6 ms·
A tiny supercritical carbon dioxide turbine can power 10k homes
- anonymouskimmer 3y ago10% is a nice gain. I wonder what that translates to in power output gains.
- exabrial 3y agoI'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 3y ago> 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-cycles/ https://www.powermag.com/what-are-supercritical-co2-power-cy...
- adrian_b 3y agoDue 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 3y ago- " 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 (<374° 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).
- Animats 3y agoMore 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 https://netl.doe.gov/project-information?p=FE0028979 [2] https://www.power-eng.com/gas/ge-powered-plant-awarded-world-record-efficiency-by-guinness https://www.power-eng.com/gas/ge-powered-plant-awarded-world...
- auspiv 3y agoIt 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.
- Animats 3y agoGeneral Electric claims 5 minute startup time for their combined-cycle 50-megawatt turbine.[1] They've shipped 1200 of those. [1] https://www.ge.com/gas-power/products/gas-turbines/lm6000 https://www.ge.com/gas-power/products/gas-turbines/lm6000
- imtringued 3y agoYou didn't read the combined cycle section which claims a cold iron start takes 30 min for combined cycle. That is plenty fast though.
- Animats 3y agoAh, right. Have to click on the combined cycle options to see that.
- perihelions 3y ago- "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 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 3y agoThat'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 3y agoI 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 3y agoThis[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 https://news.ycombinator.com/item?id=38053586
- Gasp0de 3y agoWhy 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.
- gumby 3y agoConsider the two words: "sustainable" and "fuel". As a locally generated process input, H2 appears to make sense, say for steel production or yes, ammonia. But H2 is hard to store; best is to do so cryogenically which uses a lot of energy and is heavy. storig higher temperature H2 is more difficult (those crafty molecules are tiny!). The economics likely work for many industrial processes, but not for transport, much less grid power generation. The "fuel" part doesn't pencil out; I believe H2 fuel story are just a subsidy to the fossil fuel companies in order to get legislation passed. Compared to other fuels Ammonia isn't especially energetic, but for a large vessel with a lot of space it can work. But it's really toxic and harder to manage safely than buker fuel or jet fuel. "Sustainable" doesn't mean just its production but its overall risk to human life. It lacks adequate energy density to drive something like a car much less a plane, even if you were willing to have something as nasty as NH3 in your fragile, weight-sensitive vehicle. Don't take my word for it: Maersk, who is famously commissioning ammonia (and methanol) vessels, has publicly stated that these are not long term solutions but rather (they hope) a way to push the green agenda forward.
- 10u152 3y agoThe article focuses on size over and over again. Nobody cares about the size. Efficiency, scalability is key.
- Gasp0de 3y agoLarge 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 3y agoScalability is related to the size. You can have hundred times more of a thing that's one hundredth in size.
- waterheater 3y agoInterested 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 https://en.wikipedia.org/wiki/Allam_power_cycle [2] https://netpower.com/technology/ https://netpower.com/technology/
- TSiege 3y agoThis 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?
- waterheater 3y agoNot quite. According to the EPA [1], "Emissions is the term used to describe the gases and particles which are put into the air or emitted by various sources." That includes anything, not only CO2. For example, while CO2 is a common emission from fuel-based power plants, these plants (in particular, coal) may also emit other molecules such as mercury, which is more dangerous to human health than CO2. These all fall under the umbrella of emissions. Even a hydrogen-fueled car has an emission of water, or a "waste product" [2]. And that's the key to understanding it: waste product, which is really what the term emission means. What I talked about has virtually no waste product and therefore no emissions, though perhaps "no emissions" is too optimistic. The NET Power website says "NET Power’s patented technology captures over 97% of CO2 emissions from power generation", so it's darn good but not "no emission". [1] https://www3.epa.gov/airquality/emissns.html https://www3.epa.gov/airquality/emissns.html [2] https://www.latimes.com/business/story/2023-08-16/hydrogen-fuel-cell-cars-fuel https://www.latimes.com/business/story/2023-08-16/hydrogen-f...
- tln 3y ago"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 3y agoIf 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 3y agoIt 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."
- klyrs 3y agoThe article didn't brine identity politics at all. I'll agree that the swerve into politics was weird, especially since they didn't tie it in to the article at all (except, perhaps, a reach for a pun involving "power"). Not all politics is identity politics, if words have any meaning.
- dtx1 3y agoSo 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 3y agoYou’d need a corresponding reservoir of ‘cold’ with a big enough temp delta to make it economic. So, no.
- dtx1 3y agoBut a river would be both, extract the heat with a heatpump, cool down the exhaust using that river. Assuming you can pump more heat and extract more electricity from that heat than it cost to run the heatpump, you'd have a positive energy extraction.
- lazide 3y agoDo the math, and you’ll find the delta is uneconomic. Unless the air is 600C or something. In which case, have you checked to make sure you’re not on fire?
- deleted 3y ago[deleted]
- gcanyon 3y agoAt 100 bar (minimum) that’s no joke if something ruptures.
- huslage 3y agoThis seems to be an incremental improvement on old technologies that still burn CO2. They mention the solar concentrators, but that's sort of a nonstarter in the US for various (mainly economical) reasons. I mean 10% efficiency improvement is a useful thing, but this is hardly a "clean" form of power generation.
- simne 3y agoSize could be beneficial for air-space industry. May be in transportation. For example, exist ships with special rotors for maneuvers, so this is possibility, to place somewhere very compact engine (or compressor), instead of bulky and expensive electric engine. For ground applications, I don't think this is enough beneficial, to be alternative to classic turbines.