What is tidal power?
Tidal power has nothing to do with waves or wave power. Tidal power relies on the power of the incoming and outgoing tide to turn turbines, which produces electricity. Tidal power is a renewable and clean source of energy, meaning that it will always be around, and it won’t throw carbon dioxide or other pollutants into the atmosphere.
There are three types of tidal power:
- Tidal stream – this is the capture of fast flowing tidal currents in constrained river channels. Tidal stream technologies try to capture some of the energy contained in the currents passing through them.
- Tidal range – this is the capture of energy in estuaries where there is a large difference in the height of water at high and low tide. Tidal range barrages hold large volumes of water at high tide, and then release the water through turbines at low tide.
- Tidal lagoons – these are created by building walls in the sea, which can then be used like artificial estuaries [1]. These then capture energy in a similar way to tidal range power.
Case study: The Severn Barrage
The River Severn in the UK is an ideal location for a tidal barrage. It has an estuary with extreme differences in the height of water at high and low tide (14 metres). In fact, it has the second biggest tidal range in the world. The tidal barrage would be situated between Cardiff and Weston-Super-Mare. The tidal turbines along the barrage would generate the same amount of electricity as three of the latest nuclear power stations – 8.6 GW during flow and 2 GW on average [2]. However, the huge environmental benefit of this green, clean energy source has to be weighed up against the major environmental impact to the local environment. There could be a loss of up to 75% of the existing intertidal habitat, which is internationally protected [3]. The Severn Barrage is a good example of the issues and debates surrounding barrage development and renewable energy production.
Benefits of tidal power in the UK
- Tidal power is predictable (unlike wind and sun) and can be relied upon [1].
- It works day and night.
- It will last millions of years.
- High and low tides take about 12 hours to move around the UK, therefore a collection of tide farms up and down the country could provide a more constant contribution to the national grid [1].
- Large quantities of electricity can be produced.
- Barrages can provide protection from flooding up-stream.
- Tidal power is carbon free.
- Barrages have a long life span.
Disadvantages of tidal power in the UK
- Barrages can be potential threats to sea life, preventing certain fish species, such as salmon and eels, from spawning up-river.
- It can cost billions of pounds to build a barrage.
- Coastal erosion and silting can increase in areas around tidal barrages.
- Tidal power stations could have potential impacts on ports and shipping which could affect local economies.
- Barrages can cause the loss of inter-tidal habitats by permanently flooding areas which would normally be covered and uncovered with the usual tides. This directly affects species living and breeding in these areas. In the example of the Severn Barrage, the land that would be submerged is home to about 68,000 birds in winter [5].
If you would like to learn more about renewable technologies that could generate energy for your home or business then visit our informative pages.
References
[1] MacKay, David (2009) Sustainable Energy without the Hot Air
[2] Severn Barrage Tidal Power (2010) REUK http://www.reuk.co.uk/Severn-Barrage-Tidal-Power.htm
[3] Tidal Power in the UK (2007) Sustainable Development Commission http://www.sd-commission.org.uk/publications/downloads/Tidal_Power_in_the_UK_Oct07.pdf
[4] Tidal Power (2010) Sustainable Development Commission http://www.sd-commission.org.uk/pages/tidal-power.html
[5] Severn Barrage (2010) Tidal Energy http://www.tidalenergy.eu/severntidalbarrage.html
