A diesel-electric hybrid power and propulsion contract for an unusual catamaran dive support vessel (DSV) has been won by Canada-based Aspin Kemp & Associates (AKA) who solved the owner’s quest for a system that would operate at peak efficiency while ensuring that safety and redundancy measures were in place. Australia’s Bhagwan Marine’s 56-m DSV was designed by Incat Crowther, also in Australia, and is to be built at the Keppel Singmarine shipyard in Singapore.
Multi-purpose Dive Support Vesse: Image courtesy of Incat Crowther
Now, here’s a Swiss Army knife of an offshore vessel if ever there was one, designed from the keel up to perform six key roles: dive support, geophysical survey, geotechnical survey, cargo transport, hyperbaric rescue and safety standby. Such varied roles demand a multitude of propulsion responses, including liberal idle times while under way, and AKA’s ‘Duty-cycle analysis’ with its XeroPoint Hybrid system seemed to provide the best answer to the puzzle.
Duty-cycle Analysis & XeroPoint Hybrid System
Vessels like this multi-purpose DSP have a duty cycle profile with extended periods of low to medium power requirements and are great candidates for the hybrid system as diesel engines are least efficient at these load levels.
Duty cycle analysis involves finding the most frequent load points (Xero Points) in a vessel's operational profile and designing specific power plant configurations around these points. The conventional propulsion design approach has been to optimise around a single load point at or near maximum power. The illustration below shows both conventional and hybrid design points.
Duty-cycle Analysis: Sketch courtesy of AKA
The XeroPoint Hybrid system integrates electrical and mechanical devices onboard a vessel to provide optimal modes of operation for power and propulsion. The hybrid system’s energy management system strives to eliminate the unnecessary idling of diesel engines by determining the most efficient configuration of the electrical and mechanical devices onboard at any given time.
The hybrid system, which includes a back-up battery bank from Corvus Energy, is managed by AKA’s energy management system (EMS) to give the high level of flexibility of operation Bhagwan had been seeking.
The diesel-electric propulsion system is designed for several customised modes of operation on the DSV, including two ‘Dynamic Positioning’ modes as well as an ‘Emergency Egress’ mode which permits all machinery to be shut down and low speed propulsion and critical hotel loads to be supported by the battery bank.
Designers Incat Crowther say that unlike any other vessel of its size and type, this one will have all dive equipment designed and built in from the outset. A dedicated dive control room will be fitted with a pair of decompression chambers, with a hull compartment directly below dedicated to support equipment such as compressors and dive gas storage tanks. A pair of diver launch and recovery systems is to be fitted to starboard side, whilst a separate launch and recovery system is to be fitted to port for ROV operations. The vessel will also have the capacity to launch, retrieve and store a hyperbaric lifeboat.
The new catamaran DSV will be built under ABS class supervision with the notifications ABS +A1, ⓔOffshore Support Vessel (DSV AIR, SPS, FFV1I) +AMS +ACCU, +DPS-2, GP, ENVIRO, RRDA, which reflect the multiplicity of its intended offshore roles.