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TIDAL POWER

ALAN E. SUÁREZEnergy and Environmental ProcessesProcessi per l’Energia e l’Ambiente (PEA)A.A. 2013/2014

PEA_WAVE AND TIDAL ENERGY

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• 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


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• 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


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 it’s not easily to see


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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 %


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• 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


7FUNDAMENTALS

What causes the tides?

• Moon gravitational pulls

• Sun gravitational pulls

• Sun-Moon position relative to the earth


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• 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


9FUNDAMENTALS

What influences tide behavior?

• Offshore and near-shore deep (bathymetry)

• Coastlines shape

• Declination of the Earth’s orbit

• Declination of the Moon’s orbit

• Presence of land masses

• Speed of the Earth’s rotation (inertia)

• Coriolis effect on the tide flow

• Frictional forces


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• 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


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• 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


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


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• One single tidal constituent represents just one effect (M2: Moon pull; S2: Sun pull, etc.)

• , where =amplitude, =frequency, =time, =phase constituent.

• Every place has different tidal constituents factors.

• By adding the different tidal constituents, it’s possible to find the tidal behavior for each different place (e.g. Ports).

•

Tidal constituents (Tidal Analysis)

FUNDAMENTALS


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Major Tidal constituents

FUNDAMENTALS

SpeciesDarwinSymbol

Speedrate(°/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-diurnalPeriod < 24 h

Principal lunar semidiurnal M2 28,98

Principal solar semidiurnal S2 30,00

Larger lunar elliptic semidiurnal N2 28,44

DiurnalPeriod > 24 h

Lunar diurnal (Luni-solar declinational) K1 15,04

Lunar diurnal (Lunar declinational diurnal) O1 13,94


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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.

http://www.ams.org/samplings/feature-column/fcarc-tidesiii3


16FUNDAMENTALS

M2 Tidal Constituent

AMPHIDROMIC POINT COTIDAL

LINE


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• Tide Pole (or Tide Staff) Gauges

• Float Gauges• Thomson type (1887)

Tide measurement (real data)

FUNDAMENTALS


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• Acoustic Gauges

• Pressure Gauges

• Radar Gauges

• Ultrasonic Gauges

• OTHER USES: Shipping and fishing industries; Tsunami warnings.

Tide measurement (real data)

FUNDAMENTALS


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• 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

Tides prediction

TIDAL STREAMS


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• Galileo Galilei (Discorso del flusso e reflusso del mare, 1616 ) Earth’s 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-Légé TPM

Tidal Analysis Precursors – Physics

FUNDAMENTALS


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• 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


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• 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


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Major global Nontidal Currents

TIDAL STREAMS


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• Tidal current is rotary (and slower), when not restricted (offshore)• Caused by the Earth’s 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


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Nontidal flow effect

TIDAL STREAMS

Effect on a Current rose

Effect on a Reversing current


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• 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+subsurface movement)

• Tidal current observations are made with sophisticated electronic current meters.

In general, effect of…

TIDAL STREAMS


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• Mechanical current meters

• Acoustic current meters

• Measuring current based onelectromagnetic induction

Current meters

TIDAL STREAMS


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• Coverage less extensive than for tides prediction (more unpredictable)• Information required for calculating any tidal current:

• Predicted times of maximum currents and slack times, for Reference stations

• Differences and ratios for subordinate stations• Information for current velocity at any time by using (a) and (b)• Slack durations.

Tidal current prediction

TIDAL STREAMS


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• 1 knot = 51,4 cm/s = 1,85 km/h

• As high as 13 kn (6,7 m/s; 24 km/h)

Tidal Currents Prediction

TIDAL STREAMS

Tidal atlas

Tidal diamond


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• Not yet widely used, but has a great potential for the future electricity generation.

• Energy source used since Middle age and Roman times.

• It’s the only technology that draws on energy of the Moon-Earth system.

• Energy practically inexhaustible (renewable energy resource).

• Tidal power causes losses to the Moon-Earth system, shortening the solar days (negligible effect, noticed over million of years).

Introduction

TIDAL POWER


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• TSGs o TECs (Energy Converters) use kinetic energy of tidal currents to produce work in power turbines.

• It’s used also to draw on energy from the river’s currents (nontidal).

• Conceived in 1970s, during the oil crisis.

• It’s the cheapest and least ecologically damaging of the three ways TPG

• Regarding to wind turbines, • Similar power when water speed is ca. 1 m/s (2 knots)• 4 times power approx. when water speed is 2-3 m/s (4-6 knots)

• Non uniformity of technologies; 6 principal types recognized by EMEC.

1. Tidal stream generator (TSG)

TIDAL POWER


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• Close in concept to traditional windmills, but underwater.

• The most currently operating type.

• Low head of water above Restricts individual capacity to about 25 – 50 MW.

• Installations in Canada, UK, Nor. Ireland, USA, Norway, Australia, China, India, Greek (reaching up to 5 MW); The most are pilot projects.

• Italy: Strait of Messina (Pilot projects). 25-300 kW.

• e.g. Australia, project for 450 turbines in Clarence strait. 300-400 homes each.

• Some projects also in Rivers (e.g. Thames River; nontidal source).

1. TSG – Axial turbines

TIDAL POWER

Bottom mounted axial turbine


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1. TSG – Axial turbines

TIDAL POWER

AR-1000, 1 MW @ 2,65 m/s

2011

Evopot, 2008 (Prototype)Cable tethered turbine

Northern Ireland


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• Invented by Georges Darreius in 1923.

• Installation either vertical or horizontal.

1. TSG – Crossflow turbines

TIDAL POWER

Gorlov turbineSouth Korea

Kobold BStretto di Messina

2003


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Race RocksColumbia

2006

• Use of a duct or shroud to augment the flow going into the turbine.

• Increased significantly the output power.

• They can operate at slow water flows,increasing the flow velocity

• Growing technology

1. TSG – Flow augmented turbines / Venturi

TIDAL POWER


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• Do not have a rotating component.

• They use aerofoil (hydrofoil, better)

• Growing technology (prototypes)

• England, Scotland, Australia, Canada, as precursors.

1. TSG – Oscillating Devices

TIDAL POWER

http://vimeo.com/25533045BioStream:


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• Pembrokeshire in Wales• River Severn between Wales and England• Cook Strait in New Zealand• Kaipara Harbour in New Zealand• Bay of Fundy in Canada.• East River in the USA• Golden Gate in the San Francisco Bay• Piscataqua River in New Hampshire• The Race of Alderney and The Swinge in the Channel Islands• The Sound of Islay, between Islay and Jura in Scotland• Pentland Firth between Caithness and the Orkney Islands, Scotland• Humboldt County, California in the United States• Columbia River, Oregon in the United States• Colombia (Chocó)

1. TSG – Potential sites

TIDAL POWER


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• Use a dam-like structure, capturing the energy (by turbines) from water masses moving in and out of a bay (or river).

• Two flow directions (in and out; high tide current and low tide current).

• It’s the oldest method of tidal power generation (since 1960s).

• Few operating plants.

2. Tidal barrage

TIDAL POWER

Estuary of the Rance River

France240 MW

1966


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• The basin is filled with the incoming high tide current.

• Sluice gates are closed.

• When outside water level is low enough (low tide, head enough), gates are opened to allow water going out, through the turbines.

2. Tidal barrage – Ebb Generation

TIDAL POWER


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• The basin is emptied with the low tide.


• When outside water level is high enough (high tide, head enough), gates are opened to allow the water coming into the basin

2. Tidal barrage – Flood Generation

TIDAL POWER


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• The basin is filled up (by turbines working in reverse), at a high over the outside high tide.


• When outside water level is low enough (low tide, head enough), gates are opened to allow water going out, through the turbines.

• The cost of pumping in is returned with the power generation, because potential energy is proportional to the square of tidal high variation.

2. Tidal barrage – Pumping

TIDAL POWER


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• One is filled at high tide, and the other is emptied at low tide.

• Turbines are placed between the basins.

• Offer advantages over normal schemes:• Adjustment with high flexibility• Generation almost continuously

• Disadvantages:• Very expensive to construct (extra lengh of barrage)

2. Tidal barrage – Two basins scheme

TIDAL POWER


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• It’s a both flood/ebb power generation, but at large scale.

• No plant exists.

• There’s a project called SWANSEA BAY TIDAL LAGOON (South Wales), where a high power potential exists, with a tidal range of approx. 10 m.

2. Tidal barrage – Tidal lagoon power

TIDAL POWER


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• Recent new technology (since 1997). No plants existing.

• Long dam-like structure perpendicular to the coast.

• In addition, a parallel barrier, to form together a T shape barrier.

• This structure creates water level differences on opposite sides, which generate electrical power by means of turbines.

• Properly currents for this arrangement:Some China, Korea and UK coasts.

3. Dinamyc Tidal Power (DTP)

TIDAL POWER

http://www.youtube.com/watch?v=4hT4FUlOYr4

Video:


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The biggest tidal power station nowadays, all of they Barrage type, are:(to have a reference, the biggest plant (hydro-electric) in the world produces 22 500 MW)

There are so many projects to be executed, e.g. The Swansea Bay Tidal Lagoon, or the Australian project for 450 turbines in Clarence strait. 300-400 homes each.

Biggest tidal power plants in the world

TIDAL POWER


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• Energy source completely renewable.

• Tides behavior is more predictable than wind and solar energies.

• New technologies are bringing down high costs (economical. & environmental) and improving efficiencies.

• Most of tidal producing plants do not affect marine environmental, specifically TSG and DTP types.

Advantages

TIDAL POWER

• High costs compared with another renewable (and no renewable) energies.

• Limited availability of properly sites (flows, velocities).

• Some Tidal Power Plants, specifically the barrage type, affect the sea environmental, by killing fishes and/or modifying estuaries salinity.

• Lack of concluding and contundent studies about which are the best technologies.

Disadvantages


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• Interface of the Tidal Power Stations output with National Grids, for example by associating it with the Wireless power (in study).

• Assessment of the Tidal Power Stations economic interest, in order to promote and sell new ideas for projects.

• New projects for coasts non or a few explored (e.g. South America).

• New studies for minimize the environmental impact of these technologies.

• Optimizing existing schemes.

• Optimizing efficiencies by means of fluid dynamics analysis.

Improvement Opportunities in the Tidal Power Industry

TIDAL POWER


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• http://news.enerjienstitusu.com/2012/12/fossil-fuels-still-king-in-eias-annual-energy-outlook-2013/

• http://wpage.unina.it/agodemar/eolpower/storia.html

• http://www.bbc.co.uk/news/uk-england-humber-16186209

• http://news.bbc.co.uk/2/hi/uk_news/england/8173570.stm

• http://www.tide-project.eu/index.php5?node_id=Reports-and-Publications;83&lang_id=1

• http://www.neptunerenewableenergy.com/

• http://en.wikipedia.org

• http://www.solarsystemscope.com/

• http://www.visitmyharbour.com/articles/3180/hourly-tidal-streams-irish-sea-and-bristol-channel

References

TIDAL POWER


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• http://pemsea.org/eascongress/international-conference/presentation_t4-1_kim.pdf

• Marine-Renewables-News.com

• http://www.marine-renewables-news.com/about-us

• http://www.energias-renovables-marinas.com/

• http://www.onr.navy.mil/focus/ocean/motion/tides2.htm

• http://www.marine.tmd.go.th/marinemet_html/lect19.html

• http://archive.is/s3U4F

• http://www.oceanenergycouncil.com/index.php/Tidal-Energy/Tidal-Energy.html

• iopscience.iop.org/1748-3190/8/3/036011/article

• http://www.youtube.com/watch?v=4hT4FUlOYr4

• http://www.tablademareas.com

References

TIDAL POWER


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• http://www.edumedia-sciences.com/es/a520-sol-tierra-luna

• http://asteromia.net/luna/la-luna-orbita.html

• http://archive.is/s3U4F

• http://www.gizmodo.com.au/2011/10/how-tide-predicting-machines-saved-d-day/

• http://tidesandcurrents.noaa.gov/constitu.html

• http://web.vims.edu/physical/research/TCTutorial/tideanalysis.htm

• http://www.ams.org/samplings/feature-column/fcarc-tidesiii3

• http://co-ops.nos.noaa.gov/map/

• http://msi.nga.mil/MSISiteContent/StaticFiles/NAV_PUBS/APN/Chapt-09.pdf

References

TIDAL POWER