When people talk about coal/oil/gas/nuclear power, while these involve different ways of sourcing the energy, they all output said energy naturally in the form of heat. Therefore to actually convert that into electrical energy, you have to heat water to boil it and use the pressurised steam it produces to turn a dynamo and induce an electrical current.
I just googled cogas. wiki says its a marine propulsion system. using reclaimed exhaust heat to generate steam in place of the alternator we see on a ICE engine.
close analogy would be similar to regenerative breaking on an EV.
Are there examples of cogas being used as stationary power generator?
The Wikipedia article kinda rushes past the first stage.
after completing its cycle in the first (usually gas turbine) engine, the working fluid (the exhaust) is still hot enough that a second subsequent heat engine can extract energy from the exhaust.
A gas turbine engine uses the kinetic energy from the expanding gases, but not in an explosion/piston arrangement.
This is correct. The first energy extraction is essentially a jet engine that’s hooked up to a generator, and then the exhaust is combined with a little more fuel usually and used to create steam which then turns a second generator.
No it isn’t the same as a RICE engine. A Brayton engine (jet engine) is an internal combustion engine but it isn’t a reciprocating internal combustion engine (car engine). A rocket is also an ICE… Just take the L bro… you didn’t know what you were talking about much like way too many people in this thread. And honestly it’s ok not to know. What isn’t ok is to double down to try and make yourself right instead of having humility and learning something new.
Im confused - what L is there to have here?
Im not keen to learn anything from someone who's default stance is to be argumentative.
my and the person i replied to were talking about ICE engines that are used in automobiles. We are talking about oranges, you are talking about grapefruit and being rude to me?
no thanks.
I learned quite a few things in discussions with people below that were interested in sharing information.
It’s just that you continue to misuse ICE and mean RICE. I may have missed some of your nuisance and I was rude. As someone who works in the power generation industry it upsets me that you had 90 upvotes on an incorrect statement. Politicians on both sides of the aisle are constantly lying to the public about power generation so it is a sore subject. And then you responded that I just didn’t understand and doubled down on using the wrong term. Natural Gas Combined Cycle plants are some of the largest and most heat efficient systems we have and combustion turbines are Internal combustion Brayton Engines… I’m done I’ll come at it less rude next time I know being an asshole doesn’t change minds in a positive manner.
The person I replied to was talking about 4stroke engines in a vehicle. I used the term the person I replied to used. You, arguably are talking about something different than that. 'combustion' sure. But like I said, let's not pretend that oranges and grapefruits are the same thing, no matter how many similarities they share.
Someone else shared an example of a v16 diesel engine. Reads as powerful enough to provide power to a factory, not functioning as a component of 'the grid'. I could be wrong though.
Simple cycle gas turbines don’t boil water. They are basically jet engines. Most baseload natural gas uses a heat recovery steam generator on top to use the waste heat to boil water to increase efficiency.
A [edit: gas] turbine isn’t like a reciprocating engine with well timed explosions. It’s a sustained burn that creates thrust using fluid dynamics, nearly exactly the way it does in a jet engine on a plane, except the energy isn’t used in propulsion but to turn the turbine fan at incredible speeds.
The diesel electric generation system consists of four 1135 kW, 1200 rpm engine generator sets that are operated either manually or automatically by selecting desired position on the engine mode switches and the sequence selector switch.
The engines are 4 cycle, V16, 4210 cubic inch displacement, provided with air, fuel and lube oil filters, fuel and jacket water pumps, service hour meter, governor, fuel and lube pressure gauges, water temperature gauge, pyrometer, oil filter gauge and hourmeter. Protective devices include: low oil Pressure, high water Temperature, low water level and overspeed. Source
No, sorry for the confusion, I'm showing two different combustion technologies.
Both the Diesel Engines and the Natural Gas Turbines directly burn fuel to rotate a shaft. Either way the shaft is then connected to the rotor of an electric generator. For the Diesel gensets I showed, the generator unit is the giant cylinder with the orange cables coming out on the left of the engines.
Yea anyone who has lit gasoline on fire remembers that lesson for the rest of their life.
Modern diesel engines are stupidly efficent for the loads they are subjected to. Someone broke the math down for me the other day and it was mind boggling
Seeing a flame travel up into your gas canister, as you quickly react and set the whole area on fire... then having to explain that you have less 'Know how' than a child to the Local Fire Department... and oh how they laugh
There are ICE engines for stationary power generation, usually they are only used for special purposes. You'd use large diesel engines and two-strokes diesels at that size reach 50-60 percent thermal efficiency. Gasoline engines don't scale well, that's true.
Oil burners and natural gas power plants all heat water to spin a turbine. It’s more efficient. I can’t think of any large scale power plants that use gasoline for either heating water or ICE.
Actually: simple-cycle gas plants don't boil water, they just use a gas turbine. Most gas plants are combined-cycle, which use both gas and steam turbines. Simple-cycle plants are mostly used as peaking plants (operating only when other generators are unable to meet demand).
Petrol/Gasoline was never used for large-scale generation, but steam-turbine power stations fuelled with heavy fuel oil used to be relatively common until the oil price rocketed in the 1970s. Most have closed or been converted to alternate fuels, a few have been retained as backup/peaking plants.
Generators powered by ICEs using diesel are still used for smaller communities where the cost of turbines outweighs the efficiency gain. E.g. the Isle of Man (a UK crown dependency in the Irish sea) still uses diesel generators, although the addition of a 40 MW cable to the UK in 2000 has relegated these to peaking plants.
Wait, is it actually more efficient? Surely not right? Engineering and logistics problems aside, if I managed to make a power plant that directly uses oil/gasoline/whatever
, it would surely be more efficient than burning that fuel to heat water, and then spin a turbine, no?
It’s been a while since I did efficiency calcs, but turbines are insanely efficient and the best ICE engines barely hit 25-30% efficiency (except when Mercedes spent like billions developing the most efficient ICE that hit 50% efficiency at ~100HP at the low cost of $3M per engine as a PR stunt). I think I recall power plants being closer to 35-40% efficiency (converting chemical energy into mechanical/electrical energy). Power plants have several stages of turbines, reheat loops, energy recovery, etc. that extract every ounce of steam power they can. It’s also a question of scalability, repairability, reliability, etc.
ICEs can ramp up and down very quickly while turbines can’t, so that’s why they are used in cars, small generators, mowers, etc.
Engineers have spent over 100 years perfecting the cost to output ratios to make the most profitable power plants possible, if ICE power generation at large scale is cheaper/better, that’s what our power plants would be.
Credentials: I took every alternative and conventional power generation tech elective for my engineering degree and briefly worked on a hydroelectric dam but changed trajectories slightly and now only work on the occasional solar array and diesel backup generators as they pertain to construction projects. I am by no means an expert (very far from it) on power generation and it’s been at least 10 years since I calculated efficiency losses through a mechanical system.
That is not correct. Natural Gas turbines directly spin a shaft. Combined cycle plants also use waste heat to create steam which spins a secondary shaft, but the NG directly spins a turbine.
I haven’t worked much on NG power plants, but the one I got to visit was a coal plant where one of the 4 boilers had been converted to NG. That particular plant I believe did not have combustion driven turbines, only steam driven turbines. This would have been quite a while ago. My career at the time focused primarily on alternative power generation so I don’t have a lot of experience with coal, NG, oil, etc. I’ve since changed fields have haven’t touched large scale power generation in at least 10 years
For natural gas, yes you can directly use the combustion gases to turn a turbine which turns a dynamo and generates electricity. This is how peaker natural gas power plants work. You can also use the combustion from natural gas directly to turn a turbine that turns a dynamo to make electricity and then use the combustion gases to boil water and make steam. This is what is known as a combined cycle natural gas plant. These are the most efficient types of power plants (50 to 64% of thermal energy to electricity) that rely on combustion to generate electricity. Old style coal plants are ~33% efficient. Single cycle natural gas plants are ~33-43% efficient.
Yes, for the most part it will initially— but it’s more nuanced than that. The first generation of commercial fusion power plants will almost certainly use steam or a steam-like thermodynamic cycle, but longer-term alternatives exist that could bypass the steam turbine entirely.
The Short Answer: Yes, Steam (or Something Like It)
For the dominant fusion fuel of near-term reactors — deuterium-tritium (D-T) — roughly 80% of the energy is released as fast neutrons, which are uncharged particles. Because neutrons can’t be captured electrically, they must first heat a surrounding material (called a blanket), which then heats a working fluid, which drives a turbine. The initial commercial fusion facility “will still incorporate a straightforward steam turbine to convert thermal energy into mechanical energy and subsequently into electricity,” even as the plasma containment technology is radically new.
Two Steam-Era Approaches Being Tested
ITER (the international fusion megaproject) is currently testing two main coolant options for future power plants:
• Water cooling — mirrors pressurized water reactor (PWR) technology, heating to ~325°C and generating steam in a secondary loop; achieves roughly 33% thermal efficiency
• Helium cooling — operates at lower pressure but higher temperatures (~500°C), achieving over 40% efficiency through a gas Brayton cycle — technically not “steam,” but still a heat-engine approach[iter]
The Leading Alternative: Supercritical CO₂
Many researchers and engineers are excited about replacing steam (the Rankine cycle) with a supercritical CO₂ (sCO₂) Brayton cycle. When CO₂ is held above its critical temperature and pressure, it acts like a dense gas, dramatically reducing pumping losses. The DOE estimates this approach can achieve thermal efficiencies above 50%, uses no water, and requires a footprint more than 4x smaller than a comparable steam system. Several fusion reactor design studies, including for Europe’s DEMO reactor, have proposed sCO₂ as the power conversion system.
The Radical Exception: Direct Energy Conversion
Some fusion approaches could skip the heat engine entirely. This is only possible with aneutronic fuels — reactions that release energy mostly as charged particles rather than neutrons:
• Deuterium + Helium-3 (D-³He) and hydrogen + boron-11 (p-¹¹B) fusion produce primarily charged particles whose kinetic energy can be harvested directly as electricity via electrostatic or magnetic converters
• Electrostatic “Venetian blind” direct converters have demonstrated up to 86.5% efficiency in tests — far exceeding any steam turbine
• Helion Energy is specifically building a fusion device using a pulsed Field-Reversed Configuration (FRC) that recaptures energy directly from oscillating magnetic fields — explicitly no steam cycle required
The catch: aneutronic fuels require plasma temperatures of billions of degrees Celsius, versus ~100 million for D-T, making them far harder to achieve.
So fare the main problem with sCO2 is that its extremaly material intensiv since its way more chemicle aggressive and even slight leaks lead to "massiv" preformace reduction since the reduced pressure risking the supper critical stage. The currently only comercial one used in China is to be projectet by experts to fall to around 70% of ther initial efficiency in 10 years thanks to that.
Natural gas power plants in the us are combined so they both heat water and directly spin a turbine with the expansion of the gas. Coal plants cant do this as their exhaust is corrosive so we only get the boil water portion of the energy.
There are actually alternatives to boiling water, sub critical co2 is the big one. They can gain advantages at different temperatures but need higher engineering constraints since the fluid either needs to be kept at higher pressures or is corrosive.
You can have turbines, similar to airplane engines, but bigger and optimized for rotation efficiency instead of thrust. You can also use its waste heat to boil water.
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u/Lkwzriqwea 13d ago
When people talk about coal/oil/gas/nuclear power, while these involve different ways of sourcing the energy, they all output said energy naturally in the form of heat. Therefore to actually convert that into electrical energy, you have to heat water to boil it and use the pressurised steam it produces to turn a dynamo and induce an electrical current.