OCEAN CURRENT ENERGY

Ocean Currents,Available Technology, &

Economic Feasibility

BY: MATTHEW SAVINMatthew.savin@gmail.com

Hydrokinetic vs. Hydropower

To understand ocean current energy, the distinction between hydropower and hydrokinetic power must be understood

“Hydropower” Alters the environment to create useable energy

from rivers and streams

“Hydrokinetic”Harnesses the existing flow, current or velocity of

water without altering the environment

Two Examples of Hydrokinetic Power

1. Tidal Power:Technology that attempts to harness the energy

that is created from waves

2. Ocean Current Power:Technology that attempts to harness energy from

ocean currents and streams

Although both use similar technology, we will focus mainly on “Ocean Current Power”

What Are Ocean Currents?Surface Currents:

328 Ft. (100 meters) or aboveCoastal CurrentsSurface Ocean CurrentsDevelopment of ocean current energy technology

refers to the use of “surface currents”

Deep Ocean Currents (Global Conveyer Belt)For our purposes, we will focus solely on “surface

currents”

What Drives Surface Ocean Currents?

The Coriolis Force:Wind is the primary factor in forming Surface

Ocean CurrentsThe earth’s spin causes winds to curve right in the

northern hemisphere, and left in the southern hemisphere (Coriolis Force)

Thus, in the northern hemisphere, wind from the west pushes warm waters north, and wind from the east pushes cold water south

Gyres: the circular pattern that develops from the combination of westerly and easterly wind

5 Major Gyres

Other Factors…In addition to wind & the Coriolis Force, several

other factors contribute to surface ocean: currents Thermohaline Circulation:

Temperature (Solar Heat)Water Salinity (Density)

Tidal Currents:Earth’s gravitational pull

Ocean Current Energy Potential

Ocean currents travel at speeds significantly slower than wind

However, water is 800 times as dense as air

Thus, a 12 mph ocean current would have an energy output equal or greater to a 112 mph wind

By some estimates, 1/1000 of the energy of the Gulf Stream could satisfy 35% of Florida’s energy needs

Characteristics of Ideal Ocean Current Candidates:

1. Strong Current: Some claim that a mere 1 knot current could produce

substantial energy However, most approximates say that only 4-5 knot

current could produce enough energy to justify the expenditure

2. Shallow Water Depth Available technologies (based on wind & tidal prototypes)

have only proven effective at relatively shallow depths Other issues – such as access to equipment for

maintenance – limit ocean current facilities to shallow depths

3. Close Proximity to Shore: Because transmission lines are needed to transport the

energy generated to the onshore grid

Where Are Ocean Currents Located?

In addition to the US, the UK, Ireland, Italy, Philippines, and Japan have access to potentially useable ocean currents

Three Major Currents in the United States:1. The Gulf Stream

2. The Florida Straits Current

3. The California Current

The Gulf Stream & Florida Straits

The California Current

Advantages of Ocean Current Energy

Energy Density One obvious benefit of ocean current energy is that its

energy density is far superior to wind, using similar to identical technology.

Reliable/Constant Energy Output Unlike wind and solar, an effect ocean current would

remain relatively constant Thus, unlike wind, utility companies could safely

purchase its energy output at a level near the generating facility’s capacity

No GHG Emissions

Minimal Environmental Alterations

How Would Ocean Current Technology Work?

Three basic features:1. Rotor Blades

2. A Generator

3. Transmission Lines (for bringing electricity to an onshore grid)

Two Potential Designs:1. Submerged Water Turbines

2. Parachutes

Submerged Water Turbines

The most common prototype would essentially operate in the same way as a wind turbine

The turbine would be fastened to the ocean floor, with water pushing the turbine instead of wind

Two Types of Submerged Water Turbines:1. Vertical

2. Horizontal

Horizontal Submerged Turbines

Most people are already familiar with the general design of a horizontal submerged water turbine

It would resemble & operate like a traditional windmill

The turbines would have an axis of rotation horizontal to the ground

Vertical Submerged Water Turbines

Vertical turbines (the design on the right) operate similarly to horizontal turbines

However, the axis of rotation would be vertical to the ground

“Parachutes”Another prototype would fasten a cable to the

ground, allowing the turbine to float above

This design would operate much like a person flying a kite

However, there would be a series of kites that would continuously rotate, opening to harness the current, and closing on the return trip

Parachute vs. Waterwheel

Parachutes Cont’d

Fastening to the Ocean Floor

Exactly how the turbines would be fastened remains to be seen

However, most prototypes have borrowed ideas from either offshore windmills or offshore oil rigs

Given the similarities, the same technology should work with ocean current energy…

Fixed-Bottom Substructure Technology

1. Monopile Foundation: Minimal Footprint Depth Limit = 25 meters Low Stiffness

2. Gravity Foundation: Larger Footprint Depth Limit = Unknown Stiffer, but more stability

3. Tripod/Truss Foundation: No Testing for Turbines (Wind or Submerged) Yet… Oil/Gas Depth of about 450 meters Larger footprint

3 Basic Design…

Technical Challenges Avoiding Cavitations:

Bubbles on the rotator blades may create resistance that can reduce efficiency

Marine Growth Buildup: Will need to be managed to ensure that interference with the

equipment is minimal

Reliability: Maintenance costs are typically high, which means the

equipment must be relatively reliable to avoid constant replacements and diving expeditions

Corrosion: Given the expense of equipment & maintenance, measures need

to be taken to ensure that the equipment doesn’t corrode from underwater elements

Can We Overcome Technical Challenges?

While the technical and environmental concerns are daunting, there is hope…

Innovations from the private sector have offered promising designs

The federal government has also shown a renewed interest in both hydropower & hydrokinetic projects…

Alternative DesignsGiven the technical difficulties resulting from of

underwater corrosion, maintenance difficulties, and stability concerns, the private sector has developed some innovative alternative designs...

But the practicability and expense of these designs remains relatively unknown, as most are in the preliminary stages…

EXAMPLE 1: Hydro Green Energy

Instead of fastening the turbines to the ocean floor, one such design relies upon a floating base

The turbines are connected to the flotation device on the water surface, essentially operating as an upside down horizontal turbine

There are numerous advantages to this design, including:No alteration of the ocean floorEasy maintenance, as the turbines can be replaced

by simply removing/replacing them above waterPresumably, lower infrastructure costs

Hydro Green Prototype…Hydrogreen’s

Prototype places the turbines just below the surface, attaching them to a floating foundation

This could alleviate some of the maintenance and foundation problems…

Hydro Green Cont’dCould replace each

turbine without entering the water

No need to fasten the turbines to the ocean floor, which eliminates foundation expenses and design uncertainty

What About Environmental Concerns?

Species Protection:

Shipping Route Interference

Recreational Uses

Slowing the Current Flow

Changes in Estuary Mixing

Potential Environmental Solutions…

Species Protection? Slow Blade Velocity Protective Fences Sonar Brakes

Shipping/Fishing? Fishery Exclusion Zones

Slowing Current? Unknown

Estuary Mixing? Unknown

Conclusion: Large-Scale Testing Necessary

Economic Considerations Infrastructure:

Unfortunately, the initial cost of ocean current technology would be expensive

Transmission Lines

Government Funding: Infrastructure Subsidies

Energy Output & Consumer Pricing Energy Output Maintenance Costs

Open Market or Monopoly?

Transmission LinesThe single largest expenditure will relate to

construction of the initial infrastructure

Setting up transmission lines will be the most expensive and challenging, as underwater lines will be necessary

While the initial expenditure would be great, its effect on the consumer would be marginal in the long-term, as the only costs would relate to maintenance

Google Wind FarmHowever, if

projects such as Google’s wind farm materialize, then transmission lines might be available for hydrokinetic power as well

Government Funding & Department of Energy…

In September of 2010, the DOE provided $37 million towards harnessing energy from US waterways, the largest such grant yet…

While estimates for the initial infrastructure costs are in the billions, there appears to be growing interest in ocean current and tidal energy

Federal or State Funding?How much of the financial burden should States

assume?

Regional Partnerships?

Is this a project that only the federal government can implement?

Should taxpayers in the Midwest have to pay for energy being developed on the coast?

Government Regulation: Open Market or Monopoly?

Another variable is to what extent economic factors would be left to market forces

This would depend in large part upon whether the infrastructure would allow competition among electricity distributors for the generated energy

Increased competition among distributors could lower the cost to the consumer, although federal regulation would probably be necessary to avoid “gaming the system”

Who Will Regulate? Which Agency?

DOE?FERC?

Federal vs. State?How much state control?Regional Development?

Cost to the Consumer?Two variables will influence the eventual cost to

the consumer: energy output & maintenance costs

ENERGY OUTPUT: because large-scale testing and development have yet to materialize, the actual energy output that could be utilized remains unknown

MAINTENANCE: in addition, until large-scale testing and development is implemented, the cost of maintaining the facility remains unknown, which would be passed on to the consumer

Consumer Cost Cont’d…The ultimate cost to the consumer will depend

upon the supply of energy that each generator is able produce

Greater Energy Output = Greater Supply = Lower Consumer Cost

SUMMARY Technical Challenges

Large-scale testing is necessary to determine how much maintenance will be involved with each prototype

Environmental Concerns The most significant concern is the slowing of the ocean current

itself, which requires large-scale testing as well

Economic Feasibility? Will depend upon both the maintenance costs and the energy

output Government funding will also be necessary

Government Regulation: It remains unknown which agency, and to what extent, the

government will regulate the offshore facilities

CONCLUSION: WE NEED LARGE-SCALE TESTING, BUT THERE IS HOPE FOR OCEAN CURRENT ENERGY!!