Power sources for Ships, nuclear, gas turbines, solar, etc .

[DJK]

You're off by an order here. 5MWh at 80Wh/kg would only be 62.5 metric tons. I think you could do a lot better than that even with LFPs though.

Depending on what fire protection you needed, and then transformers and switchgear.

I think the risk factor for a ship is overblown. All you have to do if thermal runaway starts is flood the enclosure with water. You can distribute these batteries all over the ship so no single failure is a significant problem.

LiFePO4 is less susceptible to thermal runaway, but things can go wrong. Even a fire in the next room would be an issue (maybe the laundry?) Solid state was supposed to be zero risk, i think.

You definitely benefit from distributing your battery capacity, preferably close to critical loads as part of your damage control.

I also estimate 30MW burst requirement for future combat systems. 5MW for propulsion at 16 knots. Total needs to be approximately 35MW.

This is why I proposed a microreactor with 10MWe and a battery with 25MW burst output and 50MWh capacity.

So we have proposals for two different scenarios, a 5MWh burst/backup battery and a 25 to 50MWh grid support battery.

I think the 5MWh version needs to allow for the main turbines going offline for whatever reason. Maybe some bright spark from GE put recuperators on them...

But seriously, if a turbine is knocked out by the first ASCM, you need to cover startup of another turbine while shooting at the next missile and manoeuvring the ship. Say 50MW for 10 minutes would require 8MWh of capacity, so 10MWh to allow for degrading over the battery life.

 

[Nicknick]

I allways heard, that solid state batteries were super safe, until three bus depots (Duesseldorf, Berlin, ...?)Germany burned out because Mercedes made solid state batteries...

Solid state batteries are not suited for high specific power btw.

 

[MadRat]

Solid state batteries are just capacitors by a different name with some pretty significant engineering hurdles. The implementation sets their function. Every production model will have strengths and weaknesses in their design so we cannot say they all do this or that.

Anything that requires high discharge rates will be using capacitor technology. So you would need to be able charge using turbines, the reactor, off diesel power sources, off auxiliary power sources, off battery storage, or god forbid transfer from one capacitor to another. And in the event equipment goes down, you need to be able to drain capacitors without killing people or fauna around the ship. And you need to do it without energizing wires and electronics proximal to the ship. By the way, these are not small tasks. Rail guns, lasers, and engines starts are just a few uses of capacitors in the ship.

 

[Nicknick]

Not true, solid state batteries are using a solid electrolyte. This should enable higher energy density but lower specifiv power, thus the characteristic is the oposite of a capacitator. They were (or might be again) used for city buses with overnight charging. This aoplication requires high energy density but low power during charging and decharging

 

[chimeric oncogene]

https://www.secretprojects.co.uk/threads/naval-nuclear-propulsion.46609/post-796544

https://www.secretprojects.co.uk/threads/naval-nuclear-propulsion.46609/post-797541

Westinghouse's eVinci in some ways harkens back to their old lightweight nuclear propulsion nuclear gas turbine idea (I think they have a different cooling setup though).

In the 1970s, presumably when they were thinking up Spruance and the DDN, Westinghouse proposed a high temperature graphite moderated helium cooled reactor powering a helium nuclear gas turbine. They claimed you could get ~10,000 hours of performance equivalent to an LM2500 on the same volumetric footprint of an LM2500 (though not the same weight - the reactor plus turbine plus shielding came to around 300 metric tonnes or so).

There is essentially no lower limit to how small you can make a nuclear powered vessel; reactors of even smaller size exist, and most of the weight is in the shielding (which you can in some cases skimp on with methods like directional/shadow shielding).

There is also a 1950s proposal for a nuclear outboard motor to be slapped on to the bottoms of battleships and suchlike. That was probably slightly crazy.

 

[insidersource]

But seriously, if a turbine is knocked out by the first ASCM, you need to cover startup of another turbine while shooting at the next missile and manoeuvring the ship. Say 50MW for 10 minutes would require 8MWh of capacity, so 10MWh to allow for degrading over the battery life.

There is not another turbine to start up. There is just one large gas turbine that is the advantage of running the large battery.

1 microreactor sized to the average load.
1 large battery.
1 large gas turbine generator.

Power outputs I estimate to
10MW from the microreactor
25MW from the battery
35MW from the gas turbine.

70MW total allows for a 30 knot sprint with all the combat systems running. This is achieved with just a single gas turbine generator. An Arleigh-Burke would need 4 large gas turbines turning the props and 2 small gas turbines running the combat systems.

In a large destroyer the microreactor allows the ship to cruise at around 16-18 knots in average conditions with no fuel usage.

The battery putting out the full 25MW combined with the microreactor would allow the destroyer to hit around 24-25 knots without starting the gas turbine. The battery with the 50MWh capacity would allow approximately 12 hours at 20 knots, 6 hours at 22 knots, 3 hours at 24 knots.

With the single large gas turbine running at full power it would allow a 30 knot sprint for about 2 hours until the battery is depleted. The speed would then have to reduce to around 26-27 knots. 2 hours at 30 knots should be sufficient.

If the battery was only 5MWh then the ship could only last 10 minutes at 30 knots before having to drop down to 26-27 knots. The Navy would probably then want a bigger or second gas turbine to allow the 30 knot sprint to be sustained for longer.

The big battery not only allows for a smaller microreactor but it allows a smaller or fewer gas turbine generators. The big battery also reduces fuel consumption as the gas turbines will run less frequently. So a 500 ton battery might save 200 ton in the microreactor, shielding and the gas turbines. The big battery might save 300 ton of fuel by reducing the gas turbine usage. That 500 ton battery now added zero weight to the ship.

 

[insidersource]

.Anything that requires high discharge rates will be using capacitor technology.

Rail guns, lasers, and engines starts are just a few uses of capacitors in the ship.

Capacitors would definitely be the obvious choice for a ship that isn't using a microreactor. Keep all the generators running and the supercaps will easily handle the radar and laser bursts. When the ship accelerates from 15 knots to 20 knots you just simpley turn on another generator.

A small diesel generator can start up and be producing 50% rated power within 3 seconds. There is no need for a large battery on a fossil fueled ship. The battery does not save any fuel.

The big battery only works when paired with a microreactor. The battery handles a surge and the microreactor can recharge it a few hours later with no fuel consumption.

 

[insidersource]

You could theoretically remove all gas turbines if the battery was big enough. A 200MWh battery would weigh similar to the fuel capacity of an Arleigh-burke destroyer. Keep the same 10MWe microreactor.

Now the microresctor gives 16 knots cruise and infinite range without touching the battery.

That huge 200MWh battery would give the following approximate ranges with the microreactor still running. Using 4MW hotel load and the Arleigh-burke power chart.

18 knots: 1,800nm range 100 hours
20 knots: 1,000nm range 48 hours
22 knots: 600nm range 27 hours
24 knots: 400nm range 16 hours
26 knots: 260nm range 10 hours
28 knots 170nm range 6 hours
30 knots: 120nm range 4 hours.
32 knots: 90nm range 3 hours
34 knots: 60nm range 2 hours

The battery would then be flat and the ships speed would then drop back down to 16 knots.

While in port the battery would get charged back up in 24 hours. In theatre the ship could slow down to 10 knots and the battery would slowly charge back up.

If the microreactor failed that 200MWh battery would allow the ship to travel 500 miles.

Going off Tesla megapacks the 200MWh battery would only cost $50 million.

A tiny microreactor and large battery would be the perfect propulsion system for an unmanned submarine.

 

[CastleBravo]

You could theoretically remove all gas turbines if the battery was big enough. A 200MWh battery would weigh similar to the fuel capacity of an Arleigh-burke destroyer. Keep the same 10MWe microreactor.

Now the microresctor gives 16 knots cruise and infinite range without touching the battery.

That huge 200MWh battery would give the following approximate ranges with the microreactor still running. Using 4MW hotel load and the Arleigh-burke power chart.

18 knots: 1,800nm range 100 hours
20 knots: 1,000nm range 48 hours
22 knots: 600nm range 27 hours
24 knots: 400nm range 16 hours
26 knots: 260nm range 10 hours
28 knots 170nm range 6 hours
30 knots: 120nm range 4 hours.
32 knots: 90nm range 3 hours
34 knots: 60nm range 2 hours

The battery would then be flat and the ships speed would then drop back down to 16 knots.

While in port the battery would get charged back up in 24 hours. In theatre the ship could slow down to 10 knots and the battery would slowly charge back up.

If the microreactor failed that 200MWh battery would allow the ship to travel 500 miles.

Going off Tesla megapacks the 200MWh battery would only cost $50 million.

A tiny microreactor and large battery would be the perfect propulsion system for an unmanned submarine.

I thought about something like that too, but decided the juice wouldn't be worth the squeeze vs keeping an MT30 and some fuel.

Another idea I had to expand on that would be a ~500MWe nuclear supply ship that could underway recharge the big battery warships. The nuke supply ship could also have equipment to make synthetic jet fuel.

I would at least double up on the microreactors for 20MW on the warship though.

 

[cccgong]

You might want to aim for more like 10-15MWh. Which is the installed power in most subs, 4x Sargo-II batteries (126 cells each battery, 270v and 11,800amp-hours capacity)

I do not think that is a valid assumption.

To my knowledge, you'd be emitting that 2MW per face more or less constantly, and a higher power level in combat from using the radar as an HPMW system, lighting up any given missile with up to the full output of the array (gotta love AESA offensive EW).

Then you add the output of the SEWIP system as another combat draw. I'd assume SEWIP uses almost as much power as SPY6v4 (24RMA), so as much as 3.5MW at 100% duty cycle.

So, 8MW for your standard air-search, with combat power adding another 12MW.


Note that 2MW per 1MW laser is the optimum, I'd suggest planning for 3MW electrical input per 1MW beam output.

Do we want to assume 4 lasers, or just 2?

That's another 5-10, maybe 12, MW for combat power levels.

That's 32MW combat power draw between SPY6BMDR, SEWIP, and 4 lasers. Above your standard power draw.

I don't agree that you'd be emitting at max duty cycle during non-active combat times (combat would start when you know something is coming imminently). I would expect the duty cycle drops to low single digit percentages and ramp up when you know something is about to come at you or if you detect something.

I do agree that if there's an inbound you can likely crank up the duty cycle in short bursts to near 100% when something is coming at you, but you'll be thermally limited. I also agree with your other statements.

In my mind there's a few levels of power consumption in wartime scenarios. Assuming hotel load is 3MW and propulsion costs are as follows with the following power generation: 15 MW reactor, 2x MT30, and some battery bank

• Transit in home waters: ~15kn, radars at low single digit duty cycle
  • ~10 MW - fully covered by reactor
• Transit in contested waters: ~15kn, radars at~10% duty cycle
  • ~ 11 MW - fully covered by reactor
• Convoy escort in contested waters: ~20kn, radars at 20% duty cycle
  • ~21 MW - 15MW covered by reactor, 1 turbine being used
• High speed transit: ~25kn, radars at 20% duty cycle
  • ~32 MW - 15MW covered by reactor, 1 turbine being used
• On station in combat zone: ~15kn, radars at 20% duty cycle
  • ~15 MW - 15MW covered by reactor, turbine spun up if you need to go fast and turn everything on
• Missiles inbound: ~30kn, everything on
  • 75MW+ - 15 covered by reactor, up to 72MW from 2 turbines

There doesn't seem to be many scenarios in which the battery would help. In many scenarios in which you'd use a battery, you need that power for days in which you'd deplete your battery even if it's 50 MWh.

The one where it could be useful is on station in a combat zone, if you don't want a turbine spun up as you're more or less completely relying on the reactor and will use the battery to buffer the system until a turbine can be spun up. But I'm not sure commanders would want that and would rather have a turbine turned on already just to be safe.

A small 5MWh battery would see that large gas turbine generator constantly. That hypothetical mission profile would see the small battery drained in under 20nm and it would then be running the large gas turbine at only 10% throttle for the 10 hours. This suggests your smaller battery would require a slightly larger microreactor to be fully optimised.

The turbines on the Type45 don't really lose any efficiency down to ~40% which is about 10MW. This also only has an intercooler and combustion air reheater. With a combine cycle step you can push that effiency plateau down to lower loads.

When last I did the thought experiment, I came up with references showing Lithium batteries being about 5x the power capacity of lead-acid in both by-weight and by-volume comparisons. Technically you can get a bit more power by-volume, but I rounded down for large battery cooling channels for safety. A fire in the battery well is called a Bonefish fire, and it was so hot that it welded the bones of one of the victims to the steel deck, in addition to melting the anechoic tiles off the hull.

So if you put in 4x Sargo-II batteries, but with lithium cells instead of lead-acid, you'd be looking at ~50-75MWh worth of storage. That's about enough for 2 hours of combat.

Hmmm looking more at it the Japanese Tagi class uses NCA batteries. So we can get things 1/3 smaller.

You could theoretically remove all gas turbines if the battery was big enough. A 200MWh battery would weigh similar to the fuel capacity of an Arleigh-burke destroyer. Keep the same 10MWe microreactor.

Now the microresctor gives 16 knots cruise and infinite range without touching the battery.

That huge 200MWh battery would give the following approximate ranges with the microreactor still running. Using 4MW hotel load and the Arleigh-burke power chart.

18 knots: 1,800nm range 100 hours
20 knots: 1,000nm range 48 hours
22 knots: 600nm range 27 hours
24 knots: 400nm range 16 hours
26 knots: 260nm range 10 hours
28 knots 170nm range 6 hours
30 knots: 120nm range 4 hours.
32 knots: 90nm range 3 hours
34 knots: 60nm range 2 hours

The battery would then be flat and the ships speed would then drop back down to 16 knots.

While in port the battery would get charged back up in 24 hours. In theatre the ship could slow down to 10 knots and the battery would slowly charge back up.

If the microreactor failed that 200MWh battery would allow the ship to travel 500 miles.

Going off Tesla megapacks the 200MWh battery would only cost $50 million.

A tiny microreactor and large battery would be the perfect propulsion system for an unmanned submarine.

A 200 MWh battery would be 1650t with NCA. That's unreasonable

 

[Scott Kenny]

But seriously, if a turbine is knocked out by the first ASCM, you need to cover startup of another turbine while shooting at the next missile and manoeuvring the ship. Say 50MW for 10 minutes would require 8MWh of capacity, so 10MWh to allow for degrading over the battery life.

You can get a turbine from cold iron to 100% power in less than 5 minutes in an emergency, but I would still plan for longer, in case of issues.

What takes the longest is the actual cranking-to-ignition. Once it's ignited and rpm is accelerating you can slam the throttle forward and be at max RPM in less than a minute. Hard on the bearings, but when the alternative is big fecking holes in your ship you accept some bearing wear.

I don't agree that you'd be emitting at max duty cycle during non-active combat times (combat would start when you know something is coming imminently). I would expect the duty cycle drops to low single digit percentages and ramp up when you know something is about to come at you or if you detect something.

Who is the forum radar expert, then? Because I was under the assumption that the radars run at the 20% duty cycle as their standard emission pattern for air search.

I do agree that if there's an inbound you can likely crank up the duty cycle in short bursts to near 100% when something is coming at you, but you'll be thermally limited. I also agree with your other statements.

Yes, super-high duty cycle for offensive EW is going to make a lot of heat. Might need to add another 15MW of electrical demand for the chillers to keep up, or get fancy with emergency cooling options related to an electronics-fire-suppression system (clean agent extinguishers, so the agent evaporates due to the heat without damaging anything).

There doesn't seem to be many scenarios in which the battery would help. In many scenarios in which you'd use a battery, you need that power for days in which you'd deplete your battery even if it's 50 MWh.

The one where it could be useful is on station in a combat zone, if you don't want a turbine spun up as you're more or less completely relying on the reactor and will use the battery to buffer the system until a turbine can be spun up. But I'm not sure commanders would want that and would rather have a turbine turned on already just to be safe.

You still want a battery of some level for things like the dewatering pumps.

Hmmm looking more at it the Japanese Tagi class uses NCA batteries. So we can get things 1/3 smaller.

That is another option for surface ships. Submarines want the additional capacity and need the same weight of battery anyways, and I tend to prefer extra capacity over smaller package in my thinking.

 

[insidersource]

Transit in home waters: ~15kn, radars at low single digit duty cycle

• ~10 MW - fully covered by reactor
• Transit in contested waters: ~15kn, radars at~10% duty cycle
  • ~ 11 MW - fully covered by reactor
• Convoy escort in contested waters: ~20kn, radars at 20% duty cycle
  • ~21 MW - 15MW covered by reactor, 1 turbine being used
• High speed transit: ~25kn, radars at 20% duty cycle
  • ~32 MW - 15MW covered by reactor, 1 turbine being used
• On station in combat zone: ~15kn, radars at 20% duty cycle
  • ~15 MW - 15MW covered by reactor, turbine spun up if you need to go fast and turn everything on
• Missiles inbound: ~30kn, everything on
  • 75MW+ - 15 covered by reactor, up to 72MW from 2 turbines

There doesn't seem to be many scenarios in which the battery would help. In many scenarios in which you'd use a battery, you need that power for days in which you'd deplete your battery even if it's 50 MWh

Nearly every scenario the big battery would help. You've increased the microreactor size by 50% compared to my 10MWe idea which helps cover the battery usage. A 15MWe reactor will be exponentially harder to transport to the shipyards as 5MWe eVinci is already at the truck size limit. A 10MWe reactor would already be oversized and require trucks taking up two lanes, avoiding bridges and require escort vehicles. It would also max out a train carriage.

Now I will summarise how a big battery could support each of your mission profiles.

Transit in home water and Transit in contested waters these two would make up more than half of the ships life. Your 15Mwe microreactor is oversized for both jobs running at 66 and 73% capacity. You are now throttling the reactor far more often which is increasing complexity and cost. Using a 10MWe reactor means it very rarely has to throttle just like it's civilian versions. The big battery handles the throttle.

Convoy escort in contested waters a large battery would also prevent the gas turbine running. Your gas turbine is producing only 6MW. The battery would give 8 hours at your speed of 20 knots. That is 160nm distance which is enough to pass through the contested waters such as the straight of Hormuz. The battery would not be big enough for all escort missions but it could cover a large percentage.

On station in combat zone this profile has the ship consuming exactly what the reactor puts out but you have the gas turbine at idle ready to handle a sprint. The battery would allow the gas turbine to be off. With 25MW output the battery allows the ship to accelerate above 25 knots nearly instantly. Within a few minutes the gas turbine can turn on to get up to 30 knots.

Missiles inbound your profile would start with a single gas turbine idling it will take a few minutes until the second turbine comes online to give you 75+MW. The missiles will hit before the second turbine throttled up. The huge battery provides huge power instantaneously and has enough capacity to give time for the gas turbine to start and then throttle up.

A 200 MWh battery would be 1650t with NCA. That's unreasonable

That is using safe LFP batteries. Tesla megapack 3 is 5MWh and weighs 40 ton with all the electrics inside. We now have a 14,000 ton fully electric passenger ferry with a huge 40MWh battery and it can hit 30 knots just on battery power. Add a microreactor that is continuously topping up that battery and that style of propulsion would perform nicely.

 

[cccgong]

Nearly every scenario the big battery would help. You've increased the microreactor size by 50% compared to my 10MWe idea which helps cover the battery usage. A 15MWe reactor will be exponentially harder to transport to the shipyards as 5MWe eVinci is already at the truck size limit. A 10MWe reactor would already be oversized and require trucks taking up two lanes, avoiding bridges and require escort vehicles. It would also max out a train carriage.

Now I will summarise how a big battery could support each of your mission profiles.

Transit in home water and Transit in contested waters these two would make up more than half of the ships life. Your 15Mwe microreactor is oversized for both jobs running at 66 and 73% capacity. You are now throttling the reactor far more often which is increasing complexity and cost. Using a 10MWe reactor means it very rarely has to throttle just like it's civilian versions. The big battery handles the throttle.

Convoy escort in contested waters a large battery would also prevent the gas turbine running. Your gas turbine is producing only 6MW. The battery would give 8 hours at your speed of 20 knots. That is 160nm distance which is enough to pass through the contested waters such as the straight of Hormuz. The battery would not be big enough for all escort missions but it could cover a large percentage.

On station in combat zone this profile has the ship consuming exactly what the reactor puts out but you have the gas turbine at idle ready to handle a sprint. The battery would allow the gas turbine to be off. With 25MW output the battery allows the ship to accelerate above 25 knots nearly instantly. Within a few minutes the gas turbine can turn on to get up to 30 knots.

Missiles inbound This profile only one gas turbine idling it will take a few minutes until the second turbine comes online to give you 75+MW. The missiles will hit before the second turbine throttled up. The huge battery provides huge power instantaneously and has enough capacity to give time for the gas turbine to start and then throttle up.


That is using safe LFP batteries. Tesla megapack 3 is 5MWh and weighs 40 ton with all the electrics inside. We now have a 14,000 ton fully electric passenger ferry with a huge 40MWh battery and it can hit 30 knots just on battery power. Add a microreactor that is continuously topping up that battery and that style of propulsion would perform nicely.

This seems to be a LLM response. It reads exactly like one including highlight sections, talking about Hormoz when we are clearly talking about a Pacific conflict, it's ignoring the fact that there's a smaller battery, and bringing up Tesla battery packs that are in no way suitable for military applications.

It's clearly missing all of the nuance.

 

[insidersource]

This seems to be a LLM response.

I typed every word. There are numerous grammar errors including inconsistency with upper and lower case. Clearly not AI bit I will take it as a compliment. The megapack weight and numbers have all been rounded up or down. Maybe it is using the bold font that tricks you.

 

[cccgong]

I typed every word. There are numerous grammar errors including inconsistency with upper and lower case. Clearly not AI bit I will take it as a compliment. The megapack weight and numbers have all been rounded up or down. Maybe it is using the bold font that tricks you.

Reactor throttle doesn't change the design much, everything is already designed to throttle. The 15MW plant allows your to transit in contested waters (between Haiwai and Asia) without needing to turn on the turbine. You're out of luck with a battery with transit durations. It does make you operate at a worse effieincy point on your turbine for convoy escorts though.

Convoy escorts in contested waters will take days, so no battery will cut it. With a 50MWh battery even something from Guam to the Phillipines you'd be looking at 10 charge discharge cycles, let alone Haiwaii to the Phillipines where you'd be looking at 35+ charge discharge cycles each way. That's crazy wear on the battery and turbine.

On station in a combat zone, I doubt any commander will not want the turbine spun up already as extra security.

I agree that spinning up a second turbine will take time, and that's why a 5MWh battery exists to take up the slack until the second one is spun up when missiles start coming in.

The tesla megapack 3 also doesn't have the transformers, extra fire protection systems, shock hardening, vibration isolation, waterproofing, additional chilled water loops (as designed would just vent heat to that room), naval venting requirements (ducting + fans as it's just designed to vent things to atmosphere). But perhaps most of all it's a Tesla product, who is notorious for inflating claims and not delivering on specs/timelines.

 

[DJK]

There is not another turbine to start up. There is just one large gas turbine that is the advantage of running the large battery.

1 microreactor sized to the average load.
1 large battery.
1 large gas turbine generator.

I was talking about a conventional IEP ship with multiple GTs, Type-45/DDG-1000ish but sort of applies to a hybrid propulsion to some extent or a concept where your micro-reactor is only sized for loiter speeds or a navy is adverse to big batteries. A second generator starts up whenever needed but you need power available for bursts or gen startup.

With the single large gas turbine running at full power it would allow a 30 knot sprint for about 2 hours until the battery is depleted.

I expect most navies would expect redundancy and separation for every power source.

You could theoretically remove all gas turbines if the battery was big enough. A 200MWh battery would weigh similar to the fuel capacity of an Arleigh-burke destroyer. Keep the same 10MWe microreactor.

Now we just need recharging tenders that can recharge almost as fast as a RAS. The destroyer would have redundant power systems, so you would recharge both concurrently to speed things up. Presumably the tender is nuclear powered with some big batteries of its own. Maybe pumped electrolyte. Or maybe destroyer also uses pumped electrolyte (but heavy) so you just pump over electrolyte instead of diesel.

A tiny microreactor and large battery would be the perfect propulsion system for an unmanned submarine.

I did wonder about that, not having to snorkel or run a diesel adds more than just convenience. Taigae class is only using lithium to extend its AIP run time so it still recharges on diesel.

Taigei-class submarin

There doesn't seem to be many scenarios in which the battery would help. In many scenarios in which you'd use a battery, you need that power for days in which you'd deplete your battery even if it's 50 MWh.

The one where it could be useful is on station in a combat zone, if you don't want a turbine spun up as you're more or less completely relying on the reactor and will use the battery to buffer the system until a turbine can be spun up. But I'm not sure commanders would want that and would rather have a turbine turned on already just to be safe.

I'm pretty sure ship commanders like to be prepared for everything

The turbines on the Type45 don't really lose any efficiency down to ~40% which is about 10MW. This also only has an intercooler and combustion air reheater. With a combine cycle step you can push that effiency plateau down to lower loads.

The WR21 still uses that recuperator after the upgrade? I would think switching to combined cycle would be more reliable, or at least switching to a cooler air intake on thermostat.

Hmmm looking more at it the Japanese Tagi class uses NCA batteries. So we can get things 1/3 smaller.

Yes but maybe not your average lithium ion, apparently Panasonic did testing to prove they were safe. Must be a lot of safety features and fire protection!

Even JMSDF wouldnt be using them on a surface ship though.

 

[insidersource]

The 15MW plant allows your to transit in contested waters (between Haiwai and Asia) without needing to turn on the turbine. You're out of luck with a battery with transit durations. It does make you operate at a worse effieincy point on your turbine for convoy escorts though.

The difference between the 10MW and 15MW microreactor would only be around 3 knots. The speed of the convoys has a lot to do with it. If this nuclear hybrid destroyer is escorting a convoy of replenishment ships, a amphibious task group or commercial ships then the 10MW microreactor will provide enough speed. The carrier battle groups usually travel faster.

I am sizing my reactor for a slightly slower transit or convoy speed. During a higher speed escort my ship would be consuming more fuel than your ship with the bigger reactor. I am assuming the vast majoirty of the convoy escorts would around 15 knots. You are assuming the vast majority of convoy escorts will be closer to 20 knots. We have both sized our reactors based on these assumptions.

The US Navy would obviously crunch the numbers and see what is the optimal reactor size.

Convoy escorts in contested waters will take days, so no battery will cut it. With a 50MWh battery even something from Guam to the Phillipines you'd be looking at 10 charge discharge cycles, let alone Haiwaii to the Phillipines where you'd be looking at 35+ charge discharge cycles each way. That's crazy wear on the battery and turbine.

In this particular example the large battery wouldn't be cycled like that. The battery would only be cycled if there is a high chance it could be recharged with the microreactor. On a planned long journey the single gas turbine would just run at low power for the entire trip. The cycling the battery to then allow the gas turbine to run at peak efficiency would still have a 5% electrical recharging loss. Fuel usage would be the same to just having the gas turbine running at low power and having a 5% efficiency loss on the

I expect most navies would expect redundancy and separation for every power source.

With IEP everything is still connected to the same high voltage backbone. I would consider the very large battery and microreactor provide redundancy to each other.

I did wonder about that, not having to snorkel or run a diesel adds more than just convenience. Taigae class is only using lithium to extend its AIP run time so it still recharges on diesel.
Taigei-class submarin

The 3 largest manned conventional submarines are near 4,000 ton displacement and could be converted to use a microreactor in the next iteration.

Taigei-class submarine
KSS-III
Orka-class submarine

A 5MW eVinci could fit where the diesel generators and fuel tanks are located. Keep the existing batteries to allow for short bursts of speed or to operate with the reactor off.

 

[cccgong]

The difference between the 10MW and 15MW microreactor would only be around 3 knots. The speed of the convoys has a lot to do with it. If this nuclear hybrid destroyer is escorting a convoy of replenishment ships, a amphibious task group or commercial ships then the 10MW microreactor will provide enough speed. The carrier battle groups usually travel faster.

I am sizing my reactor for a slightly slower transit or convoy speed. During a higher speed escort my ship would be consuming more fuel than your ship with the bigger reactor. I am assuming the vast majoirty of the convoy escorts would around 15 knots. You are assuming the vast majority of convoy escorts will be closer to 20 knots. We have both sized our reactors based on these assumptions.

The US Navy would obviously crunch the numbers and see what is the optimal reactor size.


In this particular example the large battery wouldn't be cycled like that. The battery would only be cycled if there is a high chance it could be recharged with the microreactor. On a planned long journey the single gas turbine would just run at low power for the entire trip. The cycling the battery to then allow the gas turbine to run at peak efficiency would still have a 5% electrical recharging loss. Fuel usage would be the same to just having the gas turbine running at low power and having a 5% efficiency loss on the


With IEP everything is still connected to the same high voltage backbone. I would consider the very large battery and microreactor provide redundancy to each other.



The 3 largest manned conventional submarines are near 4,000 ton displacement and could be converted to use a microreactor in the next iteration.

Taigei-class submarine
KSS-III
Orka-class submarine

A 5MW eVinci could fit where the diesel generators and fuel tanks are located. Keep the existing batteries to allow for short bursts of speed or to operate with the reactor off.

Modern container ships can hit 20kn to say nothing of military ships. You want 20kn transits to prevent subs from catching up and using torpedos as easily. Now you are only vunerable to prepositioned subs launching torpedos and missiles. The latter of which is lower threat than that from a surface ship or aircraft due to fewer total missiles.

So a large battery wouldn't be useful at all for the convoy escort mission I envisioned then?

My point is there's no benefit to having a large battery, so you can not have it.

For a submarine that usage makes allot of sense, as batteries will be allot quieter than the the steam plant from these reactors.

 

[DJK]

With IEP everything is still connected to the same high voltage backbone. I would consider the very large battery and microreactor provide redundancy to each other.

Would have minumum 2 high voltage backbones, although propulsion obviously has its own voltage so there should also be physically separated circuits for each motor, and fully redundant switchgear and VFDs. I wouldn't be suprised if a 3rd backup bus made sense for maximum resilience.

You


The 3 largest manned conventional submarines are near 4,000 ton displacement and could be converted to use a microreactor in the next iteration.

Taigei-class submarine
KSS-III
Orka-class submarine

A 5MW eVinci could fit where the diesel generators and fuel tanks are located. Keep the existing batteries to allow for short bursts of speed or to operate with the reactor off.

A reactor cant just "fit", the whole boat has to be reballasted and have enough volume to compensate for lost buoyancy. A new design UUV though...

 

[MadRat]

Batteries make sense when you have a major mishap or having taken damage on the open ocean. I would feel better under a controlled 6 knots than adrift. And oh by the way, when you have things like batteries and solar panels that may be too weak to power a radar, they sure are handy for running bilge pumps, davits, machine tools, and other useful things that keep you afloat, possibly improving the situation, and moving.

Would have minumum 2 high voltage backbones, although propulsion obviously has its own voltage so there should also be physically separated circuits for each motor, and fully redundant switchgear and VFDs. I wouldn't be suprised if a 3rd backup bus made sense for maximum resilience.

I would want a reconfigureable mesh with no fewer than three points per hub, not be limited to a simple two. You have engineers onboard for that kind of thing.

 

[insidersource]

Modern container ships can hit 20kn to say nothing of military ships.

I was curious so I checked 100 container ships currently in the open ocean. About 80% had a speed between 12 and 16 knots. This is roughly what I expected as there would be massive fuel savings for travelling slower.

However in your scenario where a convoy of ships requires an escort then saving fuel would not be a concern.

My 10MWe reactor is assuming a destroyer that doesn't exceed 10,000 ton. 10-15 MWe microreactors would be in that sweet spot.

A tiny 5MWe microreactor would still produce a 50% fuel saving over the life of the ship. Take an average 16 knot transit where the ship needs 10MW. Half is supplied by the microreactor, half by a fossil fuel generator. This is still a significant fuel saving.

By comparison a much larger 25MWe micro reactor would see all of your mission profiles being performed without requiring a gas turbine at idle. The microreactor could handle all speeds up to a swift 25 knots. Possibly 95% of the fuel would be saved over the life of the ship. Your smaller 5MWh would be sufficient to handle a power burst as the gas turbine is powering up

The sweet spot is somewhere these two sizes.

 

[CastleBravo]

I was curious so I checked 100 container ships currently in the open ocean. About 80% had a speed between 12 and 16 knots. This is roughly what I expected as there would be massive fuel savings for travelling slower.

However in your scenario where a convoy of ships requires an escort then saving fuel would not be a concern.

My 10MWe reactor is assuming a destroyer that doesn't exceed 10,000 ton. 10-15 MWe microreactors would be in that sweet spot.

A tiny 5MWe microreactor would still produce a 50% fuel saving over the life of the ship. Take an average 16 knot transit where the ship needs 10MW. Half is supplied by the microreactor, half by a fossil fuel generator. This is still a significant fuel saving.

By comparison a much larger 25MWe micro reactor would see all of your mission profiles being performed without requiring a gas turbine at idle. The microreactor could handle all speeds up to a swift 25 knots. Possibly 95% of the fuel would be saved over the life of the ship. Your smaller 5MWh would be sufficient to handle a power burst as the gas turbine is powering up

The sweet spot is somewhere these two sizes.

I would just stick with something like evinci. If you need 10 MWe, install two of them. If you need 20 MWe, install four. They use open air brayton cycle turbines just like normal warship gas turbine engines, so it would be possible to design a hybrid turbine that gets heat from the reactor(s) like it would from a recuperator, and then add more heat by burning fuel when you need additional power. This way you get to use bigger more efficient turbine, and you don't need to cold start it for high power output, it's already spun up and running on nuclear heat.

 

[Scott Kenny]

I would just stick with something like evinci. If you need 10 MWe, install two of them. If you need 20 MWe, install four. They use open air brayton cycle turbines just like normal warship gas turbine engines, so it would be possible to design a hybrid turbine that gets heat from the reactor(s) like it would from a recuperator, and then add more heat by burning fuel when you need additional power. This way you get to use bigger more efficient turbine, and you don't need to cold start it for high power output, it's already spun up and running on nuclear heat.

Had not considered that option!

Excellent point.

 

[Nicknick]

I would just stick with something like evinci. If you need 10 MWe, install two of them. If you need 20 MWe, install four. They use open air brayton cycle turbines just like normal warship gas turbine engines, so it would be possible to design a hybrid turbine that gets heat from the reactor(s) like it would from a recuperator, and then add more heat by burning fuel when you need additional power. This way you get to use bigger more efficient turbine, and you don't need to cold start it for high power output, it's already spun up and running on nuclear heat.

There are some gas cooled reactors which work with gas turbines, but they use recuperators. The working fluid is helium, because all of them use graphite as moderater and air would directly ignite the carbon fuel pellets which would cause immediately a large disaster....

 

[Scott Kenny]

There are some gas cooled reactors which work with gas turbines, but they use recuperators. The working fluid is helium, because all of them use graphite as moderater and air would directly ignite the carbon fuel pellets which would cause immediately a large disaster....

Air/helium heat exchanger instead of a direct helium turbine.

 

[Nicknick]

Despite the temperature loss, you might imagine how critical it would be to prevent absolutly every possible leakage. You can imagine what would hapoen if pressurized air will get into contact with super hot radioactive graphite....

 

[Scott Kenny]

Despite the temperature loss, you might imagine how critical it would be to prevent absolutly every possible leakage. You can imagine what would hapoen if pressurized air will get into contact with super hot radioactive graphite....

That's why you keep the helium side at higher pressure than the air side.

But yes. oxygen + graphite-moderated reaction = Chernobyl.

 

[Nicknick]

So what if something on the helium side explodes and damages the heat exchanger? You can use solutions like that anywhere else, but not in a nuclear reactor.. In this applucation yoy would have to add an additional loop for the heat transfer, like molten salt.

 

[CastleBravo]

There are some gas cooled reactors which work with gas turbines, but they use recuperators. The working fluid is helium, because all of them use graphite as moderater and air would directly ignite the carbon fuel pellets which would cause immediately a large disaster....

That's why I like the heatpipe cooled designs, there is no coolant flow through the reactor other than the working fluid in the sealed heatpipes, and the reactor vessel can be kept at 1bar. Air can't get into the reactor unless an individual heatpipe fails on both both the hot and cold ends. The main danger I see is a risk of the heatpipe failing on the cold end and leaking the neutron activated working fluid into the turbine air stream. K or NaK working fluids turn into strong gamma emitters after neutron activation, so they are out unless you are putting both the reactor and the turbine in a shielded space. Li7 would turn into a Beta emitter, so far easier to shield against, but would still kill you if you breath it. It might be a good idea to have a secondary loop between the heatpump exhanger and the turbine exchanger to keep the spicy stuff away from the main engines. I still like the idea of putting the reactor(s) on the stern where they can be separated from the ship if needed.

 

[Scott Kenny]

So what if something on the helium side explodes and damages the heat exchanger? You can use solutions like that anywhere else, but not in a nuclear reactor.. In this applucation yoy would have to add an additional loop for the heat transfer, like molten salt.

Doesn't take a very large pressure differential to prevent the cross contamination.

 

[MadRat]

Gradients tend to promote mixing.

 

[Nicknick]

Doesn't take a very large pressure differential to prevent the cross contamination.

You need to be prepared for all kinds of scenarios and protect the reactor against battel damage. If there is just one single barrier between pressurized air and hot, radioaktive carbon, it is not enough.

The heat pipe solution above would help, bue every heatpipe has a fixed narrow temperature range, this doesn't work well with a variable power output.