The group has held a successful progress meeting with the project sponsors (OPT and Converteam). The sponsors were able to give the group an overview of their companies and the team presented the results of their research.
At the heart of this research was a comparison matrix of all of the topologies identified by the group. The group recieved feedback on this comparison and the final version is available here.
The group's slides from the meeting are also available here.
A summary of the meeting are given below:-
Meeting 11th Nov 08, 09:00h-11:00h:
Dr Chris Newton, Stuart Bower, Ross Gemmell, Mark James, Rob Potter, Nick Virgo, Sam Marshall Kevin Manktelow, Annette Muetze
The group should not place too much significance on getting the very highest efficiency from the system, but focus more so on manufacturing, reliability and survivability as previously agreed. The following topics were discussed:
- Goal of product design: 3 years maintenance free.
- Grey art, using WAMIT package for hydrodynamics, Orchaflex for mooring.
- Done by specialist with a lot of experience.
- Think in terms of water displaced ⇒ thrust developed ⇒ what happens if an external force is applied: keep these few relationships simple and play with mass, stroke, etc… Control how deep the float gets immersed into the water. Also consider momentum to avoid risk of wave running over the float.
- Not as developed as rotary generator.
- Low speed ⇒ low induced voltage ⇒ need more copper ⇒ reduced efficiency.
- Electromagnetic energy conversion only happens in the zone of overlap: much of the generator is unused.
- Induction generator: end-effects.
- Relevant designs:
- Linear point absorber.
- Sprung mass point absorber.
- Angled point absorber
- Description: high torque and low rotation speed directly driving a rotary generator through part of a rotation.
- Efficient reduced due to the change in inertia.
- The drive must work well for a spectrum of waves ⇒ the drive must work well under a range of rotational angles ⇒ limited energy output.
- Relevant designs:
- Crank Converter
- Sprung mass/pendulum point absorber
- Pendulum and buoy
- Star Design.
Rank and Pinion
- OPT are testing rack and pinion designs in both Orkney and Oregon.
- Use of bio oil for lubrication (degradable). Containment of oil to reduce possibility of leakage.
- Good scope for multiple smaller power take-offs as the stress becomes very significant for larger drives.
- Consider corrosion and again: storm survival strategy.
- Investigate maintenance and survivability with a variable head/flow.
- Induction machines: (-) large, (+) better survivability.
- Permanent magnet system: (+) high efficiency, (-) when free running the high speed can damage the generator.
- The successful designs need to be costed.
- Look for potential cross over technology between different industries; this will provide more developed and cheaper technology.
- Group to quantify comparison matrix.
- Steel prices (incl. labour) to be provided by sponsor (orders of magnitudes, confidential information).
- To come back to sponsors with three to five winner designs to discuss these in more detail.
- Avoid going down one route (one design) too early.