Snapper is a new magnet based wave conversion power system appropriate for deployment in near and off-shore environments.
The intention is to develop a low cost, high efficiency linear generator for marine wave energy extraction. The device works like a typical linear generator in which a set of magnets mounted in a translator is moved up and down inside multiple coils of wire of an armature.
The concept of the Snapper electrical generator arose during attempts to overcome a fundamental difficulty of wave power generation.
The inventor, Ed Spooner has previously worked in the development of direct-drive (gearless) generators for wind turbines and tidal power turbines. However, wave power systems present a much more difficult challenge. Electrical generators produce power as a result of the movement of an applied force. The size, weight and cost are all related to the magnitude of the force but the power is related to speed as well. Sea waves have very low vertical velocities but can produce very high forces and so normal types of electrical generator would be very heavy, expensive and inefficient.
Wind turbines can use a gearbox to increase the speed and reduce the torque. However, this solution is difficult to apply in wave power systems because the force is reciprocating rather than rotating and the machinery is inaccessible and subjected so very severe forces during storms.
Instead a new approach was conceived where the continuous slow movement of the wave power machine is divided into a sequence of rapid bursts. The maximum force applied during each burst is well defined according to maximum force that can be transmitted by a coupling. Varying drive speeds are accommodated by the variation in the delay between bursts of motion.
The diagram illustrates an example of how slow continuous motion giving a total movement of 2m can be subdivided into a set of short bursts. It is analogous to a common electronic technique for converting power in the form of low current at high voltage to high current at low voltage.
Energy must be stored during the waiting periods. The Snapper machine uses a spring and a magnetic coupling in the force transmission path. As the applied force increases, the spring stretches and stores energy. When the force exceeds a certain threshold the magnetic coupling can no longer transmit the force and it snaps allowing the energy stored in the spring to be released quickly and efficiently.
The overarching objective of the Snapper project is to develop a new prototype wave energy capture and conversion system, appropriate for deployment in near and offshore environments.
Other objectives of the project are:
1. To create an understanding of the hydrodynamic and electrical machine characteristics that will define the Snapper design.
2. To provide a low friction interface between the moving parts of the electrical generator.
3. To achieve design robustness and a device that is environmentally benign with suitable environmental protection.
4. To achieve a system that can be grid connected.
WP1 - Simulation Environment
Development of a robust and detailed simulation environment of electrical machine characteristics and its hydrodynamic interface in real sea conditions. For use throughout the lifetime of the Snapper project including the assessment of design decisions in a cost effective and rigorous manner.
WP2 - Mechanical & Subsea Engineering
Design and build of the individual mechanical and marine components for validation. This will be the entire marine and mechanical assembly required to house the electrical generator components, and incorporates the float and sea bed interface.
WP3 - Electronic & Electrical Engineering
Design and build of the electromagnetic and power conditioning aspects within the Snapper device, to generate electricity and enable Snapper to be connected to a grid supply.
WP4 - Dry Validation
Dry test and evaluation of the Snapper generator on a linear test rig which simulates marine field conditions within a dry environment. This will validate the performance against technical objectives such as the electrical grid connection.
WP5 - Wet Validation
Assess the function and integration of the generator when tested in a wet marine environment. This will validate performance against technical objectives including: the low friction interface; the device robustness; and the environmental considerations.
WP6 - Consortium Management
To coordinate the management of the project taking into account Consortium meetings to discuss progress and permit a decision-making process. Additionally, Consortium Management involves formal administration responsibilities, report submissions and the management of IPR.
WP7 - Dissemination & Exploitation
Development of an Exploitation Strategy which will become a firm Business Plan including routes to market for all project results. Additionally, opportunities for financing of post-project development work will be identified along with the development of a Dissemination Strategy that will enable protection and widespread publication of the project results.
© Snapper 2010
For more information:
Please contact Pamela Robson
(Narec), Eddie Ferguson House
Ridley Street, Blyth, Northumberland, NE24 3AG