Wave Power: Spotlight on Ocean Power Delivery Ltd
We're very excited about the potential of wave power to provide lots of clean energy (if you have missed Timothy's reference post on the subject, check it out) and think it should get a lot more attention and funding. Today we're going to take a closer look at Ocean Power Delivery Ltd's P1A buoy system (no, that's not a bullet train on the picture above): To better understand how they operate, check out this animated model (flash required). Just pick "top" or "side" view and then hit "play".
From the official website:
Ocean Power Delivery Ltd has developed a novel offshore wave energy converter called Pelamis. Building on technology developed for the offshore industry, the Pelamis has a similar output to a modern wind turbine. The first fullscale pre-production prototype has been built and is being tested at the European Marine Energy Centre in Orkney.
It is anticipated that future `wave farm' projects would consist of an arrangement of interlinked multi-machines connected to shore by a single subsea cable. A typical 30MW installation would occupy a square kilometre of ocean and provide sufficient electricity for 20,000 homes. Twenty of these farms could power a city such as Edinburgh.
You can see some videos of the installation, testing and operation of the buoys here.
The Pelamis is a semi-submerged, articulated structure composed of cylindrical sections linked by hinged joints. The wave-induced motion of these joints is resisted by hydraulic rams, which pump high-pressure oil through hydraulic motors via smoothing accumulators. The hydraulic motors drive electrical generators to produce electricity. Power from all the joints is fed down a single umbilical cable to a junction on the sea bed. Several devices can be connected together and linked to shore through a single seabed cable.
To learn more about production and development, have a look at this page.
Wave power is currently a largely untapped resource but is the most concentrated form of renewable energy. In the UK for example, the total wave resource is equivalent to 2-3 times current electricity demand. Just 5% of this resource could provide a similar generation capacity to that of the nuclear industry.
Maximum individual component weight is less than 3 tonnes to allow replacement using light lifting equipment. The wave-induced motion of each joint is resisted by sets of hydraulic rams configured as pumps. These pump hydraulic fluid into smoothing accumulators which then drain at a constant rate through a hydraulic motor coupled to an electrical generator. The accumultors are sized to allow continuous, smooth output across wave groups. Output smoothness from the complete device will be comparable with that of a conventional thermal generator set. An oil-to-water heat exchanger is included to dump excess power in large seas and provide the necessary thermal load in the event of loss of the grid. Overall power conversion efficiency ranges from around 70% at low power levels to over 80% at full capacity. [...]::Ocean Power Delivery, via ::Dr. Octopus' freakingly huge new arms, or alternate energy source?
Waves produce a widely variable power input, as illustrated, for a single hinged joint. The Pelamis stores energy in hydraulic accumulators to even out this unsteady input and provide a smooth flow of fluid to the variable displacement drive motor, and a steady power output from the machine's generators.