We have confirmation that the Offshore Patrol Cutter will have a hybrid propulsion system.
Shephard Media is reporting that, “DRS Technologies, a Leonardo Company, has been selected to provide the hybrid-electric drive propulsion system for the US Coast Guard Offshore Patrol Cutter.”
As to the exact configuration, we have this. Clive Wilgress-Pipe, director of business development and strategic programs at DRS Power Technology said,
“…that the new Offshore Patrol Cutter design solution uses the gearbox mount configuration.”
This suggests to me that the electric propulsion motors (EPM) will be physically close to the main diesel engines (MDE). Assuming the ship will retain redundant machinery spaces, I will speculate and say, this probably means the ship will have two machinery spaces each with a complete propulsion set (MDE, clutch, gearbox, and EPM) for one shaft, plus one or two generators. Previously I had expected one engine room with both main diesel engines, and a motor room with both electric motors.
We don’t have a speed capability for the ship on electric propulsion alone. I had assumed it would provide at least 14 knots to give the long endurance (10,400 n.mi.) claimed for that speed, which might have required only a pair of 1,500 HP motors, but Mr. Wilgress-Pipe’s remarks suggest it might be more.
“Typically you rate it up to about 17 or 18 knots.”
That would require something more like a total of 6,000 HP. As noted, in the linked post, some configurations (COmbined Diesel Electric And Diesel, CODLAD) allow the power of the electric motors to suppliment the main propulsion engines. If that is the case, and we could add something like 6,000 HP to the two 16V 28/33D diesel engines, each rated at 9,763 bhp, then the ship would almost certainly have a 25 knot max speed. (This is of course speculation, so we can only be sure of the 22.5 knots sustained previously reported.)
Giving these ships the option of cruising on electric power, provided only by the ship’s service generators, makes these ship potentially more useful as ASW ships. In this mode, they will be quieter and, in noisy littoral environments, more difficult for a submarine to distinguish from other traffic.
Thanks to Luke for bringing this to my attention.