Anonymouses "Japanese Submarine LIB distributions & other calculations" of Nov 11, 2022 generated many comments.
Those are the comments not incorporated into the much better "REVISED Japanese Sub LIB distributions, Othercalculations" which has excellent diagrams, and is dated Nov 17, 2022.
Those great comments are below and were made between
November 12 & 16, 2022:
"I'm a different Anonymous
commented Nov 12, 2022:
A power load for propulsion of
50 kW is far too low for a 3,000 tonne submarine [like a Japanese Taigei or
Soryu MK. II]. 50 kW being more like the power of an Outboard engine for a small
amateur fishing boat or probably the power needed for a submarine to barely
stay idle in a current.
This is noting the Kuroshio current in
the Tsushima Strait is above 5 knots. 300 kW is probably the minimum for a sub, necessary to reach
5 knots.
A simple back of the envelope
calculation considering the public data (eg. French Jeumont engines):
- on the 2,000 tonne S-Br (Brazilian Navy Scorpene)
where 2,900 kW is needed to sprint at 20 knots submerged
- on the Barracuda/Suffren class SSN (5,000
tonnes) where 15,000 kW is needed to reach 28 knots
On the lower length/diameter L/D Taigei at 3,000 tonne, (the power
need evolves as the square of the speed) this rule of thumb will lead to 300+ kW
at 5 knots. This would mean a week in a real tactical situation which is
remarkable
More important is the power
density, the shape of the discharge /charge curve and the charging speed (under
snorkel) to decrese the indiscretion ratio.
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wispywood2344 commented Nov
13, 2022:
There is a serious clue about
the energy capacity of Japanese submarine LIB "SLH" hidden in a
document published on the Web by the Japanese MoD.
This is it. [1]
It should look familiar to
you.
Display the graph on the page
2 of this document and enter "Ctrl+A," you can reveal the HIDDEN (or
FAILED TO BE DELETED) LETTERS on the vertical axis. [2]
Therefore, we can assert that
the capacity of a lithium-ion cell used in "SLH" is 1000-2500 Ah.
Since "SLH" uses LCO
as the positive electrode material and carbon as the negative electrode [3],
the nominal voltage of a "SLH" module is around 37V.
Taken together, the energy capacity of "SLH" can be estimated to be around 36-93 kWh per module.
[1] FY2006
Post project evaluation "Development of new submarine main battery"
[2] http://blog.livedoor.jp/wispywood2344/others/SLH_Capacity_Leakage.gif
[3] "Realization of the world's first submarine equipped with a lithium-ion battery system", at Defense structure improvement foundation at https://ssl.bsk-z.or.jp/kenkyucenter/pdf/gyt20201210.pdf#page=2
+++++++++++++
An Anonymous commented Nov 14,
2022:
Once, an influential politician on Japanese MoD revealed there was an improved version (SLH2?) of the current lithium-ion battery (=SLH) for submarine, but due to budget constraints, the improved version could not be obtained.
So, SLH2 might be based on is
based on high performance lithium-ion battery for space (energy density
168Wh/kg), while SLH might be based on is based on large lithium-ion battery
for space (energy density 140Wh/kg).
++++++++++++++
SONARS are High Hotel Load Users
C commented Nov 14, 2022:
I think rather a lot hinges on
the hotel load. I read all sorts of numbers from 50 to 200Kwh,
but its all very iffy and vague.
My point is that is in all my
reading the composition of hotel-load is glossed over, but maybe its worth some
drilling down into this? eg: The Thales VELOX-M8 Broadband Sonar Interceptor [Control-F for "sonar" within this Barracuda SSN link] uses up to
400W when running (which I suspect is a max number). One could put some fair
estimates on air circulation systems based on industrial HVAC. Ditto for refrigeration.
Etc.
I confess I cant really
contribute very much to this, I have snippets only, but I think its critical in
understanding practical endurance for modern boats - if designers were able to
halve the hotel load, they'd double endurance!
eg. There is also the issue
that any computational system that generates waste heat, will also need that
heat removed, essentially doubling the energy cost (this is the classic cost
issue with massive datacenters), ergo a BIG incentive to use highly efficient [digital signal processors] DSPs, [central processing units] CPUs, etc. I suspect most of the big sonar rigs designed by nuclear sub
club countries are not overly concerned with power consumption (obviously), but
other vendors may (or may not) be far more judicious.
Something to chew on.
++++++++++++++++
Another Anonymous commented Nov 16, 2022:
The French SSN, Barracuda-class submarine is equipped with the Thales VELOX-M8 intercept sonar [1]. But, a conventional submarine with limited power supply cannot be equipped with this kind of high power consumption sonar [2] and is equipped with low power consumption and less sensitive sonar instead.
[1] Barracuda SSN Specs: at Very long link :
[2] SHIPS OF THE WORLD,
Special issue 159, page 21, by Ex-Fleet Commander of JMSDF [Japanese Navy] Masao
Kobayashi. [scroll down here for his photo and biodata.]
“In order to maintain long-term diving, it is essential to reduce the hotel load, and it is necessary to reduce the power consumption of the onboard equipment. This makes a great impact on the onboard equipment. For example, the [Virginia sub's BQQ-10 spherical bow sonar array] generates a uniform sonar beam toward not only in a right and left direction but also in an up and down direction and is very effective. But there is no conventional submarine equipped with the spherical array because the beam generation of this array needs a huge amount of calculations, i.e., huge power consumption.”
Replying to Anonymous's very interesting response to my Hotel load point: the comment from Fleet Command Kobayashi is revealing and useful in confirming my suspicion that boat commanders are likely judicious in what systems they run during endurance exercises.
ReplyDeleteI would add that the Velox 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 ESM 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.
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 HVAC (rough guide of 5 people per KW)
1KW for lighting (incandescents should be long gone, LED's are so vastly superior in sub context its not funny)
FOOD
3Kw for refridgeration (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 VSD which is driven by it, that does the actual hoist, will draw mush more for the few few seconds its working)
SONAR, COMBAT, COMMUNICATIONS, ETC
Well this is the big hole. I dont 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
A lot of the operating power for systems might be cooling, which might be a lot less efficient underwater and done quietly than an above ground server farm just sucking in outside air (in climates like Iceland) or running AC/heat exchangers. Offloading that heat discretely underwater I imagine is problematic.
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