"C" on Submarine Hotel Load Power Uses & Amounts

“C” on Nov 23, 2022 made a long comment on submarine hotel load power uses.

It’s a comment well worth turning into the following article:

"Replying to Anonymous's very interesting response [of Nov 16, 2022 here]  to my Hotel load point: the comment from Fleet Command Kobayashi [scroll down here for his photo and bio] is revealing and useful in confirming my suspicion that submarine commanders are likely judicious in what systems they run during endurance exercises.

I would add that the Thales VELOX-M8 Intercept Sonar example I gave (which is one of the very few examples I have found in literature where the vendor has given a power value) was 400W, or 0.4Kw, which is not a lot in the bigger picture of hotel load computations, which seem to waffle between 50 and 200 KWh. This is an intercept sonar, ie. a relatively small item of kit, an adjunct auxiliary to the primary arrays mainly used for classifying a received tone (sound electronic support measures (ESM) [intelligence gathering] essentially). The processing unit takes up about 6U of rack-space, and I'm not sure the array size, but intercept sonars are typically very small, the British type 2019 "nipple" being iconic [scroll half way down the very informative "The History Of British Submarine Sonars" for "SONAR TYPE 2019 DOME"].

Nonetheless the point that designers actively have tilted away from certain system layouts typical in nuke boats because of power consumption is good to have confirmed.

Here's my extremely rough cut of load for a medium-large boat with a crew of c. 60, and these are, in my view, very generous:

ENVIRONMENT

12KW for Heating, ventilation, and air conditioning (HVAC) (rough guide of 5 people per KW)

1KW for lighting (incandescent lighting should be long gone, LED's are so vastly superior in sub context its not funny)

FOOD

3Kw for refrigeration (A 30 cubic-meter cold room will draw about this)

5Kw for food preparation (this will flux according to usage, but this will power an oven an 4 hot plates at full tilt, but I use this number as an "average")

2Kw for misc (kettles/boilers etc, also an average as will flux)

OPERATIONAL TECHNOLOGY (OT)

This is trickier and depends on degree of automation on board, I work in Mining OT space so by way of comparison, all the OT control systems of a large processing mill, with around 250 devices draws, for CONTROL purposes, between 2 and 8 Kw, depending on how many things are in state-change at any point in time. This feels a reasonable starting point, so...

6KW for onboard OT. (eg. raising a mast will require a controller that draws only a few watts constantly, but the actual Variable speed drive (VSD) which is driven by it, that does the actual hoist, will draw mush more for the few seconds its working)

SONAR, COMBAT, COMMUNICATIONS, ETC

Well this is the big hole. I don’t know. So far everything else has come in at about 30KW, which, if numbers like 100KW for hotel are taken, leaves a ball-aching 70KW in mostly computational activity. Its plausible, but thats roughly equivalent to around 100 mainstream IT servers, which feels excessive. Each terminal station, if it includes a pair or large LCD screens, networking and computation will likely draw 0.5 to 1KW, so a boat with 8 such terminals means there is 8KW up front.

I welcome adjustments/insights/amendments to this, as at the moment its just not adding up, unless current systems are just woefully inefficient and using 90's era or older systems - which may very well be the case.

C”

Pete Comment

For further reading relevant to submarine propulsion and non-propulsion (hotel load) electrical uses see Marine Insight's "Different Systems on a Naval Submarine" of April 17, 2021 at https://www.marineinsight.com/naval-architecture/different-systems-on-a-naval-submarine/