The oceans are the world’s largest untapped source of energy. As an indication of their immense power, the total energy contained in tides worldwide is estimated at 3,000 gigawatts (3 terrawatts).
The proportion of tidal energy which is technically harvestable lies somewhere around the 1-terawatt (TW) mark, and is largely located near islands and long stretches of coastline.
A series of unique solutions have been developed to harness the potential of this natural resource. For example, tidal barrage systems take advantage of differences between high and low tides using a type of dam to block receding water during ebb periods. At low tide, water behind the barrage is released, and the water passes through a turbine that generates electricity.
Meanwhile, tidal stream systems take advantage of ocean currents to drive turbines, particularly in areas around islands or coasts where these currents are fast. They can be installed as tidal fences - where turbines are stretched across a channel - or as tidal turbines, such as Sustainable Marine’s PLAT-I technology. which resemble underwater wind turbines.
An advantage of both tidal range and tidal current energy is that they are relatively predictable with daily, bi-weekly, biannual and even annual cycles over a longer time span of a number of years. Energy can be generated both day and night.
A number of world’s superpowers benefit from strong tidal resources and around 20 countries are now making significant investments in the market, including the USA, Canada, UK, China, Japan, South Korea, Australia, New Zealand, Chile, France, Spain, Portugal, Germany and Sweden.
Back in 2014, the global tidal energy market was valued at $487million and experts now believe this will surge to circa 11.3bn by 2024.
The UK alone holds around 50pc of Europe’s tidal energy resource, with studies estimating it possesses a total tidal resource of 25 to 30GWs - enough to supply around 12pc of UK’s current electricity demand. The majority of which is located in the Severn estuary (which has between 8 and 12GW), with the estuaries and bays of the north west experiencing a similar volume and the east coast a further 5 to 6GW.
Across the Atlantic, Canada holds an estimated 35GW of tidal energy - enough clean power to displace over 113 million tonnes of CO2, equal to removing over 24 million cars off the road. The Minas Passage area of the Bay of Fundy attracts around 7GW of the nation’s tidal power, which could power two million homes – or all of Atlantic Canada.