BairdMaritime reports the Chinese are building an all electric vessel for their Maritime Safety Administration, to be used “as a command ship for use in emergency pollution response, particularly in instances of pollution involving dangerous gases at sea.”
- Length: 78 meters (256 feet)
- Beam: 12.8 meters (42 feet)
- Design speed: 18 knots
- Range 1,000 nautical miles
Reportedly ower is to be provided by two sets of 650kWh high-performance lithium battery packs.
Maybe there is an error here? That only amounts to 1,743.3 HP/hours. My estimate would be that that would allow only about a half hour at 18 knots, an hour at 14, and two hours at 10, perhaps four hours at six. Appears it would take about 75,000kWh to go 1000 miles at 10 knots. Why would it even have a stack if there is no diesel engine?
I don’t think it’s intended to be a fully-electric vessel, but more like a hybrid with battery-only operating mode for special occasions.
I think that is more likely, but it is not reported that way.
Noted. I admit I didn’t actually open the article until now.
We have an all-electric ferry operating near where my parents live. If I recall correctly, they have to run the backup diesel generators weekly to check that they are operational even though the batteries are normally charged from the national grid while the ferry is at the quay. I don’t think the technology is mature enough to drop the backup completely – losing all propulsion on a ship, even a small ferry sailing within visual range of land, can have much more severe consequences than getting stranded on the road in your Nissan Leaf.
Interested in how you built up your estimate of about 75,000 kWh to go 1000 miles at 10 knots, assuming from specs ship approx 1,600t ? Thanks
Just figured it would take about 4000 HP to go 18 knots. 2000 to go 14, 1000 to go 10, 500HP to go 6. Converted 1300 kWh to horsepower hours = 1,743.3 HP/hours. All very approximate, but definitely within an order of magnitude. CG 255 foot cutters, were about the same size, made 4000 HP and had a max speed of 18 knots.
Thanks for reply.
The only vessel I’ve looked at with partial electrical propulsion is the UK 128m/15,000t Artic and Antarctic research ship Sir David Attenborough, 19,000 nm/60 days, a Norwegian design spec’d for Polar Class 5 to break ice to a thickness of 1.5 m at a min speed of 3 knots.
One of the most stringent design requirements for the SDA was for very low levels of underwater radiated noise, vital for the underwater survey work and built to the Norwegian DNV Silent R classification rules, and when called for able to operate on electric power for limited time.
Uses Bergen medium speed diesel gensets, two 6 cylinder B33:45 DG 3,600 kW and two 9 cylinder B33:45 DG 5,400kW x 2, total 18kW to provide both mechanical propulsion and electric power generation. To reduce noise the foundation of the Bergen diesels use rigid cast iron block made from a compound with a specialized molecular structure and reduces vibration levels to 10-11 m/sec. The 9-cylinder engines are mounted on large double resilient mounted rafts to further reduce the underwater noise.
The twin shafts are driven by twin 2,750kW Indra electric motors, max 140rpm, 5,500kW per shaft, manufactured with very restrictive noise emission and vibration specs.
For near total silent operation it can be powered by SAFT Li-ion batteries with a combined capacity of 1450 kWh, claimed 5 MW peak effect battery capacity, guessing for short period batteries can withstand stressing to a factor of 3.4 from normal power draw?
Propellers are the main source of underwater noise, also need to be efficient. With a quieter propeller you need to move the thrust generated by the propeller further from the tip and closer to the hub as main source of noise is the tip vortex cavitation, unloading the propeller tip decreases the disturbance of the water by the propeller closer to the hull reducing the noise it creates, though unloading the tip reduces the efficiency, so design optimized the propeller to deliver a high Cavitation Inception Speed, CIS, like a naval vessel mitigating the tip vortex cavitation/noise, SDA uses two five bladed 4.5 m dia CPPs though dedicated naval ASW frigates use FPP which quieter than CPP?
Uses the Rolls-Royce Promas design which integrates the propeller with a hubcap, rudder bulb and a special rudder profile, providing very high steering forces yet minimizing drag, same as spec’d for the new Heritage OPCs.
I am hoping the OPCs will turn out fairly quiet. There was an objective of making them quieter for the benefit of the crew, but I doubt they went to the extremes used to create a quiet ASW ship.
For those who might want to know more about the Promas design on the OPC This is the link to the post I did on the system. Note the electric motors selected are much less powerful than I expected when I wrote this so speed using the electric motors only is likely to be 8 or 9 knots.