Edinburgh-based Pelamis Wave Power Ltd (PWP) is the manufacturer of the Pelamis Wave Energy Converter (named after a surface-swimming sea snake), a unique system to generate renewable electricity to the grid from offshore wave energy.
The Pelamis machine brings together a series of modules - accumulators, transformer and associated switchgear - for harnessing wave energy. The accumulators store and smooth the fluctuating energy absorbed from waves to allow Pelamis to generate at a steady, continuous rate. The transformer then steps up the generating voltage of 690V to the current export voltage of 6.6kV. To guarantee continual energy generation it is critical to maintain communication with the machine at all times whilst at sea.
Pelamis needed multiple communication paths with redundancy built in to maintain the safety and integrity of the machine in extreme conditions. The Pelamis machine operates three separate channels of communication with the control room which is located on shore. Fibre optics carries the primary high-bandwidth transmissions along the machine-to-shore umbilical, whilst a high-bandwidth radio/WiFi link provides a second channel of communication. The third system delivers a low-bandwidth backup communications channel via narrowband UHF radio. “This needs to be very reliable,” explains Graham Garmeson, Software Engineer, Pelamis Wave Power. “The ability to operate low-level communications with the machine, through a radio link, enables both monitoring and sending of supervisory commands, such as system reboots, should high-bandwidth communication be lost.”
PWP used Wood & Douglas’ Sentinel ER450 UHF radio modem to deliver radio failover for the Pelamis machine. The Sentinel ER450 is a digital data radio, designed for data transmission applications within SCADA systems. The ER450 radio supports Point-to-Point and Point-to-Multi-Point operation and is housed in a compact die-cast enclosure, rugged enough to meet PWP’s demanding requirements.
The ER450 includes a comprehensive network management system (NMS) requiring no operational break in the SCADA data flow and is capable of running remote self diagnostics. This means that telemetry links to the Pelamis machine are consistent and always available.
Sentinel ER450’s RF output (up to 5W) is more than powerful enough to communicate with a shore-based directional antenna some 6km from the machines’ offshore anchorage, transmitting and receiving regular reports of the machines’ temperature, oil and voltage levels.
In 2010, E.ON UK deployed and tested the first P2 Pelamis generator west of the Orkney Mainland, representing the UK's first commercial supply contract within the marine energy sector. Max Carcas, Business Development Director, Pelamis Wave Power, says “We intend the P2 to be the workhorse for multi-machine wave farms. With larger-scale deployments the increasingly complex communications links will need to be robust, reliable, and maintainable.”
Pelamis machines in the physically challenging maritime environment rely heavily on radio communication for their survivability and economic efficiency, which is why the Sentinel ER450 was the choice for a range of monitoring and control systems on this next-generation machine.
- Monitoring and control via low-bandwidth UHF radio
- Radio failover with Point-to-Point and Point-to-Multi-Point operation
- Rugged, reliable construction for marine environments