Using steam to produce electricity or perform work via steam turbines has been a thing for a very long time. Today it is still exceedingly common to use steam in this manner, with said steam generated either by burning something (e.g. coal, wood), by using spicy rocks (nuclear fission) or from stored thermal energy (e.g. molten salt). That said, today we don’t use steam in the same way any more as in the 19th century, with e.g. supercritical and pressurized loops allowing for far higher efficiencies. As covered in a recent video by [Ryan Inis], a more recent alternative to using water is supercritical carbon dioxide (CO2), which could boost the thermal efficiency even further.
In the video [Ryan Inis] goes over the basics of what the supercritical fluid state of CO2 is, which occurs once the critical point is reached at 31°C and 83.8 bar (8.38 MPa). When used as a working fluid in a thermal power plant, this offers a number of potential advantages, such as the higher density requiring smaller turbine blades, and the potential for higher heat extraction. This is also seen with e.g. the shift from boiling to pressurized water loops in BWR & PWR nuclear plants, and in gas- and salt-cooled reactors that can reach far higher efficiencies, as in e.g. the HTR-PM and MSRs.
In a 2019 article in Power the author goes over some of the details, including the different power cycles using this supercritical fluid, such as various Brayton cycles (some with extra energy recovery) and the Allam cycle. Of course, there is no such thing as a free lunch, with corrosion issues still being worked out, and despite the claims made in the video, erosion is also an issue with supercritical CO2 as working fluid. That said, it’s in many ways less of an engineering issue than supercritical steam generators due to the far more extreme critical point parameters of water.
If these issues can be overcome, it could provide some interesting efficiency boosts for thermal plants, with the caveat that likely nobody is going to retrofit existing plants, supercritical steam (coal) plants already exist and new nuclear plant designs are increasingly moving towards gas, salt and even liquid metal coolants, though secondary coolant loops (following the typical steam generator) could conceivably use CO2 instead of water where appropriate.
Must have read my mind. The comments to that video are interesting as well.
<
blockquote>That said, today we don’t use steam in the same way any more as in the 19th century, with e.g. supercritical and pressurized loops allowing for far higher efficiencies.<\blockquote>
This sentence isn’t clear. Did we use supercritical and pressurised loops in 19th century or didn’t we. Do we today. I guess a sentence with “unlike” somewhere at the beginning may better convey the message.
Do you really think it’s likely that we achieved “far higher efficiencies” over 100 years ago? You obviously understood it, so what’s the point?
So long as it is cheaper to not upgrade systems, they will not be upgraded.
or any downtime for that matter.
This would be beneficial for newly built power plants.
Are you saying that isn’t the right answer?
If the upgrade is more expensive than the fuel savings, you’d be crazy to upgrade.
This is butt simple, mouth breather MBA math.
Even if you want to do accounting in CO2…The upgrade isn’t free. Price is a decent CO2 proxy.
Finally some numbers @11:20 Efficiency of a steam turbine is apparently 40% and with supercritical CO2 this is expected to be increased to 50% and that is quite significant.
the local old coal fired powerplant here is 47% efficient making eletricity, it was the worlds best when it was build, but that is almost 30 years ago
This article is part of the multi million dollar effort of the fossil fuel industry trying to change how we think of CO2. Much like the stories where they talk about how there are other worse green house gasses or that ‘we need CO2’ messages on social media. At the end of the day, capturing sun energy and using that to heat CO2 to run a turbine is stupid. The less steps in the process the less losses. Battery tech is accelerating thanks to the universities around the world as is solar and wind / wave. If they spent one years of subsidies to nuclear and oil on green power generation the UK would be 100% self sufficient protecting us from would be dictators in the white house or the oil mafia of Russia. But the right hates that because they can’t embezzle oil subsidies.
brb, gonna go nuke some popcorn real quick
“If they spent one years of subsidies to nuclear and oil on green power generation the UK would be 100% self sufficient”
This is objectively false.
Conversely if all the green subsidies went to nuclear..
Green energy has been well proven to become self-sufficient under market terms after initial subsidies, nuclear power only ever exists at the treat of the taxpayer.
A nuclear plant can last for many decades, while wind and solar have to be constantly replaced and maintained.
Not really true on either count, Solar installs can and frequently have lasted longer than the nuclear power plants usual expected lifespan as solar is usually fit and forget in large part. Solar often don’t last that long only because the tech has been improving so massively its worth investing to replace the old with the new panels with 15% better efficiency (or maybe even more if you did manage to wait 20 odd years) and likely a much better expected degradation curve on that really good and already set up for solar location.
And wind is similar place, though does always require maintenance much of the replacements in practice have been because its easier and cheaper to replace a smaller turbine with one 3 times bigger than it is to get the the permissions to build a new farm of them somewhere else… Though Wind does come into another problem that has cost/benefits as they have scaled up so much – the tip speed and thus erosion of the blades gets worse on these larger turbines, but with larger catchment area they work in a wider wind speed and also produce more electricity overall.
Don’t get me wrong though Nuclear power is great, but it really isn’t maintenance free if you want to do it safely, and the expected lifespan and maintenance costs of a reactor is generally not very much if at all in their favour compared to many of the renewable options. The thing that really sells nuclear power as worth the investment (if you can get it) is the predictable and controllable nature of its output.
haha i’m gonna go at this from the opposite angle of foldi-one
everything takes a ton of maintenance, even solar, wind, and nuclear
It all comes down to power density.
It takes hundreds of wind turbines or thousands of solar panels in combination with huge batteries to replace one nuclear power plant. One cold winter can freeze an entire fleet of wind turbines. One show storm can cover an entire field of solar panels. Even a plain crash won’t stop a nuclear power plant.
You can build two or more nuclear reactors on the same spot if you want to save on costs.
Solar and wind are different animals.
Solar is low maintenance.
Wind, not so much.
They each have geographic issues.
You can bet that they are both being deployed/subsidized in stupid places for political reasons.
e.g. Solar in Northern Finland. Windmills in areas with low average wind and high land cost.
@Greg A It is a relative measure, when you compare solar which is very much fit and forget for the panels themselves (though sure you could clean them if you like) to Wind turbines with lots of moving parts, and now they are getting so large serious wing tip erosion….
Obviously there is still more behind that, but the substations and power transmission lines etc are barely changed between any power source and the sinks, the more distributed renewables will have higher maintance costs for those (probably anyway) but I’d suggest not by a particularly meaningful amount.
You will see significant reduction in output if you don’t. If you don’t maintain them, you can expect the output to be halved because of dirt accumulation. Because most panels are constructed with the cells in series for higher voltage, a shade (think, a stray leaf) on a part of the panel will basically turn that one cell into a resistor that will reduce the output on the whole string and cause a hot-spot to develop that will degrade or even break the panel.
Define “green energy”.
Solar panels and wind turbines are not self-sufficient because of the effect of market cannibalization. At low integration levels, they can sell all the power they produce and make profit at market terms, but at high integration levels they steal each others’ sales because they both tend to generate their power in high peaks, and those peaks occur simultaneously across vast geographical areas, so they tend to cause over-supply on the market which collapses the market price below profitability.
The subsidies granted to solar and wind producers are designed specially to combat this: they generally pay the difference between the market price and the cost of production plus some profit, in other words they pay a guaranteed price that is independent of the market conditions to make sure the producers end up in the positive on average. To remove these subsidies entirely would stop new investments into solar and wind, and has historically done so, because in the lack of a price stabilizing mechanism such as export/import or large energy storage capacities, building more solar or wind would destroy profitability.
And even where export/import, or the so-called “virtual battery” is available, it works most effectively in cases where there’s a small producer next to a big consumer, e.g. Denmark next to Germany, UK and France.
Meanwhile, as the big consumers are also building up their own inventory of renewable power, this mechanism starts to fail because they’re all producing at the same time, or all lacking power at the same time.
Consider that one time zone is a thousand miles wide. All the countries in that area are getting sun at the same time. Likewise for wind power: weather fronts are a thousand miles wide, so everyone’s getting windy or calm at the same time. While there’s local variation, the large scale effects don’t start to even out until you get to continental or even global scale, so simply saying “it’s always sunny/windy somewhere” is highly misleading.
Also, many countries, such as Germany, have right-of-way laws that demand the grid operators to pass all solar and wind power first and then others. This causes a situation where other operators are making a loss because they aren’t allowed to sell as much, which means they jack up their prices at other times and the average power prices go up. This is an indirect subsidy, again without which you couldn’t operate high integration levels of solar and wind power.
Did you know that a solar thermal power plant is more efficient than a solar panel? This is because a silicon solar panel cannot capture the entire spectrum of light while a dark surface can get very close to 100% absorption, and the conversion efficiency of the light that a solar panel captures is worse than the thermal efficiency of a turbine.
A solar thermal plant also comes with the ability to store thermal energy – usually in molten salts – so it can operate after sundown and achieves a greater utilization factor, which stabilizes power prices and yields better profits off the market with less subsidies.
Historically they haven’t yielded profits for anybody but the construction company.
Historically they’ve been unmaintainable money sinks that are shutdown after completion.
Because they can’t cover their ongoing maintenance when new (with all subsidies).
That’s a different issue, largely and ironically caused by naive subsidy policies and insufficient oversight that reward shady business and hyped up promises.
There are successful examples, like the Cerro Dominador Solar Thermal Plant in Chile. It makes power at $33/MWh for 17.5 hours a day on average. Its similar counterparts in California and Nevada have all failed because of higher than promised building costs, “technical problems” in construction, and failure to meet promised production numbers. In other words, they simply sold the government the thousand dollar hammer, pocketed the money, and ran.
Sorry, up to 17.5 hours, not average.
$33/MWh power cost is your example of success?
Yes. It’s quite cheap, especially compared to other renewable projects, but it holds itself even compared to fossil fuels. Gas is generally cheaper where it’s abundant, coal is much more expensive, and nuclear power is somewhat more expensive.
Mind, solar PV plants may bid at $20-25/MWh at the lowest but that’s after subsidies and tax breaks – they can’t actually make profit at that price. They only place the bid because the utilities would not buy intermittent power at any price higher.
Solar thermal is more valuable for the utilities because it is dispatchable – they can adjust the output according to need.
No, it’s just not ‘quite cheap’.
Most renewable generation remains hydro.
I don’t pay $33/MWh retail, in California.
That’s German power money…
It’s not the dumbest on earth, I’ll grant you.
I have no idea where you’re getting your coal numbers.
Coal is cheap, plant on the mine, transport via transmission line.
Modern way.
Just effectively banned, many places.
No, you probably pay much more, because that’s the producer price without transmission, retail and tax added. $33/MWh is 3.3 cents per kWh and you definitely aren’t paying that little. It’s a factor of 1000 between MWh and kWh.
Again:
You don’t appear to understand how a power pool works.
Powerplants bid their marginal/incremental cost. (e.g. Nukes don’t include their fixed costs in their bid.)
All plants collect the highest bid dispatched that period for their generation.
Not their bid, their bid controls if they generate.
Capacity payments handled separately. Peakers don’t make money on power in pools. Nobody makes money at their own bid.
Also. Most renewable is dispatchable but constrained, as it’s hydro.
Solar PV is not dispatchable, but is pretty schedulable.
At $1/Watt, 20 year life, 3 hours average daily full sun equivalent, solar PV gets you about $0.05/kWh cap cost. Very low maintenance costs. Assuming roof space is free.
$1/Watt maybe optimistic for installed solar, if you’re paying full retail ripoff price for rooftop, buying land to put it on or are someplace with little sun (e.g. Seattle, England, Lapland, Hades etc).
Wouldn’t want to have to troubleshoot a leaky system, though.
Being in a room with a steam leak may be miserable and sloppy, but you know it’s there and unless you stick your face right into a spraying leak probably won’t kill you. CO2 is both toxic in large concentrations and not very detectable to our senses. So… make sure the alarms are really good, I guess ???
Breathe into a paper bag and say you can’t tell.
The breathing reflex of humans isn’t based on the level of oxygen in your blood, but the level of CO2. You’ll start to feel pretty uncomfortable well before you reach toxic CO2 concentrations.