Wave Energy 101

WAVE ENERGY 101

Crashing Waves It’s obvious that waves are powerful, but how exactly do they work, and how can we go about harvesting the energy that carries a surfer, erodes a bluff, or knocks over a sand castle? Here are some resources to answer these and other related questions.

How do waves work?
Explore the ways in which kinetic energy from waves can be harvested and turned into electricity!

Energy Demands: Can Wave Energy Meet Our Needs?
The logistics of wave energy pertainign to grid assimilation and feisability can be found here.

Impacts on the Environment
Explore how wave energy can affect coastal marine zones and how researchers are looking to mitigate some of the effects of wave energy installations.

For more reading, check out these helpful wave energy publications:

How Do Waves Work?

Making Waves: How Do Waves Work?

Waves are actually a concentrated form of solar energy! Uneven heating of the Earth’s surface causes wind. Waves are generated by wind blowing over a distance of water. That distance is referred to as the fetch. Because the Pacific Ocean is so vast, the fetch is very large, leading to an energetic wave environment on the Oregon coast.

How much wave energy is out there? It is estimated that if 0.2% of the ocean’s untapped energy could be harnessed, it could provide power sufficient for the entire world. That's quite a statement. But what does this mean to the average person? Here are some facts to give perspective:

W = watt

kW = kilowatt (1,000 watts)

MW = megawatt (1 million watts)

GW = gigawatt (1 billion watts)

  • It takes 1 W to play an iPod
  • When you turn on a lamp that has a traditional light bulb, it puts out 60, 75, or 100 W of energy. 
  • A household typically has a power consumption of 1 kW. If a house used that constant amount of power every hour for a year, it would use 8760 kWh/year (1 kW x 24 h/d x 365 d/y).
  • Therefore it takes 8760 kWh of electricity to power your house for a year or 1.44 kWh to illuminate a 60W light bulb for a day (24 h).
  • 1 GW is the annual energy consumption for the state of Delaware.

How to Get Energy from a Wave

Worldwide, over a hundred conceptual designs of wave energy conversion (WEC) devices have been developed but only a few have been built as full-scale prototypes or tested. Most have been in Europe.  Currently there are four main types of WEC devices that generate or convert energy from waves: 

  • Oscillating water column
  • Attenuator
  • Overtopping
  • Point Absorbers

Below is a list of several examples of each main type of wave energy converter. Click on them to see some details regarding each particular design.

For a more comprehensive list of existing and developing technologies and companies, visit the U.S. Department of Energy’s Marine and Hydrokinetic Technology Database, providing up-to-date information on marine and hydrokinetic renewable energy, both in the U.S. and around the world.

Oscillating Water Column

water column

These devices generate power when a wave push against a horizontally-hinged flap, or waves are funneled into a structure that causes a water column to rise and fall. These devices may be fixed to the ocean floor, hang from a floating or shoreline structure, or built into harbor jetties. An example size would be put into 20 - 100 foot depths, and may be 65 feet wide.

Oceanlinx

Wavegen

Attenuator

attenuator

These devices are oriented in the direction of incoming waves that cause articulated components to bend and drive generators. Appearing somewhat like semi-submerged "train cars," they are typically moored to the ocean floor on one end. An example of the size of this device is around 390 feet long and 11 feet wide, with about 7 feet above the surface of the water.

Pelamis

Wavestar

Overtopping

overtopping

These devices have a partially submerged structure that funnels wave over the top of the structure into a reservoir. The water runs back to the sea powering a low-head hydropower turbine. An example prototype is roughly 100 by 200 feet, but may be scalable as large as 700 by 1,200 feet and 65 feet wide.

Wave Dragon

Point Absorber

point absorber

These devices capture energy from the "up and down" motion of the waves. They may be fully or partially submerged. The size depends upon the unit, but an example might be that around 8 to 10 feet rises above the surface and the rest, around 150 feet or so, extends below the surface.

OPT PowerBUOY

Columbia Power

OSU/CPT L10

Finavera AquaBUOY

Seabased / Uppsala

Energy Demands

Energy Demands: Can Wave Energy Meet Our Needs?

New forms of energy are needed. Oregon has a “Renewable Portfolio Standard” that states that Oregon’s goal is for the state’s power supply to be comprised of 25% renewable energy for all large utilities (PGE, PacifiCorp, EWEB) and 10% and 5% renewable energy for small utilities by 2025. Compared to other renewables, wave energy has a higher energy density, a high availability (80-90%), and better predictability.

Wave device

While research is ongoing to determine how efficient wave energy devices can be, consider this: a wave energy buoy is rated in the same way as the light bulb. Developers can build a buoy that can generate 40 kilowatts (kW), or one that can generate 1 megawatt (MW). Columbia Power Technologies' point absorber is rated between 250 kW and 1MW. A 250 kW buoy could power 250 homes, on average.

Energy from Waves

How to Get Energy from a Wave

Worldwide, over a hundred conceptual designs of wave energy conversion (WEC) devices have been developed but only a few have been built as full-scale prototypes or tested. Most have been in Europe.  Currently there are four main types of WEC devices that generate or convert energy from waves: 

  • Oscillating water column
  • Attenuator
  • Overtopping
  • Point Absorbers

Below is a list of several examples of each main type of wave energy converter. Click on them to see some details regarding each particular design.

For a more comprehensive list of existing and developing technologies and companies, visit the U.S. Department of Energy’s Marine and Hydrokinetic Technology Database, providing up-to-date information on marine and hydrokinetic renewable energy, both in the U.S. and around the world.

Oscillating Water Column

water column

These devices generate power when a wave push against a horizontally-hinged flap, or waves are funneled into a structure that causes a water column to rise and fall. These devices may be fixed to the ocean floor, hang from a floating or shoreline structure, or built into harbor jetties. An example size would be put into 20 - 100 foot depths, and may be 65 feet wide.

Oceanlinx

Wavegen

Attenuator

attenuator

These devices are oriented in the direction of incoming waves that cause articulated components to bend and drive generators. Appearing somewhat like semi-submerged "train cars," they are typically moored to the ocean floor on one end. An example of the size of this device is around 390 feet long and 11 feet wide, with about 7 feet above the surface of the water.

Pelamis

Wavestar

Overtopping

overtopping

These devices have a partially submerged structure that funnels wave over the top of the structure into a reservoir. The water runs back to the sea powering a low-head hydropower turbine. An example prototype is roughly 100 by 200 feet, but may be scalable as large as 700 by 1,200 feet and 65 feet wide.

Wave Dragon

Point Absorber

point absorber

These devices capture energy from the "up and down" motion of the waves. They may be fully or partially submerged. The size depends upon the unit, but an example might be that around 8 to 10 feet rises above the surface and the rest, around 150 feet or so, extends below the surface.

OPT PowerBUOY

Columbia Power

OSU/CPT L10

Finavera AquaBUOY

Seabased / Uppsala

Effects on the Environment

Effects on the Environment

impacts

Wave energy devices may exert a range of effects on the environment, not all of which will necessarily lead to relevant or negative changes in the marine environment. The deployment of wave energy devices can effect the environment in which they are sited primarily in two ways:

  • Wave energy devices will remove energy from the ocean, making less available for natural processes at the site.
  • Wave energy arrays will introduce many large, hard structures, creating new and different habitat types.

Extracting Ocean Energy

Reductions in near shore ocean energy may change current patterns and water mixing, potentially affecting organisms by altering food delivery patterns or rates, the mixing of eggs and sperm, the dispersal of spores and/or larvae, and how temperature varies throughout the water column. Changes in water movement also can affect how sand is moved along the coast. Because sediment grain size often determines which animals can live in the sand, changes to sand movement may affect the distribution of organisms. These wave, current and sediment transport effects will be technology- and location-specific. Modeling of the Oregon coast by potential device developers concluded that their project would have an undetectable effect on erosion/accretion at the shoreline. The Strategic Environmental Analysis by the Scottish Executive concluded there would be only minor effects of a wave energy array but recommended appropriate local analysis.

Introducing New Habitat

The second effects to consider are those that arise simply from having a device in the water. Because these devices are large and likely to be deployed in large groups, their presence may alter current flows, having effects similar to those described above. The effects of structures can further be divided into localized effects and those on migratory species:

impacts3A. Local effects due to the introduction of artificial hard substrate on fish and benthos:

Typically, these devices will be located in sandy bottom habitats with little vertical structure. The devices will introduce a large amount of hard material (buoys and anchors) and cables, which may be colonized by a variety of organisms, including non-native species. Further, structures with vertical relief may attract a variety of fish species typically associated with reefs. The fishes, invertebrates, and seaweeds that colonize hard structures will be different than those typically found in sandy habitats; thus, a new biological community will be present in the area. This may result in novel food or novel predators for the resident, soft-bottom organisms. Minor changes in species associated with softer sediments could occur due to scouring around the anchors.

Opinions differ as to whether these effects (e.g., bringing in species using hard substrates in areas of mainly soft substrate seabed) will be positive or negative. The described re-population of hard substrates may be considered to be a positive effect (performing like an artificial reef). Conversely, the intrusion of hard substrate in soft bottom areas may be considered a negative effect that may lead to “alienation” of species. Introduction of new species can be regarded as positive if increasing local biodiversity or biomass production is a goal. In conservation areas, habitat changes leading to “alienation of species composition” is considered undesirable and as species could displace the original species. Finally, if fishing is prohibited in the arrays, they may serve as de facto marine protected areas, possibly having positive effects on overall stocks of harvested species.

impacts2

B. Effects on migratory species and marine mammals:

Larger and migratory species may be at risk for entanglement in cables associated with the structures. Avoidance of these areas could result in longer migration times for certain species.

Noise from the devices may affect navigation and communication of marine mammals and may cause other organisms to avoid or be attracted to the area; however, it is not yet known if noise from the devices will be significantly louder or more frequent than that from vessel traffic. Studies are currently underway to assess ambient noise on the Oregon shelf and that associated with wave energy devices.

Magnetic and induced electric fields may affect navigation of salmon, crabs, some fishes and elasmobranches (sharks and rays).

Lighting of the surface elements of the devices may affect sea birds in that they may be attracted to the area, avoid the area, or be confused about their location relative to shore. Avoidance of the area may result in longer migration or forage times. However, the lighting may help prevent any potential sea bird collisions with the devices. Research is underway investigating the different effects of white versus red and flashing versus constant lights on offshore wind turbines. The findings of those studies may be helpful in informing designs for lighting wave energy devices.

 

 

B. Effects on migratory species and marine mammals:

Larger and migratory species may be at risk for entanglement in cables associated with the structures. Avoidance of these areas could result in longer migration times for certain species.

Noise from the devices may affect navigation and communication of marine mammals and may cause other organisms to avoid or be attracted to the area; however, it is not yet known if noise from the devices will be significantly louder or more frequent than that from vessel traffic. Studies are currently underway to assess ambient noise on the Oregon shelf and that associated with wave energy devices.

Magnetic and induced electric fields may affect navigation of salmon, crabs, some fishes and elasmobranches (sharks and rays).

Lighting of the surface elements of the devices may affect sea birds in that they may be attracted to the area, avoid the area, or be confused about their location relative to shore. Avoidance of the area may result in longer migration or forage times. However, the lighting may help prevent any potential sea bird collisions with the devices. Research is underway investigating the different effects of white versus red and flashing versus constant lights on offshore wind turbines. The findings of those studies may be helpful in informing designs for lighting wave energy devices.