Wave Energy Conversion 37
Wave Energy Conversion Device
A Proposal Submitted By:
Mike Buelsing
Kevin Glass
Neil Lum
John Sophabmixay
MENG491
October 17, 2008
Table of Contents
Table of Contents 2
List of Figures 4
List of Tables 5
1. Context 6
1.1. Background of Need 6
1.3. Literature Review 7
1.3.1. Prior Work 7
1.3.2. Patents 8
1.3.3. Codes and Standards 9
2. Problem Definition 9
2.1. Customer Requirements 9
2.1.1. Form 9
2.1.2. Fit 10
2.1.3. Function 10
2.2. Assumptions 10
2.3. Constraints 11
2.4. Customer Requirements Schematic 11
2.5. Test/Evaluation Plan for all Requirements and Constraints 11
3. Concept Development 12
3.1 Overview 12
3.1.1 Creative Strategies 12
3.1.2. Governing Principles 12
3.2. Synthesis and Analysis of Overall Concept 13
3.2.1. Concept 1 13
3.2.2. Concept 2 14
3.2.3. Concept 3 15
3.2.4. Concept 4 16
3.2.5. Concept 5 17
3.3. Evaluation 18
3.4. Refinements 20
3.5. Selection 21
4. Design Specifications 21
4.1. Design Overview 21
4.1.1. Description 21
4.1.2. Design Schematics 22
4.2. Functional Specifications 23
4.3. Physical Specifications 23
4.4. Product QFD 23
4.5. Subsystems 24
4.5.1 Truss and Buoy arms 24
4.5.2 Mechanical Energy conversion 25
4.5.3 Electrical Energy Converter 25
4.6. Design Deliverables 25
5. Project Plan 25
5.1. Research 25
5.2. Critical Function Prototypes 25
5.3. Design 26
5.3.1 Overall Design 26
5.3.2. Truss Beam 26
5.3.3. Flotation Units 26
5.3.4. Mechanical Power Conversion 27
5.3.5 Electrical Power Conversion 27
5.3.6 Anchoring Mechanism 28
5.4. Construction 28
5.5. Testing 29
5.6. Project Deliverables 29
5.7. Schedule 30
5.8. Budget 32
5.9. Personnel 33
6. References 34
7. Appendices 35
7.1. Team Member Resumes 35
7.2 Patents 38
7.3 Ocean Energy Calculations 41
7.3.1 Correlation between Period, Wavelength, Celerity, and Group Velocity 41
7.3.2 Energy per unit area as a function of wave height 42
7.3.3 Power per meter of crest as a function of wave height and group velocity 43
7.3.4 Power transfer and rpm per arm as a function of arm length, wave height, period, and buoy volume 44
List of Figures
Figure 1: Breakdown of worldwide energy supply 6
Figure 2: The Pelamis Wave Energy Converter. 9
Figure 3: The Customer Requirement Schematic for the Wave Buoy 11
Figure 4: A Functional Decomposition of the Wave Energy Conversion system 13
Figure 5: The Oscillating Buoy Fixed to the Ocean Floor schematic…………………………………………………………………………………14
Figure 6: Schematic of the Oscillating Buoy Fixed to an Inertial Plate……………………………………………………..……………………. 15
Figure 7: The Anchored Boat Energy Generation schematic 15
Figure 8: Schematic of the Articulated Raft system 16
Figure 9: A schematic of the inside of the Articulated Raft System 16
Figure 10: Schematic of the proposed Pulsing Water Converter 17
Figure 11: The feature schematic of the proposed system. 22
Figure 12: The functional schematic of the proposed system. 22
Figure 13: Electrical Power Conversion Unit. 28
Figure 14: Project Schedule List. 30
Figure 15: Gantt Chart Detailing Project Schedule. 31
List of Tables
Table 1: Decision Matrix for General System Type. 19
Table 2: Types of Linear to Rotary Modes of Transmission 20
Table 3: Types of near shore “Fixed to Ground” Systems. 20
Table 4: QFD Analysis Relating Customer Requirements to Design Specifications. 24
Table 5: Budget Plan for Proposed System. 32
Table 6: Organization chart detailing subsystem assignment for each group member. 33
1. Context
1.1. Background of Need
Each person on Earth consumes some portion of the world’s energy, directly or indirectly. Total worldwide consumption of energy is 500 exajoules (or 5 x 1020 Joules) per year, with renewable sources such as hydroelectric energy supplying merely 7% of this total. Oil, natural gas, and coal are the three major contributors to worldwide energy production (Figure 1), but these resources are limited. If natural gas, coal, and oil production remain constant, the natural gas will last 61 years, coal will last 133 years, and oil will last a mere 42 years. However, with population growth of over 95 million people per year, the preceding numbers surely will decrease.
A collection of international scientists have compiled abundant data regarding fossil fuels and their effect on the environment (6). They reported that fossil fuels are a “virtual certainty” to be responsible for the global warming phenomena, which five years ago they claimed as “likely.” Numerous large corporations, especially electric companies, are turning to cleaner methods of operating. Renewable energy sources, by definition, do not deplete and have no net carbon emissions. The vast amount of water power in the ocean has been relatively untapped around the world, creating a large economy for hydroelectric power in the world today.
Figure 1: Breakdown of worldwide energy supply, in terawatts [TW].
1.2. Customer Need Statement
Electric companies and their customers have an increasing need for stable and competitive pricing of their energy. Costs per kilowatt hour are increasing for the three major producers of energy (oil, natural gas, coal) because their resources are decreasing and the demand is increasing. For example, gasoline prices have risen 50% in the last two years alone; crude oil costs increased by over 90% in the same time span (3). Also, handling, production, and transportation of these resources further harm the environment.
Because of the high demand for cost reduction, the existence of finite resources and the need for “cleaner” energy production, more renewable and reliable resource must be considered. Ocean wave power is immense and estimates show that 0.02% of the renewable energy available within the oceans converted into electricity would more than satisfy the present world demand for energy (8). The potential for shoreline-based wave power generation is 50 gigawatts worldwide and having sustainable systems in place will decrease the long-term costs of energy.
In their quest to continue scoping the ocean’s physical attributes, the oceanography team at Scripps Research Institute is in need of a device that is able to generate enough energy to power their Wire Walker. The Wire Walker is a system that uses the chop or waves of the ocean to descend beneath the surface and collect data of temperature and salinity at different depths. The system uses telemetry to transfer the data. This portion of the Wire Walker is dependent on a power source. In order to power the device a minimum of 10 watts is required. Therefore, with a consistent and free renewable energy source, the Wire Walker will be able to produce better profiles.
1.3. Literature Review
1.3.1. Prior Work
Harnessing and gathering the massive energy potential in a wave efficiently is the ultimate end goal. The systems which have done this most effectively are discussed in the “Patents” section. Historically, designing a system that will be cost effective for its life cycle has been challenging because of a number of issues. Lack of experimental data makes it nearly impossible to mark the optimum location for wave energy converters. In each individual wave, the pressure exerted on the system is maximized just before the wave height peaks. However, at the peaks and crests of wave, the pressure created drops to zero. Also, the power generated must be transported great distances, as most of the existing systems are located miles offshore. These transportation costs and the maintenance of the power transmitting mechanism must be kept minimal as to provide power cheaply.
Placing the energy conversion system into the ocean presents two major issues: the water is composed of salt and living organisms inhabit the majority of the ocean. Any component of the system will be exposed to the corrosive elements in the water, therefore creating a need for water-tight seals at all interfaces. These systems are also subject to extreme weather conditions. In regards to the living organisms, the key concerns are: changing migration routes, noise, navigational hazards and creation of artificial habitats.
Historically, one of the major impediments of wave generation technology has been the lack of research support, and therefore funding. The United States has very little research in progress, whereas European efforts have been funded and put into place.
1.3.2. Patents
Many solutions have been developed to harness wave energy in the past. Some of the notable and most successful systems are:
· OWEC (Ocean Wave Energy Company): US Patent # 4,232,230…US Patent # 4,672,222
· Pelamis P-750 (Pelamis Wave Energy Converter)
· SPERBOY (Embley Energy)
· S.D.E. Energy Ltd Wave Power
· CETO Zero Emission Power and Fresh Water
· Checkmate SeaEnergy
· DEXA Converter
The Pelamis Wave Energy Converter is currently placed off the shoreline of Spain and the United Kingdom. It has been designed to be a fault tolerant system having multiple levels of redundancy along its 100-meter long links. Its major subsystems are structure, moorings, hydraulics, electronics, and control. Controlling the fault tolerances allows the Pelamis to be placed in the harshest of environments off the coastline. Pelamis has been designed to attach and detach rapidly, with machines that are able to be installed on site with little to no manned intervention. The time of attachment and detachment are also very short, with two hours allowed to assemble large linkages and less than one hour to disassemble.
The Pelamis design is fully modular, and the next step in its service life is to include a service base to decrease maintenance times and transmission of energy. Some of the ideas and initial requirements for a Pelamis service base would include:
· Suitable maneuvering space for berthing and unberthing
· Sheltered from adverse weather
· Level access for vehicles
· Conditions suitable for use by mobile cranes
· Safe navigational route to and from offshore site
The Pelamis Wave Energy Converter has been considered to be the most cost-efficient commercial system in place today. A picture of the Pelamis can be seen below (Figure 2), taking into perspective how long the linkages are in the system.
Figure 2: The Pelamis Wave Energy Converter. The Pelamis uses a hinged linkage system to transmit hydraulic power to a generator, and has been successfully implemented in European countries.
1.3.3. Codes and Standards
With electrical components in the system, all testing and building will adhere to the ‘Electrical and Electronic Testing Collection’ (ANSI), the National Electric Code (N.E.C), and the ‘Other Electrical Accessories Collection’ (ANSI) standards. Also, since parts will most likely be submerged in salt water, the ‘Paint Requirement for Corrosion Protection’ will be followed regarding coating of the system.
For testing in the open ocean, contact lines are being opened with officials to discuss the lawfulness of testing. Appropriate laws and standards will be followed; more data will be available in 2-3 weeks time.
2. Problem Definition
2.1. Customer Requirements
The proposed system will be deliverable to the Scripps Institution of Oceanography. The team at Scripps needs a wave-energy device that outputs 10 Watts on average. The following section documents customer requirements and prioritizes their rough importance. For each requirement a number is assigned to designate relative importance, 10 being most important.
2.1.1. Form
The proposed Wave Energy Converter will have the following physical limitations:
1. Must have no component larger than 6’ x 4’ x 3’ to allow storage in Loma Hall room number 005 (6)
2. Be highly visible to boaters and/or ocean species (5)
3. Size to provide optimal energy extraction from predominant waves (7)
2.1.2. Fit
The system will interface with the environment by the following conditions:
1. Density must be less than ½ ocean water (8)
2. System must reside at surface of water (8)
3. System must interface with the “Wire Walker” Buoy (7)
4. Must generate electricity for the “Wire Walker,” which runs on 10 Watts of power (9)
5. Must provide power at a depth of 5-50 meters above the ocean floor (6)
2.1.3. Function
The following list describes the primary actions the customer needs from the system:
1. Turn output shaft at a speed of greater than 1500 rotations per minute to run a common generator (10)
2. Output minimum average of 10 Watts (8)
3. Endure severe storm situations (wave heights reaching 5-10 meters) (5)
4. Produce isolated, off-the-grid-energy at competitive price: competing with approximately 25 cents per kilowatt hour for solar (6)
5. Be sustainable for 1 year (3)
6. Be fully modular (7)
7. Maintain its position with respect to the “Wire Walker” buoy (7)
8. Resist marine growth (algae, etc) (6)
9. Lab testing apparatus will be feasible and results measureable, generating waves that will be scalable in height and power to ocean waves (9)
10. Have electrical components contained in water-tight areas (8)
11. Have components that touch salt water be corrosion-resistant (8)
2.2. Assumptions
Throughout the life cycle of the project, it is assumed that the following will be true in order for the proposed system to succeed:
1. That the waves produced by wind chop will be sufficient enough to generate energy.
2. That there will be enough energy in the storage cell to provide power during “flat days.”
3. That our system will not hinder the data collection of the “Wire Walker.”
4. Budget and final time scale will not change in the middle of the project
5. Suppliers will deliver parts on time and correct as ordered.
6. Delivered parts will meet and perform to all specifications during a 1-year time frame.
7. An abundance of fossil-fuels will not be discovered (for example, oil), again making alternative energy methods less attractive
8. Global Warming theories remain a pertinent issue in society throughout the next 10-20 years, and there will exist a market for non-emissive power producers
9. The ocean water temperature will be greater than the freezing point and will not be higher than 80 degrees Fahrenheit
10. Ocean testing will be feasible: system can be placed in front of the Scripps Pier.
2.3. Constraints
The following are the boundaries on the design, design process, team, resources, and budget. They are the parameters limiting the design and the design process. The constraints for the proposed Wave Energy Conversion device are: