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Everything You Wanted to Know About Tidal Power but Were Afraid to Ask

Everything You Wanted to Know About Tidal Power but Were Afraid to Ask

Don’t be afraid, +Samantha Andrews has a full summary for you describing where tidal power comes from and the various ways scientists and engineers are trying to harness it with lots of links to further reading.

Originally shared by Samantha Andrews

What the oceans do for us: powering our needs in the future

Figuring out how we are going to keep generating energy is a political nightmare, and technologically challenging.  There are all sorts of issues with fossil fuels, and renewable energy solutions are (at the moment) generally a little more costly to get up and running.  There are also some issues over energy-delivery reliability.  These aren’t insurmountable problems, and slowly but surely people around the globe and thinking of new – and sometimes old solutions to producing more sustainable and less polluting energy.  Solutions like harnessing the power of the ocean.

Tides occur from the rotation of the sun and moon around the Earth.  Each orbiting body exerts a gravitational force that pulls the ocean around.  Here’s a great 2-minute video explaining how it works (though some parts of the world have more than two tides a day!).  There are two important things about the tides that make them intriguing from an energy point of view.  First tides exert energy.  Second tides are predictable – we already know what the tides are going to do for the next few years.  So if we can capture that energy efficiently we could power our fancy electronic gizmos with tidal power.  This isn’t a new concept as such.  Many of you will have seen images or even visited old mills next to streams and rivers with a big wooden wheel sitting in the water.  Those wheels are pushed by the water movement, and in turn that wheel turns some cogs which grinds up some wheat which throws out flour.  

The development of tidal power as a viable energy source is ongoing.  There are a number of projects in progress across the globe.  Some are very small scale, some much larger.  Here are just a few examples of the latest thinking on tidal power.  All links are open access.

What are the options

Generally speaking, there are three ways in which we could harness the power of the tides – turbine farms, barrages, or fences.  Here’s an example of each:

> Turbine Farms are a little like wind farms – but underwater. Scottish Power are in the process of developing a ‘tidal array’ consisting of 10 turbines in the Sound of Islay, Scotland.  Pop along to their webpage to read a non-technical summary as well as updates of environmental surveys.

> Tidal barrages are essentially damns built across the entrance of a bay or estuary that control water flow through sluices.  In these sluices are turbines which are powered by water flowing past them.  La Rance Barrage in France opened back in 1966 as the world’s first tidal power station.  It’s still going today, and provides around 90% of Brittany’s energy needs.  EDF who own the power plant haven’t given much information about the plant on their website, but if you want a look, here’s the link to their page

> Tidal fences are rows of turbines laid over the mouth of an estuary.  Unlike barrages, they are not surrounded by any sort of dam , and so don’t have the same environmental impacts.  The downside is that they are less efficient.  For this reason, proposals for a barrage across the Severn estuary in the UK were thrown out, and consideration into a tidal fence is in.  Back in 2010, the Severn Tidal Fence Consortium explored the pros and cons of a fence system.  Their final report makes for an interesting read

How much can we get

Tidal flow is pretty powerful, but just how much energy we can expect to gain from trying to harnessing tidal flow?  The figure is likely to differ depending on where you are in the world (different tidal flows) and on what sort of tidal power technology is used.  In this study by Roy Walters of the Institute of Ocean Sciences and other Canadian-based researchers focused on a hypothetical turbine farm in the Bay of Fundy – an area well known for having the highest tide in the words (  Using a ‘numerical flow model’, the researchers demonstrate that the amount of power that could be realised from the turbine farm is far less that its theoretical maximum.  It seems that there are physical barriers to the technology itself.

Understanding the impacts

Everything we do has an impact on the environment and other species.  The trick is to minimise our footprint.  There has been a fair bit of research to determine the potential impacts of tidal power systems on marine ecosystems.  Here are just a few examples:

>  Shallin Busch and colleagues at the Northwest Fisheries Science Centre undertook some simulation work to determine how tidal power development in the Puget Sound, USA and climate change may affect species listed under the US Endangered Species Act.  They took a whole host of things into consideration including ocean acidification and changes to primary production.  Climate change came out as likely to have the biggest impact, but concerns about blade strikes from the turbines couldn’t really be fully assessed, simply because we do not know if and how individuals may avoid the blade.

> Back in 2010 Andrew Gill and Mark Bartlett of Cranfield University produced a report for Scottish Natural Heritage focusing on the impact of marine renewable energy – particularly wave and tidal power – on three species of fish.  The Atlantic salmon (Salmo salar), sea trout (Salmo trutta), and European eel (Anguilla Anguilla) are all considered species of ‘conservation importance’, and we have done a number of studies on these species.  Never the less Andrew and Mark hit a similar problem to Shallin’s team.  We just don’t know how the species will react to the energy plants – including electromagnetic fields, and noise. 

> Because La Rance is the oldest tidal power plant, it is a good place to look for environmental impacts.  Which is exactly what Engineer Richard Kirby and Christian Retière of the Muséum National d’Histoire did back in 2008.  As you can expect a whole host of changes to the estuary were found, including changes to species composition and sediment flow.

Image:  SeaGen tidal current turbine in Strangford Lough, Northern Ireland.  Credit – Siemens 

#scienceeveryday   #renewableenergy   #tidalpower   #openaccess  


Join the Conversation


  1. Samantha Andrews  Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon and the Sun and the rotation of the Earth.

    When saying: “Tides occur from the rotation of the sun and moon around the Earth.  Each orbiting body exerts a gravitational force that pulls the ocean around”, this means sun rotates around earth and that is a wrong statement since people and scientists have died for not accepting that idea.

    Science on Google+ Please do check every scientific statement before sharing with communities and misleading people.


  2. Joe Chahoud – just a mis-edit from my original write-up which waffled on for a whilst about how tides form (which I opted to replace with a link to a video – the post was getting far too long).  Thanks for pointing it out so nicely


  3. Samantha Andrews i was going to also comment about this misstatement, which is pretty jarring in an otherwise great post, but saw that you had corrected it in your original post… Odd that the edit does not propagate, bit I guess the concern is someone sharing a post only to have it edited to something they would not want to share, like an advertisement… Maybe Google should add an update button.


  4. Hudson Ansley  I wish there was a way to edit reshares too – or for reshares to be ‘live’ so they reflect what the OP is at any given time.  Even though I re-read what I’ve written before posting, I do occasionally miss things where I’ve changed my original text – just like this example.  I guess my brain was processing what I wanted to say rather than what I had actually written (the curse of spending far too long every day reading and writing on a computer I guess!).

    The other thing I thought would be quite nice is a way to collect all comments across shares onto the OP, rather than having them fragmented across G+.  


  5. Samantha Andrews Whenever a new idea is shared, that idea faces the doubters and the praise, alike. President Kennedy asked a scientist what it would take to send a man to the moon and back. The answer was ‘The will to do it”. Keep up the good work, Samantha.


  6. Oh sure! Let’s push the Moon away even faster!!! First you enviro-hippies wanna use up all the wind for your turbines, now you’re gonna use up all the Moon’s gravity too??? Where does it end???


  7. 🙂 It constantly amazes me how much criticism any renewable energy project gets when fossil fuel just gets a pass for all the environmental destruction it has and continues to cause. Can you imagine a fossil fuel project even attempting to do legitimate studies to determine if it will have negative impacts on the environment? Almost none of it is even factored into the cost which makes them artificially appear to be competitive with renewables when the public and the environment have to bear the burden of the resulting pollution. I’m not saying that there are no drawbacks to energy projects by virtue of them being renewable, but the relative scales of the environmental damage between most renewable projects vs fossil fuel are enormous. 


  8. What do you mean by no free are you mad are something like i fellz you but i mean like if you mad then idk but like i get mad to if that happen to me but just come bown i now you are mafd but i mean if like you get mad it’s a reson


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