Is tidal power the future of energy? The science of wave technology understands the sea as a massive source of power.
The oceans of the globe combined represent approximately 1.35 billion cubic kilometres. That is 1,260,000,000,000,000,000,000 litres of water.
Thought leaders believe that if only a fraction of the kinetic power of the ocean’s tides was captured then it would meet the energy needs of the world several times over.
The aim of tidal power technology is to do just that, producing a source of unlimited, renewable clean energy.
Since tides are predictable, construction of hardware is built to scale and it is conceivable that such technology would have a long lifespan making it cost competitive.
A form of hydropower, tidal power, as a technology dates back centuries. Today’s technology uses several different forms to harness the power of the tides.
A tidal stream generator is a turbine that can be placed at the bottom of say a bridge column to take advantage of powerful currents.
The United Kingdom boasts the SeaGen, which is based on this technology. Constructed in the Strangford Narrows in Northern Ireland it generates 1.2MW and is connected to the main grid.
But the technique that is put to use more commonly is based on the concept of a dam that traps water at high tide in a large basin.
When the water is released at low tide, it generates turbine power.
Called a tidal barrage, this technology is already at work in South Korea (the home of the globe’s largest such installation near Seoul), Russia, Canada, China and France, where the world’s first tidal power station was opened in 1966 at the Rance River in Brittany.
The Wave Dragon is based on ‘over-topping’ too, though instead of a dam it is a floating offshore wave converter where water fills a reservoir which is then forced through a turbine. A prototype has been tested by the Wave Dragon company in the Nissum Bredning, an inland waterway in Denmark.
The Wave Star Energy company are developing a process – called the Wave Star – that converts the energy from waves through floats on the surface of the ocean.
These designs are still relatively small scale (though could be enlarged).
But a new project based in Swansea, Wales, not yet underway, is both ambitious and a spectacular innovation on the barrage technique.
The plan here is to build an artificial harbour, with a sea wall 9.4 kms long that reaches the bottom of the seabed, capturing an area of 11.5 sq kms.
26 turbines will be installed in the harbour’s ‘mouth’. These will produce 420GWh annually – enough energy to power 155,000 homes for 120 years – say the company behind the project, Tidal Lagoon Power.
The disadvantage of the tidal barrage model is that it requires the right geography that occurs naturally – like a river mouth – which is relatively small in scope – for the technology to be effective.
What the Swansea Bay Tidal Lagoon will do is create the optimum conditions for success artificially.
BBC estimates the cost of tidal power from this project to be $315 MWh across 35 years. A rival to TLP has already emerged.
Green energy company Ecotricity has told the UK government that the site TLP has chosen to build is not feasible and their energy price could be bettered.
This news broke in February and within a week of the UK government announcing a six-month enquiry into the tidal power sector.
This is significant to TLP and the Swansea Lagoon project as the UK government has been in negotiations for over a year with the company concerning subsidies in support of their ‘£1 billion plan’
TLP has already announced a raft of similar projects worth £12 billion, including four more lagoons big enough to generate 7,300MW, which they say is enough power to meet the electricity needs of ten per cent of the UK.
The UK government’s review of this space is timely.
The International Energy Agency has supported the notion that tidal power has the potential to reduce greenhouse emissions by an estimated 1 billion tonnes for some time.
This is based on the IEA prediction of tidal power technology producing as much as 337GW of power by 2050.