1.4 MW Buoy: In this format the buoy would be installed with 8 200kW Aegir Dynamo's and produce enough energy for around 2,000 homes, it will only be approx 9-12 meters in diameter (depending on the prevailing wave conditions) and have a manufactured mass of approx 65 tonnes. Importantly it would also produce its maximum rated output (1.4MW or 1400kW) in the average sea state in UK coastal waters of 2.5 meters.
The manufacture of the 1.4MW buoy is the long term goal of Ocean Navitas. In this format the technology will be of a sufficient scale to perform at it's optimum mass to power output ratio, thus providing a cheaper price per kW of electricity generated.
Wave Farms
Due to the high initial investment involved in offshore installations, predominantly the manufacture and laying of sub-sea cable, it is obviously more cost effective to install the buoys in arrays of multiple devices, often referred to as 'farms', that can be linked together and use the same cable to transfer the power back to shore.
Both the 200kW and 1.4MW buoys can be deployed in this manner, however it is the larger 1.4MW buoys that have been expressly designed with this in mind. A linked dynamic mooring system, together with the smaller size of Ocean Navitas' devices compared to other designs, will mean that not only will the eventual cost per kW be reduced, but the amount of sea area required to produce 'X' amount of power will be smaller. An important consideration, not only in-terms of environmental/navigational impact, but also as the sea bed is likely to leased at a premium as the popularity of offshore power generations increases.
Maintenance & Survivability
As all components of the Aegir Dynamo are manufactured to British Standards that have a predetermined wear and life-cycle, maintenance schedules to be accurately calculated. The buoys will be fitted with sensors that will relay any problem to shore via fibre optic cable, will require inspection every six months, minor maintenance at six monthly intervals (replacements of seals and cathodic protection etc) and will have a minimum life in excess of 20 years - far in excess of their pay back period. The buoys have been designed so that the Aegir Dynamo modules can craned out of the buoys whilst still at anchor and maintained on a vessel, thus removing the need for expensive re mooring and removal.
Survivability at sea is a major concern for all offshore devices and installations. The marine environment is one of the most inhospitable on earth, however these problem are not insurmountable with a correctly engineered solution. It is worth remembering that the oil and gas industry have been working off-shore for decades and navigational buoys have been moored offshore for far longer than that.
Ocean Navitas buoy designs will utilise a dynamic mooring system to secure the devices to the sea bed (similar to those used by the oil and gas industry to keep vessels in a stationary position above sub-sea installations). Should a device be struck by a large storm wave the moving parts are designed to lock (effectively creating a solid object), the device will be swamped by the wave and return to the surface when the wave has passed due to it's buoyancy.
In the event of a collision at sea the buoyancy chamber (the cylindrical component marked in orange above, which would likely be the point of contact in any collision) is constructed with internal chambers. Should it be 'holed' then this chamber would flood, but the device as a whole would remain afloat until it could be retrieved for repair.
Risks to Navigation
Members of the Ocean Navitas team are often asked by yachtsmen and commercial sailors about the hazard to shipping, and although this is a risk, it can be mitigated with the correct planning and procedures. A wave farm or even a single buoy would never be deployed in a shipping lane, or any other area of heavy traffic, not only from a common sense perspective, but also as consent would not be given by the relevant government agencies during planning.
All devices will be painted in high visibility colours, fitted with the appropriate marine warning lights and emit a radar signal. This together with marking on marine navigational charts should prevent collision.
Environmental Impact
Wave energy converters are one of the most environmentally benign forms renewable energy generation. As a point attenuating buoy is largely submerged the visual impact is minimal (a maximum of 5 meters above the surface at full 1.4MW scale) and devices are not visible to the naked eye from shore when placed 1 kilometre or more (Navigational regulations require devices to be fitted with flashing lights visible for 2 kilometres at night).
When in operation the main noise created by an Aegir Dynamo is the sound of the waves impacting on the structure and a wurring noise from the energy converter. In practice this is quieter than a diesel generator. This is expected to have no effect to underwater wildlife.
Aegir Dynamo buoys are designed to ‘ride’ waves (rise and fall with the swell) rather than to directly take energy out of the wave and reduce the wave height at the lee of the device, thus having little impact on the wave energy that impacts on the shore.
The dynamic mooring system uses clump weight anchors and will cause some damage to the sea bed during installation, this will however be superficial, and as the devices are designed to stay in situ for a number of years and damage to living organisms will quickly repair and the clump weights are expected become home to an increased number of urchins and fish species. The clump weights can be left in place on decommissioning so as not to disturb the new habitat.
The effect to marine life is expected to be positive in the long term as fish are known to congregate around floating structures (man made or artificial), and a significant array of devices would cover a sufficient area to prevent fishing/trawling, and therefore provide a 'safe haven' where stocks can replenish and eventually spill over into areas that can be fished.
Carbon Emissions & Reductions.
As an Aegir Dynamo does not rely on combustion to produce energy, or produce any bi-product other then electrical energy, no gasses are produced during it's operation.
By producing energy in this way rather than by burning fossil fuels actually reduces emissions. It is estimated that every kW of energy produced by fossil fuels produces 0.43Kg of CO2. It can therefore be calculated that each 200kW buoy generating at full capacity 80% of the time will save over 600 tonnes of CO2 being released into the atmosphere every year, and a single 1.4MW buoy would reduce carbon emissions by over 4000 tonnes.
