A wave energy device being tested in Orkney has managed the highest sustained output in the world amid bad storm conditions, its manufacturer has revealed.
Aquamarine Power released performance figures for the Oyster 800 device as the unit was shut down for improvements at at the European Marine Energy Centre (EMEC) in Orkney.
The Oyster 800 has been operating since February and generated 10MWh in 144 hours of operation. On April 29, the device generated 1MWh in five hours on just one of its two cylinders.
Aquamarine said it was thought to be the highest sustained power output of any wave energy machine in the world.
Over the summer, the company plans to carry out work in five specific areas with a view to improving overall performance, reliability, and availability of the nearshore wave technology.
Aquamarine Power chief executive Martin McAdam said: “Since the Oyster 800 flap was raised from the seabed on February 14 this year, we have learned a tremendous amount about how Oyster operates in real sea conditions.
“This year the Oyster 800 has been operational in significant wave heights of 5.3 metres* and peak waves of 9 metres. The concept works, and our onshore hydroelectric plant is operating well. The Oyster 800 structure has performed well in the most arduous storm conditions.
“We are now starting to see some very promising power production figures – including sustained generation of 1MWh in a five hour period. Normally the system operates on two power production cylinders, but since February Oyster 800 has been operating on only one functioning cylinder – a capability we included in the original design – which makes the figures even more encouraging.”
Mr McAdam said although the device operated intermittently during the 2012 summer, the initial challenges and commissioning difficulties resulted in minimal electrical output. Therefore this year was the first time it has generated significant power and operating data.
“We have been as open as we can about the challenges we face, particularly in this hostile offshore environment,” he said.
“Many components, including control and instrumentation cable connectors, hydraulic hoses, non-return valves and accumulators have performed much less reliably than expected.
“For example, Oyster uses four non-return valves on each of its two hydraulic cylinder modules.
“As part of the Oyster 800 test programme we installed four from one manufacturer on one cylinder and four from a different manufacturer on the other cylinder.
“Whilst the valves on one cylinder have operated perfectly since installation, the other set of non-return valves failed from the outset.
We’ve spent time with the manufacturer of the failed valves to understand the failure and design upgraded valve components. This way we are both learning, and developing expertise within the supply chain. It is a similar story with our hydraulic hoses, accumulators and control and instrumentation systems.”
Mr McAdam said most of the component that failed are used regularly in the deep water offshore oil and gas industry. However, they failed in the “highly turbulent, highly oxygenated nearshore wave environment”.
“We are now working with the supply chain and are testing new components. Already we have redesigned many of them to cope with these conditions,” he said.