1. Ocean Wave Energy Energy Domain Presentation Nicholas McNeill
28 Feb. 2017
E.E.E.

2. Presentation Overview
Forms of Ocean Energy
Wave Energy Overview
Wave Energy Converters
Benefits and Drawbacks
Current Status
Moving Forward
Key Questions

3. Ocean Thermal Energy Conversion
Energy Source: OTEC utilizes the temp. gradient of the ocean in heat exchangers of a Rankine turbine
Largest test facility in Hawaii produces 105kW after a $5 million upfront
Rather inefficient but is continuous
High upfront costs but pretty low running costs
Need large temperature delta
Could use cold water return to cool building in HI
Potential to also desalinate ocean water in the process
Estimates 20 cents per kWh
120 houses
[1]

4. Ocean Current Energy
Energy Source: continuous flow of ocean due to surface winds, water salinity, temperature, ocean floor topography, and the earth’s rotation
Similar turbine tech to tidal but far less mature
Much more difficult to construct
Much more power cables would be needed
Harder to determine ecological ramifications
A famous 2006 report from United States Department of the Interior estimates that capturing just 1/1,000th of the available energy from the Gulf Stream would supply Florida with 35% of its electrical needs
[2]

5. Tidal Energy Energy source: gravitational pull of the moon forms tides
Tidal Barrages
Tidal Streams
Turbines capture energy from differing water levels
Dam is full of turbines
Energy collected in both directions
Free standing wind turbines anchored to the sea floor
Lower upfront costs
Less concentrated energy
Based on moon-earth
Tidal:
Benefits: Highly predictable and low running costs
Drawbacks: High upfront costs and impacts the habitats of coastal creatures
Large plant in Scotland powers over 200,000 homes, plan to increase it to 750,000 homes: uses tidal stream concept
[4]

6. Ocean Wave Energy Overview
Unit: kW/m
Energy Source: Wind blowing on the ocean surface
Latitudinal wind belts—especially Westerlies—are most promising locations
Took off after oil crisis of 1973
2/3 of US energy consumption could be supplied via ocean energy
Wind Direction
[5]

7. Wave Energy Converters
Different WEC’s absorb surge, sway, & heave
Components of wave energy tech
Structure and prime mover to capture the energy of the wave
Foundation and mooring
Power take-off system that converts mechanical to electrical energy
Control systems for safety and optimization
WEC Technologies (>1000 pat)
Attenuator
Point Absorber
Oscillating wave surge converter
Oscillating water column
Overtopping device
Submerged pressure differential
[6,7]

8. Attenuators (~14%)
Long, multi-segment structures float parallel to the wave direction
“Ride” the wave: device motion follows wave motion
Relative motion of pontoons convert energy through a hydraulic circuit or mechanical gear train
180 M long, 4M ⌀: 750kW
[6,7]

9. Terminators/Overtopping Devices (~33%)
Capture water waves as they enter into a storage reservoir
Water passes through a top head turbine and is returned to the ocean
Shoreline or floating moored structures
overtopping
reservoir
turbine outlet
Large 100M ⌀: 12MW
Small operation: 20kW
[6,7]

10. Point Absorber (~53%)
Floating buoy that rises and falls with each passing wave
Movement is used to pump a hydraulic fluid in a column below the surface which is used to rotate the generator
First WEC to achieve large scale deployment
Height: 41m
Diameter: 11m
P: 150kW
[6,7]

11. Wave Energy Prize 1st place winners AquaHarmonics
18 month public design/ build/test from the DOE
Goal: “increase the diversity of organizations involved in Wave Energy Converter (WEC) technology development, while motivating and inspiring existing stakeholders”
Point absorber with superior control strategies
[8]

12. Pros & Cons Benefits Drawbacks + Clean energy - High upfront cost
+ Renewable
+ Abundant
+ Slightly intermittent (90% compared to 30%) but predictable
+ More energy dense than air/wind
+ Bulk of population lives near water reducing energy loss
+ Different WEC available for differing environments and needs
+ Reduces damages to land
+ Low operating costs
Drawbacks
- High upfront cost
- Rarely breakages are costly
- Low rate of improvement
- Only suitable in certain locations
- Duck curve
- Issues with bad weather
- Effects on marine life
- Boating concerns
- Noise and Aesthetics
Wildlife: home & migration hurt due to structure, noise, and magnetic/electric fields, but some grow there
[9,10]

13. Current Status of Ocean Energy
Still early stage of development from conceptual up to demonstration stage (tidal is a little further)
Best locations and projected energy/upkeep is far along
Need more data for environmental issues (empirical) other than carbon LCA
Need more data for cost at the commercial scale
Need to figure out regulations to streamline mass deployment
[11]

14. SI Ocean’s Energy Cost Projections
Costing Approach
Cost Breakdown
Tidal Energy Cost vs Throughput
Wave Energy Cost vs Throughput
Used different “Learning curves” to estimate lower costs as a function of deployment
For now, the best wave generator technology in place in the United Kingdom is producing energy at an average projected/assessed cost of 7.5 cents kWh, which is more optimistic than these estimates.
[12]

15. Regulations & Government Funding
Bulk of regulation is done at the state level but there is overlap
Several federal organizations:
Office of Energy Efficiency & Renewable Energy
Bureau of Ocean Energy Management
Federal Energy Regulatory Commission (FERC) says its hydroelectric
Federal Funding
Wave energy prize in 2016
$7.4M from Energy department for MHK
Marine and Hydrokinetic Renewable Energy Promotion Act of 2010 was not passed and would have invested $800M reauthorizes the Department of Energy’s Water Power program with a total amount of $800 million for MHK
30% tax credit
[13]

16. Why Hasn’t Wave Energy Made a Bigger Splash?
Difficult technical challenges
Vast differences in WEC
High upfront costs due to installation
“Where wind energy was three decades ago”
No major players entering the market
Difficult to install because areas have lots of wave action…
Salt water is difficult on electronic equipment
[14,15]

17. Moving Forward/Challenges
Improve and converge WEC designs to drive down costs
Get a big player into the game
Invest in combined wind and wave farms
Secondary energy option after easy wind locations have been saturated

18. Discussion Questions What Wave Energy Converter will become the norm?
How large of an effect would widespread ocean wave energy converters have on the environment?
How should ocean energy play into the US/World’s energy portfolio? How should funding reflect this? Is it worth pursuing currently?

19. Works Cited
[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15]