K Controls sub-sea valve position monitors have been specified for use Aquamarine Power’s Oyster wave energy device that captures energy in near shore waves and converts it into clean sustainable electricity. The valves will control the flow of the high pressure water that is generated by the movement of the wave flap and associated hydraulic pistons and then moved onshore, via a pipeline, to drive a conventional hydro-electric turbine. Low pressure pipes will transport the water back from the hydroelectric power station to the wave energy device.
There are a number of important application requirements:
- The position monitors have to be capable of being installed and commissioned sub-sea.
- They must be rated for continuous submersion at 15 metres depth.
- The feedback limits must be adjustable sub-sea and in such a way that dive times are minimised.
- Subsea connectors must meet an existing standard.
- Status indication must be provided and be visible to a diver.
- Extended life and reliability is required.
K Controls has been able to meet these requirements using a unit rated for submersion to a depth of 130 metres that has been widely used in the oil industry.
It meets all of the clients requirements and can be calibrated remotely using the HART® protocol without diver intervention.
The field proven sub-sea position monitor has been used on applications that include:
- Monitoring the position of hydraulically actuated valves that flood the jackets on the legs of oil rigs during satellite guided positioning.
- Monitoring the position of failsafe valves on conventional tanker buoy mooring systems.
- Monitoring the position of valves in the ballast tanks of semi-submersible oil rigs.
Wave energy devices are important because the central aim of UK Government energy policy is to establish a supply of energy that is diverse, sustainable, secure and competitively priced. Ocean waves represent our planet's last untapped natural renewable energy resource. The energy contained within waves has the potential to produce up to 80,000TWh of electricity per year - sufficient to meet global energy demand five times over. Wave energy is, by its nature, a clean energy resource. Aside from the energy expended in manufacture and installation of wave energy devices, it produces no carbon emissions. In the future, subsea pipelines will connect multiple wave energy devices to a single onshore plant creating wave farms of several hundred connected devices generating hundreds of megawatts of electricity. The devices sit largely underwater so there is minimal visual impact.
There is also a link between wave energy and desalination - the process of removing salt from water to produce freshwater. Energy fuelled by diesel generators is currently used to pump high pressure saltwater over special membranes to produce freshwater. A wave energy device offers a cleaner, more cost-effective solution. It could be configured to produce high pressure saltwater direct to a desalination plant, without the need for any fossil fuels.