Gas Turbine uses Hot Carbon Dioxide - Ideal for Mars

tahanson43206 · 2023-09-06 10:55:49

This topic is intended to offer a place for members to collect links and text about the use of CO2 to drive a gas turbine.

The subject has come up previously in other topics, but this topic is dedicated to the technology, because it is so well suited for Mars.

(th)

tahanson43206 · 2023-09-06 10:56:42

Google search: is there such a thing as a gas turbine that runs on hot carbon dioxide

Generative AI is experimental. Info quality may vary.
Yes, there are gas turbines that run on hot carbon dioxide gas. These turbines use supercritical carbon dioxide, which is kept at high pressure and temperature. The carbon dioxide is in a state between a gas and a liquid, allowing the turbine to generate power.
The Japanese company Toshiba developed a gas turbine that uses CO2 gas produced at 1150°C and 300 bar. Echogen Power Systems in Akron, Ohio designed an 8-MW generator that uses supercritical CO2 to turn waste heat into electricity. The process produces about 20% more power than a gas turbine alone.
Supercritical carbon dioxide is easier to compress than steam. This allows a generator to extract power from a turbine at higher temperatures. The result is a turbine that can be 10 times smaller than a steam turbine.

(th)

kbd512 · 2023-09-06 17:03:15

tahanson43206,

The Toshiba device is a supercritical CO2 turbine / SCO2 turbine. It's "spun" using highly compressed CO2 in a supercritical state, as opposed to liquid or gas state. SCO2 "gas turbines", which look a lot like gas turbines because they're a special type of gas turbine, operate in a closed-loop cycle using a heat exchange device, but without the pressure dropping below that required to maintain CO2 in its supercritical state. A separate Methane / oil / coal burner / other heat source, such as a nuclear reactor or geothermal well, must supply the input thermal energy into the CO2 loop. These are useful because they're generally about 1/10th the size and weight of traditional steam turbines for a given power output. The rotating assembly of a 10MW SCO2 turbine can be picked up using one hand. You'd need a crane to do the same thing with a 10MW steam turbine.

The casing halves surrounding the 10MW SCO2 turbine are much heavier, though, each one weighing approximately the same as a big block V8, to contain the very hot and very highly pressurized SCO2. 300 bars of pressure is about 4,410psi. 1,150C is turbine inlet / "hot section" type of "hot", for a normal gas turbine. The difference is pressure / compression associated with a normal "jet engine hot section" is about 30 bar / 441psi. SCO2 turbines are suitable for powering ships, locomotives, and power plants. In terms of total weight, GE's LM2500 marine gas turbine that powers Arleigh Burke class destroyers and Ticonderoga class cruisers comes closest. LM2500s and LM6000s are aero-derivative engines, based upon the GE CF6 engine core that powers the Airbus A300 and A330, Boeing 747 and 767, McDonnell Douglas DC-10, Lockheed C-5 Galaxy.

A 20MW SCO2 turbine skid weighs about as much as the LM2500 turbine skid, which weighs 23,000kg on shock mounts. The new LM2500+ will have a better power-to-weight ratio, as compared to the non-optimized SCO2 turbine designs, which are still in their infancy. The attached motor-generator skid to provide electrical power output, vs direct mechanical shaft horsepower for a ship, weighs about the same as the LM2500 skid. Integrated Electric Propulsion eliminates propeller shafts, but azipod thrusters are more delicate, typically less reliable, drastically more expensive to repair, and add considerable total weight over gearboxes and prop shafts. Azipods are not more efficient or lighter, despite misleading marketing claims to the contrary, as they only eliminate the propshaft(s). Azipods can and typically do make the ship more maneuverable at low speeds. You lose 10%+ of the attached engine's mechanical horsepower output by converting mechanical horsepower into electricity, using an electric power cable to transmit the electrical power to the azipod thruster, which also contains an equally large / heavy / expensive electric motor.

LM2500 Pocket Guide for Sailors

What, you don't carry around a 311 page guidebook in your back pocket?

People on Mars will have an iWatch or something similarly sized, a helmet with a projector screen, and complete assembly / disassembly instructions with videos. They'll know exactly what parts and tools are required for every job, with every nut / bolt / washer containing laser-etched QR codes, and diagrams to show our new repair worker all possible places that pesky extra nut or bolt might have come from on the machine they're attempting to repair.

Anyway...

The physical components on the SCO2 turbine skid are more compact than the LM2500, with the SCO2 turbine itself being drastically smaller- roughly the same size as a kitchen trash can, but there's also more of them. The SCO2 turbine skid contains a dual-pass turbine, almost exactly like the high / low pressure steam turbines of a ship, a reduction gear drive, control panel, heat exchanger, and burner. The motor-generator skid contains a large generator, lube oil and heat exchanger setup, controller, and terminals for the wiring. SCO2 turbines use lube oil or gas bearings. The newest rotating assemblies and major components have been designed for 100,000hr service life.

Specialized steel alloys like Inconel (Nickel-Steel) must be used for the turbine itself, with various stainless or Inconel castings used for the casing halves. The piping and heat exchanger must also be made from Inconel or stainless. At 1,150C, everything has to be Inconel. Stainless would be silly putty at that temperature.

tahanson43206 · 2023-09-06 18:08:10

For kbd512 re Post #3

Thank you for the detailed analysis of the new turbine in comparison to it's peers!

Thanks in particular, for pointing out the closed loop design, which (I understand) permits the system to maintain the high pressure that allows it to operate.

There is a question that occurs to me, that might round out your presentation, if you have a few more minutes to devote to it. The closed loop system you've described is going to need a ** very ** effective heat sink to draw off the thermal energy not consumed in conversion to mechanical power. While a shipboard installation has an ocean to help with cooling, is it possible the system would not be well suited for Mars because there is so little water, or is it possible that the naturally cool environment might be capable of dissipating the waste heat?

On several occasions over time and recently, Calliban has made the point that low grade heat on Mars would be useful for space heating. Is it possible that the low grade thermal energy consuming infrastructure can be sized to match this turbine, which (I presume) would be matched to an appropriately sized nuclear reactor?

The mass you've cited for a power plant based upon this techology appears to total up to less than the 40 tons NASA is said to want to be able to land gently on Mars, so it seems possible an entire plant might be delivered to Mars without further assembly required.

A nuclear reactor might be shipped in a separate 40 ton delivery.

The combination could go to work shortly after landing, making propellant and materials needed for life support, as well as such other related activities as may be considered high priority.

(th)

kbd512 · 2023-09-06 20:04:17

tahanson43206,

For the 40kWt KiloPower type reactors, it should be possible to generate 20kWe. A 250kWe SCO2 gas turbine is about the same diameter as the US Quarter Dollar coin and approximately 1" long including the bearing shaft on either side of the turbine blades. A 20kWe SCO2 power turbine would be tiny. We need an electric motor of similarly small size, perhaps something using Copper-doped CNT wiring and high temperature capable Iron-Nitride permanent magnets. Beyond that, we need Carbon Fibers brazed onto Inconel radiator tubing to drastically reduce the size and weight of the radiator compared to the all-metal one. The only practical way to reduce the size of the core is to use Pu239 or HEU, which has been ruled out, so HALEU is what we're stuck with, which will require a modest increase in core size over the original KiloPower design.

tahanson43206 · 2023-09-06 20:27:00

For kbd512 re post #5

Thanks for this important addition to the topic!

Your explanation of the physical size of the turbine is particularly helpful, and I hope there are readers of this forum beyond our existing membership, to benefit from the word picture you've created.

Can I bring you back to the heat sink question?

There needs to be a way to direct the 60% (or so) of the reactor thermal energy that is NOT consumed by the SCO2 turbine to a useful purpose.

On Earth, the ocean is available to absorb thermal energy that must be removed from the system, if the engine is located on a ship.

On Mars, there is no ocean, and water is going to he in short supply.

The NASA vision for their little 10 Kw reactor was to point radiators at the sky.

That seems unlikely (to me at least) to be a viable solution for a reactor/turbine system as large as is needed for a ** real ** propellant manufacturing plant.

Calliban has spoken of using waste heat for a productive purpose, such as heating habitats and greenhouses. That would require a working fluid. If water is found an any quantities on Mars, that would seem to be a reasonable choice for the coolant. Otherwise, designers will have to come up with something else.

(th)

kbd512 · 2023-09-07 02:42:59

tahanson43206,

All of the generated heat could be dumped into a water tank and then used to slowly generate mechanical and thermal power using a refrigerant loop, such as CO2, Ammonia, or Propane inside a normal refrigerator's refrigerant loop. This would be an example of a thermal battery. It's largely mechanical rather than electrical technology, but electrical power could also be generated. If water is truly in short supply, then humans won't be living on Mars for very long. That said, other "found on ground" materials such as Sulfur or salts could be substituted, and then the thermal battery can be operated at higher temperatures for improved efficiency, no steam pressure to counteract with a thicker storage tank wall, and so on. You still have to melt ice somehow, assuming we're going to live on Mars, and a reactor is a better-than-average way to do that.

We've yet to demonstrate the Sabatier process at commercial scale here on Earth, so we won't have any "real propellant plants" until NASA becomes seriously interested in using the technology on Mars. Thus far, they've conducted a few lab experiments, but nothing remotely resembling a full scale propellant plant demonstrator.

Calliban · 2023-09-07 10:54:05

Kbd512 has already provided some excellent information on this concept. It has been almost 10 years since I designed an S-CO2 cooled, direct cycle fast reactor. I havn't really kept up with the technology since then. Back then, most of my reference material came from research carried out at MIT. They were looking at developing a power conversion system for use in Gen 4 reactors. Their baseline assumed an inlet temperature of 550°C into the turbine. A recouperator was included, which raised the cycle efficiency. The inlet temperature was chosen to allow the cycle to achieve a 40% generation efficiency at a pressure of 20MPa. A temperature of 550°C, allows stainless steels to be used for pressure systems. This is a lot cheaper than nickel alloys and easier to form and weld.

The power density of the turbine is indeed huge. A 10MWe unit would be about the size of tube of pringles. Unfortunately, the heat exchangers tend to be quite bulky. To mitigate this problem, the MIT researchers suggested the use of printed circuit heat exchangers. Even with this innovation, the heat exchangers ended up having 10x the volume of the turbine itself.

My choice of a direct cycle, CO2 cooled fast reactor was driven by two considerations. I wanted a compact plant concept overall. A direct cycle suited that goal. I also wanted a hard neutron spectrum, for rapid breeding. My concept design was a 2000MWe four-loop plant, with compact hexagonal fuel assemblies and a system pressure of 20MPa. The fuel was uranium-plutonium nitride, clad in stainless steel. The fuel rods were regularly cross-braced to dampen the extreme vibration that would occur due to the high flowrate of CO2 through the high power density core. One big problem with using gas to cool a fast reactor core is potentially high pumping power requirements. To mitigate this problem, the blowers were directly coupled to the turbine shafts. From memory, I was able to achieve a power density of 500MWth/m3. But to achieve that pumping power consumed about 20% of the shaft power from the turbine, which was excessive. I noted at the time that tube-in-shell fuel (which consists of a stainlesssteel clad coolant tube passing up the middle of a solid hexagonal fuel assembly) would have reduced pumping power requirements and could have allowed higher fuel temperatures and better heat transfer. Each of the four loops had its own S-CO2 turbogenerator set, with its own heat exchangers.

The reactor system, generating loops and containment volume, would have had about one tenth of the total volume of an AP1000 PWR containment dome, despite producing twice as much power. The S-CO2 power generation loops were actually about the same size as the AP1000 steam generators. So the entire 2000MWe plant (including generation loops) would fit inside an AP1000 containment dome with room to spare. These crazy system power densities would have allowed SMR factory construction techniques to be applied to a reactor producing GWe power levels. So components could be shipped in by road and rail and only needed to be welded or flanged together onsite.

The reactor vessel itself was a composite structure. The core included breeder blanket assemblies, which also helped provide gamma shielding. The core was housed within a relatively thin stainless steel vessel. The stainless steel vessel transferred pressure load to surrounding interlocking cast iron segments. Cast iron has much higher compressive strength than concrete. The iron plate also functioned as both baffle plates, protecting the surrounding concrete from high gamma-neutron and a thermal shield for the concrete. The cast iron structure was surrounded by concrete pressure vessel, with the pressure stress being absorbed by pre-stressed steel tendons running through tubes in the concrete. This was a development of PCRVs developed for UK gas reactors. However, the 20MPa operating pressure of the gas cooled fast reactor, required an inner lining of cast iron to spread the load and keep compressive stresses within the crush strength of the concrete.

The hard neutron spectrum would have resulted in a high breeding ratio. One advantage that this should allow (but I wasn't able to confirm) would be a breed and burn cycle. After the first fuel load of plutonium-uranium fuel, all additional fuel loaded into the reactor at the outer edge of the breeder blankets would have been natural or depleted uranium. This would breed fissile plutonium by absorbing neutrons and would gradually be shuffled towards the centre of the core. By the time it reached the inner core, it would contain about 20% plutonium. It woukd be discharged at 10-20 atom% burnup. Reprocessing would only be needed to turn spent fuel into starter cores for new reactors.

Last edited by Calliban (2023-09-07 11:28:30)

tahanson43206 · 2023-09-07 11:12:00

For Calliban re #8

Thank you for building in kbd512's post, and for reporting on your design work.

I have no way of knowing if your work could be built in the Real Universe, but I'm hoping it could and that the obvious need in Panama is an opportunity.

Your recommendation to size plant(s) for Panama so they run "normally" at some reasonable fraction of their full power capability, so that industry and citizens of Panama can count upon reliable electric power that does not require imported fossil fuels.

The backlog of ships waiting to cross the Isthmus of Panama is reported to be up to 21 days, not including those whose owners pay an extra 1-3 million USD to jump the line.

I am still not clear on who (or what organization) might be best to receive a proposal for a nuclear plant (or pair of the) to solve the water problem for the canal itself, while delivering reliable baseline power to the citizens and selected industries.

I presume at a minimum the Government of Panama (His Excellency Laurentinno Cortizo) and the Panama Canal Authority (Dr. Ricaurte Vasquez Morales) would be key players in any project along these lines.

wikipedia.org/wiki/Laurentino_Cortizo >> Incumbent President of Panama (2019) ... the turm of office is 5 years, so it expires in July of 2024. That ** may ** be enough time to initiate a major power project on the scale we are discussing here.

(th)

Calliban · 2023-09-07 11:39:08

From what I can tell, a system like I designed would be over the top for what your Panama canal project needs. The pumping power needed for the canal itself would be a few ten's MW from what you have described. The population of Panama is 4.3 million. Assuming roughly UK levels of electricity consumption, just one of these 2GWe reactors would cover the power needs of the whole country. Then you have the problem of how to meet demand when it shuts down for refuelling.

My designed system was intended for large grids, such as those seen in US, Europe and East Asia. My assumption was that we were going to experience an energy crisis and needed a system that could increase capacity very quickly to ramp up power production. US annual electricity demand is about 4000TWh, which is an average power of 460GWe. So 120 of these 2GWe units would meet around half of US electricity demand. If we could factory build these things and assemble a dozen of them a year, this could be achieved in about a decade of construction. The best option wouod be to build 2-4 units on a single site, thereby sharing site services and keeping overall costs down.

On Mars, a system like this would allow nuclear capacity to increase rapidly as population expands into the millions. We have established that Mars settlements will have very high per capita power requirements. Mars also appears to be depleted in uranium and thorium. If population is to grow fast, we need breeder reactors. To build rapidly and cheaply, we need modular systems in which individual components are all factory made and quickly assembled onsite. Combining high power with modular construction points to a requirement for high system power density. There are only a few systems that can really do that and be safe at the same time.

Last edited by Calliban (2023-09-07 11:54:45)

tahanson43206 · 2023-09-07 12:46:45

A proposal for Panama needs to be sized appropriately.

The highest priority (I would think) would be a perception of safety.

It seems clear that the Nation has the ability to raise billions of monetary units for a project that makes sense to them.

Google came up with this citation:

About 13,600,000 results (0.48 seconds)
But as thousands of ships have used the canal since then, some much-needed improvements of the waterway were necessary, and now the $5.2 billion Panama Canal Expansion Project was completed on June 26th under the direction of a Texas A&M University at Galveston graduate.
Panama Canal Expansion Completed with Texas A&M ...

I would think that the design team would be conscious of the need to provide reassurance against disaster due to:

1) Tsunami (not an idle concern)
2) Sea level rise (inevitable)
3) Earthquake
4) Terrorist attack
5) Supply exhaustion/denial

There may be other concerns that must be addressed.

If the project proposal comes out of the UK, the support of the government and the population would be a plus.

If the project proposal comes out of the UK, a major partner (such as Rolls Royce) would be a plus

The global power supply vision could follow a success on the scale of a (small) Nation.

(th)

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#1 2023-09-06 10:55:49

Gas Turbine uses Hot Carbon Dioxide - Ideal for Mars

#2 2023-09-06 10:56:42

Re: Gas Turbine uses Hot Carbon Dioxide - Ideal for Mars

#3 2023-09-06 17:03:15

Re: Gas Turbine uses Hot Carbon Dioxide - Ideal for Mars

#4 2023-09-06 18:08:10

Re: Gas Turbine uses Hot Carbon Dioxide - Ideal for Mars

#5 2023-09-06 20:04:17

Re: Gas Turbine uses Hot Carbon Dioxide - Ideal for Mars

#6 2023-09-06 20:27:00

Re: Gas Turbine uses Hot Carbon Dioxide - Ideal for Mars

#7 2023-09-07 02:42:59

Re: Gas Turbine uses Hot Carbon Dioxide - Ideal for Mars

#8 2023-09-07 10:54:05

Re: Gas Turbine uses Hot Carbon Dioxide - Ideal for Mars

#9 2023-09-07 11:12:00

Re: Gas Turbine uses Hot Carbon Dioxide - Ideal for Mars

#10 2023-09-07 11:39:08

Re: Gas Turbine uses Hot Carbon Dioxide - Ideal for Mars

#11 2023-09-07 12:46:45

Re: Gas Turbine uses Hot Carbon Dioxide - Ideal for Mars

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