Grounded jet engines take off again as datacenter generators

AI-driven datacenter energy needs are causing a shortage of gas turbines to power generators, with some operators reportedly turning to old aircraft engines instead. The rising demand for compute to feed the current AI development craze has seen datacenters adding capacity and new ones popping up, with a knock-on effect on the …

[Anonymous Coward]

Not that novel

Aero-derivative gas turbines are already offered by various suppliers into the industrial powergen market. In this context it's worth knowing that aero engines are a fraction of the size of self-respecting grid scale gas turbines - a CF6 will offer about 40MW, but for most purposes a grid-scale gas turbine starts at 200MW and goes up to around 700MW (a good chunk of that being thanks to combined cycle operation). Aeroderivatives are also normally a lot less efficient around 40% compared to the 60% or more that might be wrung out of a grid scale CCGT.

[Mishak]

Efficiency

Yep, which is why open cycle are only used as a "last resort" (in the UK at least) when there is nothing else available to keep the grid stable.

They are relatively cheap to build, but expensive to operate - a demand a high strike price as a consequence.

[Like a badger]

Re: Efficiency

Very few OCGT in the UK - about 1.7GW of capacity compared to over 31GW of CCGT. Whilst OCGT are less efficient in continuous running, in practice there's less difference because the increasingly intermittent calls for CCGT generation means that a lot of the time they can be running short cycles. The cost and complexity of combined cycle is mostly only installed because the original expectation was much longer running hours.

As an example, yesterday at 18:00 total demand was about 37GW, solar output was nil, wind output was a paltry 1.8GW, CCGT was providing 20.1GW. As of 08.00 this morning, total demand around 34GW, solar 0.3GW, wind 11.2, CCGT 5.4GW, and at both times OCGT was zero. Which means at the moment there's over 5 times as much CCGT capacity sitting around doing nothing as there is in use, but we need that capacity for when the wind isn't blowing, or of system failures.

[Anonymous Coward]

Re: Efficiency

… and why all UK electricity is comparatively expensive as tied to the gas generated price.

Even the record 113% (in 2022) of electricity consumption generated by Renewables in Scotland.

Still waiting on UK Government to work with (scum) Centrica to repair/expand the UK Strategic reserve at Rough Storage Field.

https://www.theguardian.com/business/2025/jul/24/fears-uk-gas-stockpile-drop-for-winter-british-gas-owner-centrica-sell-off

[Like a badger]

Re: Efficiency

"Still waiting on UK Government to work with (scum) Centrica to repair/expand the UK Strategic reserve at Rough Storage Field."

As I recall it was government rule changes that meant that the costs of maintaining the Rough storage field were disallowed from recovery through energy bills, so irrespective of your view of Centrica you'll need to direct your ire at government.

[frankvw]

Re: Efficiency

"which is why open cycle are only used as a "last resort" (in the UK at least)"

Indeed.

Eskom (South Africa's national electricity producer, state-owned and therefore astronomically expensive and dismally ineffective) has relied on OCGTs for years to keep the lights on. Ostensibly OCGTs were only an emergency measure, but they have relied on it as a matter of course since 2008, whenever demand exceeds available power station capacity. These OCGTs are diesel-powered and burn through fuel at a ridiculous rate to a point where the national diesel price fluctuates along with the availability of electricity - that's how much they've been burning.

Right now, with Eskom's bungling and astronomical costs having driven many South Africans to PV panels and home generation, which has taken a lot of load off the grid in recent years, this is less of an issue than before. But your point about why OCGTs should be considered a last resort only is well taken.

[anothercynic]

Re: Efficiency

Well, it's nice to see that the fact Eskom has been so comprehensively screwed up for the last decade has driven South Africans to move to micro generation (of green and not so green kind)! I know Eskom's not particularly pleased with this, and I know some energy suppliers elsewhere in southern Africa aren't either because their own populations have discovered that maybe using something that is available in abundance from that big ball in the sky instead of paying through the nose is preferable, but deprives the electricity suppliers of income.

This shows the law of unintended consequences in action. :-)

[Adrian Harvey]

Re: Efficiency

'Last resort" isn't the best description. They are frequently used as 'peaker' plants to cover surges in demand or drops in renewable production. A CCGT takes about an hour to spin up to full load, but an open cycle can be running full tilt in 10 mins. This on-demand capability is what allows them to command a high price in the market.

Yes, they can be used as last resort as well, scheduled for when they know all cheaper sources will be fully used, but they are mostly there for short-notice stuff. Grid scale batteries would start even faster, of course, but have other limitations, and there aren't so many of them.

[EricM]

What is doing more damage to humanity?

Repurposed jet engines that heat the environment by releasing excessive CO2 for a power output to be fed into AI models?

Or the unreliable advice generated by that "AI" model, that is trained on all things they could scrape off the Internet?

Well, together those 2 will probably get the job done - which obviously is the destruction the environmental _and_ mental basis of humanity.

[Evil Auditor]

Re: What is doing more damage to humanity?

But isn't AI going to solve all of our problems such as global warming, micro plastics, food contamination, all the wars? Well, for the latter not much intelligence is needed, apparently. The Orange One is going to bring world peace.

[blu3b3rry]

Re: What is doing more damage to humanity?

AI hype is the new "drinking the kool-aid".

[Anonymous Coward]

Re: What is doing more damage to humanity?

I think preppers may have it right.

When Zuck needs more sketchy AI near-porn Reels fire up the afterburners…..

[bombastic bob]

Re: What is doing more damage to humanity?

Repurposed jet engines that heat the environment by releasing excessive CO2 for a power output to be fed into AI models?

You seriously STILL believe the "climate doom" CO2 lie???

[Sorry that handle is already taken.]

In response to the shortage, US company ProEnergy has now turned to offering repurposed jet engines, which is what gas turbines basically are.

Well... yes but gas turbines designed for electricity generation are significantly more efficient than repurposing ones designed for aviation. What a disaster.

[Chris 15]

my thoughts too

Aircraft gas turbines, at least more recent ones, are heavily optimise to operate most efficiently at certain atmospheric pressures (not sea level..) and power/thrust levels, and this does not even consider the wasted wall of hot high speed air coming out of the back of them, to put it crudely.

They're also optimised with weight in mind.

You'd be better off efficiency wise using diesel generators, or having them built out of old diesel motors with better static cooling loops added, and a generator slapped onto the crankshaft I suspect. And eoled diesel motors are much cheaper and vastly more available.

[Like a badger]

Re: my thoughts too

"You'd be better off efficiency wise using diesel generators"

In terms of environmental impact probably better using spark ignition engines running on LNG, or diesel engines modified to run an LNG/diesel mix. Of course, all combustion generates a lot of waste heat, so absent the ability to use the waste heat efficiency remains stuck around 55% level.

[bombastic bob]

Re: my thoughts too

Carnot efficiency of a heat engine is (combustion temperature - rejection temperature) divided by combustion temperature. This is the theoretical maximum.

When you increase combustion temperature for better efficiency, you create oxides of nitrogen in the exhaust, i.e. "acid rain" components. So the exhaust might need a little scrubbing. (CO2 is irrelevant in spite of the warmist doomers making noises).

So in all cases, you'll have a combustion efficiency (i.e. burning all of the fuel) vs thermal efficiency vs pollutant "balancing act". But co-generation helps if you can recover exhaust and engine cooling heat to generate hot water and chilled water (via an absorption chiller). The thing is, co-gen is only COST efficient when it runs (more or less) continuously. So you might "sell back" power to the power company at times, and use the heating and cooling water made from recovered engine heat to provide heating and/or cooling for the buildings. That last part means the co-gen units lower regular electric consumption for at least the cooling load (and possibly heating if heat pumps were involved), and lower possible fuel cost for the heating load.

And hopefully the cost of fuel and equipment and maintenance is less than that of "the grid" as the only power source. Also the buildings would need to be designed around use of hot and chilled water for heating and cooling, the obvious elephant in the room.

[Anonymous Coward]

Re: my thoughts too

If you can find a use for the rejected heat from the combined cycle plant then you can (still within Carnot's laws) improve efficiency still further. I used to work for the company who commissioned the Grain CCGT plant, and as built had a waste heat connection to the nearby Isle of Grain LNG import terminal, with the heat used for regasification of the arriving cargo. That heat demand is a seasonal and non-continuous, but if I recall correctly the effective plant efficiency is around 77% when the LNG terminal can use the low grade heat.

[bombastic bob]

Re: my thoughts too

True, like co-generation. I was thinking more in terms of using low pressure turbines to recover additional heat as electricity... i.e. "closed cycle" as I understand it.

[Peter2]

Re: my thoughts too

Yeah; that's an open cycle gas turbine in a nutshell.

Combined cycle gas turbines also have a triple expansion steam plant tacked on to the end to basically get every last bit of power out of that heat, however the steam plant is expensive to manufacture and has long lead times.

[bombastic bob]

Re: my thoughts too

that's why co-gen might make more sense. see my previous post.

[bombastic bob]

Re: my thoughts too

I would expect that the turbofan portion would be re-configured to get more energy out of the turbine as a power generator. Turbofans have a secondary turbine in the exhaust stream that drives the induction fan which moves unheated air for significantly better thrust (and efficiency). So really to refurb a jet engine to move 'trons you'd remove the turbofan portion and replace it with a slightly more optimized power generating turbine plus a shaft leading to the generator.

So actually it would be fit for service when they get done with it.

[xyz]

I'd better start breeding more hamsters

This is getting ridiculous. If you're waiting 3 years for a gennie, AI will have taken over the planet by the time you get it and Ai will feed you to it to keep itself alive.:-)

[Roland6]

Re: I'd better start breeding more hamsters

> If you're waiting 3 years for a gennie,

Don’t forget there is also a multi year wait time for high voltage transformers and switchgear, which is impacting the speed of upgrade of the UK grid etc….

[ParlezVousFranglais]

Sounds like good business for The Boneyard

[Anonymous Coward]

Engines are normally the first bits stripped after final landing. For resale/parts depending on the condition.

[Like a badger]

I'd hazard a guess that due to shortages of materials like tungsten for making new engines, the engine OEMs or their suppliers are snapping up end of life aero engines, and the price will have gone up rather a lot.

[retiredFool]

Next week's headline

Shortage of natural gas to feed all these turbines. As a result, coal gasification plants will be constructed pronto.

[Steve K]

Re: Next week's headline

Easy fix - chuck coal in at the front end and collect the dust (or what's left of it - probably works better with a high-bypass engine...)...

[Like a badger]

Re: Next week's headline

Fact of the day: A gas turbine will run on coal dust, my dad worked at Pyestock as an apprentice in the 1960s, and (for some reason) they did try this. As you'd expect the wear was phenomenal and soon resulted in an engine fit for nothing, but it does work until something breaks.

[Aladdin Sane]

Re: Next week's headline

Not coal, but IIRC gas turbine powered helicopters can run on diesel.

[Like a badger]

Re: Next week's headline

Indeed. Anything that can burn and is vapourised or suspended in air will do. Diesel has an energy content not far off paraffin (avtur, Jet A1 etc), but where it's more viscous I'd expect a substantial efficiency hit, and (from my position of ignorance) a risk of residue build up.

Any flammable liquid, any flammable gas, some metal powders, flour, very fine sawdust, any powdered product from coffee to dried mango to chilli, etc can all drive a gas turbine, but what you really want is the highest energy content and easily mixed with air.

[Roland6]

Re: Next week's headline

>” Anything that can burn and is vapourised or suspended in air will do”

So if we run it on flour, we will be able to claim our turbine is “green” because it runs on renewable bio-fuel…

[bombastic bob]

Re: Next week's headline

USA should be exporting lots of LNG in the near future. Frack Frack Frack!

[Anonymous Coward]

Must be an interesting task doing the gas turbine conversion. Does it mean taking the turbofan off and adding a gearbox and generator, with a resulting change to the compression of the air entering the combustion chamber, or do they add a turbine and generator at the back? Also be interesting to know whether it's a combined cycle arrangement with a steam turbine....

[Anonymous Coward]

The article says ‘In this case, ProEnergy buys and overhauls used General Electric CF6 engines, a type used in commercial airliners, and adapts them to drive a generator rather than produce thrust.“

[IGnatius T Foobar !]

Been there, done that

I've had turbine generators running in some of my data centers before. They're all gone now. It sounds like a tremendously great idea until you learn that the maintenance is ridiculous; it requires so much specialization in parts and knowledge that the TCO becomes far higher than your good old 12 cylinder diesel engines.

[Brian J]

Re: Been there, done that

Problem is, in the scale of things, using diesel generators quickly becomes unattainable.

Example, xAI site. 420MW installed capacity, divided over 35 turbines. You would need 105 of CATs biggest Diesel generators to match that. That's a lot of realestate to take up

[Sam not the Viking]

Re: Been there, done that

Some years ago, as part of a major contract to a utility, we supplied a (used) aero gas turbine, converted to generate electricity. The site needed electrical power for continuous operations plus a substantial heat source. The site-consumption of electricity resulted in waste heat from the turbine almost exactly equal to the site requirement. This raised the energy efficiency from about 30% (electricity only) to 90+% overall. A dual on-line connection to the turbine supplier/service company ensured 24-hour, off-site, monitoring of the set. Part of the agreement included an annual sum for a 24-hour guaranteed replacement engine/turbine.

An excellent scheme when everything was at full load but the maintenance costs on the turbine were eye-watering. Of course, the system didn't run at full-load much of the time so the economics didn't materialise quite as envisaged.

Those ongoing costs of fuel, running, maintenance and servicing still give me the collywobbles. The initial purchase cost was almost negligible.

[Wellyboot]

Cheap as chips

These engines are first generation high bypass turbofans dating back 50+ years and can literally be found by the dozen in aircraft bone-yards, so they're a nice and simple motor to rework into gen-sets.

The AI bubble equivalent to selling picks & shovels during a gold rush.

[Contrex]

London Transport installed 8 Rolls-Royce Avon gas turbines to their Greenwich power station in 1972 to provide standby power for the London Underground. This is still owned and operated by Transport for London for that purpose.

[anothercynic]

There are still several other black start sites in the UK that use RR gas turbines. Didcot has apparently a set of four turbines, but that's separate from the Didcot B station that is a CCGT power station.

[Zolko]

Titanium

shortage of gas turbines

do you know what the main material of gas turbines is ? Titanium, because it is very strong and very heat resistant. Do you know what country is the main producer/exporter of titanium ?

At some point, the only thing one can consider is the stupidity of the western politicians who sanction the exact countries it is at war with and which provide the very materials – titanium or rare earth or otherwise – that the west needs to produce weapons to defeat the very enemy that provide the materials needed to make war with ... the very enemy.

And we didn't even begin to talk about pure silicium wafers to produce the very chips or the very solar panels .... or the uranium bars that the very enemy ... the only question that I don't have answers for is : do we deserve these "leaders" (leader = führer in German, literally) or did we at some point take the wrong turn ?

[Anonymous Coward]

Re: Titanium

Err - no! Titanium is used in parts of the compressor stages, some casings and accessories, but it is hardly "the main material". All the materials in an engine are a compromise: aluminium, titanium, nickel and cobalt alloys (as well as steels, polymers and others) are all used in various components and stages. Material selection depends on the optimum balance of strength, weight/density and temperature resistance - not forgetting considerations like fatigue, creep and corrosion resistance. Overall engine weight may not be the same issue with ground running but the rotating mass still has a big impact (sometimes literally if blades or discs fail). Titanium alloys are good for many components but they're too heavy for some of the larger rotating parts at the front and have insufficient heat resistance for the hotter parts at the back. And when it comes to casings, they're relatively easily substituted for less exotic alloys on the ground.

Things may have moved on a bit with design and materials since I worked in R&D for a major aero engine manufacturer, but the underlying physics remains.

[bombastic bob]

Re: Titanium

I would expect a lot of tungsten as well, for high temperature alloys.

[NXM]

Pure Silicium

Is this only found in Silicy?

Are we at war with Silicy??? Should we be?

[anothercynic]

Re: Titanium

That might've been the case in the early years, but the hot parts are a lot of alloys and ceramics these days, along with a lot of boundary layer cooling tech that doesn't require exotic titanium metal construction. :-)

Silicon wafers for solar panels are not constructed from pure silicon anymore either... a lot of the panels are more a mix of doped metals, although Perovskite metals and crystals are now even more interesting despite lead being a component. :-)

[Anonymous Coward]

It's an interesting concept, but I'd like to see the efficiency numbers for an adapted engine from an airliner vs a purpose built turbine for a generator. At the inlet end, the compressor will probably be designed to accept air coming through a turbofan, but to extract power from the engine, I'd imagine you need to take off the turbofan and put on a gearbox and generator, otherwise you're generating thrust, not electricity. At the exhaust end, I have no idea whether there is a fundamental difference between an airliner engine and one designed to work in a combined cycle power plant* Does anyone know?

*They *are* building combined cycle plants I hope, otherwise the efficiency will be awful....

[John Brown (no body)]

"I'd imagine you need to take off the turbofan and put on a gearbox and generator, otherwise you're generating thrust, not electricity. "

Nah, they just point the exhaust at nearby windfarms.

[TVU]

I guess the mild consolation is that natural gas is the least worst of all the carbon based fossil fuels.

[Roland6]

Once burnt…

[bombastic bob]

didn't you post that already? I downvoted that one, too.

[EricM]

I did, but neither the first nor this second post did show up that evening, "submits" resulted in timeouts.

I just was surprised to see these posts at all...

[bombastic bob]

comment system burps

oh yeah I ran into that the other day, something cloud-related probably, especially when you consider AWS's recent outage

[that one in the corner]

Boeing may have a few power plants to loan out

If the latest calls to ground Dreamliner don't go their way.

[FirstTangoInParis]

For peak loads ….

…. Maybe a fighter engine with afterburner?

[Hurn]

So, what's the conversion process for an engine from Jet-A1 to Natural Gas?

I take it, it's a little more complex than switching a stove back and forth between propane and methane by adjusting venturi aperture size?

Seems like specific energy of methane (natural gas) has got to be lower than an air/fuel mixture of Jet-A or Jet-A1 (mostly kerosene).

What's the trick?

Preheat it? -- Maybe a partially closed loop, where a percentage of hot exhaust is mixed with incoming (fresh) air, to pre-heat the air?

High pressure / high volume of gas -- use the shaft to drive a gas compressor?

Maybe partially cover the turbine air intake, so less air is sucked in, to mix with the fuel? (Similar to canvas on a truck's radiator, in the winter, to keep it from getting too cold?)

Does mercaptan residue cause any issues?

Inquiring minds wanna know.

[Wellyboot]

Re: So, what's the conversion process for an engine from Jet-A1 to Natural Gas?

To answer your first question, it may be almost that simple, the motor just needs the correct fuel/air mix to be pushed through the burners with the calorific value of the different fuels only affecting the consumption rate.

What you have next is a classic business case trade off situation.

The more you change on the motor converting it from an air blower to turning a genny the more efficient it becomes, the cheapest simplest fix is to literally bolt on a bigger gearbox & generator(Open cycle*), a full conversion has the turbine buried in a very complex heat exchanger & feedback loop to optimize the exhaust heat recovery (Closed cycle).

If the return on investment time for the efficient conversion doesn't beat the cheap (practically a bolt-on) solution during the expected wait time until grid connections can be made then we can all guess what's going to happen.

These converted jets won't go away in the long term either, they'll be kept as backup until the annual maintenance costs start to approach replacement cost by a more efficient system.

As for the Mercaptan issue (Sulfur), as long as the gas doesn't go wildly over the levels found in aviation kerosene the engines will operate.

* The exhaust heat (vast amounts) is lost.

[CountCadaver]

Re: So, what's the conversion process for an engine from Jet-A1 to Natural Gas?

sticking a heat exchanger on the exhaust flow to warm any areas inhabited by meat sacks would seem a sensible move but tech bros operate under a "fuck you I got mine" mindset

[Aladdin Sane]

If only they could find a way to capture all the hot air spouted around AI, their energy woes would be over.

[G R Goslin]

Old hat!

In the mid 1960's, I and a group of engineers were given a guided tour of Cottam Power station, which was till being built. They had two such generators. It was explained, that at times of very high load, these would be powered up to provide site power, to avoid loss of full unctionality of the site, with declining output voltage.

[nijam]

Re: Old hat!

> ... full unctionality of the site ...

Because the tour was run by the PR team?

[spireite]

My server crashed.....

..... "sorry sir, it was powered by engines off a 737MAX"

[Anonymous Coward]

Re: My server crashed.....

Upvoted for the poor taste.

[FuzzyTheBear]

green ?

AI seems to be one of the biggest source of pollution there is. IMHO it's wasted energy and only interest those up there in power to get rid of human employees. Judging by Amazon's 500000 robots to replace employees , i hardly see any defense that holds for the whole AI industry.