Don't like this old calculation that I've quoted several times recently? Coal-fired power stations are thermodynamic heat engines; they do not get to break the laws of physics. The maximum achievable thermodynamic efficiency depends on the ratio of the absolute temperatures...
…The ratio of the (Kelvin) temperature of the 'cold side' of the engine (~condensing steam in the condenser) to that of the 'hot side' (~the hottest steam in the boiler). Under idealised low-heat-flow conditions, the well-know Carnot formula applies:
ηₘₐₓ = 1 - Tc/Th
...But under more realistic high-flow conditions, it becomes the square root of the temperature ratio, which is what I applied:
ηₘₐₓ = 1 - √(Tc/Th)
That's an extremely simple representation, there are multiple confounding effects, but guess what the quoted numbers for the newest coal-fired power station attached to the national electricity grid give...
That's the 750 MW single-unit, supercritical-steam, dry-cooled (and highly unreliable) Kogan Creek power station near Chinchilla in SE Queensland. Quoted operating parameters are:
steam pressure 25 MPa
steam temperature 560 °C
efficiency 40%
It is direct-condensed dry cooled, so the cool-side temperature is ~that of (fan-forced) ambient air; lets say 25°C. Put those numbers into the simple thermodynamic formula and guess what (+273°C to convert to Kelvin):
ηₘₐₓ = 1 - √((25+273)/560+273)) == 40%
What a surprise. Remember this is a simplistic treatment -- there are confounding effects, but the point is the thing cannot depart far from what it says, because physics.
Next time someone spruiks 'HELE' coal-fired power at you, ask them how much more efficient that will be that Kogan Creek, or Millmerran, or Callide C, or Tarong North. Answer: about 5% more (42% efficient vs 40%).
'High-efficiency low-emission' is a deliberate, semantic lie, made up of words that have been carefully chosen to obscure facts: 42% efficiency is not 'high', and a kilogram of CO₂ emitted for every kilowatt-hour of electricity is not 'low'. That's ultra-supercritical 'HELE'.
There are now (hugely expensive) designs with even higher steam temperatures and pressures -- up to as high as 700°C, for ~45% calculated efficiency. We call those 'advanced ultra-supercritical' ... just add another hyperboliser to the list.
The only qualifier there with any meaning is the 'super' in supercritical. But that doesn't mean super-good -- it means 'operating above the critical point of water' (below). The others are hype.
Above the critical point, water no longer has separate liquid and gas (steam) phases -- it's all the one watery-steam fluid. Changes the boiler design, because no longer need to design to separate water and steam (in the great big steam drum of a conventional coal-fired boiler).
(Long ago, as a very junior eng., helped with a full check of the boiler house structural design for a certain major power station. Wanted to do the huge, 3m deep, steel plate girder that the steam drum hangs from. Not allowed.)
• • •
Missing some Tweet in this thread? You can try to
force a refresh
'High-efficiency low-emissions' (HELE) coal-fired power is an outright lie. Each time you hear some politician spruiking it, ask who is paying them, what have they been promised, who are they working for (hint: it isn't you).
We've been over this ground so many times, but still they flog it. Things: 1. Australia already has multiple 'higher-efficiency' supercritical coal-fired power stations. They're our newest and *least reliable*: Callide C (currently broken), Kogan Creek (breaks often), Millmerran.
2. What liars ('proponents') are mostly talking with HELE is 'ultra-supercritical' -- slightly higher steam temperature and pressure than standard supercritical. The extra efficiency gain from that is *small*, about 5%.
That Science Show segment from Karlie Noon and Corey Tutt was just ghastly. How, still, after all this time, are we still doing this? Australian is deeply, fundamentally racist at levels that are incomprehensible to me.
...And sexist. Apart from anything else, it's a vast societal and economic waste to not make the best of every child, every student, at every school, especially at every public school. Why do we not see this? Why can't we manage it? WTF is wrong with us.
Sure, some will manage to achieve anyway. What about the rest? Yet we still spend bulk public funds on wealthy private schools that: 1. Do not educate most students 2. Do not educate the most challenging students 3. Waste our limited resources on grandiose pretence.
ABC 'Back to Nature' -- wonderful pics; absolute crap commentary. Is she making it up as she goes along, cherry picking half-baked nonsense stories?
Once again, how drones have transformed filmmaking, and not just docos.
'Finke River on the same course as 100 million years ago' ...really, maybe cite? The world was an unrecognisably different place 100 million years ago – 10-15°C hotter than now, with crocodiles and turtles living near the north pole. Australia was still connected to Antarctica!
Vote albatross! (Yes that is the right one, but pic was in Nzud.)
Is very much an Australian bird -- it breeds on three little islands in Tasmania and nowhere else, anywhere: Albatross Island, Pedra Branca, and the Mewstone.
COVID sewage detections continue to spread in NSW -- the result of Berejiklian-Barilaro's refusal to effectively cordon Sydney, three months ago. Eventually that will all be red.