Sea Clam Wave Energy Converter

Abstract

After five years of research, the U.K. wave energy programme is nearing a point of decision on whether to progress towards full-scale testing or to continue on a research basis with reduced funding . The decision will be almost certainly based on the potential economics of wave energy and as a result, several device research teams are firming up on their designs prior to a cost assessment by consultants towards the end of this year. The chosen device or devices will probably have to produce electricity for the national grid at an estimated cost of less than 5 pence per unit at today's prices based on the costings of a 2 GW station located off the Outer Hebrides. Sea Energy Associates Limited and the Coventry (Lanchester) Polytechnic have been involved in the national wave energy programme since 1975, first, on the 1/lOth scale duck programme, (1, 2) and then more recently, on the second generation device known as the Clam (3). The Clam arose out of the need to redl'ce the high costs attributed to the first generation of wave energy devices and represented a new approach to the problem by an experienced team. By defining a sjmple concept which utilised components already identified as attractive, whilst at the same time avoiding known problem areas, the Clam quickly evolved into its 1979 design (3). This design has been tesled at 1/SOth scale in both natural and indoor waves with very satisfying results. Optimisation of the 1979 design has led to further design improvements which reduce the capital cost and increase the overall productivity. The final 1981 design should meet the cost criteria laid down and still retain some potential for further development. This paper discusses the merits of the Clam device and reviews the progress to date. of a floating spine breathe in response to wave forces. This causes air to be forced through self-rectifying turbines into and out of the hollow spine, allowing interchange of air between Clam bags. The randomness of sea wave patterns allows phased operation of the Clam elements, enabling the spine to act as a stable reference body. Typically a 1 OMW generating unit would feature ten Clam elements on a 27 5 m long spine, moored at an angle to tne waves, as illustrated on the cover.