|The Pelamis Wave Energy Converter
GE’s Technology Lending is providing capital to Ocean Power Delivery, Ltd. (OPD), developer of the world’s first commercial facility that will generate electricity from offshore ocean waves. The transaction, made in conjunction with GE Energy Financial Services, extends a loan facility of $2.6 million (£1.5 million) to UK-based OPD.
Additionally, GE is taking an equity position as part of OPD’s $22.5 million (£13 million) equity financing as OPD prepares to deliver on its first commercial contract for a wave power farm.
OPD developed the Pelamis Wave Energy Converter, which generates 750 kW of electricity from offshore wave motion. In early 2005, OPD announced the signing of an order with a consortium, led by Enersis, to build the initial phase of the world’s first commercial wave-farm at a site 5km off the coast of northern Portugal.
The first stage consists of three 750kW Pelamis machines with a combined rating of 2.25MW. A letter of intent has also been issued to order a further 28 Pelamis machines before the end of 2006. When complete, the eventual 22.5MW project is expected to meet the average electricity demand of more than 15,000 Portuguese households while displacing more than 60,000 tonnes per year of carbon dioxide emissions from conventional generation using fossil fuels.
|Pelamis Power Conversion Module
The Pelamis is a semi-submerged, articulated structure composed of four cylindrical sections linked by hinged joints, at each of which is placed a Power Conversion Module, each rated at 250 kW. The Pelamis, which is 120-meters long and 3.5-meters in diameter, swings head-on into incident waves.
Each of the three Power Conversion Modules resists the wave-induced motion of the joints with four hydraulic rams—two for heave (horizontal axis), two for sway (vertical axis). The rams pump high-pressure oil through hydraulic motors via smoothing accumulators.
|Placement of the Power Conversion Modules
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.
The Pelamis uses a novel joint configuration to induce a tuneable, cross-coupled resonant response, which greatly increases power capture in small seas. Control of the restraint applied to the joints allows this resonant response to be “turned-up” in small seas where capture efficiency must be maximized or “turned-down” to limit loads and motions in survival conditions.
A proprietary mooring system comprising a combination of floats and weights which prevent the mooring cables becoming taut holds the machine in position. The mooring system maintains enough resistance to keep the Pelamis positioned but allows the machine to swing head on to oncoming waves.