Hydroelectric Dams

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 Hydroelectric Dams?

Hydroelectric dams are huge manmade structures that can generate substantial amounts of energy from rivers.3 They do this by blocking the natural course of the river in order to create a huge reservoir of water,4 often several hundred metres deep.5 This places the water at the base of the reservoir under huge amounts of pressure which, when released, creates an extremely powerful flow of water.6 This water is directed onto turbines that are connected to generators in order to create an abundance of electricity.7 Unfortunately though, hydroelectric dams can be extremely harmful to the environment. Not only do they deprive agricultural land and fish downstream of essential nutrients and minerals,8 but they also result in a huge amount of greenhouse gas emissions. This is because several thousand kilometres of natural habitat is flooded, including tress, plants and wildlife – all to make space for the new reservoir. The remains from the flood are then left to rot at the bottom of the reservoir, whereby they release enormous amounts of greenhouse gases.9 In fact, the greenhouse gases emitted can be more than twice the amount that would have been emitted by an equivalent coal power plant.10 Currently, hydroelectricity is the most widely used form of renewable energy, however, it still produces less than 3% of the world’s energy demand.11 It does have the potential to generate some 14 PWh of energy – around 13% of our planet’s current demand.12

What’s Good About Them?

  • They provide an extremely reliable source of energy.13
  • The energy can be stored in the reservoir until required.14
  • They last for a long time with little maintenance required.15
  • The reservoir’s water can be used for irrigation purposes.16

What’s Bad About Them?

  • There is a limited number of viable sites.17
  • They can cause substantial greenhouse gas emissions.18
  • Construction can lead to substantial ecological damage.19
  • The reservoirs can take up a huge amount of space.20

How Much Area Do We Need?

To power the UK using hydroelectric dams, a reservoir roughly 93% the size of the country would be required.21 What’s more, to catch all the rainfall, a land area of around 38 times the country would be needed.22

What Do Hydroelectric Dams Look Like?

To be completed.

Where Are Hydroelectric Dams Best Located?

Hydroelectric dams work best in mountainous regions with high rainfall.23 This means they have the most potential in South America, central Africa and much of Asia.

How Do They Perform?

¢8/KWH2420 Years257 GWH26
Energy PriceLife Spanper KM² per Year
16 Years272814 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 Andy and reproduced under license from Adobe Stock.

United States map created by SUPER RADICAL.

Image of Russian hydroelectric dam taken by Evgeny V and reproduced under license from Shutterstock.

World map shows all countries that have a gross theoretical hydraulic energy potential greater than 300 MWh per square kilometre. World map based on 2004 data sourced from Energie-Atlas GmbH – ‘Hydraulic Energy Potential’ and 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. U.S. Geological Survey – ‘Hydroelectric Power: How it Works’ – usgs.gov.
  4. U.S. Geological Survey – ‘Hydroelectric Power: How it Works’ – usgs.gov.
  5. Based on at least twelve dams being taller than 200 metres. Sourced from Encyclopaedia Britannica – ‘Dam’ – www.britannica.com.
  6. U.S. Geological Survey – ‘Hydroelectric Power: How it Works’ – usgs.gov.
  7. U.S. Geological Survey – ‘Hydroelectric Power: How it Works’ – usgs.gov.
  8. International Rivers – ‘Environmental Impacts of Dams’ – www.internationalrivers.org.
  9. Area based on Brazil’s Tucurui Dam and sourced from Fearnside, Philip M. – ‘Environmental Impacts of Brazil’s Tucurui Dam: Unlearned Lessons for Hydroelectric Development in Amazonia’ – Page 382. Methane emissions sourced from International Rivers – ‘Dirty Hydro: Dams and Greenhouse Gas Emissions’ – Page 1.
  10. International Rivers – ‘Dirty Hydro: Dams and Greenhouse Gas Emissions’ – Page 4.
  11. Based on 2012 data sourced from International Energy Agency – ‘World: Balances for 2012’ – www.iea.org.
  12. Please note, figure does not include power conditioning, distribution and transmission losses.
  13. U.S. Geological Survey – ‘Advantages of Hydroelectric Power Production and Usage’ – usgs.gov.
  14. U.S. Geological Survey – ‘Advantages of Hydroelectric Power Production and Usage’ – usgs.gov.
  15. Maintenance sourced from U.S. Geological Survey – ‘Advantages of Hydroelectric Power Production and Usage’ – usgs.gov. Long life span based on large scale hydroelectric plants lasting for 200 years and other renewable energy sources lasting as little as 20 years.
  16. U.S. Geological Survey – ‘Advantages of Hydroelectric Power Production and Usage’ – usgs.gov.
  17. Based on a global potential of only 14 PWh.
  18. International Rivers – ‘Dirty Hydro: Dams and Greenhouse Gas Emissions’ – Page 4.
  19. International Rivers – ‘Environmental Impacts of Dams’ – www.internationalrivers.org.
  20. Based on the reservoirs requiring more than twice as much space as onshore turbines and the reservoirs created having extremely limited use.
  21. Based on a calculated area of 231,290 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. Figure based on hydroelectric dams generating 0.02 Watts of energy per square metre of rainfall. Figure sourced from MacKay, David J.C. – ‘Sustainable Energy – Without the Hot Air’ – Page 55. 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. Please note that figures assume the use of every drop of rainwater for hydroelectric power. Realistically, we would only be able to exploit a fraction of this rainfall because it would not be possible to create a dam for every stream. Furthermore, much of the rainfall would evaporate before it could be used to generate energy.
  23. Rheinisch-Westfälisches Elektrizitätswerk (RWE) AG – ‘Fact Sheet – Hydro Power’ – Page 1.
  24. Based on projected costs for 2020 sourced from U.S. Energy Information Administration – ‘Levelized Cost and Levelized Avoided Cost of New Generation Resources in the Annual Energy Outlook 2015’ – Page 6.
  25. Figure based on a standard hydroelectric dam having a typical lifespan of between 50 to 100 years and a large hydroelectric dam having a lifespan of between 200 to 300 years. Sourced from Chiras, Daniel D. – ‘Environmental Science’ – Jones and Bartlett Publishers, Inc – Page 333.
  26. Figure based on 1 TWh being generated each year for every 152 square kilometres of reservoir. Data sourced from Diolettas, Stamatios – ‘Distributed Energy Resources: Prometheus of Renewable Energy’ – Page 153.
  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 U.S. Energy Information Administration – ‘Levelized Cost and Levelized Avoided Cost of New Generation Resources in the Annual Energy Outlook 2015’ – Page 2.
  28. Based on detailed studies undertaken by Ivan Lima and his colleagues from Brazil’s National Institute for Space Research (INPE) that demonstrates registered dams greater than 15 metres tall emit a combined 104 million tonnes of methane annually via reservoir surfaces, turbines, spillways and rivers downstream. Data sourced from International Rivers – ‘Greenhouse Gas Emissions from Dams FAQ’ – www.internationalrivers.org.
  29. Hoogwijk, Monique and Graus, Wina – ‘Global Potential of Renewable Energy Sources: A Literature Assessment’ – Page 39.

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