The assessment has resulted in the selection of four main tidal power technologies that will be taken forward for fuller analysis.

“This initial selection of technically suitable options represents a major step in the process to select a viable tidal power scheme for the Mersey Estuary,” says Anthony Hatton, Development Director, Peel Energy. “Our main aim as we progress the feasibility study is to formulate an acceptable scheme on which we can base a planning application by the end of 2011.”

The four technologies selected are:

• A tidal barrage incorporating conventional tidal turbines similar to those routinely used in low head hydroelectric power applications;
• A tidal power gate – which could perform as a very low-head barrage – containing a grid of specially designed, smaller tidal turbines This is the kind of technology used to produce power from, for example, reservoir spillways and sluices;
• A tidal fence – a means of capturing energy from the natural or constrained velocity of the tidal flow – with either horizontal- or vertical-axis turbines designed for generating electricity in open streams; and
• An alternative tidal fence based on a new proprietary device that concentrates the energy contained in a large body of slow-moving water into a smaller body of fast-flowing water using the Venturi effect.

The developers warn that the list may be revised and developed as the study proceeds and further information becomes available.

The feasibility study

The feasibility study is being led jointly by a consulting team comprising Scott Wilson, Drivers Jonas and EDF, on behalf of Peel Energy and the Northwest Regional Development Agency (NWDA).

The study aims to identify a tidal power scheme that meets three prime objectives:

• The tidal power scheme has to be capable of generating a meaningful amount of electricity at a price that the country can afford;
• The direct impacts on the environment, shipping, local businesses and communities must be kept to acceptable levels (in determining their acceptability, measures may need to be provided to mitigate or compensate for the impacts); and
• The tidal power scheme should be to the maximum possible benefit of the region in a socio-economic and environmental sense.

Next steps

In the next stage of the feasibility study, indicative sites within the estuary where the different tidal power technologies could be best deployed will be identified and possible scheme layouts established.

There will be an economic analysis that looks at the likely energy yields of the different tidal power schemes set against their anticipated construction and operating costs.