OCEAN CURRENT
ENERGY
Ocean Currents,
Available Technology, &
Economic Feasibility
BY: MATTHEW SAVIN
Matthew.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 above
Coastal Currents
Surface Ocean Currents
Development 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
Currents
 The 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

2.
energy
However, most approximates say that only 4-5 knot current
could produce enough energy to justify the expenditure
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 Designs
 Given 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 floor
 Easy maintenance, as the turbines can be replaced by
simply removing/replacing them above water
 Presumably, 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’d
 Could 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 Lines
 The 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 Farm
 However, 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!!