Yes it doesn’t look good, but is not a structural problem.It is quite common on newer vessel built anywhere. (incl. in the US) It is partly because of the welding method used today and because the hull plates are generally thinner today than before computers were used to calculate required thickness.
PS> Thinner plates in the superstructure is nothing new.
Do not believed the battery power is meant to be used while steaming. It is meant to be used on stand by where demands are low and batteries have the capability to meet demands.
Would make sense to use the batteries to load up gens during DP. When you would otherwise be running the gens at low load or biasing thrusters. I could have this wrong though.
Steaming in rough weather the battery will help by providing a spinning reserve any time the vessel hits a nasty wave. So the DG sets can run on optimal curve all the time. The battery will smoothing out the load peaks.
But it’s during DP operations that the big savings are done.
yes perfect for when on DP but helping on transit??
Hence no fuel or emission reduction in transit and your DE vessel in transit is using more fuel than if it was direct drive due to less loss
During calm weather I would agree that the battery bank would be a waste to keep on the grid. But during situations where you are steaming head on into the waves you will appreciate the battery bank quickly. Even if the savings in fuel are small.
I can’t remember all the times the power management system has put a extra DG on the Grid because of a nasty wave. A battery to take the peak would have made my life easier.
Sounds like the PMS needed a tweak. It must have been one hell of a wave if the ship was climbing it long enough to start and put another genset online.
Also consider that the extra fuel burned climbing the wave is returned on the way down.
In that case if the condition lasted more than a few minutes it seems like the battery drain would be enough that the power required to recharge would cancel whatever benefit the operator perceived. Maybe backing off the speed a bit or changing course would have saved more fuel? There are so many variables to consider that debating the benefits without data logs is almost pointless. It’s a good way to pass the time anyway.
Could run the DG sets on optimal power curve and use the battery to smoothing out the draw. Would save on maintenance on the engines.
But enough vessels with battery banks now that the data to reach a conclusion should be available.
It looks like those who has the data available (Shipowners/managers and equipment suppliers) is convinced that it is good business, as do those who pay the fuel bill (Charterers)
That may not be such a good idea, (unless the weather is such that it is unsafe to proceed at normal speed and/or course) since it will add time to the voyage, thus adding cost for the Charterer.
The name of the game is to get there on time, with minimum fuel consumption.
Once there, to do the job with maximum of safety, minimum of time and as low fuel consumption as possible.
It appears that having the generators running at optimal efficiency and battery power available to shave off the peak load has been established as a way to obtain this.(Until a better solution comes along)
Nobody is suggesting to run only on battery power, except for a few minutes in case of blackout, or to get out of an emergency situation etc.
PS> Looks like the idea is catching on, even in benign GoM:
The ship’s propellers must not push the ship to climb the waves; even drifting, powerless ships move up and down. The waves lift the vessel up; therefore, to account for the energy transfer, the wave’s height will probably diminish by some millimeters, locally.
The water movement inside an undisturbed deepwater wave (e.g. swell) is vertically circular.
In a big wave, the water movement at the surface goes always with the direction of the wave’s propagation, on the crest or the through; the backward movement is far below the keel of any ship.
For this reason, oceanic swell goes always straight forward, the Coriolis deviation has no influence; there is no displacement of masses, they go just back and forth.
When the waves are locally wind driven, or when they reach shallower waters, they become steeper, then these natural movements of the water become disturbed.
It is always more economic per mile to proceed with the waves, than against them…
I think most readers here know that more power is consumed driving into a sea than with the seas and more power is consumed as the bow rises than when it falls.
It’s not common on a ship with a low-speed diesel to need a lot of HP at low speeds but it does happen from time to time .
From having driven both hybrid and all-electric cars the nice thing about them is the amount of of power at low speed from the electric motor. Flooring it at a stop sign the hp from the gas engine is far from max but the available power from the electric motor is max through the entire speed range.
I’d think having quick response like that when maneuvering would be advantageous.
The motor produces the greatest torque when slip is greatest. Slip is the difference between synchronous speed and rotor speed - in an AC motor. A DC motor is a different animal, it may be synchronous and torque at max rpm is lowest. The motor control laws for propulsion can be very complex and interesting if you are into that kind of stuff.
As gas turbine will exhibit the same characteristic, when the velocity of the gas reaches the point where there is little difference between the velocity of the gas leaving the nozzle and the rate the power turbine blade is passing by, the power drops off. In both cases it is like there is nothing to push against so no power is produced
The vessel I see that is ripe for a hybrid application is the chase boat used in seismic survey. A diesel electric set up with machinery room forward under the house, electric propulsion room and battery room aft.
Between the two fuel tanks for refuelling the seismic ship.
3 diesels plus an emergency/ harbour generator.
During seismic ops on station at speeds of up to 5 knots one diesel running with batteries taking up the slack for a short period at the end of a line. At times the speeds can be as low as just under 4 knots.
Emergency towing of seismic vessel 3 diesels on line.
Supply runs to base 2 diesels on line with one extra if using bow thruster to berth.
Supply alongside 3 diesels, crane, cargo pumps etc.
Alongside harbour genny with added bonus of a quiet engine room for maintenance.
Most of the time a chase boat spends its time leading or following the seismic ship at very slow speeds.
