How Tidal Power is Riding the Crest of a Wave

But how is tidal power evolving? Where does it fit in the wider landscape of renewables? Is it a magic bullet that could solve all our energy needs? And if it isn’t, how do we address non-renewable production?

A strong case

The argument for tidal power is overwhelming: it’s a practically infinite supply of clean energy and has one of the smallest carbon footprints of any power source; it’s reliable, cost-efficient, has minimal effect on the marine environment and virtually zero effect on sea-gazing aesthetics. Most importantly, The World Energy Council estimates that the energy that can be harvested from world’s oceans is equal to twice the electricity that the world produces now.

A reason many energy experts are looking at what tidal may be able to contribute, compared to other renewable sources like wind power, is that the amount of energy generated from a power-generating turbine is proportional to the density of the fluid that flows back and forth – meaning a water turbine has several hundred times the power of an air turbine.

Why? Seawater is denser than air; a lot denser – 832 times to be exact, meaning an 8 knot tidal current has more energy than a 380kph wind. This means a wave farm of ‘sea snakes’ – devices built by Scotland’s Pelamis Wave Power – covering half a square mile of ocean could produce 30 MWh of power, which is estimated to be enough for 20,000 homes. A wave farm covering 472 square miles could supply 24 million households – enough for the entire UK.

An underrated source

Impressive stuff. So it’s strange that tidal power has failed to enjoy the widespread media attention that has been lavished on other renewable energy sources. While solar and wind have featured as the public face of a world powered by sustainable energy, tidal has lurked somewhere in the background.

Partly this has been due to the uncertainty of how to harness all this abundant marine energy. While it’s great that there’s the potential to harness up to 153 GW of tidal power in the UK alone, the question has remained over just exactly how we do that; past efforts at tidal design have failed to produce practical and cost efficient energy-gathering systems.

There’s also the issue of implementation and maintenance; the most viable sources of tidal power are in the most turbulent and inhospitable environments. Sub-sea tidal installations are challenging, costly and must contend with the corrosive surroundings.

But there’s a stage in the history of any innovative technology when development reaches a turning point, and the concept behind the technology is suddenly viable. This is the time when major industrial players take notice and begin to act on the potential to deliver the technology on a mass scale.

For tidal power, that time is now.

Turning the tide

Tidal has been used as an electricity producer for decades, of course; the Rance tidal barrage power plant in France has been producing energy since the 1960s; the Jiangxia tidal power plant in China has been operating since the 1980s. But now we’re seeing a flood of different tidal production methods being championed, and Rolls Royce and Kawasaki Heavy Industries are among the giants now exploring the development of tidal power.

Tidal stream power is being backed by Siemens, who are behind SeaGen’s operation at Strangford Lough in Northern Ireland – the world’s first commercial tidal system, which powers 300,000 homes. With their underwater propeller turbines, SeaGen’s twin rotors model captures kinetic flow, generating power from flood and ebb tide.

Wave power is being utilised by Aquamarine Power in Scotland. Interestingly, Scotland has been called ‘the Saudi Arabia of tidal power’. Hyperbole, yes, but it makes a valid point. Aquamarine Power’s Oyster 800 machine – which generates an 800 kW output capacity – has been set to work off the coast of the Orkney Islands. The ‘Oyster’ machine has a 20-year lifespan and has already generated hundreds of local jobs.

Scottish Power’s Hammerfest is a giant three-bladed propeller perched atop nearly 1,000 tons of steel structure sitting on the seabed. Although a thousand of the devices are required to match the energy generation of one nuclear power plant, proponents of the technology believe this is realistic.

The new wave

Down in Wales, Tidal Lagoon Swansea Bay wants to design, construct and operate a lagoon tidal system to generate renewable energy. The lagoon would hold on to water and then let it out through turbines at both high and low tides which would generate electricity. The system would be designed with a 100-year lifespan, generating 400,000 MWh of renewable energy every 12 months.

And that’s without mentioning even other companies taking impressive and demonstrably successful steps forward. Eco Wave Power’s medium-scale wave energy generation system devices – the ‘Wave Clapper’ and ‘Power Wing’ – have genuine large-scale potential. Two of these medium-scale floaters can provide stable electricity for up to ten households. Hundreds of commercial scale floaters could power whole towns.

Elsewhere, Tidal Energy Pty took ten years to develop their Venturi Davidson-Hill Turbines - shrouded underwater turbines that generate the highest efficiency ever produced from a water turbine. Large subsea areas covered with these devices could offer a significant energy solution. 

Future energy strategy

There are many more emerging tidal technologies, and it’s clear that tidal power is an underrated and momentous part of the renewable energy landscape. This is not to say that tidal deserves to ‘take over’ from other renewable energy sources. If we’re going to legitimately move from a model of fossil sources with renewable contributions to a model of renewable sources with fossil contributions, all renewable methods will need to be effectively implemented.

And there’s the fact that certain areas of the world are better for some renewable energy generation sources than others – the wild coast of Scotland is better placed for tidal, the scorching dunes of the Sahara are better for solar, and the gale-swept plains of mid-west America are better for wind, etc.

Tidal power technology looks like a genuine future energy solution. But it’s not the only one, and it’s clear renewables will not be able to completely fill the gap in the foreseeable future. Fossil energy sources will be with us for years to come, and while we should continue striving for the best energy strategy, we must also be responsible and acknowledge hazardous waste management in the oil and gas industry.   

So what does all this mean? Well, I think it’s obvious that tidal technology has developed to the point where it’s now taken seriously as a mass energy contributor. Tidal energy could be one of several contributors of commercial renewable energy. It might even be the leading source, due to its power, reliability and abundance.

Tidal could generate huge profit margins and create thousands – maybe hundreds of thousands – of new jobs in clean energy. But it’s also obvious that planning for a world in which renewables could be a dominant part of the picture involves managing our current non-renewable sources effectively and with accountability.

Lead image: Waves via Shutterstock