Tidal Energy

SeaGen Device in Strangford Lough

 

What is It?

Marine current energy is one of the most exciting emerging forms of renewable energy. Marine currents, unlike many other forms of renewable energy, are a consistent source of kinetic energy caused by regular tidal cycles influenced by the phases of the moon.  Intermittency is a problem for wind, wave and solar power as the sun doesn’t always shine and the wind doesn’t always blow.  These sources of renewable energy often require backup from traditional forms of power generation. However, the inherent predictability of tidal power is highly attractive for grid management, removing the need for back-up plants powered by fossil fuels.  Tidal turbines are installed on the seabed at locations with high tidal current velocities, or strong continuous ocean currents where they extract energy from the flowing water.

How it Works

Tidal turbines are very much like underwater windmills except the rotors are driven by consistent, fast-moving currents.  The submerged rotors harness the power of the marine currents to drive generators, which in turn produce electricity. Water is 832 times denser than air and consequently tidal turbine rotors can be much smaller than wind turbine rotors thus they can be deployed much closer together and still generate equivalent amounts of electricity.

Devices that harness marine current energy present a unique set of engineering challenges in terms of design, installation and maintenance. During operation, the force of the tidal flow in Strangford Lough is equivalent to a 345 mph wind generating 100 tonnes of thrust on the rotors.

The unique design of SeaGen allows capture of the maximum amount of tidal energy whilst keeping maintenance and connectivity costs low.

Rationale

Against the backdrop of climate change and energy security, the European Union have set a target to obtain 20% of their energy generation from renewable sources by 2020.  The UK Government have signed up to this agreement and have furthermore pledged to reduce the UK’s carbon emissions by 80% of 1990 levels by 2050.

The UK currently generates just under 10% of its power from renewable resources and the UK Government has committed to increasing this percentage over the coming decade. Approximately 25% of the UK’s existing stock of fossil fuel power generation is due to come offline by 2020 whilst energy demand during this period is predicted to increase. The issues of energy security and rising energy costs to the UK and Europe are of growing concern in today’s society and renewable solutions such as marine current energy can contribute to a reliable solution.

Viewed against this backdrop there is a strong case for supporting the UK Government’s drive towards renewable energy.  Vast quantities of predictable, reliable and consistent marine current energy are available in UK waters and beyond.  This form of electricity generation can play an important part in the future global energy mix.

The Benefits of Tidal

In addition to helping reduce carbon emissions, the tidal energy sector can bring significant economic benefits. Tidal energy has the potential to power 15 million homes, save 70 million tonnes of carbon and create 16,000 jobs in the UK alone. The UK Government has indicated that tidal energy projects that are installed and operational by 2017 will be eligible for five Renewable Obligation Certificates (ROCs) as part of the Renewables Obligation scheme put in place to support the emerging renewables industries. This type of support will be crucial in attracting the necessary private investment to ensure that the UK retains its position as the global leader in the tidal energy sector.

Global Resource

Global Resources

While estimates of global potential may vary, it is widely agreed that tidal stream energy capacity could exceed 120GW globally.  The UK has one of the largest marine energy resources in the world, estimated to be more than 10GW, representing about 50% of Europe’s tidal energy capacity.