Structure
The structure of a WEC usually represents between 25-45% of the capital cost of a wave energy project consisting of a single device. In the majority of the cases, the structure is made of steel, as robustness and reliability are very important requirements for the device to survive in the hostile conditions of the sea. The survivability of the device is one of the main requirements, and at the same time one of the principal challenges, as they are supposed to function in very energetic sites with extreme conditions.
The structure of the device is very different depending on the type of the device, although there are some similarities between some devices. This fact simplifies the establishment of cost reduction opportunities for the structure of the device, as the WECs can be grouped together regarding the structure cost reduction potential.
The structure of the device is very different depending on the type of the device, although there are some similarities between some devices. This fact simplifies the establishment of cost reduction opportunities for the structure of the device, as the WECs can be grouped together regarding the structure cost reduction potential.
Pelamis structure. Source: Julie White Designs
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In the case of the Pelamis, the structure consists of four cylindrical steel sections plus a nose, with a total weight of 700 tonnes. The tubular sections are made of steel plates that are rolled forming a cylinder. This is not an automated process and therefore its manufacture is quite expensive. Moreover, each cylindrical sections needs an expensive protective coat in order to be able to survive ocean's conditions. All this process makes the structure quite expensive.
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Steel rolling process. Source: EPRI
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One of the principal cost reduction measure that is contemplated in most of the literature comes from alternative materials. Concrete (pretensioned concrete), for example, has been regarded as an alternative material for the construction of Pelamis, as it would reduce material and construction costs. However, lighter materials that at the same time can survive ocean's extreme conditions would be the best chance to approach cost reduction. Another possible material with great scope to reduce costs is GRP (filament ground composite). The cost of the structure could probably be more expensive, but the consequence in the installation procedures, mooring system and others, could significantly reduce the overall cost.
The report SI Ocean (2011) points that the Anaconda device is a possible example of structure cost reduction. The device is made of rubber, a cheaper material that at the same time combines the properties of the structure and the power take off. This material change involves a lighter structure, and therefore, a consequence on cost reduction of other figures. For example, a lighter structure means that the station keeping system needs less weight to stay in its place, and so the cost of anchors and cables can also be reduced. Moreover, the less weight of the device, the simpler the installation vessel can be. In conclusion, if the wave industry is able to find an alternative cheaper material such as rubber that at the same time can survive the ocean's hostile environment, this would mean a significant cost reduction in the overall cost of a wave energy project, and therefore, a greater chance of becoming viable. In the following video we can understand how the Anaconda device works.
The report SI Ocean (2011) points that the Anaconda device is a possible example of structure cost reduction. The device is made of rubber, a cheaper material that at the same time combines the properties of the structure and the power take off. This material change involves a lighter structure, and therefore, a consequence on cost reduction of other figures. For example, a lighter structure means that the station keeping system needs less weight to stay in its place, and so the cost of anchors and cables can also be reduced. Moreover, the less weight of the device, the simpler the installation vessel can be. In conclusion, if the wave industry is able to find an alternative cheaper material such as rubber that at the same time can survive the ocean's hostile environment, this would mean a significant cost reduction in the overall cost of a wave energy project, and therefore, a greater chance of becoming viable. In the following video we can understand how the Anaconda device works.
Futhermore, if the device manufacturers are able to automate the process and economies of scale are achieved when the first arrays appear, the cost of the structure will decrease substantially. However, these are longer term opportunities.
Other cost reduction opportunities will come from the hand of experience and innovation. As designers and manufacturers gain experience in the field, and the construction of wave energy devices become more usual, design margins will decrease so less material and cheaper components are used.
Other cost reduction opportunities will come from the hand of experience and innovation. As designers and manufacturers gain experience in the field, and the construction of wave energy devices become more usual, design margins will decrease so less material and cheaper components are used.