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Offshore Wave Power

Using offshore wave devices, a one-kilometre stretch of coastline could provide some 128 million kWh per year.1 That’s enough energy to power some 6,800 typical homes,2 slightly more than we could power using nearshore wave devices.3 However, are there enough waves available for us to meet the world’s energy demand using offshore wave devices?

What Is Offshore Wave Power?

Offshore wave devices are located far out in the sea where they extract energy from waves at their peak.4 Located in depths of around 50 metres or greater, the devices generally float on the surface of the sea and use the movement of the waves to generate energy. To stop the devices floating away, they are usually tied to the seabed using cables. Probably the most well-known example of this technology is the Pelamis, a long snake-like structure that converts wave movement into hydraulic pressure.5 This pressure is then used to drive a hydraulic turbine in order to produce electricity.6 Technically, these machines can be placed anywhere in the ocean, but they are most effective in areas with consistently large waves. Currently, offshore wave devices have only been tested in a few locations around the world,7 however, they do have the potential to generate around 26 PWh per year.8 That’s equal to around a quarter of worldwide energy demand. That said, no device is 100% efficient, and as such, the global potential for offshore wave energy is likely limited to about 10 PWh.9

What’s Good About Them?

  • They have minimal visual impact.10
  • They provide a predictable and reliable energy source.11
  • They don’t take up valuable land area.
  • They have minimal impact on the environment.12

What’s Bad About Them?

  • They would have to be replaced regularly due to their short life span.13
  • Maintenance can be more complex as a result of the maritime environment.
  • They are expensive compared to other renewable devices.14

How Much Area Do We Need?

Assuming the United States benefited from high energy waves for the entire length of the coast, we would need to cover the country’s coastlines with offshore wave energy devices six and a half times over to meet the country’s current energy demand.15 This is of course not possible as, even if all of the United States benefited from high energy waves, the most offshore wave energy could deliver would be 15% of the nation’s current energy demand. In fact, even for the UK, we would need to wrap the entire country one and a half times over with offshore wave energy devices.16 This again assumes high energy waves for the entire length of the coast.

What Impact Do They Have on the Landscape?

Offshore wave devices are generally very large – some over 100 metres in length!17 However, because offshore wave devices are located several kilometres from the coastline,18 and the devices protrude only a modest amount from the water, any visual impact would likely be minimal.

A typical Pelamis device would likely generate some 2.5 GWh of energy per year.19

Where Is Offshore Wave Power Best Located?

Like onshore wave devices, the bigger the waves, the more energy offshore wave devices generate. As a result, offshore wave devices are also best placed in large oceans in subtropical and temperate zones. This means that the Unites States, Canada, Chile, Norway, the United Kingdom, France, Portugal, Morocco, Nambia, South Africa, Australia, New Zealand and Japan could all potentially take advantage of offshore wave energy.

How Do They Perform?

Energy PriceLife SpanEnergy per KM²
¢18/KWH2020 YRS21100 GWH/YR22

Economic OffsetEnergy OffsetWorld Potential
20 YRS2320 MTHS2410 PWH25

How Do They Rate?

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

Offshore Wave Power in a Nutshell

To summarise, offshore wave devices are expensive and can only supply a small fraction of our current energy demand. Furthermore, they are challenging to maintain and would likely require regular replacement. Despite this, offshore wave devices provide a predictable and reliable energy source that has minimal impact on the environment. Furthermore, because they are so far away from the coast, the visual impact would be minimal. When it comes to generating energy though, there are more sources available than just the world’s water. Why not see what energy we can generate from the world’s land 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 P123 and released into the public domain.

United States map created by SUPER RADICAL.

Image of Pelamis Wave Energy Convertor taken by Jumanji Solar and reproduced under Creative Commons license CC BY 2.0.

World map created by SUPER RADICAL. World map based on all coastlines not covered by ice that benefit from waves 30 kW of energy per metre or higher. Wave power sourced from Mørk et al. – ‘Assessing the Global Wave Energy Potential’ – Page 4. Areas of ice cover sourced from Koistinen, Ville – ‘The Main Biomes in the World’ – commons.wikimedia.org.

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. Based on wave energy providing an average of 350 MWh of energy per year per metre length of coastline and a 60% loss due to offshore device inefficiencies. Offshore wave energy data sourced from MacKay, David J.C. – ‘Sustainable Energy – Without the Hot Air’ – Page 74. Offshore device inefficiencies based on the Pelamis device and sourced from Carcas, Max – ‘The Pelamis Wave Energy Converter’ – Page 4. 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 United States Department of Energy – ‘Frequently Asked Questions – Electricity’ – tonto.eia.doe.gov.
  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. Based on nearshore wave devices being able to power some 5,500 typical homes per kilometre of coastline. Figure based on wave energy providing an average of 350 MWh of energy per year per metre of coastline, a 50% loss due to the proximity to the coastline, a 35% loss due to coastal device inefficiencies and a UK home using an average 18,738 kWh of energy. Offshore wave energy data sourced from MacKay, David J.C. – ‘Sustainable Energy – Without the Hot Air’ – Page 74. Coastal losses sourced from Henry et al. – ‘Advances in the Design of the Oyster Wave Energy Converter’ – Page 2. Losses due to device inefficiencies assume a 24-metre-wide device and sourced from Henry et al. – ‘Advances in the Design of the Oyster Wave Energy Converter’ – Page 6. UK home energy consumption based on 2014 data and sourced from UK Department of Energy and Climate Change – ‘Energy Consumption in the UK’ – Page 7. Calculation 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 United States Department of Energy – ‘Frequently Asked Questions – Electricity’ – tonto.eia.doe.gov.
  4. Based on typically 50% of energy in ocean waves is lost as it approaches the coastline. Sourced from page Henry et al. – ‘Advances in the Design of the Oyster Wave Energy Converter’ – Page 2.
  5. McGrath, Jane – ‘How Wave Energy Works’ – howstuffworks.com.
  6. McGrath, Jane – ‘How Wave Energy Works’ – howstuffworks.com.
  7. Based only six operating sites globally. Based on 2013 data sourced from James, Vicki – ‘Marine Renewable Energy: A Global Review of the Extent of Marine Renewable Energy Developments, the Developing Technologies and Possible Conservation Implications for Cetaceans’ – Pages 115 to 117.
  8. Assumes all coastal areas not covered with ice that provide power greater than 5 kW of energy per metre. Sourced from Mørk et al. – ‘Assessing the Global Wave Energy Potential’ – Page 452.
  9. Based on a 60% loss due to offshore device inefficiencies. Figure based on the Pelamis device and sourced from Carcas, Max – ‘The Pelamis Wave Energy Converter’ – Page 2. Please note, figure does not include power conditioning, distribution and transmission losses.
  10. Carcas, Max – ‘The Pelamis Wave Energy Converter’ – Page 4.
  11. The Carbon Trust – ‘Variability of Wave and Tidal Stream Energy’ – Page 4.
  12. E.ON – ‘Pelamis Wave Energy Project: Information Sheet’ – Page 1.
  13. Based on a lifespan of just 20 years.
  14. Based on nearshore wave energy currently being the joint second most expensive renewable technology available.
  15. Based on the United States of America having a coastal length of 19,924 kilometres, the United States of America demanding 16.8 million GWh of energy per year, offshore wave energy devices generating 140 GWh per kilometre of coastline, a 2% loss due to power conditioning and 6.5% loss due to transmission and distribution. Coastal length sourced from Central Intelligence Agency – ‘World’ – The World Factbook – www.cia.gov. Energy demand based on 2012 data and sourced from International Energy Agency – ‘United States: Balances for 2012’ – www.iea.org. Energy generated by offshore wave energy based on wave energy providing an average of 350 MWh of energy per year per metre of coastline and a 60% loss due to offshore device inefficiencies. Offshore wave energy data sourced from MacKay, David J.C. – ‘Sustainable Energy – Without the Hot Air’ – Page 74. Offshore device inefficiencies based on the Pelamis device and sourced from Carcas, Max – ‘The Pelamis Wave Energy Converter’ – Page 4. 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.
  16. Based on the United Kingdom of America having a coastal length of 7,918 kilometres, the United Kingdom demanding 1.48 million GWh of energy per year, offshore wave energy devices generating 140 GWh per kilometre of coastline, a 2% loss due to power conditioning and 6.5% loss due to transmission and distribution. Coastal length sourced from Nations Encyclopedia – ‘United Kingdom’ – www.nationsencyclopedia.com. Energy demand based on 2012 data and sourced from International Energy Agency – ‘United Kingdom: Balances for 2012’ – www.iea.org. Energy generated by offshore wave energy based on wave energy providing an average of 350 MWh of energy per year per metre of coastline and a 60% loss due to offshore device inefficiencies. Offshore wave energy data sourced from MacKay, David J.C. – ‘Sustainable Energy – Without the Hot Air’ – Page 74. Offshore device inefficiencies based on the Pelamis device and sourced from Carcas, Max – ‘The Pelamis Wave Energy Converter’ – Page 4. 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.
  17. Based on the Pelamis devices at Agucadoura. Sourced from Future Power Technology – ‘Pelamis, World’s First Commercial Wave Energy Project, Agucadoura’ – www.power-technology.com.
  18. Distance based on the Agucadoura Wave Farm in Portugal. Sourced from Jha, Alok – ‘Making Waves: UK Firm Harnesses Power of the Sea … in Portugal’ – www.theguardian.com.
  19. Based on the Pelamis device having a rated power of 750 kW and a capacity factor of up to 40%. Sourced from Carcas, Max – ‘The Pelamis Wave Energy Converter’ – Page 2.
  20. Based on a predicted 2035 price inclusive of accelerated cost reduction. Sourced from The Carbon Trust – ‘Accelerating Marine Energy’ – Page 36.
  21. Greenemeier, Larry – ‘Turning the Tide on Harnessing the Ocean’s Abundant Energy’ – www.scientificamerican.com.
  22. Calculations based on the Pelamis device and assumes a rated power of 750 kW, a capacity factor of up to 40%, and 39 devices in three rows occupying an area of ocean, about 400 metres long and 2,500 metres wide. Number of devices sourced from MacKay, David J.C. – ‘Sustainable Energy – Without the Hot Air’ – Page 309. Rated power and capacity factor sourced from Carcas, Max – ‘The Pelamis Wave Energy Converter’ – Page 2.
  23. Calculation undertaken within the ‘Renewable Solution’ section of the ‘ZERO-FIFTY World Energy Database’ and based on a lifespan of 20 years. Lifespan sourced from The Carbon Trust – ‘Accelerating Marine Energy’ – Page 14.
  24. No carbon offset data available so substituted with energy offset period. Sourced from Ecogeneration – ‘Pelamis Wave Power Powers Up in North Portugal’ – ecogeneration.com.au.
  25. Calculation based on extractable energy from waves of 26.1 PWh per year and a 60% loss due to device inefficiencies. Global potential assumes all ice-free coastlines above 5 kW of energy per metre and is sourced from Mørk et al. – ‘Assessing the Global Wave Energy Potential’ – Page 452. Device inefficiencies sourced from Carcas, Max – ‘The Pelamis Wave Energy Converter’ – Page 2. Please note, power conditioning, distribution and transmission losses have not been considered.

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