OPC to Have Hybrid Propulsion

OPC "Placemat"

OPC “Placemat”

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. 

16 thoughts on “OPC to Have Hybrid Propulsion

  1. Though you might want to compare the OPC design with that of the Dutch Holland Class Offshore Patrol Vessel. https://en.wikipedia.org/wiki/Holland-class_offshore_patrol_vessel.

    It seems to suggest that the OPC will be about 4,000 tons full load, That is about 89% the displacement of the National Security Cutters. I had really thought the Holland class were too large for the OPC program, but in fact it seems they are slightly smaller. The Holland class’ displacement at 3,750 tons full load is 83% that of the NSC.

    Comparative dimensions:

    355’8″ length overall compared to 360 for the OPC
    52’6″ beam compared to 54′
    14’11” draft compared to 17′

    Additionally the Holland class uses the same series engines used on the OPC, but the 12 cylinder version instead of the 16 cylinder units used on the OPC, meaning the OPC should have about a third more HP. The Hollands’ speed is reportedly 21.5 knots while that of the OPCs is 22.5 sustained.

      • Would be surprised if a single 1.5MW motor could power AB Flight IIA to just under 13 knots, may be 9/10 knots. The original 2008 plan by Dr Timothy McCoy, director of the electric ships office (PMS 320) at Naval Sea Systems Command (NAVSEA), was to fit motors to both MGR’s, but when contract placed with L-3 it was for only for one motor. The HED will not be fitted to Flight III’s, my guess is that Flight III with its top heavy AMDR and to a lesser extent Flight IIA are both severely limited in weight growth margins limiting the HED installations.
        PS Not sure if the DRS 1.5MW PM electric machine/motor is used for the Flight IIA as DRS was subcontractor to General Atomics and they lost out to L-3 in competition for the AB HED.

      • yes, I miss read the report on the motors for the 34 flight IIA DDGs. The selected motors are not DRS, but it does sound like the HP may be the same.

  2. Now information on the ship’s service generator capacity which will also power the propulsion motors in the cruise mode. (Thanks to Lee)
    “Four EPA Tier 3 compliant MTU 12-cylinder Series 4000 (1000kW) generator sets will provide each vessel with electrical and loiter propulsion power. The units are Naval Vessel Rules (NVR) certified by ABS.”
    So potentially four 1,000 kW generators could provide the equivilant of 5362 HP. so it is a good match to the two 1500 kW motors discussed above, but it would require all four on line to provide both full power 3,000 KW (4,000 HP) for propulsion and ship’s service power.
    In case you missed it, “Each of the new 360-foot (110-m) cutters will be powered by two (2) MAN 16V28/33D STC engines, developing 7,280 kW each @ 1,000 rpm.” That is about 19,500 HP, essentially the same power as the two diesels in the Bertholf class National Security Cutters.

    Only question remaining now is can the power of the electric motors be added to the power of the diesels to increase the maximum speed?

  3. May be the OPC is CODLAD design, will have to wait to see choice of the main gear reduction gearbox, favourite supplier would be RENK, if the more complicated/costly/heavier MGR chosen, allowing the electric motor power to be combined with MAN main diesel power input.

    The Burke Hybrid Electric Drive motor pdf as shown Northrop Grumman, replaced by L-3, used an Electrical Machine, presumably the DRS PM 1.5 MW designed for the Burke was also an EM and if same as the one chosen for the OPC. An EM works either as a motor or generator, PTI/PTO. The EM working as a generator powered by the MAN main engines would allow the MTU gensets to be shut down as appropriate and save fuel as using main MAN diesels are more economical than the smaller MTU gensets.

    For reference/comparison the new Italian PPA frigates, 50% larger than the OPC at 4,500 mt light displacement, are also installed with a Hybrid Electric Drive. It is said to use two 1.4MW motors, not mounted on the MGR, has the advantage of no MGR noise will be generated when using HED in its ASW role, disadvantage CODLAD not possible. Four MAN 12V175D gensets 1,640 kW each and feature double-elastic mountings and sound enclosures for the two gensets in the aft machinery room.

    Quoted max. HED speed powered by its two 1.4MW motors 10 knots.

    (PPA main engines are 2 MTU 20V 8000 M91L 10MW ea. plus a GE/Avio LM2500G4+ 32MW, CODAG)

  4. Pingback: Innovation in the OPC’s Propulsion System | Chuck Hill's CG Blog

  5. Pingback: Admiral Papp Interviewed–OPC/Inland AtonN/Budget | Chuck Hill's CG Blog

  6. I was just informed by DRS Naval Power Systems that while the two motors are rated at 625HP each, in this application they will produce 450HP.

    That sounds like 9 maybe 10 knots, also not enough to make any significant in top speed if run in conjunction with the main propulsion diesels.

    • A second note from DRS indicated that they had been considering using 1,000 HP motors, but decided to stay with the smaller motors at least for now. This probably explains Adm. Papps remarks, when he said the electric motors would provide 9 knots or possibly 13 knots so presumably 9 knots with the planned installation. With two 1,000 HP motors would probably have been 13 knots. https://chuckhillscgblog.net/2017/04/06/admiral-papp-interviewed-opcinland-atonnbudget/

      Really think it would have been wise to go with larger motors, particularly if these ships are ever to be used as ASW vessels. Hopefully it would not be too difficult to switch to more powerful motors in the future if needed.

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