SeaKinetics has developed an innovative, tethered tidal and marine current energy converter known as the HydroWing, for the purpose of generating renewable, zero carbon emission energy.
SeaKinetics has developed an innovative, tethered tidal and marine current energy converter known as the HydroWing, for the purpose of generating renewable, zero carbon emission energy. The device is patented, and has been developed in an iterative process over five years.
The HydroWing is a marine current turbine power system which operates anchored, submerged at a variable depth, and is capable of operating in depths of up to 150 meters.
A power station or farm is composed of an array of HydroWings connected to an underwater power substation which acts as their hub to the ground grid link. Each individual HydroWing self-aligns to the flow and can be independently controlled to vary its depth according to the operating program in use.
For stability and balance, each HydroWing is equipped with a hydrofoil lifting surface which counteracts the downward pull created by the mooring cable acting against the drag forces created by the turbines generating power.
The key benefits of the HydroWing design concept are:
- Operates submerged at the most favourable depth in order to harvest an optimal amount of energy from the current.
- Access to virtually all of the economically significant tidal sites, due to ability to operate in deep waters.
- High load factors (40%) are feasible due to the controlled depth capability.
- Operating below the sea surface the HydroWing does not risk being destroyed by storms or wave action as wave loading is negligible.
- Given a typical operating depth of greater than 30 meters below sea level, the HydroWing Arrays will not present an obstruction or hazard to shipping.
- Debris including containers, logs and plastic bags tend to either float on the surface or sink. Operating below the surface means not risking these and other very real hazards.
- The Hybrid Hydrofoil Nozzle technology provides an effective means of achieving the lift that is essential for all submerged moored configurations thus enabling the turbines to operate in an optimal position in the current flow.
- The Hybrid Hydrofoil Nozzle technology also provides the Diffuser Augmentation action which accelerates water flow through the turbines providing more power per square meter of turbine surface area.
- The combination of Diffuser Augmentation and optimal placement in the current which is a unique feature of this design allows the HydroWing to operate also in slow current speeds (1.6 m/s TBC) which provides the opportunity to extract industrial quantities of power from ocean currents.
- High power to turbine size ratio due to the VASAF augmented nozzle configuration leads to low cost of energy.
- The Navionics package governs the HydroWing via hydroplane control surfaces and ballast trim tanks which provide the required stability and manoeuvrability.
- A multiplicity of cross-axial turbines are mounted on coupled counter-rotating shafts allowing them to share gearboxes and generators thus substantially reducing costs and simplifying maintenance.
- This modular system allows for the HydroWing to be scaled up in size to create a power generators potentially larger than horizontal axis turbines systems.
- The tethered configuration provides self aligning capabilities which considerably simplify the system by eliminating the need for yaw control.
- As the tidal stream reverses the HydroWing is designed to manoeuvre by drawing power from the grid to operate its turbines. It can thus be brought to its new position in a controlled operation, ensuring that the mooring cables do not get caught up on themselves or on obstacles.
- The cross-axial configuration adopted by the HydroWing allows for faster shaft speeds thus reducing gearbox size, complexity, and cost. Reliability also increases and thus maintenance costs and downtime are reduced.
- Ease of deployment and installation.
- On site maintenance leading to reduced downtime
An actual power plant configuration will be made up of an array of identical HydroWing units sharing the ground-link between national grid and seaside substation, in the same way off shore wind farms are configured.
A marine energy farm based on an array of identical elements enables the farm to capture economy of scale in two ways:
- transmission of power produced through a common ground link;
- modular construction of array elements.
Elements of the array may differ in minor details, specifically in tether-line length, if the channel depth varies substantially. However, all other aspects are common to all elements.
UK tidal resources have been independently assessed showing that two areas of particular interest are located in Scotland and in the Channel Islands. Both areas are characterized by strong currents and deep waters, ideal conditions for the HydroWing. Several sites are present in both these areas so that further scale economies may be achieved as maintenance infrastructure can by shared among nearby sites.