A Tidal Barrage is a Dam built across an Estuary or Bay to generate Electricity from the Flow of Tides.It works using the same principles that is used in production of the mainstream hydro powered electricity.In this form of Tidal Power,a Barrage is built near the coast where water is collected during the periods of high tides.During low tide the barrage allows the water from the reservoir to move towards the ocean or sea.The potential energy of the water at a higher level is converted to electricity using Turbines.Note Tidal Barrages can only be built in areas where there are high tides with a difference of at least 5-8  metres which is measured in the form of a Ratio.Note the US DOE has identified about 40 locations globally where Tidal Barrages can be built to generate Electricity in Commercial Scale.

Uses of a Tidal Barrage

A Tidal Barrage can be used for one/many of the following uses

1. Generation of Electricity
2. Increase the depth of a river
3. Prevent Flooding
4. Protect Coastal Erosion
5. Promote Water Sports and Coastal Development
6. Maintain a separation between fresh and salt water

Principle of Working of a Tidal Barrage

A Tidal Barrage has gates in it that allow the water to pass through. The gates of the Tidal Barrage are closed when the tide has stopped coming in, trapping the water within the basin or estuary . Turbines are able to be powered in reverse by excess energy in the grid to increase the water level in the basin at high tide (for ebb generation). This energy is more than returned during generation, because power output is strongly related to the head.As the tide recedes gates in the Tidal Barrage that contain turbines are opened,driving the turbines and generating power.The basic elements of a barrage are caissons, embankments, sluices,turbines and ship locks. Sluices, turbines, and ship locks are housed in caissons (very large concrete blocks). Embankments seal a basin where it is not sealed by caissons.

Economics of a Tidal Barrage

Tidal Barrage require a huge amount of initial capital investment during construction and take a long time to build ( around 5-10 years).The design of the Tidal Barrage is quite complicated and not an off the shelf simple design like that of a Thermal or a Gas Fired Nuclear Power Plant.The long payback period,the cost and time overruns and the massive investments implies that only government is an investor in Tidal Barrages.

Environmental Impact of Tidal Barrage

Tidal Barrages cause a major disruption to the marine life on the estuary or the bay on which it is built.This is one the major cons of a Tidal Barrage.Fishes frequently get killed in the Turbines of the Tidal Barrage and it also may lead to change in the migration pattern of Fishes.The quality of the water would also be affected, the sediment levels would change, affecting the turbidity of the water and therefore affecting the animals that live in it and depend upon it such as fish and birds.Many governments have been reluctant in recent times to grant approval for tidal barrages.Sandbanks and Beaches can Disappear and high-speed currents develop near sluices.

List of Tidal Barrages

1) Le Rance Tidal Barrage is the world’s first and the most famous Tidal Power Plant in the world.The 240 MW power plant is located on Rance River,Brittany,France and was started almost 45 years ago.The Tidal Power Station is run by French state owned electricity giant EDF .Construction took three years and was completed in 1966.

2) Tees Barrage – This is a barrage across the River Tees in North East of England and is used to control the flow of the river, preventing flooding and the effects of tidal change.  The waters above the barrage are permanently held at the level of a high tide.The Tees Barrage and Teesside White Water Course are developments of the Teesside Development Corporation.The barrage was opened on 1995.This Barrage does not generate Electricity

3) Annapolis Royal Tidal Barrage is North America’s only Tidal Power  Station and is located in Nova Scotia,Canada with a 20 MW power capacity.This Tidal Power Plant is built on the Bay of Frundy was built in 1984.

4) Uldolmok Tidal Barrage is Asia’s 2nd largest Tidal Power Plant with a capacity of 1 MW.The South Korean plans to expand the capacity to 90 MW by 2013 and is located in Jindo County of South Korea.

5) Jiangxia TidalBarrage is China’s only Tidal Power Station and has a capacity of 3.2 Mw.It is located in Zheijiang,China.

6) Cardiff Bay Barrage lies across the mouth of Cardiff Bay Wales\.The bay is part of the \Bristol Channel which has the second largest <\tidal range in the world.Construction started in 1994, following the successful passage of the\Cardiff Bay Barrage Act of 1993.\The barrage successfully created a large freshwater lake iattracting investment into the docklands.

7)  Marina Barrageis a dam in Singapore built across the mouth of the bay, between Marina East and Marina South. It was opened in 2008.It provides water supply, flood control and watersports

Most Famous Tidal Barrage Cancellation

The Severn Barrage was a proposed Tidal Barrage to be built across the Bristol Channel (Severn Estuary). The River Severn has a tidal range of 14 metres – the second highest in the world – making it perfect for tidal power generation.
The £30 billion Tidal Barrage would involve 10 mile long Dam  between Lavernock Point south of Cardiff, Wales, and Brean Down in Somerset, England. It would be the world’s largest ever renewable energy project, and the UK’s largest engineering project since the Channel Tunnel.The Severn Tidal Power Group (STGP) was  a consortium of engineering and construction companies (Balfour Beatty, Taylor Woodrow, Sir Robert McAlpine and Alstom) formed in 1981.

The UK had scrapped plans for a £30 billion Severn tidal project, claiming it would be ‘very costly to deliver and very challenging to attract the necessary investment from the private sector alone’.The Severn tidal barrage could have met 5 per cent of UK Electricity Requirements, if it was built

GreenworldInvestor Articles

1. Uses of Tidal Energy – Tidal Electricity the Biggest One
2. Advantages and Disadvantages of Tidal Energy
3. List of Tidal Power Plants and Future Tidal Stations- Facing Difficult Times
4. Tidal Wave Energy – Quick Guide to Costs,Investment and How Tidal Generators Produce Tidal Power