SR250 Technology

Turbine

The intermediate full-scale 250kW prototype comprises a 33m long steel tube with a 2.3m diameter. The SR250 encompasses all the design features of future commercial devices. Fixed-pitch rotor blades minimise the number of moving parts in the system and increase reliability. The counter-rotating rotors each have a diameter of 8m, and drive separate gearboxes and variable-speed electrical generators within sub-surface nacelles. The generator power is then transmitted via cable to the hull for power-conditioning through Variable Speed Drives. A transformer then steps up the voltage to 6.6kV for export to shore via a wet-mate electrical connector and subsea cable. The vast majority of equipment including control system, hydraulic power packs, drives, transformers and switchgear are located within the main hull tube which allows for easy access at harbourside and in the future, onsite. 

Mooring System

The mooring system is a critical underpinning technology for the future success of floating marine energy converters. Scotrenewables Tidal Power Limited has developed an innovative and unique single point catenary mooring system with a patented mooring turret system designed for rapid mechanical and electrical connection and disconnection. This mooring system allows the device to self-orientate in the tidal flow and is a key element in the overall system.

The catenerary mooring system has a high degree of elasticity; which in turn increases the survivability of the device, whilst keeping the cost of manufacture and installation time down.  It should be noted that the majority of existing tidal energy designs, are either seabed mounted (which requires expensive installation equipment, and limits the access to the device for maintenance), or are fixed to pile structures (which are expensive to install, and construct).

All installation and retrieval operations can be carried out using a small multi-cat type vessel, eliminating the need for very large and expensive vessels such as jack-ups, anchor handlers or DP vessels. The SR250's low draft in the transport mode eliminates the need for large-scale facilities to maintain the device and makes way for maintenance to be carried out at shore bases with limited draft.  There is now little doubt within the industry, particularly by those with expert inside knowledge, that marine renewable energy will never be economically viable unless low cost installation and maintenance vessels are used.