[HN Gopher] A tiny supercritical carbon dioxide turbine can powe...
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A tiny supercritical carbon dioxide turbine can power 10k homes
Author : thelastgallon
Score : 74 points
Date : 2023-10-30 16:34 UTC (6 hours ago)
(HTM) web link (cleantechnica.com)
(TXT) w3m dump (cleantechnica.com)
| anonymouskimmer wrote:
| 10% is a nice gain. I wonder what that translates to in power
| output gains.
| exabrial wrote:
| I'm guessing with a significantly smaller footprint, you can
| have more of them in a single building. I'm also guessing this
| means because more of them, you gain more redundancy. Whats not
| mentioned is if there is a decrease is part count, which are
| usual drivers of cost, maintainability, and reliability.
| abdullahkhalids wrote:
| > the Energy Department calculates that a 20-meter steam turbine
| would shrink down to one meter if replaced with an sCO2 turbine.
|
| Where do these improvements come from [1].
|
| > CO2 has a relatively low critical pressure of 7.4 megapascal
| (MPa) and a critical temperature of 31C ... A consequence of this
| is that it can be compressed directly to supercritical pressures
| and readily heated to a supercritical state before expansion. In
| a heat engine, this can facilitate obtaining a good thermal match
| with the heat source. The critical temperature is also
| sufficiently high for ready heat rejection from the cycle at
| terrestrial ambient temperatures. Therefore, the system has a
| great potential for high efficiency since a large temperature
| difference is available ... CO2 near its critical point becomes
| more incompressible and hence, the compression work can be
| substantially decreased leading to high cycle efficiency.
|
| > The high density and volumetric heat capacity of sCO2 with
| respect to other working fluids make it more energy dense,
| meaning that the size of most system components such as turbine
| and pump can be considerably reduced, which leads to a smaller
| plant footprint and possibly lower capital costs.
|
| [1] https://www.powermag.com/what-are-supercritical-co2-power-
| cy...
| adrian_b wrote:
| Due to the high pressure in the closed circuit, the density of
| supercritical CO2 is similar to that of a liquid, and this
| allows very small turbines and pumps for a given power.
|
| Nevertheless, the circuit must also include heat exchangers and
| those are not reduced in size as much as the turbines and the
| pumps.
|
| Therefore the very small sCO2 turbine will be accompanied by
| much larger heat exchangers, so the reduction in size of a
| complete system is not so impressive as the shrinking of the
| turbine.
|
| Even so, the sCO2 system has another advantage over the
| traditional steam turbines, when used for the recovery of the
| waste heat from a gas turbine, or when using any other high-
| temperature heat source, like a nuclear reactor. Because the
| steam generation happens at a constant temperature, which must
| be relatively low for reasonable pressures, the heat transfer
| from a high-temperature source is inefficient. Due to this, for
| the recovery of the waste heat of a gas turbine are used
| typically 3 steam turbines whose steam generators work at
| different temperatures and pressures, not a single turbine.
|
| Supecritical CO2 can be heated with a heat exchanger having a
| gradient of temperature along it, which allows a single sCO2
| turbine to replace 3 steam turbines in a combined-cycle power
| plant.
| perihelions wrote:
| - _" or when using any other high-temperature heat source,
| like a nuclear reactor. Because the steam generation happens
| at a constant temperature, which must be relatively low for
| reasonable pressures, the heat transfer from a high-
| temperature source is inefficient "_
|
| Nuclear (fission) reactors really aren't high-temperature
| heat sources. The working fluid inside reactors is itself
| liquid water, which doubles as a neutron moderator. That
| severely limits their temperature range (<374deg C), so,
| there's no downside to limiting yourself to steam on the
| energy conversion side as well.
|
| The linked articles make brief mention of a nuclear/sCO2
| combination, but, to be clear, they're talking about
| radically different types of nuclear reactors. Not types that
| are currently commercialized/mature technology. Types where
| you replace the working fluid on the nuclear side with
| higher-temperature compatible substances--molten metals,
| molten fluoride salts, or inert gases like CO2 or helium.
|
| edit: Also applies to nuclear _fusion_ , I guess. IIRC, the
| proposed working fluids for those are molten lead/lithium, or
| molten lithium fluoride--both match with the sCO2 temperature
| range. (Lithium is the common factor, because the overriding
| concern of the working fluid is to transmute lithium into
| tritium, using the fusion reactor's neutron flux, to
| hopefully allow a sustainable fuel cycle).
| amluto wrote:
| > The working fluid inside reactors is itself liquid water,
| which doubles as a neutron moderator.
|
| There are fission reactor designs with different working
| fluids that operate at much higher temperatures.
| abdullahkhalids wrote:
| Thanks for the perspective. The reduced size is also dwarfed
| by however the CO2 is being heated. If by concentrated solar
| field of many acres, than the size of the turbine doesn't
| matter on its own. What matters is if the reduced size leads
| to reduced complexity/cost/maintenance burden.
| adrian_b wrote:
| There are different methods for concentrating the solar
| light, some of them are able to achieve only lower
| temperatures, for which it is more efficient to use organic
| Rankine cycles (i.e. like the steam turbines, but instead
| of using water some organic fluids, which are similar to
| those used in air conditioning or in refrigerators, are
| used in closed cycle), while other methods, e.g. the solar
| towers, can achieve higher temperatures that are suitable
| for supercritical CO2 cycles.
| matthewdgreen wrote:
| Over the past few years I've heard a number of complaints
| that new steam turbines are very hard to buy: they're big and
| complex to manufacture, and the supply chain for them is very
| restricted. This has apparently held up some new power plant
| deployments over the past few years. Are those issues still
| significant, and will the ability to use smaller (and fewer)
| turbines make a big difference?
| moffkalast wrote:
| So does that also mean that SMRs could be made even more
| compact? Or that one could increase reactor size and run a
| 20-meter sCO2 turbine generating as much as a 400-meter
| turbine?
| KennyBlanken wrote:
| I don't see how reducing turbine size is a good thing. Power
| plants aren't just a source of power; they're a source of
| mechanical inertia for the grid.
|
| I suppose you can compensate by incorporating energy storage,
| which also has the side benefit of allowing the plant to be
| self-sufficient for cold-start.
| Animats wrote:
| More useful: [1]
|
| This is just a natural gas powered generating plant using a
| different working fluid. The goal is to get from current
| efficiencies approaching 48% to somewhere above 50%.
|
| The record for a natural gas powered plant is 68% efficiency.[2]
| That's a gas turbine. Indirect heating, with combustion to
| working fluid to turbine, is less efficient. However, if CO2 as a
| working fluid results in a smaller plant, it might be worth it
| for some applications.
|
| [1] https://netl.doe.gov/project-information?p=FE0028979
|
| [2] https://www.power-eng.com/gas/ge-powered-plant-awarded-
| world...
| auspiv wrote:
| It is worth noting that the highest efficiency gas turbines are
| combined cycle. That is, the waste heat is captured almost in
| entirety to make steam to run other turbines (potentially part
| of the same generating unit) to increase efficiency.
|
| From a grid standpoint, peaker gas turbines can go from 0 to
| 100% in a few minutes. Combined cycle turbines can take a
| couple hours. They are precision machines and need to warm up
| to operating temperature much slower.
| perihelions wrote:
| - _" steam turbines[...] are based on 19th century technology...
| new supercritical carbon dioxide turbines... high tech
| supercritical carbon dioxide ..."_
|
| For some grounding context: gas turbines are also century-old
| technology, and supercritical CO2 as the working fluid is pretty
| obvious and was extensively looked at in the 1970's [a] (and
| perhaps earlier). There's no qualitatively new stuff here; it
| looks more like a reopening of old and simple ideas due to
| shifting economics.
|
| I'm definitely not trying to assign a pro-/con- valence on the
| tech--I just prefer clearly-grounded discussions, not puff
| pieces.
|
| [a] e.g., https://ntrs.nasa.gov/citations/19760016593 ( _" Energy
| Conversion Alternatives Study (ECAS), General Electric Phase 1.
| Volume 2: Advanced Energy Conversion Systems. Part 2: Closed
| Turbine Cycles"_ [1976])
| ilaksh wrote:
| That's interesting and sounds like a significant improvement.
| What I am really interested in though are sustainable fuels like
| ammonia, hydrogen or anything else.
|
| Making fuel from solar and wind seems key to me. Because you need
| long term energy storage and batteries don't cut it.
| gumby wrote:
| I don't think anyone seriously believes that ammonia or H2 are
| in any way sustainable fuels.
|
| But you're right that we definitely need something better than
| batteries for certain applications, particularly transport.
| sn0wf1re wrote:
| This[1] was posted yesterday. I think people are hopeful that
| ammonia production can be made cheap enough to use as a
| seasonal battery or for applications such as planes or ships.
|
| https://news.ycombinator.com/item?id=38053586
| Gasp0de wrote:
| Why not? With a 100% renewable energy supply, there needs to
| be a lot of overprovisioning. This means that in summer, we
| will have excess energy, which can be converted to hydrogen
| or other forms. This will easily be enough to get us through
| the few days per year where neither sun nor wind can deliver
| enough power. Efficiency doesn't matter much, since the
| energy is excess/free. What matters is the rest of the cost,
| e.g. building electrolyzers, hydrogen storage and power
| plants that are only used a few days per year.
| 10u152 wrote:
| The article focuses on size over and over again. Nobody cares
| about the size. Efficiency, scalability is key.
| Gasp0de wrote:
| Large percentages of renewable energy will require a large
| amount of power plants powered by fossil gas or hydrogen for
| those few days per year where there is not enough renewable
| power. If these can just be integrated into cities due to their
| small size that's definitely a plus, as it makes the transport
| of energy more efficient.
| scotty79 wrote:
| Scalability is related to the size. You can have hundred times
| more of a thing that's one hundredth in size.
| waterheater wrote:
| Interested folks should check out the Allam cycle [1] and NET
| Power [2], which has successfully built and operated a carbon-
| dioxide turbine test facility and is now building a full-scale
| plant in Texas.
|
| NET Power's approach has some significant differences from the
| DoE's. In their cyclical approach, natural gas and pure oxygen
| (obtained from an on-premises air separator) are combusted to
| form high-pressure CO2 and water. This mixture goes through a
| turboexpander, which generates electricity and lowers the
| pressure of the CO2-water mixture. After passing through a heat
| exchanger, the water is separated out as byproduct, and some
| amount of CO2 is also pumped out as byproduct. The remaining CO2
| passes through the heat exchanger, brought back to high-pressure,
| and returns to the start of the cycle.
|
| It's a quite incredible all-byproduct, no-emission energy
| generation process.
|
| [1] https://en.wikipedia.org/wiki/Allam_power_cycle
|
| [2] https://netpower.com/technology/
| TSiege wrote:
| This doesn't seem to me that it's "no-emission" it reads more
| that it the co2 is captured at the source. As a lay person I
| would assume "no-emission" means no co2, but maybe I'm wrong
| here?
| tln wrote:
| "Though only about the size of an office desk, household
| refrigerator, pony, credenza, or golf cart"
|
| Wow
|
| "the new turbines are powerful enough to generate the electricity
| equivalent of 10,000 typical homes"
|
| Average home power consumption is about 1kW... 10MW output in a
| turbine the size of desk/refrigerator/pony/credenza/golf cart??
|
| Wind turbines are 10-20 MW and just the generators are around 150
| tons... or 300 ponies
| exabrial wrote:
| If anyone wonders why technological innovation with green tech
| often runs into roadblocks, it's because we can't go 10m without
| brining identity politics into the discussion. The bottom
| paragraph has absolutely nothing to do with supercritical c02
| turbines, but instantly turns it into a red vs blue issue.
|
| I'm on the side of efficiency, note vote harvesting, and it
| doesn't need to part of the discussion; handle it elsewhere.
| KennyBlanken wrote:
| It runs into roadblocks because an overpowered minority faction
| refuses to support policy and funding decision-making using
| evidence-based scientific consensus, and given the new speaker
| is a political extremist who has declared all his decision-
| making is based on a fictional book, is known to be a
| creationist and climate-change denier, and comes from a party
| that almost as a matter of policy opposes virtually all
| evidence-based science when it comes to policy...yeah, I think
| it's relevant to mention it.
|
| Claiming disagreements are "just identity politics" is a way of
| shifting an argument from factual debate to "you don't like me
| because I don't agree with you."
| dtx1 wrote:
| So this has got me thinking, tell me where this breaks down: If
| we take a heatpump and extract heat from the air or better, a
| river or the ocean, could these turbines be used to generate
| enough electricity from the extracted heat to be overall energy
| positive?
| lazide wrote:
| You'd need a corresponding reservoir of 'cold' with a big
| enough temp delta to make it economic.
|
| So, no.
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