Scientists use supercritical carbon dioxide to power the grid When it comes to turning turbines, steam is out and supercritical carbon dioxide is in – as demonstrated by Sandia National Labs when it connected a closed-loop system to the local grid, supplying about 10 kilowatts of power for nearly an hour. Sandia's experimental unit uses carbon dioxide in a supercritical state ( …
kWh is the problem. There are two distinct quantities to measure: power and energy. It would be easier for people to understand if everyone used the two distinct units: kWatts and MJoules. The usual complaint is that most people do not have a feel for how big or small kWatts and MJoules are. Perhaps they would if the standard units got used regularly and we could stop using house power for a day per Olympic swimming pool.
While we are at it, measuring weight in pounds does not help either. Measure mass in pounds (0.4536kg) if you have to then weight in pounds force (4.448Newtons). The unit of pressure should not be pounds per square inch (pounds force per square inch). Pound foot and foot pound are equally messed up. The way things are going, Twitter users will measure rocket thrust in tonf then fail to land on Mars. About the only way to make things worse would be to do thermodynamics in Fahrenheit.
Presactly. I gave up at that point and came to the comments to look for the green ink button and start writing because I cannot trust someone to write about thermodynamics (that's what this is all about right?) if they can't distinguish units of power (10 kW) and units of energy (10 kWh).
If the person writing is that ill informed then there's nothing stopping the people feeding them this information from pulling the wool over their eyes. Fine, Sandia are unlikely to do that, but what if someone lets them interview the latest of those series of chancers doomed to failure peddling wireless power for your x (where x has been several things, but the latest set of chancers are targeting gaming gear) - cf Batteroo, uBeam, Energous et al. The latest, the one targeted at gaming, is called Quaze (which sounds like a school kids' Metal band).
10kW of power, just under 10kWh of energy.
The grid connection was just a publicity stunt. I guess it worked though.
Rather silly that they felt they had to do such a stunt to fund the next stage of scaling it up.
Worse, that the article (or press release) didn't make any useful comparisons to existing top-flight steam turbines - which are actually 45-50% thermally efficient.
CO2 is supercritical at 100bar or so, so the entire loop has to be at least that pressure - which is quite the challenge to scale up, I'd think.
How does that compare with the full loop of supercritical steam turbines?
Stunt? It's a necessary test step. You've acquired all the data and proved it will work in isolation. Now to connect it and confirm nothing untoward happens. It's a tick in a box (at least you really hope it's just a tick in box rather and you don't up fuck the grid) but until it's done, you don't know. And watching it work makes you feel good; it's an emotional payback for all the effort.
The grid connection is a publicity stunt.
The generator and its control systems are separate from the thermal cycle and the turbine, the two are connected by a rotating shaft running at a nearly constant speed. It's the CO2 based cycle they're trying to prove here, the generator part at grid scale was proven decades ago.
I was curious as to where the heat came from for this test, reading the press release confirmed my suspicion that it was an electrical heater, no doubt connected to the same grid.
I think more test rigs should recover energy somehow to use (if only to power the office lights!), but 10KW is pretty small beer.
The grid connection is a publicity stunt.
I think more a call to action given the necessary hoops to jump through before that's permitted. Also like the power vs energy issue, which is science/engineering meeting marketing. So the 'enough to power x homes' bit that sounds vaguely impressive, but probably needs revision. AFAIK there's no real official definition of a home's power requirements, and it'd vary. But trend is upwards if home has 1 or more EVs and a heat pump.
Basically they've done some interesting legwork, now they're pitching it to investors in the hope of generating filthy lucre as well as 'clean' energy.
The generator and its control systems are separate from the thermal cycle and the turbine, the two are connected by a rotating shaft running at a nearly constant speed.
I like that bit. Inertia's rather important in keeping grids stable, at least until everything can be persuaded to switch to DC. And it's also an area where most 'renewables' create problems rather than solutions by being mostly inertialess or highly variable, unless much money is spent to keep frequency stability.
So something that improves efficiency and creates less stability problems is a GoodThing(tm). Unless you're part of the Green Blob. Then you probably realise it's a bad thing, because it means a supercritical coal + supercritical turbine loop generates more power for less CO2 emissions, making crap like windmills and solar ever more pointless. Or it makes thermal sources like SMRs even more attractive.
"The grid connection was just a publicity stunt. I guess it worked though."
Agreed. We've had hundreds/thousands of windmill and solar farms hooked up to, and synced to, the grid in the past 20-25 years, so there's already a large pool of expert talent out there that knows exactly how to do this and what it requires. It seems like that part of the project would be easy and shouldn't really vex the scientists at one of the country's top research labs. Why re-invent the wheel?
After running out the clock on steam as a working fluid we move up to the next available thing. There isn't anything controversial here, quite the opposite, it's been agonizingly slow adoption. We already have cars and fridges using supercritical CO2 in their refrigerant cycle, and we have explored many other working fluids over the years, both in those applications and in turbines.
So as it turns out the pressure isn't particularly challenging or problematic, nor at scale is the cost, and in many applications it's cheaper, in others it's just safer. Supercritcal steam was already capable of being lethally exciting if mishandled (or shot at, as it was pervasive in old warships) so these are small changes. The plumbing gets a bit beefier, but the fundamentals are pretty much the same.
It then goes on to say 10KW is about a third of the daily use of a US home, implying that a US home uses around 30KW a day, or about 1.25KWh on average.
The important difference between power, and energy.
Watt= 1 joule per second and is a power unit. Can also be defined as moving 1kg a meter, which is important (or confusing) when trying to move a recalcitrant horse. Energy gets a lil more complicated, but is your basic joule.
So 30KW a day is pretty meaningless, because a Watt is a 1-second unit. So unless you're a cryptominer or weed grower, you're not using 30KW for 86400 seconds. So in reality, a home would be turning on & off appliances as needed, for varying amounts of time, and drawing various amounts of power. So boiling a kettle or taking a shower would be lotsa Watts for a short duration. So for convenience, and billing purposes, those Watts get counted and converted into KWh. So that could be a 1KW device operated for 1hr, a 100W for 10 hours etc.
And then the whole mess gets spun to make 'renewables' look more attractive by confusing people with units, usually by abusing KWh.
if the average US home uses, as you put, it 1.25kWh /24hrs that's less than a couple of low energy lightbulbs.
I believe the 30kW figure was really 30kWh or in layman's terms 30 measured units of electricity.
If the price of 'leccy in US is going the same way as it here in Blighty that 30 is gonna get cut down soon! £0 would be a reasonable figure if you have A/C, but sounds crazy to me as our average is around 10kWh/24hr period, but then i only have the A/C on when the sun is shining - ie its hot and the solar panels are making the juice :)
if the average US home uses, as you put, it 1.25kWh /24hrs that's less than a couple of low energy lightbulbs.I believe the 30kW figure was really 30kWh or in layman's terms 30 measured units of electricity.
Ermm.. Not exactly, but it's where it gets confusing. Or used misleadingly. So figure the claim that their test system can produce 10kW, or 10kJ/s. That's a limiting factor. Assuming that's constant power, in any given second you could have 10x1kW kettles running, or any combination of power users. If the load exceeds 10kW in any given second, bad things happen wrt voltage or frequency. So stuff stops working, things trip out and may have to be reset etc etc. Which is why this kinda thing is a problem-
https://gridwatch.co.uk/Wind
minimum: 0.29 GW maximum: 13.885 GW average: 3.94 GW
So it's all over the place, which doesn't make system planning very easily. But that's the fundamental problem with wind, ie it's based on wind speed, which fluctuates. And of course so does demand-
minimum: 0.636 GW maximum: 37.34 GW average: 29.043 GW
Both from the month to date. So the imbalance between minimum demand and minimum wind output doesn't look so bad, whereas for the max... It's huge, which means hugely expensive. As is faffing around with batteries and stuff to paper over the fundamental inadequacy of wind as a reliable, dependable power source. Thermal generation doesn't have this problem. So build a 1GW nuclear plant and it'll give you 1GW, 24x7x365, give or take maintenance shutdowns, refuelling etc. Other thermal power plants and some nuclear designs can vary the power, but key point is it's far more consistent and predictable.
Deception tends to come in when kWh get used because it glosses over the importance of instantaneous power, and renewable's complete inability to deliver that reliably. So the 'renewables' lobby tends to focus on kWh and 'enough to power' messaging because it can be presented as a big number that looks impressive to people that don't really understand the implications, and especially the downside risks.
There's also some other policy fun stuff, like if you track average wind speeds across the UK, they've been declining over the last few years. So windmills are even more useless. Or that wind and solar are far more vulnerable to weather 'extremes' than thermal generation. We're told that 'global warming' will lead to more of these extremes, so why are we being forced to waste money on critical power generation that can't deal with it?
I believe the 30kW figure was really 30kWh or in layman's terms 30 measured units of electricity.
Yes, (as a layman), I meant 30KWh a day, with an average of about 1.25KWh every, erm, hour.
I suppose this is just one of those laymen vs 'correct' term confusions. (KCal vs Cal, GiB vs GB).
At the end of the day it gave me a mental 'yardstick' which was really the point. :)
Yeah, it's fixed. It was a bit obvious from the context in the first par. But, fine.
For those saying why trust a whole article if some simple thing is wrong in it. That's a very 1D way one of looking at it. We're most concerned with making sure the main, sensitive parts of a story are correct.
Sometimes that means little things like saying 10 kWh in the first sentence and 10 kW later get overlooked.
Don't forget to email corrections@theregister.com if you spot anything wrong, please.
C.
A couple of clicks told me that "recuperator" is just a word for a heat exchanger.
What I didn't find is an understandable reason why the same technique can't be use with a water/steam system. A closed loop is a closed loop, regardless of what is in the pipes. You have to properly manage the heat flow in both cases. It's probably all in the math as to why the Rankine cycle has to lose so much of the input energy doing the state changes.
Exactly the same technique is in use with a water/steam system. Recuperators were a standard part of rail steam engine. They get called different names depending on what industry and what country you are in.
All of these thermal power cycles are theoretically 100% efficient, it's the real world that gets in the way. Which is why you use a two part, or three part, or 7 part cycle. With turbine, or turbine+recuperator, or high pressure piston followed by medium pressure piston followed by low pressure piston followed by recuperator. Or turbine + turbine + turbine + recuperator + ....
The words "Brayton Cycle" here just mean "using supercritical C02" and "Rankine Cycle" just means "using water/steam". The important difference there is that a water/steam cycle is constrained by the temperature/pressure/volume curve of the water/steam and steam/water transitions.
And 'closed loop' in this article means that they aren't exhausting the C02 to the atmosphere. If you run the Brayton Cycle with parts of it run at ambient/atmospheric/input-output pressure and temperature, you can run open Brayton Cycle systems (motor car engines using petrol and air) They don't want to do that here, because they want to use C02, so running closed loop is part description and part achievement.
Why they think that using supercritical C02 is better than water is not explained by this article. They are just pleased with their technical achievement of two important steps: including the recuperator, and connecting to the grid.
> Why they think that using supercritical C02 is better than water is not explained by this article.
The critical temperature of Carbon dioxide (31.0 °C) is much closer to room temperature that the critical temperature of water (374°C). And the critical pressure for Carbon dioxide (73.8 bar) is less that 33% of the critical pressure required for water (221.1 bar).
My guess would be that because the pressure and temperature to create and maintain supercritical carbon dioxide is much lower than is needed for water as the working fluid, building a device using materials that are available today, means that the temperature and pressure differential between the high end and the low end can encompass a larger area within the thermodynamic cycle. And that larger area would correspond to more energy that can be extracted from the exact same source of thermal energy. Basically if your hot end is hotter or your cold end is colder, or both, then you can usually extract more energy.
Carbon dioxide becomes super critical at a critical temperature of 304.13 K (31.0 °C; 87.8 °F) and a critical pressure (7.3773 MPa, 72.8 atm, 1,070 psi, 73.8 bar).
Water becomes super critical at critical temperature of 647 K (374°C; 705 °F) and a critical pressure (22.11 MPa, 218.4 atm, 3210 psi, 221.1 bar ).
My guess would be that because the pressure and temperature to create and maintain supercritical carbon dioxide is much lower than is needed for water as the working fluid,
I was also wondering about density benefits. So if supercritical CO2 is denser than supercritical steam, it'll have more mass to spin a turbine at the same flow rate.
The grid connection is a publicity stunt, it's meaningless.
If you can spin any generator under load for a long time then you've proven your turbine cycle works at that power rating. I don't care what the load was.
Ships under construction or test in shipyards used to just run a massive water heater to prove their generators worked. They sometimes feed the local grid during these tests now because it recovers some of the cost of the fuel, but it doesn't affect the test.
>The grid connection is a publicity stunt, it's meaningless.<
Do you feel the same way about testing your backups? You skip the unit tests and the integration tests because other people have demonstrated application software?
The next stage will require a realistic load, and the grid connect people aren't going to let them connect until they've passed test. It may be a publicity stunt to you, but to the supply and transmission people it's the difference between 'real' and 'unbelievably stupid"
Those numbers, at least for water, are wrong too.
Back around 1990 Vestkraft in Esbjerg passed 50% efficiency on pure electricity production, using coal. Of course most production in Denmark is combined heat and power, but even so 45% was regarded as normal efficiency for electric only mode.
I was at a job interview with one of the power generation companies and learned they were working with producers of ion exchange resins to improve the water quality.
All of these thermal power cycles are theoretically 100% efficient, i
No they're not. All heat engines are have an upper efficiency limit of (derived from second law of thermodynamics)
log(Tout/Tin)
where Tin is the input temperature and Tout is the output temperature, both in absolute units.
this is why power stations need cooling towers: to reduce Tout and thus give a big ration (Tin tends to be limited by available materials: superheated liquids tend to be highly corrosive).
El Reg have decided to standaize[sic] on "North American English style guides. Although why that means using F in this case I have no idea. A very large part of North America standardised on Celsius some time ago, especially since it works well as a word in both of their main languages, English(Canadian) and French(Canadian) :-)
I have this dream that Big Tech will announce that on a particular New Year's Day, there will be an end to what can only be called, nowadays, the American Exception. In other words, all maps, measurements and weather reports, all recipes and, where possible, news reports will be presented as they are shown to the rest of the world: in Metric units.
Oh, there will be ways for the drones to find their way back to FFOMP (that's Fahrenheit, Feet, Ounces, Miles and Pounds) but given that most can't find their arses with both hands and a map, they'll have to live with what the rest of the world takes for granted.
And no Galleons, Sickles and Knuts either!
"Ounces, Miles and Pounds"
In an IT world we really shouldn't be promoting decimal based units. Binary would be far more logical and ounces and pounds fit into that. There's a historical reason for that, of course - when you're weighing with a simple balance the easiest way to divide up some quantity is into two equal halves.
I always thought that decimalising UK coinage was a mistake: just make the new penny 256 to the pound instead of 240, a new hexadecimal shilling of 16 pence and reintroduce the groat (4 pence) as being midway between the old threepenny bit and the tanner.
Thanks to inflation, the penny has no real intrinsic value any more. About the only practical use for it is to be given in change because marketers like to price things ending in 99p for psychological reasons, ie they are trying to fool people that £9.99 is actually cheaper than £10.00 by enough to matter :-)
A very large part of North America standardised on Celsius some time ago
In a discussion of the Rankine cycle, how can we not use the Rankine scale for temperatures?
The US is 56% of the population of North America, so the majority does not use Celsius.
And the only appropriate icon for a debate over the benefits of metric vs imperial... Have a pint, mate. --->
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"are these REAL scientists?"
Probably. They're trying to translate it to what they think an ordinary american can understand, I see this sort of nonsense elsewhere.
I've never understood why it's degrees anything. Was Mr. Fahrenheit's thermometer a dial type using a Helix protractor re-purposed for the scale? Can we convert it to radians?
Degrees are for things that are unitless ratios.
<lawyer>Yes it was perverted, but was it a crime? It's a matter of degree
<judge>Well it was only 1/5 as perverted as what I can imagine, so he's getting 1 year inside.
So degrees Celcius/Farenheit/Perviness/Inclination is correct and degrees Kelvin is wrong. (Radians and gradians are also degrees)
If degrees are unitless ratios, can we measure temperature in deciBels
I don't think "unitless ratio" in the original post is correct. 100°F is not twice as warm as 50°F. A better statement might be that "conventionally, 'degree' has been used for a unit in an arbitrary linear scale". Thus we have angles measured in degrees because dividing the circle into 360° is arbitrary, and we have degrees Fahrenheit and Celsius because those scales were created without knowledge of absolute zero and where it stood relative to them.
Kelvins, on the other hand, are based at absolute zero and thus serve as proper units. 100K is twice as much heat energy as 50K.
On the third hand, apparently "degrees" is used with Rankine, when Rankine is used, so, ugh, it's all an inconsistent mess. Welcome to language!
How would one convert degrees to dB?
You could certainly express temperature changes (or other ratios) in dB. Apparently the forecast low and high today here are 48°F and 72°F, or 8.8°C and 22°C, or 283K and 295K. That's a ratio of 1.04. Log base 2 and multiply by 10 and we have a 0.56 dB temperature change today. That's ... I guess pretty normal, around here.
In the winter sometimes it drops to 0°F outside (or colder; this is just an example) and the exhaust from the stove, when it exits the flue, might be around 800°F (judging from what I read online; I haven't measured it). So my smoke-to-atmosphere (s/a) ratio there is about -15 dB.
Assuming I haven't messed up any of my arithmetic.
And so we see that expressing temperature changes in decibels is extremely easy, barely an inconvenience; and also terribly useful.
It looks like a beautiful article, but would a beautiful article sit down next to me?
I want to pass this onto my even stupider friends because optimism is rare, but I know what they are going to ask and if any of you could provide intellectual back-up then I'd be grateful.
Isn't this just energy storage? I got that one, energy storage is essential for renewable energy.
Isn't CO2 causing global heating? I assume they know that, it's 2022 so I assume everyone knows that.
Does free energy have to be efficient? No, it's free, it just have to be distributed better.
Why aren't the names of the supposed scientists not under their photo? Trump's USA, some idiot would shoot them.
Better answers would be appreciated, because I'm the smartest bloke in my admittedly daft social circle but they deserve good news.
Is this really good news? Great news? Positive news?
It's a great article, I just need help explaining it.
I, for one, don't mind the kWH v kW mistook, it happens and I can explain that to my even stupider friends. "But how many homes in Wales can it power?"
They are good questions, except for the "supposed scientists" line, so I'm taking a shot at answering.
It's not just energy storage. It's basically a more efficient way of turning heat into electricity. Quite a lot of power generation works that way: nuclear, coal, gas, but also geothermal, non-photovoltaic solar, probably something else too. So, anything that makes that process more efficient means that the same type and size of plant can produce more power from the same amount of fuel (or area, in the case of renewables).
CO2 is causing global warming. However, the technology described does not make more CO2. It just reuses the same CO2 over and over again. Some will escape, but it won't be very much and it will be replenished from sources that would have let it into the atmosphere anyway eventually, so the carbon accounting remains neutral.
If we had truly free energy, we wouldn't need efficiency (well, not as much). Unfortunately, we do not have free energy, and it's unlikely that we ever will. Consider nuclear plants, where the cost of fuel is marginal, or renewable plants, where you don't even have fuel: those power sources are still hard-pressed to compete with coal-fired plants, simply because, kilowatt for kilowatt, the plants are far more costly and complicated to build and operate.
Even if we achieved the holy grail of commercially-viable fusion, I guarantee that just building the plant will incur such a high capital cost that the energy will have to be significantly costly, just to recoup the capital expense. A scenario where we have truly free energy is sci-fi, and not even particularly plausible sci-fi at that.
In fact, I predict that the biggest obstacle to large-scale deployment of this tech will be the additional capital and operating costs. It could well turn out that they are greater than the efficiency gains. I hope not, though!
The tech described in the article won't power any homes in Wales, not by itself: it's not a power generation method; it's an improvement to efficiency. So, you apply it to a plant that can power 1000 homes in Wales, and now the plant can power 1100 homes in Wales.
Hope this helps!
Thankin' you much Filippo, it helped greatly because you not only answered, you explained. I mean I like all the jokes here too but I knew I could goad someone smarter than me into helping me understand. I have to explain this stuff to my even stupider friends and family.
[To the jokers to the left of me, clowns to the right, my nephew pulled two people from a river two months ago saving their lives, I was hugely impressed. Then I learned he was flatmates with the daughter of Cerys Matthews, and shamefully I was even more impressed. "Tell me, every morning when she awakes does she thank the Lord she is Welsh?"]
Whilst the use of per-revolutionary units does irk, I'm more confused by the grid connection and dynamo being a big thing.
Thermal power plants use turbines, and they have the power take off and grid connection part sorted.
If you have lower power requirements then you just use an inverter (with efficiencies of >98% so minimal losses), what's the big thing here? Other than replacing steam with CO2 which apparently provides some advantages in operational efficiencies. This is the second article discussing 'Sandia' does a relative work there? I've never come across the institution? before.
The main campus is in Albuquerque, NM. SNL is named for the Sandia ("Watermelon") Mountains.
Sandia has been around since 1949, and was established by the Department of Energy, so yeah, they're best known for energy-related work, including nuclear. But they're allowed to bid on other Federal jobs, so they've worked on things like anthrax decontamination (remember when mailing anthrax spoors around was a thing?) and mining-industry safety.
A casual look at the diagram suggests the existence of two external thermal components:
A heat source
(and)
A heat sink
Since a single stage heat pump wouldn't close the loop, perhaps some efficiency might be gained by using waste heat to make cold, ala this recent El Reg article: https://www.theregister.com/2022/07/29/bill_gates_aircon_venture_funding/
Assuming the cooling part of the equation is easy to solve, there remains the question:
What supplies the heat?
> What supplies the heat?
From what I understand, I think the answer is "whatever". The tech improves the efficiency of turbines, no matter where you get the heat from (although, looking at the temperatures, it has to be something really hot). Given it's Sandia labs, I expect they are thinking about nuclear.
... what is the pressure in the system, compared with that for existing steam turbines? At the temperatures of the run that they have done, and at the proposed future higher temperatures that would give the claimed 50% efficiency?
... what will that do to the reliability/maintainability of an actual industrial system?
Very good things. The pressures are less than some supercritical steam systems, higher temps allow greater efficiency as well, and aren't really a huge engineering challenge. Preventing live steam from eating pipes is harder than you think, and making turbine blades that aren't allergic to water is pretty limiting on design and materials as well. Pure water is corrosive as all get-out, and in a closed cycle system you have to keep it from depositing stuff somewhere else problematic. CO2 is significantly less of a hassle that way.
So in addition to higher cycle efficiencies, they may be able to run more hours between maintenance cycles, and be cheaper to run and maintain. It is likely that the manufacturing costs will be similar/cheaper at any kind of scale, but that won't matter in the real world, where new=expensive, and bettter=expensive. Good news is that once the engineering risk is sorted out, the tech should be viewed as profitable to manufacture.
Another benefit is that the stages and operating principals are the same as a steam plant, so re-certifying personnel should also be straightforward. The big down side just seems to be the slow rates which we upgrade or build new plants.
So what?
First off modern coal plants (outside of the US) are Ultra Super Critical plants that run at 600/620c and 275bar or 3990psi.
The US is "Special" in that it stopped at about 538c and it's aging coal boiler fleet hits about 34% efficiency on average (A modern USC plant like those in germany can hit 47.5% efficiency, world average is about 38%)
Also CO2 has a higher molecular weight (44 Vs 18) so the molecules will be harder to accelerate and as we all know KE is proportional to V^2 but only proportional to mass. So more (heat) energy to get them so they hit the turbine blades as hard.
So basically it looks like its benefits are lower maximum operating temperatures and pressures --> potentially cheaper power plants due to lower operating pressures and component sizes and (potentially) less chemcially agressive working fluid (compared to supercritcal water. See "Supercritical wet oxidation" as a method for destroying nerve gas for example).
Provided the whole thing is built from the ground up to use CO2 instead of water of course.
IOW it's about a TRL4 level technology against a fully deployed TRL9 technology. Addressing primarily an American problem with an American solution.
BTW AFAIK no US utility has been able to get funding to build a new coal plant for years, despite the mininimal needs for SO2 cleaning on the exhaust.
Good luck to them.
Well, the cold side is going to be down about say 60C if you use CO2. Thats a much more useful temp - it's a longer working range than SC H2O and it's just the right temperature for district heating as well - I can see one of these plants generating electricity and the waste heat from it being piped around for a communual heating scheme. Not a very big thing in the UK, but for the USA with a small community in the middle of nowhere having process heat and electric from one plant is quite attractive.
"but for the USA with a small community in the middle of nowhere having process heat and electric from one plant is quite attractive."
You're thinking like a European. This is the US of A. If there's not an ongoing profit or a huge tax boondogleincentive pushing it, it will never happen. We aren't altruists here.
Ugh. People like you really bug me. Pretending to know science because you can remember an equation.
Well I can remember A level chemistry, this was nearly 20 years ago now, but pretty sure things haven't changed...
"Only proportional to mass"? We all know that do we? Sure, kinetic energy is proportional to mass but that's not the only factor in determining how much energy it takes to get a molecule to a temperature.
Water has 3 degrees of freedom, which means energy is absorbed by rotational, longitudinal and vibrational motion, not just whizzing around speed (kinetic a.k.a. temperature)
CO2 has less degrees of freedom, as its a different shape, so less energy to get it up to temp.
Boiling water from a kettle is 100C, and will burn your skin. Open an oven and shove your hand in at 200C, its hot, but you'll be fine....... Why? Well, dearest, air is mostly N2, kettle water is mostly H2O. Same temperature, different available energy for skin burning
Stop pretending you know better than the *actual scientists* and get back in your box.
It will take less energy to heat CO2 to the same speeds as water, which makes for a more efficient system, which is the whole point of the article
"It will take less energy to heat CO2 to the same speeds as water, which makes for a more efficient system, which is the whole point of the article"
I thought the point of the article was that it was the lack of phase changes in the working fluid made it more efficient. To quote the article, "The Rankine cycle is inefficient and loses a lot of energy turning steam back into water", but I think it's a bit more complicated than that really.
And the available working temperature range is a bit better too, for future designs.
Yes, I was trying to say the - efficiency - was the point of the article. Not the benefits outlined by OP, or the specific reasons. Again I'm not claiming to know more than those involved, I'm just remembering some science lessons
No need to have a brain seizure, they aren't going to take your precious black rocks away. This may actually stretch a variety of fuel sources in the face of pressure from Hydroelectric, solar, and wind power.
Literally the same design and technology, just with a different working fluid. No one here would be freaking out if the article said they got an efficiency gain by replacing the water in a coal fired plant with 10% cheap scotch by volume.
However, the fact that the lab was able to connect its test loop directly to the grid is a huge deal, said lead researcher Darryn Fleming
So they connected their 10kw generator to the grid......... Aren't there millions of rooftop solar power installs around the world that generate several kilowatts of electricity and put them onto the grid? No doubt there are stringent requirements that need to be met in order to do this, but doing so is hardly cutting edge research.
The 'real world' moment is generating the power. Putting it onto the grid is an engineering irrelevance to the research. Whilst the first solar connection to the grid was probably even smaller, that was a long long time ago. Now it's just routine commodity stuff, not "cutting edge" research. You can just get a "Grid Tie Inverter" from ebay that does the "stringent" stuff. It that takes the generated electricity in at one end and feeds the grid at the other. If it's a different frequency/voltage coming out of their generator that the Grid Tie needs then so what just put another convertor in between and you are done.
"Epic. Rapp battles to connect Greehouse Gas Turbine to power grid"
On a slighly more serious note this is qute a big deal.
DC power sources like PV arrays can be fed through an inverter, which precisely matches the power in phase and frequency.
But the biggest converters are not solid state. They are rotating machines IE Alternators.
If not matched it's output into the grid could start to pull other generators off frequency. Not by much perhaps (iit's not that big) but enough to disrupt stuff that relies on very stable 60Hz (yes there is stuff like that. Not everything can use a GPS time signal) and the power utilities have very strict rules about letting anyone connect to their network because of this.
I have often wondered if all heat engines which require heat AND cooling to generate/transfer energy from one place/form to another - are a major contributor of global warming NOT just because of the burnt fuels and their greenhouse effects on the planet, but because of the excess heat that has to be released.
We humans have been using them for many years now (steam, ICE, etc)
Mind experiment: Imagine we had been using the same heat engines all these years but somehow magically they produced no exhaust gases (CO2 etc) but were the same efficiencies we've had over the years and so released excess heat - would we still have global warming? (I'm not a denier - just curious and not a good enough scientist to work it out)
If we get fusion to work, we will still have excess heat to get rid of - is unlimited energy such a good thing?
Sorry a bit off track from the original article.
*Where the heat came from is not the point of the question.
A very simplified example to illustrate this point -
Your toaster literally gets red hot, all the excess heat radiates away without problem.
Wrap the toaster in a thin blanket*, the heat can't leave quickly enough and eventually... oh dear.
Toaster > Earth / Blanket > global warming.
*Do not try this at home.
Expanded example, using a hair-dryer, not a toaster, but the principle is the same:
so does heat from all other sources. Reflectance/albedo on the bright side is driven by input to the system, where the dark side is predominantly blackbody emissions that don't care where they came from. In reality that's still happening on the bright side too, but as the other poster pointed out the incoming signal is still overwhelming.
Only matters because if the day side didn't also shed a ton of blackbody infrared into space we would still be toast.
> 59% of that is re-radiated from the night side as infra red radiation. Good thing too, things would be rather toasty if it wasn't.
Wot? The sunny side is hotter and must rereadiate even more than the cold side. The sum of reradiation from both sides can't be other than 100%.
True.
Unfortunately the re-radiated longer wavelength IR is now much better trapped in the atmosphere.
And since all of the main green house gases have looong lifetimes (only water vapour and ground level Ozone are in days) they are going to go on trapping that heat, with the polar caps operating as a global "swamp cooler," dumping ever more water vapour into the air.
The ultimate endgame for this can be seen on Venus (or it could, if the sulphuric acid clouds didn't get in the way) with a full-on runaway greenhouse (which I've always thought sounds like an invention of Rohald Dahl's) effect.
"excess heat"
What happens to the rest of the energy that wasn't released as excess heat? Some of it might be stored in the longer term as potential energy or chemical energy but for the most part it ends up as heat in some way - aerodynamic drag, friction, boiling kettles or whatever. You have to take all of it into account although as brainwrong points out, it's not very significant.
You have to take all of it into account although as brainwrong points out, it's not very significant.
That's kinda global warming in a nutshell. Lots of money and recriminations trying to answer questions of significance. So arguably man-made CO2 isn't that significant, especially compared to natural CO2 fluxes. Man-made heating (or even volcanic/geothermal) isn't globally significant, but can be locally. So natural sub-sea or surface heating under ice flows or glaciers.
But localised heating gets far more significant when it comes to potential polluting of temperature records. In the UK, Heathrow Airport regularly sets temperature records. But since 1929 it's changed from a small grass strip with a few piston engined aircraft puttering around to today's acres of concrete & tarmac with lots of hot jet exchaust. So the UHI, or 'Urban Heat Island' effect. Poor siting and land use changes arguably explain much of what's currently considered as 'global' warming, when in reality it's localised.
So arguably man-made CO2 isn't that significant, especially compared to natural CO2 fluxes
Just because nature changes the CO₂ levels does not mean only nature changes the CO₂ levels.
Yes there are natural variations but they are slow, what's happening now is happening nearly 1000 times faster than normal natural causes can account for and is far too fast for natural systems to adapt to.
Man made climate change is beyond reasonable doubt, which it seems only leaves unreasonable doubt.
Leaks?
Gosh, in a "steam" plant, leaks in various places might cause puddles, high humidity, or the occasional severed digit, if careless. Such leakage might even be tolerable and repair deferred to a normal maintenance period.
But CO2 leakage, well, not quite a breath of fresh air, is it?
I wouldn't be so casual about a leak of superheated high pressure steam.
Imagine: superheated steam pipe on the left, walkway in the middle, cloud of steam hovering some 10m to your right.
Q: would you walk over that walkwaty?
A: no, because the condensation you see on your right is because you have a micro leak in your steam pipe (corroded weld), and due to the high pressure and temperature it only starts condensating further out. In other words, if you walk over that walkway you'll most likely be killed by the invisible high pressure jet of steam you'll be crossing.
This is not a joke, this actually happened in a chemical plant (where they use superheated steam for process heating as it's safer in the context of warming up combustible things) and the consequences were beyond horrific. After this, an order went out to inspect anything near a gangway and then insulating all of that. It would make any leak more noticeable as it would fling away a large chunk of the insulation instead of remaining an invisible micro leak.
No, they are not, because walkways are supposed to be safe corridors when moving around a plant full of danger and this blade of steam is invisible at the point where it has the most energy and is thus the most dangerous.
By way of illustration, the above (which happened about 3 decades ago) pretty much cut the operator in half before inertia stopped the remains. The poor guy never stood a chance.
Proper you posted AC. "Walkways . . . you keep saying that word. I don't think means what you think it means (in support of your fabricated scenario)".
You initially bought up walkways as a red herring and and when I did not bite, you kept fishing anyway, landed nothing, and built a "fish tale" upon it.
You're one of those guys that makes statements well know to be true, (high pressure steam leaks are invisible within several feet of a leak and can cause detachment of body parts), using that as a cudgel to attempt a beat down of point that was not made..
Further, "because walkways are supposed to be safe corridors" is a statement only a fool would make, as no one in a high pressure steam plant assumes any place is a "safe corridor" and exercises extreme caution at all times, or pays a price.
But, you win the Pedants Prize today.
Yup, speaking English as a foreigner could be at the root of that, and I'd welcome a better term for it if you have one - you're never too old to learn IMHO. If you see red herrings in that I would suggest you need help.
"Walkway" is what I use to describe a walking path made by metal grids between metal beams, including and not limited to caged ladders and metal staircases that have to comply with rigid safety standards regarding fixing, size, width, stability and minimum acceptable loads they should be able to handle (and by that I don't mean exceptionally fat people, but also being used as a mounting point for scaffolding should the need arise) and are well lit, usually with emergency power so it stays lit.
They provide a path to use for plant operators to reach parts that are used to manage, control and maintain a plant because it is, for instance, a bit of a pain to reach the top of a storage tank otherwise. The economics of construction disctate that supply lines frequently run parallal to them - which in this case turned out to be a less than sterling idea.
Yes, plants are dangerous for the unitiated, that's why you have safety training, rules, signage et al. But a walkway (or whatever word you'd want to replace it with, oh alleged Perfect English Speaker who has not quite worked out what actually defines pedantry), is exactly set up to provide a defined route which thus can be made safe. Until, in this case, it was not, due to a leak.
For my thesis work - a very long time ago - I used supercritical CO2 to dry samples for electron microscopy. The samples were in an aqueous or solvent solution to start with. I ramped up the pressure to above the critical point of CO2, let the sample be rinsed thoroughly by the liquid CO2, then pull it around the critical point into the gas phase, then it was dry and intact. Beautiful samples!
One thing that really stood out to me - any rubber parts in the system - O-rings, gaskets, etc - would absorb huge amounts of CO2 and swell to obscene sizes. It was totally weird. I eventually found that putting them on a vacuum stage with mild heat would gradually degas them back to normal.
That said - they're just using CO2 as the working fluid. I bet ammonia would work well too.
Lastly, our house in California in the summer - no A/C, modest appliances, uses about 10 kWh/day. That's about 36Mj per day in SI land. I think.
Well given the discussion around the lower temperatures of CO2 and the power output levels for the size of equipment they are using, I suggest they have an eye on lower temperature heat sources such as solar-thermal and geothermal, at worst 60C is well within the capabilities of a domestic gas boiler and on packaging it into something that would sit in a corner of a shed/garage. IE. an environment where high-pressure steam would be dangerous...
Perhaps the slightly more shocking thing is how long it’s taken to seriously consider and demonstrate an alternative to steam to up temperatures.
Efficiencies of thermal gradients have been known for a very, very long time; nor has manufacturing capability for pressure systems significantly changed.
Perhaps, in a fuel-rich world it didn’t matter so much…
There currently exists a 50 MW super critical gas turbine generator brought on-line in The following is from the article at https://gasturbineworld.com/supercritical-co2-carbon-capture/
This uses a fundamentally new power cycle, called the Allam Cycle. This is more fully described in Gas Turbine World, September-October 2016, but in basic outline, it produces its own carbon dioxide as a pipeline-ready by-product. The Allam Cycle does this by combining two processes. Firstly, it uses oxy-combustion, in which fuel is burned in pure oxygen. The combustion products from burning methane in oxygen rather than air are just CO2 and water. If this stream is cooled, the water drops out as a liquid, and the stream consists of pure CO2.
It is smaller and more efficient that other generators and does 100% carbon capture/
With the minor disadvantage you have to pre-process the air or seawater to get your input oxygen.
Not that difficult to do but usual methods for refining oxygen from atmospheric air are pretty energy intensive. Nuke submarines produce it from seawater by electrolysis, or you can play games with pressures and temperatures - a lot of industrial oxygen is a by product of producing liquid nitrogen. The former probably not practical to produce the quantities needed for a turbine.
And the latter, by the time you account for energy losses in your production process; you are using a lot more fuel to get your capture line in place.
Basically, we should be following the lead of Thunderbirds and using nukes for everything :-P
PSA extraction/concentration and similar methods are less of a stretch when you are already dealing with high pressure systems, and it is likely the described system could operate with nitrogen contamination without becoming useless.
Big upside of a process like this is being an open loop system resulting in a net negative footprint for things we want less of like CO2 and methane. Not going to be replacing the rest of the power mix, but one of many tools that may be a way to recapture and re-use what are currently waste emissions. Plenty of NG just getting flared off these days, a total waste. Plenty of high methane sights that could use this process for carbon sequestration for onsite emissions, even if it isn't net energy positive on the local scale. It will be less expensive then venting it to atmosphere then either separating it back out or living with the problems it causes.
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