Share reportPower Take Off
This programme supported a wide range of Power-Take Off systems that each proposed a step change in the capital cost and/or efficiency/performance over current technology.
Lead contractor
Ecosse Subsea Systems Ltd
Sub-contractor(s)
Pure Marine Gen Ltd
Supply Design Ltd
Bathwick Electrical Design Ltd
University of Edinburgh
Applied Renewables Research
Overview
The PECMAG PTO system is a modular all-electric system with magnetic gearing that has been developed to suit a variety of WEC devices, offering both rotary and linear actuator systems. The PECMAG linear to rotary magnetic gearing system offers a wide speed range, long stroke length, high efficiency, overload survival and complex software control in a single compelling package. Medium scale prototypes of PECMAG systems have been manufactured and bench tested – with measurements confirming the high conversion efficiency performance figures expected from the contactless gear system. The PECMAG prototypes have been developed with input from WEC developers, which has resulted in a thorough understanding and refinement of the PECMAG technology. Advanced studies and component testing have identified areas where performance and manufacturability improvements can be realised.
The PECMAG system comprises a magnetic gear and permanent magnet generator coupled to an integrated electronic rectifier and control system. It is a contactless gear system and produces electro-mechanical conversion efficiencies greater than 80% across a wide range of speeds. The PECMAG embodies a novel slip mechanism, which provides a failsafe to damage to the PTO system from overload conditions. The ability to overcome overload conditions, re-engage quickly and continue to operate without long term degradation in performance provides advantages that are potentially game-changing in terms of meeting availability targets and mitigating key risks to survivability that have hampered the development of wave energy to date.
Stage 1
June 2017
The feasibility study outputs from the design, analysis, numerical modelling and bench testing of vital components has helped to quantify and demonstrate the fundamental advantages of the PECMAG PTO system. These results highlight how the PECMAG system can help the industry improve upon critical performance metrics required to meet the LCOE targets set for wave energy. The key findings were generated from the result of modelling a variety of sea states, magnetic gear and power converter designs and configurations. The work unearthed a variety of design options, showcasing the PECMAG flexibility, which can be tailored to different systems and conditions to improve overall WEC performance.
Stage 2
July 2018
This project focused on the design, construction and performance testing of a linear system with a force capacity of 30kN and a stroke of 0.5m. The test rig consisted of a motor driving a generator through a linear magnetic gear. The motor drives a magnetic gear which surrounded a threaded round iron bar. The generator is driven by its own magnetic gear which surrounds the same iron bar. It is therefore possible to use the motor to rotate the magnetic gear so that the threaded bar moves. The moving bar in turn rotates the generator through its magnetic gear. If required, it is possible to use both machines as motors so that the combined axial force results in a rig which could produce a force up to about 6.5‐7 tonnes. This means that the existing test unit can be used for commissioning other PECMAG units developed for prototype sea trials. The 30kN prototype constructed for the Stage 2 project fits a space envelope of 1.2m diameter by 1.75m long. The large, open design is due to the back to back configuration, requirement for access, modularity and torque measurement. A real machine of the same rating would be the same length and about 0.5 to 0.6m.
Stage 3
April 2021
The activities in this project stage included designing and manufacturing a 10kW PECMAG. This system was then tested on both a bench test rig and a simple wet testing platform to acquire quantitative and qualitative data on the performance of the PTO system.
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About Wave Energy Scotland
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