Simplified tidal energy

Italian renewable energy company Fri-El Green Power is developing flexible tidal energy technology that it claims is simpler, cheaper and lower maintenance than existing systems.

The Sea Power system consists of an anchored floating vessel, which trails a number of modular lines each bearing several turbines a regular distance apart, kept at a fixed depth below the surface by floats. No sensitive electrical components are submerged and mechanical parts transfer the energy to generate power aboard the vessel.

Fri-El has been a pioneer in alternative energy, including hydro electric, wind power and biogas, since the 1990s.

The Sea Power concept is the brainchild of Josef Gostner, chief executive, who worked with Naples University's aircraft design and aero flight dynamic group, headed by Prof Dominico Coiro, to develop the project. 'The aim is to make tidal energy much simpler,' said Patrick Pircher, Fri-El's head of finance. 'There are existing projects like SeaGen (the 1.2MW tidal energy converter installed in Strangford Lough, Northern Ireland, last April) which involves a huge rotor blade and massive amounts of steel. Ours is much lighter, easier to build and less complex.'

Sea Power is designed to generate maximum power in one-directional water flow, and automatically turns 180º as the tide turns. Submerged structures are constructed from steel and carbon fibre, and its modular nature means the lines can be extended or arranged in a variety of configurations to take best advantage of the currents in any given location.

Based on scale models, Fri-El estimates that a Sea Power setup with four lines carrying 16m diameter turbines could generate 4.8MW with a flow speed of 2.5m/s. An eight-line vessel with 23m turbines could generate 20MW under similar conditions.

Sea Power generators close to the shore would feed energy directly into the Italian national grid, and Fri-El envisages that fleets further from the shore — 160km away — would generate hydrogen through electrolysis of seawater, which would be stored and transported to the shore for distribution.

Fri-El is now testing a 500kW prototype of Sea Power in the Strait of Messina, where the current flow reaches peaks of 2.5m/s.

'Like wind parks, it will be efficient at around 20MW,' said Pircher. 'The next stage is to build enhanced prototypes until one vessel has a 1MW capacity. A fleet of 20 vessels with the generating technology would be like a wind park at sea.'

Development started about two years ago, and an industrial system could be ready in another two years.

Pircher said there has been a lot of interest in Sea Power from big energy companies, and two partners have approached Fri-El with a view to entering into a joint venture.

Berenice Baker