The Viability of Wave EnergyThe Viability of Wave Energy

Applicability for the Pacific Applicability for the Pacific Northwest?Northwest?

Relative Strength to Wave Energy

Best sites are a) North Atlantic b) Gulf of Alaska – units are KW/meter

More Continuous Data

Conceptual DifficultiesConceptual Difficulties

In a wave, the energy content is In a wave, the energy content is distributed throughout the wavedistributed throughout the wave

Therefore, one needs to build a device to Therefore, one needs to build a device to focus or collimate that distributed energyfocus or collimate that distributed energy

Design challenge then becomes a) how big Design challenge then becomes a) how big of device is needed and b) what is the of device is needed and b) what is the efficiency of converting wave mechanical efficiency of converting wave mechanical energy into electricity?energy into electricity?

Wave energy is variable hourly and Wave energy is variable hourly and seasonalyseasonaly

Three Basic Kinds of SystemsThree Basic Kinds of Systems

Offshore (so your dealing with swell energy Offshore (so your dealing with swell energy not breaking waves)not breaking waves)

Near Shore (maximum wave amplitude)Near Shore (maximum wave amplitude) Embedded devices (built into shoreline to Embedded devices (built into shoreline to

receive breaking wave – but energy loss is receive breaking wave – but energy loss is occurring while the wave is breaking) occurring while the wave is breaking)

Some PhysicsSome Physics

Ocean waves are irregular and are not Ocean waves are irregular and are not easily characterized by an average heighteasily characterized by an average height

Relevant parameter is A, or amplitude of Relevant parameter is A, or amplitude of the wave (above mean sea level)the wave (above mean sea level)

More PhysicsMore Physics

Power per meter is the product of the Power per meter is the product of the energy density and the wave front velocity energy density and the wave front velocity (essentially the period of the wave)(essentially the period of the wave)

On the PNW coast, values for average wave amplitude and for wave period are such that wave power is in the 30-50 kw/m area.

So potential yield along the Oregon Coast, assuming 10% efficiency is:

40 kw/m x 1000 m/km x 600 km = 24000 MW

Devices 1: The Air Devices 1: The Air PistonPiston

Incoming wave pushes water level up to basically compress air in a piston to turn the crank on a generator. When water recedes, air comes back into the chamber.

This device is known as the oscillating water column (OSC).

OSC ContinuedOSC Continued

In principle, one could modify extant coastal headline topography to build these devices.

Note: Red Line is average sea level – front wall must be located below that line to make a seal so that the air doesn’t rush out – tidal variations are therefore important

Difficulties with OWC Difficulties with OWC approachapproach

• Initial cost of barrier wall is high – Initial cost of barrier wall is high – due to lack of access to the site (not due to lack of access to the site (not easy to build anything on a coastal easy to build anything on a coastal headland)headland)

• Zoning regulations protect most Zoning regulations protect most coastal headlandscoastal headlands

• Rich marine life is often found thereRich marine life is often found there• Device must withstand potentially big Device must withstand potentially big

stormsstorms

Unit Capacity of OWCUnit Capacity of OWC

• Physics is similar to that of a wind turbine but Physics is similar to that of a wind turbine but wave power is more dense wave power is more dense

• Yield depends on total square meters of rotor Yield depends on total square meters of rotor area but efficiencies are very difficult to area but efficiencies are very difficult to calculatecalculate

• Near Shore anchored devices capture highest Near Shore anchored devices capture highest amount of wave energy but sensitive to local amount of wave energy but sensitive to local mean sea levelmean sea level

• Reliability of waves is about 2 times higher Reliability of waves is about 2 times higher than windthan wind

Unit Capacity/FootprintUnit Capacity/Footprint

• Based on existing ON shore facility in Based on existing ON shore facility in India (operational around 1993)India (operational around 1993)

• 50 KW plant requires50 KW plant requires• 100 square meter footprint and 3000 100 square meter footprint and 3000

tons of concretetons of concrete• Scaling up to 100 MW implies 2000 Scaling up to 100 MW implies 2000

individual 100 square meter individual 100 square meter installations or roughly 5 per mile installations or roughly 5 per mile along Oregon coastline and this is just along Oregon coastline and this is just for 100 MWfor 100 MW

Conclusions about OWCConclusions about OWC

Shoreline installations probably don’t Shoreline installations probably don’t make sense – even if previous make sense – even if previous calculation is wrong by a factor of 10 calculation is wrong by a factor of 10 (which is unlikely)(which is unlikely)

Therefore, look towards large Therefore, look towards large installations in near shore installations in near shore but that but that could be expensivecould be expensive

Ocean Power Technologies Claim

• The footprint of a 100MW conventional power plant, including surrounding grounds, fuel unloading areas, waste settling ponds, and additional facilities can be up to 2 sq miles. A comparable OPT power plant would occupy less than 1 square mile of unused ocean surface out for sight from the shore (okay?)

The Tapered Channel DeviceThe Tapered Channel Device

• Works like a hydroelectric dam

Waves rush in to fill reservoir which then drains through a turbine system back into the ocean. Simple idea really. Power depends on total volume of water.

Pros and Cons of TAPCHANPros and Cons of TAPCHAN

• Could incorporate this into new kinds of seawall/jetty/harbor protection projects

• Average wave energy must be high in order to push all the water into the reservoir

• Reservoir needs to stay full and can’t drain at low tides

• Significant capital cost and large coastal footprint per MW because the depth of the reservoir is shallow

• Likely not practical in most locations

The Power Buoy

• Video explanation

Power Buoy ContinuedPower Buoy Continued Unit capacities are small (20KW) so Unit capacities are small (20KW) so

you need a large network – possibly you need a large network – possibly subject to catastrophic failure in subject to catastrophic failure in severe weathersevere weather

An Offshore Buoy Farm

Current Problem is that unit capacity is only 50 Watts for a 12 foot cylinder – need millions

Principle Advantage: Can Withstand severe Weather

The Overtopping DeviceThe Overtopping Device

Similar to TAPCHAN idea but can easily be installed near short instead of on shore. Power basically depends on incoming wave amplitude (height above mean sea level)

The The Wave DragonWave Dragon Project Project

Ambitious project to harvest up to 10 Ambitious project to harvest up to 10 Gigawatts of Power in the North AtlanticGigawatts of Power in the North Atlantic

Floating sea monstersFloating sea monsters

Pros and Cons of Wave DragonPros and Cons of Wave Dragon

In principle this could actually workIn principle this could actually work Unit capacity appears to be 16 Unit capacity appears to be 16

Turbine 4 MW individual dragonTurbine 4 MW individual dragon 25,000 then gives you 10 GW of 25,000 then gives you 10 GW of

powerpower Principle challenge is then “grid Principle challenge is then “grid

connection” but scale of project does connection” but scale of project does not seem formidablenot seem formidable

Attenuation devicesAttenuation devices Use Bernoulli principle to increase Use Bernoulli principle to increase

pressure and velocitypressure and velocity Tapered long columns that intercept Tapered long columns that intercept

surface wavessurface waves Might be good at beaches – not well Might be good at beaches – not well

developed idea yet, howeverdeveloped idea yet, however

UK Pelamis ProjectUK Pelamis Project

Unit Capacity is 750 KW; Power is generated at each of the hinged locations essentially through a device that converts pressure wave energy into electrical current.

Each tube is 150 meters long and 3.5 meters wide

UK project employs 7 tubes to generate 5.25 MW

Biggest potential problem (besides grid connection) is durability

The Pelamis ProjectThe Pelamis Project

To set the scale of the devices

The Future The Future Sea Snake FarmSea Snake Farm ? ?

Footprint argument is favorable: 30MW Footprint argument is favorable: 30MW facility would occupy 1 sq km of ocean.facility would occupy 1 sq km of ocean.

Look to the UK to seriously develop this Look to the UK to seriously develop this resource if initial prototypes prove succesfulresource if initial prototypes prove succesful

SummarySummary

There is much potential in worldwide wave There is much potential in worldwide wave energyenergy

Capturing wave energy and converting that Capturing wave energy and converting that into electricity is difficultinto electricity is difficult

Large scale projects very capital intensiveLarge scale projects very capital intensive Optimum technology not yet discovered so Optimum technology not yet discovered so

best to experimentbest to experiment Surface sea snakes, however, seem to be Surface sea snakes, however, seem to be

the best optionthe best option

Potential Local ProjectsPotential Local Projects

OPT facility at off shore from ReedsportOPT facility at off shore from Reedsport Oregon State wave energy research facility Oregon State wave energy research facility

at newportat newport Tidal power project in Tacoma NarrowsTidal power project in Tacoma Narrows