Environmental Engineering Reference
In-Depth Information
Chapter 3
T
IDAL
P
OWER
-
M
OVING
A
HEAD
David Elliott
*
Energy and Environment Research Unit, The Open University,
Milton Keynes MK 7 6AA, UK
Abstract
The idea of extracting power from the tides is not new, and some tidal barrages have been
built across estuaries with large tidal ranges. However, in recent years interest has also
emerged in smaller potentially less invasive impoundment options, known as tidal lagoons. In
addition, a new concept has emerged, free-standing tidal current turbines, operating on tidal
flows.
This paper reviews the state of play with tidal energy developments around the world,
looking at barrages and lagoons, but covering tidal current turbine projects in more detail. It
draws out some of the key design issues and assesses prospects for the future of tidal energy.
Introduction
The Tides can be exploited for energy collection in two basic ways. Firstly, by using the
potential energy in the head of water that can be created behind a damn across an estuary, or
in a bounded reservoir in an estuary, to drive a turbine- i.e. tidal barrages or lagoons.
Secondly, by harvesting the kinetic energy in the horizontal tidal flows or streams, using tidal
current turbines immersed directly in the flow.
Tidal barrages have been the main focus of attention until recently, but tidal lagoons and
tidal current turbines have increasingly been portrayed as possibly preferable, in that, it is
claimed, they are less environmentally invasive. It is also argued that, being smaller, and in
the case of tidal current turbines, modular, they should be easier and quicker to deploy, so that
investment costs will be lower.
*
E-mail address: D.A.Elliott @open.ac.uk
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