Don’t underestimate the force of water power

When the government granted planning permission for the £1-billion Swansea Bay tidal lagoon project earlier this month, it was hailed as a game-changer by Mark Sharrock, chief executive of Tidal Lagoon Power, the company behind the project. “Locking in a 120-year life, zero carbon energy infrastructure – we have the potential to help transform our industrial economy and the UK’s energy mix,” he says.

The 320-megawatt (MW) project, which will be able to generate 500 gigawatt-hours (GWh) of electricity a year to power 155,000 homes, is not just a UK first. It’s a world first. Along with the 398MW MeyGen tidal stream project, being developed in the Pentland Firth in the far north of Scotland by Atlantis Resources, it consolidates the UK’s position as the global leader in development of tidal power technology, ahead of main rivals France and Canada.

As an island nation, harnessing the power of water has long been on the UK’s energy radar. The key areas of focus have been large-scale hydro power, which has now virtually all been exploited, small scale hydro, tidal energy and wave power, where the UK is also at the forefront of development. While often mistakenly grouped into one category, these energy sources differ significantly.

“Hydro generally refers to the potential energy from water stored at height, falling through a turbine to a lower level. So if you’ve got a reservoir or a lake at the top of a mountain, you install a turbine house through which that water is let out and passed down a river to flow lower down and generate energy that way,” explains Dee Nunn, wave and tidal development manager for trade association RenewableUK. With small scale, including small run of river, hydro you have a turbine in the river and the turbine turns and generates electricity as the water flows through it.

How tidal power works

Large-scale hydro is well established, already being the world’s leading source of renewable energy. In the UK, it has been supplying electricity to the nation for decades, with the fleet generating 6,000GWh last year to meet 1.4 per cent of the UK’s power needs, according to the Department for Energy and Climate Change (DECC). In Scotland, where the majority of the UK’s large hydro resource is located, hydro accounted for 12 per cent of its electricity supply. However, with most sites suitable for large-scale projects already developed, the focus now is on small-scale developments. DECC says 850 to 1,500MW of new small hydro projects could be developed, contributing 1 to 2 per cent of our power needs.

Marine power – wave and tidal power projects – holds far more potential, however, and could, says Ms Nunn, see more than 20,000 jobs created in the UK over the next decade. Collectively, DECC believes wave and tidal stream, one of two main tidal technologies, could meet around 20 per cent of the UK’s current electricity needs, equating to an installed capacity of 30 to 50GW, while a further 8 per cent could be met by tidal lagoons. That’s why vast sums of money have been ploughed into research and development programmes. “We’ve seen over £480 million spent with UK companies as a result of wave and tidal stream development in the UK,” notes Ms Nunn.

Six potential lagoon locations have been identified around the UK which combined could provide up to 8 per cent of the UK’s electricity

“In terms of security of supply, you can not underestimate this idea that tidal power is predictable,” says Tim Cornelius, chief executive officer of Atlantis Resources. Andy Field, head of communications for Tidal Lagoon Power, concurs: “When built, we will be able to tell the National Grid on any given day, any given hour, when we will be generating and how much we can generate.” That is something neither wind nor solar can do.

Tidal barrage systems, as with the Swansea Bay lagoon project, trap water at high tide in specially constructed pools and release it through turbines to generate low-carbon electricity. Water also passes through turbines as the tide comes in, generating more electricity. The artificial lakes created for this purpose can be used for leisure activities such as boating, creating a tourist attraction, which is exactly the plan for Swansea Bay.

The lagoon will provide electricity 14 hours a day for 120 years and save more than 236,000 tonnes of carbon emissions each year. It will require government support to guarantee the price of the electricity for an initial 35 years, but as the developer points out, that is less than a third of its lifespan and the long-term returns, both economically and in security of supply, are high.

Six potential lagoon locations have been identified around the UK which combined could provide up to 8 per cent of the UK’s electricity and add up to £27 billion cumulatively to the UK GDP by 2027, according to The Economic Case for a Tidal Lagoon Industry in the UK, a 2014 study by the Centre for Economics and Business Research.

Even closer to commercial viability is tidal stream technology. With this there is no need to block water off, rather turbines sit under the water and literally generate electricity as the tides move through the turbine. Atlantis Resources’ MeyGen project in Scotland is the one global eyes are watching on this front. The project will use the company’s new 1.5MW AR1500 tidal turbine, being constructed by Lockheed Martin, as “the triumph of policy”, says Mr Cornelius.

While being equivalent in power capacity to a traditional generation station and having a similar 25-year lifespan, Mr Cornelius points out that the entire 400MW of MeyGen fits into just 3.5 square kilometers of seabed. “That’s absolutely tiny compared to the amount of space required for a similar sized offshore wind farm,” he says. Moreover, as a subsea project, it will not be visible to the general public, it will not create any noise disturbance and site selection is chosen to ensure no other industries, such as fishing, are affected.

Wave energy, in the meantime, is still some way off commercial reality, says Ms Nunn, although there is lots of work going on in the UK. In terms of output, it will be less predictable than tidal power, as it is dependent on wind passing over the surface of the sea. “The most significant developments have been made in the UK so far, but there’s a way to go compared to tidal,” she concedes.