Ship Propulsion

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Joined: 16 Mar 2017, 20:22

03 Feb 2018, 19:23 #11

I've been thinking about this also, especially in regard to the FFG(X) design.  I think this is a big benefit of at least partial electric propulsion, most likely some sort of CODLAG arrangment.  Have one set of diesel gensets forward, one aft, have the GT and it's transmission amidships, keep at least one compartment between each one.  I'm also toying with the idea of a large amount of battery storage distributed around the ship for instantly available backup power.
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Joined: 30 Aug 2005, 09:15

03 Feb 2018, 19:48 #12

You are more or less describing a diesel electric submarine. Think about how much battery they need to get the equivalent of a running for a couple of hours on the diesels.
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Joined: 16 Mar 2017, 20:22

07 Feb 2018, 21:30 #13

WarshipAdmin wrote: You are more or less describing a diesel electric submarine. Think about how much battery they need to get the equivalent of a running for a couple of hours on the diesels.
That's not the purpose of the battery in this application.  The idea would never be running for hours on battery power.  

The use of the battery would be to cover short term spikes in use or to provide instant redundant power if a generator goes down.  The idea would never be to drain the battery for more than 15-20 minutes.

In a ship set up as I describe, only enough generators would run to cover the average constant draw.  In many cases, this would be only one genset.  But if you get a spike that's greater than that genset can cover, or that genset drops out, you have a problem.  In may take several minutes to get another genset spun up.  Because of this, procedure would be to have an extra gen set spun up and idling or to run multiple gensets at partial output.  Both of these are highly inefficient.  With the battery capacity available, the ship could run just the optimal number of gensets necessary to keep them running at their most efficient (which is near max output), and if more short term electrical power is needed suck it from the battery.  If that draw looks like it's going to continue, then spin up another genset to cover it (and recharge the battery.)  If the running genset dies, let the battery cover the full draw (shedding load gracefully if necessary), until generator power is recovered.
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