Revolve

3 February 2015

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Harnessing The Power Of The Tides
3 February 2015
Revolve |

water Feature by RevolveTeam

At 320MW installed capacity, with first power expected in 2018, the Swansea Bay Tidal Lagoon will be one of the largest marine energy developments in the world. Developed by Tidal Lagoon Power Limited, it will have an entirely predictable 495GWh output each year of clean, green electricity and will power more than 155,000 homes for 120 years – that’s about 11% of Wales’ domestic electricity requirement. Tidal Lagoon Power plans to follow with five full-scale tidal lagoons in UK waters; generating up to 8% of the nation’s electricity requirements from the fleet. Andy Field, Head of Communications at Tidal Lagoon Power, explains how the Swansea Bay project could influence Europe’s future energy mix.

In 2012, renewables provided just 11.3% of UK electricity generation and while this figure has since increased, we know that Britain’s electricity reserve generating margin could fall to as low as 2% by the winter of 2015/16. As is the case across much of Europe, we need to invest in new sources of low carbon generation at scale. It’s not such a tricky puzzle to solve. The UK is an island nation with a largely untapped marine energy resource. Humankind has Employed tide mills for centuries; find a reliable and responsible way to harness this resource for energy generation at scale and the picture changes dramatically.

That is why we think the Swansea Bay Tidal Lagoon will be a game-changer. The UK has always had a wonderful tidal range resource. It now has an economically, environmentally and socially viable way of harnessing it. Tidal lagoon power is a renewable technology which uses the rise and fall of the tides to generate electricity. While no tidal lagoon has ever been built before, tidal range technology has been in operation in barrage schemes since the 1960s, demonstrating the reliability and resilience of low head hydro turbines in a marine environment. The Crown Estate has identified theoretical UK tidal lagoon resources of 14GW of the six projects our business intends to take forward, starting with the flagship scheme in Swansea Bay, could provide over 15GW of installed capacity, or approximately 30 TWh per annum. That’s8% of the UK’s generation capacity taken care of by a fleet of tidal lagoons designed to last for 120 years. But the emergence of tidal lagoons could have a much wider impact, helping deliver on the European vision to secure up to 100GW of EU electricity supply from the oceans by 2050, while exploiting pan- European supply chains to drive employment and economic growth. Academic studies have noted the potential for tidal lagoons to diversify energy supply in other EU Member States, most notably France but also in Germany. As with a UK roll-out, early deployment could open up a potential global market of 80GW or more to specialist European hydro manufacturing, construction and civil/marine engineering businesses. Energy sector analysts, industrialists, policymakers and entrepreneurs are beginning to train their eyes on a particular section of the South West Wales coast. Establishing a Blueprint The Severn Estuary holds the second highest tidal range in the world and Swansea Bay benefits from an average tidal range during spring tides of 8.5m. This tidal range or ‘head’, the difference in sea level between high and low tide, offers significant potential for the extraction of renewable energy through the construction of tidal lagoons. A tidal lagoon is a man-made enclose of ocean and, similar to a hydroelectric dam, generates electricity by releasing water through a series of turbines in combination with a pressure difference caused by the difference in water level between lagoon and sea. Although the lagoon is the first of its kind, all component parts of the project have been proven elsewhere in the world, keeping technology challenges and risks low. The turbine mtechnology has been proven in the field for almost fifty years and the seawall will employ the same construction techniques as many of the world’s harbour walls, coastal defence  schemes and ocean road bridges. The scheme will generate electricity in both ebb and flood conditions, employing turbines that can work efficiently in both flow directions to make the most of the natural resource available. There is no guesswork; up to 100,000 Olympic swimming pools of sea water will drive our turbines each and every day.

We have a fantastic opportunity to deliver clean, green and predictable electricity from a network of lagoons. With differing high tide times around the UK, the fleet could provide a predictable and round-the-clock supply of renewable electricity.

The general sequence is as follows: with flood generation the lagoon is empty and the turbines and sluice gates are closed. The sea level rises and when it reaches about 4 to 5 metres above the lagoon water level, the turbines are opened. While the lagoon is filled through the turbines, electricity is generated. When the head difference drops down to about one metre, the power generation and flow through the turbines reduces, and so the sluices are opened to quickly fill the lagoon to a maximum level. When the sea level equals the lagoon level, the turbine and sluice gates are closed. This marks the start of ebb generation, where exactly the reverse sequence takes place. Because the tidal water levels are entirely predictable, it is possible to compute the expected energy output for years to come. Through an ongoing process of operational optimisation, we expect power output for the Swansea Bay Tidal Lagoon to exceed 495 GWh per annum, enough to power more than 155,000 homes. That’s about 11% of Wales’ domestic use. An Industry is Born The commercial roll-out of tidal lagoons can be quick. The Swansea Bay scheme will take a little over three years to build and will present engineers, environmentalists, investors and politicians with the real-world evidence required to inform full-scale projects. Larger lagoons with an installed capacity of approximately 2GW or more will require between three and six years to complete. Within the space of a decade, a fleet of tidal lagoons could be making a significant contribution to energy security in the UK and in other European territories with access to the natural resource. The energy output of a tidal lagoon is directly related to the tidal range and the area of water enclosed by the lagoon. Construction costs are driven by the length and height of the wall and the cost of the turbines and sluice structures. An important ratio to quickly assess the viability of a tidal lagoon in any given location with a suitable tidal range is the ratio of seawall length versus the enclosed area of the lagoon.

Studies suggest that the cost of power from larger tidal lagoons in the UK is comparable to nuclear and gas-fired generation.

Larger lagoons therefore produce cheaper power, allowing countries with tidal range resource to manage the cost of decarbonisation. There is no assumption of technical advancement and innovation built into larger lagoons; they are simply larger. Meaning that the single step from proof-of-concept at Swansea Bay to full-scale lagoon elsewhere can be taken with a high degree of certainty. Larger lagoons will however need to demonstrate that, as at Swansea Bay, they can work with nature and not against it. The importance of environmental and ecological criteria in assessing the suitability of any tidal energy scheme should not be underestimated. Indeed, 4000 pages of our planning application for Swansea Bay and many hours of subsequent discussion have been dedicated to this very detail. Coastal processes, water quality, fish and birds, on and offshore ecology and more: all potential impacts must be understood and, where necessary, managed and mitigated. But the Swansea Bay scheme has shown that this can be achieved and has underlined the inherent flexibility in a tidal lagoon’s siting, design and interaction with its surrounding environment. More Than a Power Plant Tidal lagoons can generate power at a scale not really seen before in renewable energy. They can also redefine the role of the power plant. The Swansea Bay Tidal Lagoon will be a catalyst for social and economic growth, providing a diverse public amenity, a dramatic sporting and cultural venue, coastal flood protection and localised adaptation to climate change, and a magnet for tourism. It will generate jobs, local industry, biodiversity, education opportunities, regional wealth and, we hope, a pride of place. It will perform a variety of functions at the heart of the community. Our plans include a watersports centre, fully equipped for disability sports, which will host a range of national and international events, from triathlon to sailing. And a unique Offshore Visitor Centre that will work with local schools and colleges, as well as welcoming up to 100,000 tourists to the Bay each year. These facilities, and the homes and businesses within the footprint of the lagoon, will sit behind a structure that is optimised for long-term stability. They will be protected against coastal erosion and a rise in sea level, and will draw comfort from the knowledge that even in a 1 in 500 year storm event, the integrity of the lagoon wall will not be called into question. For the wall itself, we are running a number of competitions to bring forward ideas for public art and cultural installations that will enrich the lagoon experience for local residents and tourists alike.

We are also working with conservation and academic groups to make the most of opportunities to protect and simulate biodiversity. The scheme includes the creation of new habitat, sea reefs and seabed sanctuaries where oysters, lobsters, mussels and fish can replenish themselves; the reintroduction of species through an onsite hatchery; and the protection of large chunks of coastline. An independent industry advisory group has worked tirelessly to prepare local industry to play a major role in turbine and construc-tion supply chains. Helping to ensure that the project’s impact on the Welsh economy will be material; studies show up to £316m Gross Value Added during construction and a further £76m per annum GVA throughout operational life. With such a variety of functions, our intent is for the power plant to mean something positive for everyone living in and around Swansea Bay. During consultation we found 86% of local people to be in support of the lagoon. Since then over 1,000 local residents have formed active supporters groups to try and ensure that the views of the ‘silent majority’ are heard. The Final Mile After four years of careful preparation, we enter the final mile for Swansea Bay and the birth of an industry. The remaining pieces of the jigsaw are falling into place: Prudential has become the cornerstone investor in the project; we’ll shortly award the three main tenders, for turbines, marine works and offshore construction; a short list of potential sites for a local Turbine Assembly Plant has been pulled together; a final planning decision will come in 2015 and with it, financial close and the start of construction. Should the blueprint pass the test, the game changes: ocean energy at scale becomes a real possibility; the prospects for meaningful green growth in Europe are boosted; and the way in which a power plant is understood to interact with the people and the natural environment surrounding is redefined.