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Tidal Energy (Power) is that one transported by the tides currents in the ocean in form of mechanical energy. The objective of this presentation is to show the basic concepts and the different ways it can be converted from sea energy to electric energy.


  • TIDAL POWER ALAN E. SUREZ Energy and Environmental Processes Processi per lEnergia e lAmbiente (PEA) A.A. 2013/2014
  • PEA_WAVE AND TIDAL ENERGY 2 To show the sea energy presented in the tides. To show how is possible to take advantage of this energy to convert it in another useful kind of energy (work). To show the history in the world of development of this transformation. To show the currents plants and projects using tidal energy. To show the pros and contras of this renewable energy. To show some ideas about new projects using tidal energy, be it for improve the current technology or for creating new ways to take advantage of or new uses. The aim of this presentation is: SCOPE
  • PEA_WAVE AND TIDAL ENERGY 3 Tidal Energy (or Power) is the energy transported by the tides currents in the ocean in form of mechanical energy. It can be converted into a useful forms of power (energy), mainly electricity generation. What is Tidal energy? INTRODUCTION
  • PEA_WAVE AND TIDAL ENERGY 4INTRODUCTION What is the difference between Waves and Tides? Tide is the cyclic rise and fall of sea level, caused by the gravitational pulls of the sun and moon. Ocean Wave (or Wind Wave) is an surface wave generated by local wind. Earth land masses also move because of the Moon and Sun pulls, but its not easily to see
  • PEA_WAVE AND TIDAL ENERGY 5 Percentage for Total World Energy Consumption Tidal Energy INTRODUCTION < 0,00016% 2009 2010 16,7% x 0,001% = 0,00017 % 2011 19% x 0,001% = 0,00019 %
  • PEA_WAVE AND TIDAL ENERGY 6 Currently: 250 MW approx. Potential in ocean currents to produce ca. 450 TW 1,8 million times current production 0,00019% x 1 800 000 = 342% of current total world energy consumption! But, statistics Total World Tidal Energy Production INTRODUCTION Source: Energy Information Administration, Annual Energy Outlook 2013, http://www.eia.gov/forecasts/aeo/er/pdf/appa.pdf http://www.eia.gov/forecasts/aeo/er/pdf/tbla17.pdf http://www.forbes.com
  • PEA_WAVE AND TIDAL ENERGY 7FUNDAMENTALS What causes the tides? Moon gravitational pulls Sun gravitational pulls Sun-Moon position relative to the earth
  • PEA_WAVE AND TIDAL ENERGY 8 Sea level rises over several hours, covering the intertidal zone (flood tide). The water rises to its highest level, reaching high tide, and stopping (slack tidal; slack water). Sea level falls over several hours, revealing the intertidal zone (ebb tide). The water stops falling, reaching low tide, and stopping (slack tidal; slack water). THESE MOVEMENTS GENERATE CONSTANT TIDAL STREAMS, WITH A HIGH AMOUNT OF ENERGY Tide changes FUNDAMENTALS
  • PEA_WAVE AND TIDAL ENERGY 9FUNDAMENTALS What influences tide behavior? Offshore and near-shore deep (bathymetry) Coastlines shape Declination of the Earths orbit Declination of the Moons orbit Presence of land masses Speed of the Earths rotation (inertia) Coriolis effect on the tide flow Frictional forces
  • PEA_WAVE AND TIDAL ENERGY 10 Diurnal tides (daily tides): 1 high tide 1 low tide each tidal day Unusal (e.g. Gulf of Mexico) Semidiurnal tides (semidaily tides): 2 high tides 2 low tides each tidal day Equal tides during each period Period of 12 hrs and 24.5 minutes (e.g. Moon passing through equator) Mixed tides: 2 high tides 2 low tides each tidal day Unequal tides during each period Most common type FUNDAMENTALS Tides classification I
  • PEA_WAVE AND TIDAL ENERGY 11 Spring tides: Both Sun and Moon pulls in the same line (syzygy) Neap tides: Moon in quadrature respect to the sun (90) Metereological tides (storm surges): Wind and barometric pressure changes Shallow seas and near coasts. FUNDAMENTALS Tides classification II
  • PEA_WAVE AND TIDAL ENERGY 12FUNDAMENTALS Tides datum Reference level Vertical datum Reference plane MLW Spring generally taken as reference Tides can also vary with the meterological conditions Winds Pressure
  • PEA_WAVE AND TIDAL ENERGY 13 One single tidal constituent represents just one effect (M2: Moon pull; S2: Sun pull, etc.) h t = ( + ), where =amplitude, =frequency, =time, =phase constituent. Every place has different tidal constituents factors. By adding the different tidal constituents, its possible to find the tidal behavior for each different place (e.g. Ports). Tidal constituents (Tidal Analysis) FUNDAMENTALS
  • PEA_WAVE AND TIDAL ENERGY 14 Major Tidal constituents FUNDAMENTALS Species Darwin Symbol Speed rate(/hr) Higher harmonics Period < 12 h Shallow water overtides of principal lunar M4 57,97 Shallow water overtides of principal lunar M6 86,95 Shallow water overtides of principal solar S4 60,00 Semi-diurnal Period < 24 h Principal lunar semidiurnal M2 28,98 Principal solar semidiurnal S2 30,00 Larger lunar elliptic semidiurnal N2 28,44 Diurnal Period > 24 h Lunar diurnal (Luni-solar declinational) K1 15,04 Lunar diurnal (Lunar declinational diurnal) O1 13,94
  • PEA_WAVE AND TIDAL ENERGY 15 Tide Predicting Machine FUNDAMENTALS CURIOUS FACT: These machines were used in the World War II to predict the tides for planning the invasion of Normandy.
  • PEA_WAVE AND TIDAL ENERGY 17 Tide Pole (or Tide Staff) Gauges Float Gauges Thomson type (1887) Tide measurement (real data) FUNDAMENTALS
  • PEA_WAVE AND TIDAL ENERGY 18 Acoustic Gauges Pressure Gauges Radar Gauges Ultrasonic Gauges OTHER USES: Shipping and fishing industries; Tsunami warnings. Tide measurement (real data) FUNDAMENTALS
  • PEA_WAVE AND TIDAL ENERGY National Ocean Service (NOS) information: For various part of the world, in 4 volumes (+1 for Alaska). Each volume: Table 1: Tides for Reference stations Table 2: Tidal differences and ratios for subordinate stations Table 3: Information for tide at any time between HW and LW Table 4-5: Sunrise-Sunset for various latitudes and conversions 19 Tides prediction TIDAL STREAMS
  • PEA_WAVE AND TIDAL ENERGY 20 Galileo Galilei (Discorso del flusso e reflusso del mare, 1616 ) Earths rotation Isaac Newton (Principia, 1687) Gravitational forces Pierre-Simon Laplace (1776) Partial differential equations William Thomson (Lord Kelvin; 1860) Laplace eq. + Curl component / Fourier analysis / First Tide predicting machine. George Darwin (Tides prediction, 1891) Best approach Harmonic analysis Dr. Arthur Thomas Doodson (1921) Best approach, including new Lunar theory / 388 tidal frequencies / Doodson-Lg TPM Tidal Analysis Precursors Physics FUNDAMENTALS
  • PEA_WAVE AND TIDAL ENERGY 21 Horizontal movement of water, product of the constant and rhythmic pulls over the oceans, as seen before. Depending on the place, and even on the Earth-Moon-Sun position, they can be stronger or weaker. Slack water (stand of the tide) Unstressed water; no movement time. Spring tide has a speed about double that of a neap tide. Else streams are between these two numbers. Spring tides have shorter slack times than average. Tidal Streams (Currents) TIDAL STREAMS
  • PEA_WAVE AND TIDAL ENERGY 22 Tidal current: it depends on the rise and fall of the tide. Nontidal current: includes currents not due to tidal movement: Permanent currents in the general circulatory system Temporary currents from meteorological conditions (e.g. wind) Real currents are a combination of these both kind of currents. Tidal and Nontidal Currents TIDAL STREAMS
  • PEA_WAVE AND TIDAL ENERGY 23 Major global Nontidal Currents TIDAL STREAMS
  • PEA_WAVE AND TIDAL ENERGY 24 Tidal current is rotary (and slower), when not restricted (offshore) Caused by the Earths rotation Clockwise in the Northern hemisphere; Counterclockwise in the Southern one Speed varies throughout the tidal cycle 2 maximums and 2 minimums in opposite directions Tide current is Reversing (and higher), when restricted to channels General features TIDAL STREAMS Current rose (Current ellipse) Reversing current
  • PEA_WAVE AND TIDAL ENERGY 25 Nontidal flow effect TIDAL STREAMS Effect on a Current rose Effect on a Reversing current
  • PEA_WAVE AND TIDAL ENERGY 26 Time of Tidal Current vs. Time of Tide (not always the same) Relationship Between Speed of Current and Range of Tide Variation Across an Estuary (speed profile) Variation with Depth (velocity, e.g. slack+sub