Making a bridge between flood defences and renewable energy

The world’s seas and oceans contain almost unlimited, inexhaustible power. Along the rugged coastlines and waterways of the United Kingdom and Ireland for example, tidal surges could provide plentiful clean renewable energy if harnessed in a cost-effective manner. The Eurostars SAFE COAST project has provided some much-needed momentum (and a wake-up call to governments) by demonstrating that affordable renewable energy can be combined with robust flood defence.

“The overall goal of this project was to optimise technical solutions to reduce the risks of flooding whilst generating electricity at a reasonable cost,” explains project coordinator Arne Kollandsrud, CEO of Norwegian company Tidetec. “We wanted to develop a flood barrier prototype in combination with a tidal lagoon that can generate electricity, and also verify the concept from a technology and market perspective.”

Potential confirmed

Much of the practical work focused on a case study in the lower Thames Estuary. The river has in the past burst its banks and almost flooded the UK capital. SAFE COAST developed a turning mechanism that allowed turbines to operate in both flow directions. This can be installed on flood barriers capable of generating electricity from tidal power. A major conclusion of the project was that flood barriers that obstruct seawater surges and fill a lagoon could substantially lower flood levels.

The SAFE COAST project also made some important conclusions regarding financial viability. “We realised that it is difficult to get paid for flood protection,” says Kollandsrud. “So, you have to have high amounts of tidal head and tidal power to make this financially viable. For example, near Cardiff or in the Bristol channel (both in the UK), we can generate energy at low cost at a level similar to that of offshore wind. In the Thames however, where there is less tidal head, we found it would be difficult to compete with offshore wind if you only examine levelised cost of energy (LCOE).”

This flags up a critical issue concerning flood defence. Unless policy makers are prepared to fund important R&D work, there is always the risk that potential cost-effective solutions will remain at the prototype stage and never be fully commercialised. “Unfortunately, governments sometimes need a big flood to happen before they will wake up and invest,” adds Kollandsrud.

Benefits of collaboration

Kollandsrud has been CEO of Tidetec since 2013; the company was founded by his father in 2000. The idea for an “energy bridge” came about after the Norwegian State Road Company proposed moving a coastal road in northern Norway further inland. Kollandsrud’s father instead proposed keeping the coast road and making a bridge crossing with power-generating turbines, which would be cost-effective, protect the road and add value.

Tidetec was granted the first of three patents for its two-way optimised turbines, and the firm began to look for ways of scaling up the concept. This is where Eurostars came in. “We wanted to identify and develop the most suitable turbines and technologies for our concept, work out the cost of the barrier and the potential benefits of power production,” says Kollandsrud. “This was quite a big task.” To accomplish this, SAFE COAST brought Tidetec together with German engineering partners Mareval (who worked on concrete structures), the Technical University of Munich (a leader in hydropower) and UK partner Metrotidal (who are involved in flood installations along the Thames).

Renewing coastal defence

This successful three-year collaboration resulted in a new coastal defence innovation. “We started by screening all kinds of turbine solutions to fit into our turrets,” explains Kollandsrud. “It was important that the turbines were highly efficient but not too big.” They chose a straight-flow (Straflo) turbine with a permanent magnet generator. The turbines can be turned when the tide changes to yield electrical power in both directions, and can also be run as pumps in both directions. This provides additional flood protection and also opens up the potential to store energy.

One-way Straflo turbines have already been used in a tidal barrage application at the Annapolis Tidal power plant facility in Nova Scotia, Canada,” says Kollandsrud. “The turbines there have proven to be more fish friendly, as the generator is placed at the periphery of the mechanism rather than in the centre.” The Tidetec solution houses turbines in rotating turrets based on a cylinder rotating around a horizontal axis. The turrets then fit into concrete structures that form part of the actual flood defence infrastructure.

“The turbines, turning mechanisms and turrets were all developed and optimised before being tested in the water for two to three months,” says Kollandsrud. “We have shown they work perfectly. Projects like these are so big that you really need the collaboration of turbine producers, technology firms and governments.”

Ready to capture the market

Since completion of SAFE COAST, Tidetec has worked on other coastal protection projects, including the Wyre Tidal Bay project and the Mersey Tidal Power project (both in the UK). “A key challenge has been finding the funding,” says Kollandsrud. “The Wyre project has been put on hold due to Brexit uncertainties.” However, the Mersey tidal power project appears to be on track. The scheme is designed to harness the power of the River Mersey as part of plans to make the city region zero carbon by 2040.

“We are doing all we can to develop this technology, but projects like these do not appear every day,” explains Kollandsrud. “It is difficult to get paid for our R&D work because the tidal power market has not quite kicked off yet. While things move fast in the offshore wind sector, hydropower tends to be a slow business.”

Nonetheless, Kollandsrud believes that once the market takes off, the partners involved in the SAFE COAST project will be well-placed to capitalise. Extreme weather and flooding have increased rapidly in recent years, causing destruction in low-lying areas across the world. Investment in flood prevention has been proven to save money in the long term. “At the same time there is a pressing need for sharing power available on the grid sustainably,” says Kollandsrud. “Both offshore wind and solar power are intermittent, and our lagoon technology provides for a renewable solution to this. It is only a question of time before the market takes off.”

Partners: Tidetec AS (Norway), Mareval Ag. (Germany), Technische Universität München Acting Here Lehrstuhl Für Wasserbau Und Wasserwirtschaft (Germany), Metrotidal Ltd. (United Kingdom)

Project ID: 9116 SAFE COAST (Eurostars)

Project duration: November 2014 to July 2017