Following trials, further MRC units will be added to create the first commercial array. Focused on survival and reliability, the system is designed to meet international marine standard – DNV OSS-312.
So how does it work? The MRC consists of three independent oscillating water column (OWC) chambers that have the same cross-sectional area but different lengths. This allows the device to maximise energy extraction from any sea state as the buoy responds to a broader wave spectrum. Indeed, the MRC can capture significantly more energy per year than single chamber designs.
Waves rising and falling within the chambers act like pistons and alternately drive and suck the air trapped in the chambers backwards and forward through the air turbine, which is directly coupled to a generator. The electrical power produced is fully compatible with the electrical grid. The final stage passes the power through a step-up transformer that increases the voltage to 33 kV in order to minimise losses in the shore connection cable.
The control system in the MRC automatically optimises power extraction and reacts to the constantly changing wave environment. Orecon uses a unique tension mooring system, which means that the equipment remains stationary in the water and does not "bob up and down" in response to waves. This increases power capture by more than 90% compared to conventionally catenary moored devices, which are held by long mooring lines with one end partially resting on the seabed. More importantly, the MRC has little impact on its environment because there are no moving parts in contact with the water; this also reduces the need for heavy maintenance schedules and specialist support vessels.
According to Orecon's engineering director Fraser Johnson, the cost of power produced will be about 7.5 pence /kWhr (roughly $0.15 /kWhr). Projected costs for large arrays are compatible with those for offshore wind but Orecon’s capacity factor is higher, he said.
Finally, a power cable on the sea floor will bring power ashore and connect to the UK’s national grid, explains Johnson. The beauty of the system is that it requires no secondary sub-sea or surface platform "booster" station because the buoy is large enough to carry all the equipment needed. Arrays will use a "master" buoy which will collect the power from neighbouring buoys, transmitting it to the shore via a single cable.
And that's not all: the power conversion system onboard will not only deliver active power (that is, in kW), but reactive power (in kvar) too. Reactive power is used to support the grid and can be delivered irrespective of the state of the ocean – even in calm conditions.
The company says it is looking for multi-megawatt array opportunities and is actively seeking partners to achieve this. "We believe that the true impact of wave energy will not be realised until large scale deployments are underway," said Orecon chief executive officer David Crisp. "This is a fantastic opportunity to bring skilled employment to the UK and ensure that our nation continues to lead this massive market worldwide."
A syndicate of international venture capitalists has invested a total of £12.25 million in Orecon this year; the company ultimately hopes to build and install MRC buoys in the UK and worldwide.