Tidal Power

1. SustainableEngineering@Edinburgh Environmental Impacts Group 16: Ronan Kelly 0840408; Zafeirios Triantafyllidis0789807; Jonathan Phair 0679681 IMS3 Sustainability Module Introduction Tidal Technologies Tidal Range Tidal stream Barrages Lagoons Tidal Power • Some of the main considerations are; • • Ecology– Even the most fish friendly of turbines have a 15% fish mortality rate on passing. Fish migration, loss of habitat can occur due to changes • in physical environment. Fish, birds and mankind all effected. • • Noise, visual environment, water/air quality and cultural heritage • - Changes in salinity and turbidity can occur plus possibility of algae blooms which feed on pollutants. Potential for commercial shipping, fishing, recreation • and tourist damages in construction and operation • • Seabed, sediments and currents - Tidal power schemes will • reduce the tidal range it encloses, but also physical change • due to erosion and deposition occurs around structure • resulting in sandbanks disappearing • Butreduced carbon emissions • compared with other • generation techniques • Tidal energy is extracted • from the movement of water in • the oceans caused by the interaction • between the gravitational fields of the • sun, moon and earth with the water • bodies in the oceans. • Potential of meeting 8-10% of UK electricity • demand – approximately 4.7% could be met by • the Severn Estuary alone (~17 TWh/year). • Positive overall carbon benefit – zero CO2 • emissions during operation. • Tidal energy extraction is variable with time, but it is • periodic and completely predictable. The power • output can be forecasted accurately at any given • time. • Small operation and maintenance costs – greatest expenditure is capital cost. Existing and Proposed Schemes Generation • Tidal Lagoon • A solid structure used to impound water by isolating part of a channel • As the tide goes out water is trapped within the structure • When the tide has fully gone out, the water is released through sluices • The released water works turbines to extract water • Tidal Barrage • A solid wall spans an estuary or basin • Sluices in the barrage are opened to allow approaching tide to fill behind the wall • As the tide goes out the sluices are closed , trapping the water. • Sluices are then opened allowing the trapped water to flow back out to sea (by gravity) • The energy from the flowing water is harnessed from turbines placed at the sluices • Tidal Stream • Smaller than Barrages or Lagoons ( no need for a long solid barrier) • Extract energy from the tidal stream flowing past by using an actuator • Only aims to extract a fraction of the energy from the flow • Farms can be installed in stages and can be expanded • References •Kerr, D. (2005) “Marine energy: getting power from tides and waves”, Civil Engineering, 158(6), 32-39 • •Sustainable Development Commission (May 2007), Research Report 2 -Tidal technologies overview • http://www.sd-commission.org.uk/publications/downloads/TidalPowerUK2-Tidal_technologies_overview.pdf • •http://en.wikipedia.org/wiki/Tidal_power