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Tidal Barrages

The Sihwa Lake in South Korea generates some 550 million kWh of energy every year.1 That’s enough energy to power some 29,000 homes.2 However, is there enough movement in the tides to meet all our energy demand? Furthermore, what are the downsides to disrupting tidal movement?

What Are Tidal Barrages?

Tidal barrages are large scale energy generators that take advantage of sea-level changes that occur between tides. They consist of a large dam that spans the width of a river within which a series of gates is incorporated.3 As the tide rises, the water is allowed to flow through the gates in order to create a huge body of water,4 as much as 500 square kilometres in some places.5 The gates are then closed until the tide has lowered, at which point, they are opened once more.6 This forces the water back through the gates, within which, a series of hydraulic turbines is housed.7 The high-pressure water spins the turbines, which in turn generate large quantities of electricity.8 Unfortunately, despite the large amounts of energy tidal barrages can generate, they also come with a large price tag.9 This can usually be partially offset, as tidal barrages can double as bridges, flood defences, or even both.10 In addition to the cost, tidal barrages often cause significant damage to the environment. This includes the destruction of wildlife habitats and the interruption of marine animals’ travel routes.11 As a result, the development of tidal barrages is often considered unacceptable.12

What’s Good About Them?

  • They provide an extremely reliable source of energy.13
  • They offer a cheap energy source once the capital cost has been offset.14
  • They can protect upstream towns and ports from flooding.15
  • They can double as a bridge to reduce capital costs.16

What’s Bad About Them?

  • The capital cost is prohibitively expensive.17
  • There are only a few viable sites around the world.18
  • They can only provide energy for approximately ten hours each day.19
  • They can damage wildlife habitats and coastal ecosystems.20

How Much Area Do We Need?

To meet the United States power demand using tidal barrages, a body of water some 8% the size of the country would be required.21 Furthermore, to meet the UK’s power demand, a body of water some 28% the size of the country would be required.22 This is based on the energy output of the La Rance Tidal Power Plant, the second biggest tidal barrage in the world.23

Map showing the equivalent area of the United States of America that would need to be a body of water in order for tidal barrages to meet the country's energy demand.

What Impact Do They Have on the Landscape?

The La Rance tidal barrage has been generating energy for over 50 years now.24

Tidal barrages look similar to bridges and, when designed well, they can be impressive structures. Some even become major tourist attractions. As such, tidal barrages generally have a positive visual impact on the surrounding landscape.

Where Are Tidal Barrages Best Located?

For barrages to be economical, a tidal range greater than seven metres is generally required.25 This severely limits Tidal Barrage’s global potential, with just 20 sites currently identified.26Specifically, these sites are located on the coasts of France, China, Canada, the UK, Australia, India, Pakistan, Argentina and Russia.

How Do They Perform?

Energy PriceLife SpanEnergy per KM²
¢33/KWH27250 YRS2824 GWH29

Economic OffsetEnergy OffsetWorld Potential
35 YRS304 YRS310.7 PWH32

How Do They Rate?

Value for Money|★ ★ ★ ★ ★
Reliability|★ ★ ★ ★ ★
Eco-friendliness|★ ★ ★ ★ ★ ★
Global Potential|★ ★ ★ ★ ★
Overall|★ ★ ★ ★ ★ ★

Tidal Barrages in a Nutshell

To summarise, tidal barrages provide a reliable source of energy while also offering a way to protect upstream towns and ports from flooding. Furthermore, tidal barrages can double as bridges to reduce capital costs. Despite this, tidal barrages are expensive, even though they provide a cheap energy source once the capital cost has been paid off. On top of this, tidal barrages can only provide energy for approximately ten hours each day. Furthermore, tidal barrages can damage wildlife habitats and coastal ecosystems. Finally, for tidal barrages, there are only a limited number of viable sites around the world. However, when it comes to our tides, barrages are not the only option available. Why not find out about tidal lagoons by clicking the link below? Alternatively, find out other ways we can stop climate change by returning to the main menu.

Image Credit

Title image taken by Francois Boizot and reproduced under license from Shutterstock.

United States map created by SUPER RADICAL.

Image of La Rance Tidal Power Station taken by Antoine2K and reproduced under license from Shutterstock.

World map based on data sourced from Boyle, Godfrey –’Renewable Energy: Power for a Sustainable Future’ – Oxford University Press – Page 227. World map created by SUPER RADICAL.

General Notes

All figures presented in this section are estimates based on best available data, assume optimum locations, and, wherever possible, are based on comparable studies. That said, many of the studies assume different economic conditions, climatic conditions, time frames and locations. Furthermore, the technologies discussed in this section are in a constant state of development. As a result, the figures presented within this section provide a rough guide only and should not be viewed as a definitive performance level.

For the total world energy demand, a figure of 104.4 million GWh has been used. The figure is based on 2012 data and sourced from International Energy Agency – 'World Balances for 2012' – www.iea.org.

All UK to USA currency conversions have been set at $1.656 USD for each £1 GBP. The figure is based on the conversion rate as of the 1st January 2014 and sourced from XE – 'XECurrency Table: USD - U.S. Dollar' – www.xe.com.

Article Endnotes

  1. Ha Kim, Yun – ‘Technology Case Study: Sihwa Lake Tidal Power Station’ – www.hydropower.org.
  2. Based on a UK home using an average 18,738 kWh of energy in 2014. Sourced from UK Department of Energy and Climate Change – ‘Energy Consumption in the UK’ – Page 7.
  3. National Geographic – ‘Tidal Energy’ – education.nationalgeographic.co.uk.
  4. National Geographic – ‘Tidal Energy’ – education.nationalgeographic.co.uk.
  5. Based on figures related to the Severn Estuary. Sourced from MacKay, David J.C. – ‘Sustainable Energy – Without the Hot Air’ – Page 84.
  6. National Geographic – ‘Tidal Energy’ – education.nationalgeographic.co.uk.
  7. National Geographic – ‘Tidal Energy’ – education.nationalgeographic.co.uk.
  8. National Geographic – ‘Tidal Energy’ – education.nationalgeographic.co.uk.
  9. Based on a cost of ¢33 per kWh for the first 30 years of service.
  10. Bridge connection sourced from Tethys – ‘Tidal’ – tethys.pnnl.gov. Flood protection sourced from Natural Energy Wyre – ‘Wyre Eco-THEP Project’ – naturalenergywyre.co.uk.
  11. Natural Environment Research Council (NERC) – ‘Tidal Power: In or Out?’ – nerc.ac.uk.
  12. Krewitt et al. – ‘Role and Potential of Renewable Energy and Energy Efficiency for Global Energy Supply’ – Page 157.
  13. National Geographic – ‘Tidal Energy’ – education.nationalgeographic.co.uk.
  14. Based on cost data sourced from House of Commons Energy and Climate Change Committee – ‘Memorandum Submitted by Parsons Brinkerhoff Ltd’ – Paragraph 16.
  15. Natural Energy Wyre – ‘Wyre Eco-THEP Project’ – naturalenergywyre.co.uk.
  16. Tethys – ‘Tidal’ – tethys.pnnl.gov.
  17. Based on electricity generated from tidal barrages appearing to cost nearly five times as much as electricity generated from gas over the course of the first thirty years of service.
  18. Based on global potential of just 0.7 PWh.
  19. Harris, Frank – ‘Catching the Tide: A Review of Tidal Energy Systems’ – Page 126.
  20. Natural Environment Research Council – ‘Tidal Power: In or Out?’ – nerc.ac.uk.
  21. Based on the United States of America having a total land area of 9,147,420 square kilometres, the United States of America demanding 16.8 million GWh of energy per year, tidal barrages generating 24 GWh per hectare, a 2% loss due to power conditioning and 6.5% loss due to transmission and distribution. Land area sourced from The World Bank – ‘Land Area (SQ. KM)’ – data.worldbank.org. Energy demand based on 2012 data and sourced from International Energy Agency – ‘United States: Balances for 2012’ – www.iea.org. Energy generated by tidal barrages based on the La Rance Tidal Power Plant having an enclosed basin of 22.5 square kilometres and generating 533 GWh per year. Sourced from Xia et al. – ‘Estimation of Annual Energy Output from a Tidal Barrage Using Two Different Methods’ – Page 7. Power conditioning losses based on data sourced from Fuji Electric – ‘Large-scale Photovoltaic Power Generation Systems’ – Page 7. Transmission and distribution losses based on 2007 data for the United States and sourced from U.S. Department of Energy – ‘Frequently Asked Questions – Electricity’ – tonto.eia.doe.gov.
  22. Based on the United Kingdom having a total land area of 248,532 square kilometres, the United Kingdom demanding 1.48 million GWh of energy per year, tidal barrages generating 24 GWh per hectare, a 2% loss due to power conditioning and 6.5% loss due to transmission and distribution. Land area sourced from The World Bank – ‘Land Area (SQ. KM)’ – data.worldbank.org. Energy demand based on 2012 data and sourced from International Energy Agency – ‘United Kingdom: Balances for 2012’ – www.iea.org. Energy generated by tidal barrages based on the La Rance Tidal Power Plant having an enclosed basin of 22.5 square kilometres and generating 533 GWh per year. Sourced from Xia et al. – ‘Estimation of Annual Energy Output from a Tidal Barrage Using Two Different Methods’ – Page 7. Power conditioning losses based on data sourced from Fuji Electric – ‘Large-scale Photovoltaic Power Generation Systems’ – Page 7. Transmission and distribution losses based on 2007 data for the United States and sourced from U.S. Department of Energy – ‘Frequently Asked Questions – Electricity’ – tonto.eia.doe.gov.
  23. Future Power Technology – ‘Tidal Giants – the World’s Five Biggest Tidal Power Plants’ – www.power-technology.com.
  24. Based on the La Rance tidal barrage being built between 1961 and 1966. Future Power Technology – ‘Tidal Giants – the World’s Five Biggest Tidal Power Plants’ – www.power-technology.com.
  25. Ocean Energy Council – ‘Tidal Energy’ – www.oceanenergycouncil.com.
  26. Number of sites sourced from Ellen MacArthur Foundation – ‘Marine Power Generation’ – Pages 1 to 4. Map sourced from Boyle, Godfrey –’Renewable Energy: Power for a Sustainable Future’ – Oxford University Press – Page 227.
  27. Based on estimates sourced from House of Commons Energy and Climate Change Committee – ‘Memorandum Submitted by Parsons Brinkerhoff Ltd’ – Paragraph 15.
  28. Tidal Energy – ‘Severn Tidal Barrage’ – www.tidalenergy.eu.
  29. Based on the La Rance Tidal Power Plant having an enclosed basin of 22.5 square kilometres and generating 533 GWh per year. Sourced from Xia et al. – ‘Estimation of Annual Energy Output from a Tidal Barrage Using Two Different Methods’ – Page 7.
  30. Calculation undertaken within the ‘Renewable Solution’ section of the ‘ZERO-FIFTY World Energy Database’ and based on a lifespan of 30 years. Lifespan sourced from of House of Commons Energy and Climate Change Committee – ‘Memorandum Submitted by Parsons Brinkerhoff Ltd’ – Paragraph 16.
  31. Average figure obtained from ‘UK Department of Energy and Climate Change – ‘Severn Tidal Power: Feasibility Study Conclusions and Summary Report’ – Page 37.
  32. Based on the annual global potential of tidal head energy available in shallow waters being 2,500 PWh and tidal barrages having a capacity factor of up to 29%. Sourced from International Institute for Applied Systems Analysis (IIASA) – ‘Global Energy Assessment (GEA)’ – Page 853. Please note, power conditioning, distribution and transmission losses have not been considered.

For further information about any of the above sources, please visit the ZERO EMISSION WORLD Works Cited page.

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