Hobart

Seminar Abstract

Wednesday 9 June 2010, 11.30am (Tas time)
CSIRO Auditorium, Hobart

David Prandle
ANNIMS (Australian National Network in Marine Science) Visiting Fellow for 2010
based at the UWA Oceans Institute

Offshore Renewable Energy - potential and environmental impacts

Recent pressures to exploit ‘renewable’ energy sources have led to fresh interest in the extraction of wind, wave and tidal energy offshore. Small scale tidal mills have operated in estuaries for centuries. However, despite long-standing interest in large-scale ‘impounded-barrier’ schemes in many countries, La Rance in France is the only full-scale scheme, (250MW) remaining in successful operation since 1978. A similar sized Korean scheme, SIHWA, (256 MW) is under construction (www.tidaltoday.com).

A simplified approach to the design of impounded estuarine tidal power schemes is shown - providing optimum design parameters based on the mean tidal amplitude, Z, and the surface area of the enclosed basin, S. Comparisons are made between these optimised parameters and actual engineering designs for La Rance, SIHWA and proposed schemes in the Bay of Fundy and the Bristol Channel.

The power potential of tidal-stream energy in estuaries is derived and compared with equivalent values associated with impounded-barrier schemes and with the (upstream) energy dissipation from bed friction. The practicalities of extraction are examined for deployments which span various fractions of a cross-section. It is shown that ‘fences’ spanning large fractions are required for effective energy extraction.

Perversely, protecting the global environment by investment in marine renewable energy may have adverse effects on the local environment. Indications of such adverse effects have been shown from experiences around off-shore oil and gas rigs. In sedimentary terms, these include both scour and settlement.

However, the full effects from large ‘fields’ of near-shore energy devices has yet to be rigorously explored. Again, in sedimentary terms, the major concern is with disruption to existing patterns of cross-shore and long-shore sediment exchanges. Accretion might be expected in the leeward (for net tidal or wave energy propagation) shadow zone. Perhaps, of most concern, is that any obstacle to existing sediment exchanges could introduce larger scale scour patterns (possibly first becoming evident during a particular extreme event) – with consequent threats of coastal flooding etc.

*Offshore Renewable Energy’ Inst. Civ. Eng. Maritime Engineering 162 MA4 (2009).

Seminar recording

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Location:
CSIRO = Marine Laboratories Auditorium, Castray Esplanade, Hobart

For further information, or to schedule a seminar, contact:
To schedule a seminar, contact:
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Last updated 15/06/10