Power Take Off
The power take off (PTO) systems covers around a 25% of the capital cost of a single wave device project. This varies significantly from one device to another, as depending on the type of the device, the power conversion system is different. Wave energy conversion is usually performed through hydraulic systems, linear generators, air turbines, or hydraulic turbines.
In the case of the Pelamis device, the power take off systems consists of three power conversion modules, each rated at 250kW. The cost of each of this modules is around 450,000€, constituting one of the main costs of the device.
In the case of the Pelamis device, the power take off systems consists of three power conversion modules, each rated at 250kW. The cost of each of this modules is around 450,000€, constituting one of the main costs of the device.
Power take off system of Pelamis. Source: Interesting Engineering
Generally, hydraulic systems are the most commonly used, but linear generators are now under investigation. As experience is gained, the efficiency of the systems will improve and at the same time, components of the PTO systems will become cheaper. Moreover, turbines for power take off in oscillating water column (OWC) devices for example, are now increasing its efficiency, improving the yield in recent devices compared to their predecessors.
Carbon Trust (2011) stated that other improvements are possible through changes on the design of the device itself, specifically by a better coupling with the sea. Maximising the energy extraction from a specific device is a key area of focus for wave developers. The main opportunity resides in increasing the capacity factor by operating much closer to their generating capacity. Some WEC's can improve their energy capture without changes in the structure, for example by changing control systems.
There are more sophisticated control systems under development that are able to forecast the characteristics of the waves allowing a better performance of the device. Although these improved systems are more expensive, they are a big opportunity to increase in yield and improve the performance of the device, resulting on a major energy production and a lower overall cost.
However, investment in the investigation and innovation of new PTO and control systems appears to be the only way to approach cost reduction of these systems.
Carbon Trust (2011) stated that other improvements are possible through changes on the design of the device itself, specifically by a better coupling with the sea. Maximising the energy extraction from a specific device is a key area of focus for wave developers. The main opportunity resides in increasing the capacity factor by operating much closer to their generating capacity. Some WEC's can improve their energy capture without changes in the structure, for example by changing control systems.
There are more sophisticated control systems under development that are able to forecast the characteristics of the waves allowing a better performance of the device. Although these improved systems are more expensive, they are a big opportunity to increase in yield and improve the performance of the device, resulting on a major energy production and a lower overall cost.
However, investment in the investigation and innovation of new PTO and control systems appears to be the only way to approach cost reduction of these systems.