Tidal Barrages

A typical onshore turbine can generate as much as 6 million kWh per year.1 That’s enough energy to power some 1,500 homes.2 The question is, could onshore turbines provide us with enough energy to replace our existing fossil fuel power plants?

What Are Onshore Turbines?

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
  • Their long life means they offer a cheap energy once the initial cost has been offset.14
  • They can protect coastal towns and ports from flooding.15
  • They can double as a bridge to reduce capital costs.16

What’s Bad About Them?

  • They have prohibitively expensive initial costs.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 UKs power demands, a body of water some 28% the size of the country would be required.21 This is based on the performance world’s largest tidal barrage in La Rance.

What Do They Look Like?

To be completed.

Where Are Onshore Turbines Best Located?

For barrages to be economical, a tidal range greater than seven metres is generally required.22 This severely limits Tidal Barrage’s global potential, with just 20 sites currently identified across France, China, Canada, the UK and Russia.23

How Do They Perform?

¢33/KWH24240 Years2525 GWH26
Energy PriceLife Spanper KM² per Year
35 Years274 Years280.7 PWH29
Economic OffsetEnergy OffsetWorld Potential

How Do They Rate?

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

Onshore Turbines in a Nutshell

To be completed.

Image Credit

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

United States map created by SUPER RADICAL.

Image of 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.

Article Endnotes

  1. European Wind Energy Association – 'Wind Energy's Frequently Asked Questions' – www.ewea.org.
  2. European Wind Energy Association – 'Wind Energy's Frequently Asked Questions' – www.ewea.org.
  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 a calculated area of 68,600 square kilometres required to meet the UK’s energy demand. Figure includes losses of 2% due to power conditioning and 6.5% due to transmission and distribution. 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. Ocean Energy Council – ‘Tidal Energy’ – www.oceanenergycouncil.com.
  23. 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.
  24. Based on estimates sourced from House of Commons Energy and Climate Change Committee – ‘Memorandum Submitted by Parsons Brinkerhoff Ltd’ – Paragraph 15.
  25. Tidal Energy – ‘Severn Tidal Barrage’ – www.tidalenergy.eu.
  26. Based on the 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.
  27. 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.
  28. Average figure obtained from ‘UK Department of Energy and Climate Change – ‘Severn Tidal Power: Feasibility Study Conclusions and Summary Report’ – Page 37.
  29. 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.

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