It is possible to achieve the benefits of both diesel and GTs without IEPS through a hybrid drive like on the FREMM/ Constellation. Diesel prime movers power electric motors at speeds up to 17 knots, while the GT mechanically connects to the propeller shaft at higher speeds. This arrangement is also called CODLAG.
054B/new generation frigate
- Thread starter Blitzo
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The drawback is that when GTs are engaged, diesel engines are disengaged. There is a large power gap, in case of Type-45, that is 10MW, a very large gap. Any power setting higher than diesel but lower than the minimum GT must be run by GT with low efficiency. This is the very reason of moving to IEPS.
So I'd say no, CODLAG doesn't achieve the benefits of both diesel and GT (running on their efficient setting). IMO, CODLAG is a compromise of the builder who wants to but lacks the competence in moving to reliable IEPS (MDVC with energy storage). US and UK tried MVAC(without energe storage) IEPS and failed, the others like French and Italy aren't strong players in the game. FREMM/Constellation are the compromised/scale-backed alternative before they master MDVC (with energy storage).
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Thanks for correction.
Sorry, my reply in 1752 was to CODLOG.
For CODLAG, it will have the benefits of both if the frequency syncing (RPM and phase of GT and E motor) is garanteed. Keep in mind though, that is only half of the equation of going IEPS. The other half is distributing electricity among generators from all installed prime movers depending on the need, which is another efficiency to gain.
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Run out of time to update, here is a more thorough answer.
For CODLAG, it will have the benefits in one of two issues that IEPS addresses. The other is distributing electricity among generators from all installed prime movers depending on the need, which is another efficiency to gain.
For example, you have 5+5MWe from two diesels, 5 for propulsion, the other 5 for everthing else. Now you want to go faster, propulsion needs 6MWe, you have a 10MW GT, what do you do? In CODLAG, you have to turn on that 10MW GT to run at 60% power. You shut down one 5MW diesel because you only need 5MWe for everything else. The reason is that your GT is not able to drive generator.
In an IEPS setup, you turn on 10MW GT and shut down one diesel. You can have the GT to run at 100%, let the diesel run at 20% which is still more efficient than a GT at 60%.
So the answer remains, CODLAG doesn't really benifit both compared to IEPS, but of course it is still an improvement over others.
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