Trident Energy is developing a simple wave energy system, the Direct Energy Conversion Method (DEMC) that uses the up and down motion of a buoy to cause a magnetic translator to move up and down along a coil to generating electricity. The small British company based in Southend-on-Sea has tested a 1/5th scale model in a large wave tank and results indicate that a full scale model should be able to produce 100 kW. The generators would be attached to a stationary platform in the ocean and buoys located below the platform would move with wave action. A linear generator, which consists of an electrical coil, attached to the buoy, and a translator, consisting of a stack of magnets which would move up and down past the coil in a housing attached to the platform, generating an alternating electrical current. No mechanical devices that are frequently used in wave generators to translate the wave motion to the rotary motion needed drive a conventional generator are required, thus greatly simplifying the units.
The feasibility of DECM's and the anticipated advantages and problems were the subject of a study by the University of Durham, which is refererenced below. They concluded that
- a permanent magnet translator was desirable
- that the motor chamber did not necessarily have to be sealed
- the units must be installed in clusters (not single units), of at least four, in order to obtain a smooth electrical output
- the efficiency of the system is likely to be higher than hydraulic systems
- the system could be maintenance free
- the basis for a control system was outlined
The DECM's would be self protected against stormy conditions. This is achieved by having a sensor that could detect storm conditions which would change the mode of the equipment from generators to motors. The (now) linear motors would lift the floats out of the sea into protective chambers, where they would be held until the storm or adverse wave condition had passed.
Following extended research, Trident Energy has been able to obtain energy conversion rates among the highest for any known marine energy device. Trident is planning to build four full size generators as their next step. They hope to test these generators at the European Marine Energy Centre in Orkney by the end of 2007.
The founder of Trident Energy Ltd, Hugh-Peter Kelly, is also the inventor of the Tubular Linear Motor / Generator that is being adapted for the wave generator. This is an internationally established product and was invented by him in the early 1980’s for use in the automation industry. (There are over 32,000 motors of this type in use world wide and a further 15,000 actuators.)
This sounds like a great idea, fairly obvious once it is explained. A long way to go before commercialization. I wish them luck. I hope they do not limit themselves to 100kW generators.
Site revised 10/16/05 based on information obtained from website.
Trident Energy, Southend-on-Sea, UK
"Comparative Study of Linear Generators and Hydraulic Systems for Wave Energy Conversion", University of Durham, 2001
"Swell magnet strokes support for wave power", News-Nature.com, 10/11/05