Extraction Of Power From Sea Waves: Interim Report -1979
Consulting Engineers GIFFORD AND PARTNERS
Wave energy, in common with other renewable energy sources, is a diffuse resource. Its exploitation requires large numbers of collection devices to be distributed over a long front. For any given output, the economics are very substantially dependent on the capital cost of the system as the fuel is "free". It appeared from work done in 1978 that the cost of power delivered, calculated from the current typical prices for materials and fabrication, was so far above the present costs of power generation that it was difficult to imagine that sufficient cost reduction was possible simply from improvement of the device it was a conclusion of that the adoption of mass concept or Wavepower production performance. However Ltd's 1978 studies allied to design for production could offer very significant improvement 1n costs. This year, the earlier work on mass production has been continued and expanded to cover all appropriate aspects of system construction. In particular attention has been focussed on factory technology geared to producing the hulls of wave energy devices in quantity. Much of the more detailed work has been based upon Cockerell Rafts. However the concepts explored and developed are applicable to a wide variety of hull shapes. Detailed studies have been undertaken in collaboration with A & P Appledore Ltd on steel hull production and with Sir Robert McAlpine & Sons Ltd on concrete hull production. Gifford and Partners, in addition to their general work on structural and civil engineering aspects, have produced a report setting out their ideas on concrete hull production. Various general aspects of these studies are discussed here and fuller summaries are given in the section devoted to the Cockerell Rafts. However the original reports should be referred to for full details. The studies have looked at both the development of the hull design for production and at the process of construction and the type and layout of factory or facility required. These facets of production engineering must be considered together with the operational design requirements. Distinct designs in both steel and concrete have been developed for production in a capital intensive, highly mechanised and automated facility operating on production line principles. Outputs of up to 80 rafts per year have been considered - that is one raft every three (working) days. An interesting conclusion of the work on concrete hulls was that any particular hull design has an optimum rate of production determined by its breakdown into component sub assemblies. For instance the optimum rate for the concrete hull d e sign considered lay between 56 and 67 rafts a year. Thus a design optimised for production, must also be related to the total requirement for devices, the service life of the hull and the optimum pattern for installation at sea. In other words the hull design cannot be considered in isolation from the total system. However the development of this size of facility for the manufacture provides a unique opportunity to deploy mechanisation more widely than current best practice. This may mean the development of certain technologies beyond those available at present - for instance the automation of vertical welding is desirable at certain work stations. The basic technologies are in existence now, but the combination of various separate technologies is needed to provide the desired equipment. A facility costing £83 million to produce 80 rafts a year is envisaged. With this degree of capitalisation, the overall labour content is reduced to 5 man hours per tonne. This is very much lower than is achieved in any British Shipyards at present but comparable figures have been achieved in Swedish and Japanese yards. For instance, productivities in the range of 2 man hours per tonne have been achieved in Swedish yards on the double bottom structures of large tankers and 12-15 man hours per tonne for the overall hull, which includes the complex fore and aft structures. The employment of capital facilities 1n this manner shifts the dependency of the costs substantially away from labour costs to a situation where materials and equipment costs dominate the cost build ups. Precise estimation of manning levels in these circumstances is not important to the accuracy of the estimated costs. Since the economics of these kinds of facility are very dependent on high output, serious consideration must be given to questions of labour relations. The high interdependence of operations within the facility and the requirement for a steady deli very of materials and components does make such a factory prone to disruption. This can be mitigated to an extent by the provision of buffer storage at key points to take account of small disturbances to the even flow of work from whatever source. However, lessons drawn from current industrial problems may be misleading. The creation of a completely new industry or a green field site offers an opportunity for the careful structuring of work to provide incentive and job satisfaction and can avoid the problems arising from trade rivalries and inherited working practices. The present studies have established that the product ion technology is in effective use elsewhere in the world. It must be possible to make it work in Britain.