from the Surface

BUOYANCY ANALYSIS Ensuring that the system remains buoyant is critical to the

success of the buoy. The main components, the magnet case and solenoid case, are analyzed and tested for buoyancy. The equation for the buoyancy force is

= . = = (5)

For equation (5) ρ is the density of the submerged mass, g is the gravitational acceleration, and V is the volume displaced by the submerged mass. This equation is also known as Archimedes’s Principle. In order to calculate the buoyancy of the magnetic case, the volume is determined by using

= 4 = 0.3754 5.17 = 0.571 (6)

For equation (6) V is the volume, D is the diameter of the pipe, and L is the length of the pipe. The gravitational acceleration constant is given as

= 32.2 (7)

Also, the mass of the submerged body is needed. In this case this can be found by weighing the body and dividing the result by the gravitational constant

= = 26.6 32.2 / = 0.826 (8)

The density can now be found by using the relationship

= = 0.826 0.571= 1.447 / (9)

The density of seawater is ≈ 1.988 / (10)

When comparing this value to the density of the magnet case it is observed that the density of water is greater than that of the case. Therefore, if fully submerged the magnet case floats.

PROTOTYPE CONSTRUCTION The team first tests the prototype under a controlled

environment. The buoy is taken to one of the team member’s house pool. This way the size of the waves and frequency can be controlled. The buoy is safely monitored and minor adjustments are made accordingly. The buoy is also taken to be tested in the ocean. Figure 13 shows the team preparing to deploy the buoy at Biscayne Bay, Florida.

Figure 13 – From Left: Dr. Tansel, Alfonso, Bader, Francis

The buoy results are given in terms of voltage and current output. Additionally, the wave frequency is adjusted to simulate ocean water conditions. Buoyancy and ability to stand are monitored and analyzed.

Figure 14 - 2011 Biscayne Bay Buoy Launch

ASME 2011 Early Career Technical Journal - Vol. 10 147

The energy output during the bay testing was less than 3 volts for all results recorded. However, had the buoy been properly positioned and anchored at the correct level the voltage could have been more in line with the results obtained from the pool, where the buoy was properly anchored and positioned. Once the tests are completed the team heads back to shore. The original intent was to generate 5 W with a larger magnet. The results of these tests are listed in Table 3. The average power generation is approximately 0.093 Watts.

Table 3 - Prototype Test Results

Voltage (V) Current (mA)

1 2 1.8

2 3 0.575

3 12 1.36

4 3 0.557

5 10 1.087

6 12 1.891

7 11 1.02

8 10 1.61

9 10 0.752

10 8 0.93 CONCLUSION

This research highlights the benefits that current

technologies are able to bring into mainstream along with new challenges that are presented. One of the main focuses is to encourage the use of renewable resources that are currently available and in abundance. This team remains hopeful that further studies and developments are made in the fields of wave energy harnessing in the future. FIU’s team construction and testing of the prototype proves that there is plenty of room for improvement in the energy field. Examples of future work required include automatic depth adjusters to account for tidal effects and minimization of environmental hazards to and from the buoy system.

The overall goal, research the generation of energy through

natural means, such as undulation of ocean waves, has been accomplished with mixed success. The overall experimentation of energy production is low. And indeed much more work is needed to further advance the research in this area. However, the theory is sound and with future tweaks and improvements it is possible to generate a significant proportion of energy in this manner. In order to continue building on this research, it is recommended that the buoy be able to efficiently operate in

environments with low wave heights, such as the eastern coast of the United States.

It is important that research is made with interdisciplinary

teams, including expert areas in electrical engineering and marine sciences. The success of follow-up work requires that such teams maintain technical communication so that the performance of power buoys is maximized. ACKNOWLEDGEMENTS

The team acknowledges and thanks the following persons

and organizations for their contribution to this project: • Dr. Ibrahim Tansel • Rick Zicarelli • International Hurricane Research Center (IHRC) • National Oceanic and Atmospheric Administration

(NOAA)

REFERENCES

[1] Bedard, R., Hagerman, G., Previsic, M., Siddiqui, O.,

Thresher, R., & Ram, B, 2005, Final Summary Report, Project Definition Study, Offshore Wave Power Feasibility Demonstration Project. EPRI Global.

[2] Brekken, T., & von Jouanne, A., 2008, Overview of Wave Energy Activities at Oregon State University. Oregon State University.

[3] Elwood, D., Yim, S., Amon, E., von Jouanne, A., & Brekken, T. (n.d.), 2008, Experimental force characterization and numerical modeling of a taut-moored dual-body wave energy conversion system. Journal of Offshore Mechanics and Arctic Engineering , 132.

[4] SIE-CAT, 2010, The energy of the future is here. One wave at a time. Retrieved July 24, 2011, from www.wave-energy-accumulator.com: http://www.wave-energy-accumulator.com.

[5] U.S. Department of the Interior, 2006, OCS Alternative Energy and Alternate Use Programmatic EIS Information Center. Retrieved 2011, from www.ocsenergy.anl.gov: http://www.ocsenergy.anl.gov/documents/docs/OCS_EIS_WhitePaper_Wave.pdf.

[6] Adhikary, K., 2010, Environmental Systems. [7] NOAA. National Digital Forecast Database, 2011, NDFD

Graphics. [8] Pelamis Wave Energy Converter, 2009, Changing Ideas:

Pelamis-Wave-Energy-Converter/Electricity.

ASME 2011 Early Career Technical Journal - Vol. 10 148