Wave and Tidal Energy Overview
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Questions and Answers

Wave energy is a form of concentrated solar energy.

True (A)

What percentage of the Earth's surface is covered by oceans?

71%

Which of these is NOT a factor hindering the deployment of wave energy converters (WECs)?

  • Concomitant high costs
  • Abundant availability of wave power (correct)
  • A number of other factors
  • Lack of maturity in the technology

What is the name of the company behind the Ocean Energy Buoy Ireland?

<p>Ocean Energy Buoy Ireland</p> Signup and view all the answers

Wave-activated bodies (WABs) or oscillating body converters (OBCs) are a simpler technology compared to OWCs.

<p>False (B)</p> Signup and view all the answers

What does PTO stand for in the context of wave energy?

<p>Power Take Off</p> Signup and view all the answers

Which of these is NOT an advantage of oscillating body converters?

<p>Their simplicity (C)</p> Signup and view all the answers

What type of WEC does the OPT PowerBuoy employ?

<p>Wave-activated Body (B)</p> Signup and view all the answers

What is the primary mechanism used by SeaBased for power take off?

<p>Directly driven linear generator</p> Signup and view all the answers

What is the main difference between barrages and lagoons in tidal energy systems?

<p>Lagoons are offshore, while barrages are in estuaries. (C)</p> Signup and view all the answers

Tidal range energy is highly dependent on weather conditions.

<p>False (B)</p> Signup and view all the answers

Which of these is NOT a common type of tidal energy system?

<p>Tidal current (B)</p> Signup and view all the answers

What is the acronym for tidal stream turbines?

<p>TSTs</p> Signup and view all the answers

Tidal stream turbines require the storage of water.

<p>False (B)</p> Signup and view all the answers

What is the maximum theoretical efficiency of a tidal stream turbine according to Betz's Law?

<p>59.3%</p> Signup and view all the answers

Which of these challenges is NOT faced by tidal stream turbines?

<p>Low maintenance requirements (C)</p> Signup and view all the answers

Vertical axis turbines are the most common type used in tidal stream energy applications.

<p>False (B)</p> Signup and view all the answers

Flashcards

What are wind waves?

Waves generated by wind blowing over the sea surface. They are a concentrated form of solar energy.

What is the global wave energy resource?

The vast amount of wave power available globally, estimated at 32,000 TWh per year.

What are WECs?

Devices used to capture wave energy and convert it into electricity.

What is an Oscillating Water Column (OWC)?

A type of WEC that uses the rise and fall of waves to compress and release air, driving a turbine to generate electricity.

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What is a Wells turbine?

A turbine that rotates continuously in one direction regardless of airflow direction. It's specifically used in OWCs.

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What are Wave Activated Bodies (WABs)?

A category of WECs that use the motion of a floating or submerged body to generate power.

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What are Oscillating Body Converters (OBCs)?

A type of WAB that uses the vertical motion of a floating body to generate power.

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What are Overtopping Devices?

A system that uses a ramp to collect water from waves, storing it in a reservoir and then releasing it through a turbine to generate power.

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What causes tides?

The periodic rise and fall of sea level caused by the gravitational pull of the Moon and Sun.

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What is a tidal barrage?

A structure built across an estuary to harness the tidal energy by capturing the water flow.

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What is tidal stream energy?

A method of harnessing tidal energy by placing turbines in the flow of tidal currents.

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What is tidal range?

The difference in vertical water level between high tide and low tide.

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What is tidal range energy?

A system that captures the potential energy created by the tidal range, often using reservoirs and turbines.

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What is a tidal barrage?

A type of tidal range technology that creates an impoundment across an estuary, using sluice gates to control water flow.

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What is a tidal lagoon?

A type of tidal range technology that uses a standalone, often offshore, impoundment to capture tidal energy.

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What is one-way power generation using tidal range?

A way of generating power using tidal range technology where water is collected at high tide and released through turbines at low tide.

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What is two-way power generation using tidal range?

A way of generating power using tidal range technology where turbines are used to capture the flow of both incoming and outgoing tides.

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What are tidal stream turbines (TSTs)?

A type of tidal energy technology that directly harnesses the kinetic energy of tidal currents using turbines.

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What are tidal currents?

The flow of water caused by the tides, creating strong currents that can be harnessed for energy.

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What is the tidal stream resource?

The amount of kinetic energy present in a tidal current, which can be harnessed using tidal stream turbines.

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What is tidal stream power density?

The power density of a tidal current, typically measured in watts per square meter.

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What is the tip speed ratio (TSR) of a tidal turbine?

The ratio of the tip speed of a turbine blade to the speed of the fluid it's rotating in (water in this case).

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What is Betz's Law?

The maximum possible efficiency for extracting power from a free-flowing fluid, like water or air.

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What are the key factors in developing wave energy?

A key factor in WEC (Wave Energy Converter) development that involves understanding the resource, costs, and environmental impacts.

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What is transitional water?

The transition zone where waves start to interact with the seabed as water depth decreases.

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What is wave celerity?

The speed at which a wave crest travels.

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What is group velocity?

The speed at which wave energy travels.

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What is wave energy density?

The amount of energy per unit area of the sea surface, averaged over a wave period.

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What is wave power (or wave energy flux)?

The amount of wave energy passing through a unit width perpendicular to wave propagation.

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What is linear wave theory (or Airy wave theory)?

A simplified theory used to describe wave motion, assuming small wave amplitudes and linear behavior.

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Study Notes

Wave and Tidal Energy

  • Wave energy originates from solar energy, concentrating wind energy into waves.
  • The global wave power resource is estimated at 32,000 TWh per year.
  • Wave energy conversion devices (WECs) have a similar history to wind energy in the 1980s.
  • Wave energy is plentiful along coastlines.
  • High costs and technological maturity hinder current development.

Wave Energy Converters

  • Oscillating Water Columns (OWC): These devices use a semi-submerged chamber to trap air, which moves in response to waves, creating a continuous air flow that drives a turbine.
    • Fixed or floating structures.
      • Pico OWC
      • Oceanlinx
      • Mutriku
  • Wave Activated Bodies (WABs): These devices use either floating or submerged bodies that move with the waves to generate power.
    • Typically more complex than OWCs.
      • WaveRoller
      • Oyster
      • Pelamis
      • Carnegies CETO
  • Overtopping: These devices use reservoirs that fill with water when waves overtop them, using the resulting potential energy to drive turbines.
    • Fixed or floating structure.
      • WaveDragon
      • SSG
  • Point Absorbers: These devices capture energy from the waves with a single point.
    • OPTs PowerBuoy

The Wave Resource

  • Many wave types exist in the ocean, driven by different mechanisms and characterized by different properties.
  • Wind waves are one category of significant waves.
  • The term wave energy refers specifically to wind waves.

Linear Wave Theory

  • In linear wave theory, the displacement of the free surface can be determined using a sinusoidal function.
  • Amplitude, wavelength, period, wave number and angular frequency are related.
  • The waves energy density varies with the square of the wave height.
  • Wave power and group velocity are key concepts in this theory.
  • Important wave parameters are described here.

The Tidal Resource

  • Tides are caused by the gravitational pull of the Moon and Sun.
  • Tidal energy is collected from barrages (imposing impoundment across an estuary) or (lagoons).
  • Tidal stream turbines are direct energy harvesters.

Tidal Range

  • Tidal range is the difference in the highest and lowest points of the tide.
  • Both predictable and important to consider.
  • Potential energy from the water difference is harvested
  • Two different systems exist, barrages and lagoons, which are used to harness this energy.

Tidal Stream

  • The kinetic energy of the tide-driven water flow can be harvested using turbines.
  • Local tide velocity, depth, and seabed considerations affect the method.
  • Technologies are often derived from the wind industry's solutions, despite different environmental conditions.
  • There are also significant aspects to consider when considering tidal stream generation: the strength and nature of the current, structural loads, biology, maintenance, and considerations (among others).

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Wave and Tidal Energy PDF

Description

Explore the fundamentals of wave and tidal energy, focusing on how wave energy originates and its potential as a renewable resource. This quiz covers various wave energy conversion technologies such as Oscillating Water Columns and Wave Activated Bodies, along with their operational principles and challenges.

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