Oversizing a heat pump

[SteamyTea]

The 'exploding' demand for giant heat pumps

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  7 hours ago

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IMAGE SOURCE,MAN ENERGY SOLUTIONS Image caption,

This MAN heat pump system in Denmark is one of the biggest in the world

 

By Chris Baraniuk

Technology of Business reporter

 

There are 2.5 million litres of water in an Olympic-sized swimming pool.

If for some reason you wanted to bring it from a pleasant 20C to boiling point, German firm MAN Energy Solutions has a heat pump that could do it. And it would take less time than Kenneth Branagh's film version of Hamlet.

"We can do this in less than four hours," explains Raymond Decorvet, who works in business development at MAN Energy. "Or we could freeze the whole thing in about 11 hours."

Theirs is among the largest heat pump units in the world. Heat pumps work by compressing gently warmed refrigerants to raise the temperature of these fluids. That heat can then be passed on to homes or industrial machinery.

Heat pumps require electricity to work but can produce around three or four kilowatts of heat for every kilowatt of power they consume, making them highly efficient. Plus, some designs can provide cooling as well.

Heat pumps are increasingly popular with some home owners but domestic devices are relatively small and tend to have outputs of several kilowatts or so. MAN Energy's biggest commercial heat pump is thousands of times more powerful - with a total heating capacity of 48 megawatts (MW).

It can produce temperatures of up to 150C and heat thousands of homes, not just one. The company recently installed two of these machines in the port city of Esbjerg, in Denmark.

In this installation, the heat pumps' CO2 refrigerant will absorb a small amount of heat from seawater. Compressors boost the temperature of the CO2 and the system can then transfer this heat, providing water of up to 90C to a district heating system serving 27,000 households.

 

IMAGE SOURCE,MAN ENERGY SOLUTIONS Image caption,

Industrial-sized heat pumps are a thousand times more powerful than domestic versions

 

"The demand for district heating is exploding," says Mr Decorvet. An urgency to move away from fossil fuels is leading to a rush - particularly in Europe - for bigger and beefier heat pump systems that can power entire towns. But who has the biggest, megawatts-wise?

It might seem like a relatively straightforward question but it is actually quite tricky to answer definitively. Not least because heat pumps don't tend to work at maximum capacity all the time. In Esbjerg, MAN Energy's heat pumps will run at about half their potential output, for instance.

And trying to compare the world's largest heat pump systems is difficult because, often, they are made up of multiple smaller heat pumps chained together. Take the district heating system in Stockholm, Sweden, often referred to as the largest heat pump set-up in the world.

This is probably true, it has a maximum capacity of 215MW - but that total is the sum of seven heat pumps, two 40MW and five 27MW devices, a spokesman for energy provider Stockholm Exergi explains.

Elsewhere in Sweden, Gothenburg has a 160MW heat pump system that consists of four units. Two of them are actually bigger than those in Stockholm, with capacities of 50MW each.

They have been in operation since 1986 and probably hold the title of the most powerful individual heat pumps currently in use, though they are clearly rivalled by newer devices such as those made by MAN Energy.

Last year, German chemicals firm BASF and MAN Energy announced their intention to build a 120MW heat pump that would, reports suggested, be the world's largest.

It would have provided heat for industrial uses at a site in Ludwigshafen. However, it was not to be. "BASF has decided not to proceed with the project," a spokesman told the BBC. The firm is exploring other potential heat sources instead, which it hopes will be more economically attractive.

 

IMAGE SOURCE,GETTY IMAGES Image caption,

In countries like Sweden big heat pumps are used to heat whole districts

 

Size isn't necessarily everything, notes Dave Pearson, group sustainable development director at Star Refrigeration. Efficiency matters and he argues that ammonia - his firm's choice of refrigerant - helps to make heat pumps particularly efficient.

Veronika Wilk at the Austrian Institute of Technology and colleagues have studied the use of heat pumps for industrial applications, to provide heat in pharmaceutical, food or paper factories, for example.

So long as they don't require very high temperatures beyond 200C, companies are increasingly turning to heat pumps, Dr Wilk argues, because it allows them to move away from natural gas, which has become extremely expensive following Russia's invasion of Ukraine.

But industrial heat pumps tend to be merely several MW in capacity or so. You are more likely to spot truly giant heat pumps in a district heating system, such as those mentioned above, says Dr Wilk.

"The beauty of district heating is that you can decarbonise a lot of households at once," she adds.

 

IMAGE SOURCE,AIT & KRISCHANZ Image caption,

Veronika Wilk points out that district heating can decarbonise a lot of homes in one go

 

There are many other examples of heat pump-powered district heating systems springing up. In Vienna, a 55MW system using three heat pumps is due to go live this autumn.

The machines will harvest heat, around 6C, from treated wastewater, explains Linda Kirchberger, division manager asset decarbonisation and new technologies at Wien Energie.

The treated water used to go straight into a river. "Now it does a detour and we take it through the heat pump system," she says.

The system will lift temperatures from 6C to 90C and the heat will go on to supply 56,000 households. In 2027, Wien Energie plans to double the system's capacity with three more heat pumps, reaching 110MW in total.

While still impressive, and weighing more than 200 tonnes each, these individual units have a capacity of less than 20MW. The manufacturer, Johnson Controls, confirmed to the BBC that its largest heat pumps have a maximum output of 28MW.A similar system, also using heat from wastewater, is planned in Hamburg, according to reports. It will have a capacity of 60MW, though this too will rely on multiple heat pumps linked together, a spokeswoman for Hamburg Wasser, the water company involved in the project, says.

But keep an eye on the future. In the Finnish capital Helsinki, a plan is afoot to construct a gargantuan heat pump system with a total capacity of 500MW.

This will likely be comprised of multiple units, as in Stockholm, Gothenburg and Esbjerg, but Helen, the energy company behind the scheme, has not yet revealed how it will all come together.

MAN Energy is one firm bidding for the contract. A spokesman declined to explain exactly what configuration of heat pumps would allow the company to provide 500MW of heat. Mr Decorvet says, simply, "I hope we are going to win."

[Gone West]

@SteamyTea That's interesting, not something I had ever thought about. Are you able to explain how they seem to work differently from domestic heat pumps. It mentions input temperatures of 6C and output temperatures of 90C, with CoPs of three to four. The only differences between those heat pumps and domestic heat pumps seems to be the size and refrigerant used, CO2 or ammonia, so is that the reason? If so why can't domestic heat pumps use ammonia?

[joe90]

https://www.bbc.co.uk/news/business-65321487

 

[Merged from another thread]

[SteamyTea]

6 minutes ago, Gone West said:

The only differences between those heat pumps and domestic heat pumps seems to be the size and refrigerant used, CO2 or ammonia, so is that the reason? If so why can't domestic heat pumps use ammonia?

Basically the refrigerant gasses, and much sturdier engineering.

You can get CO₂ heat pumps for domestic installation, they just tend to be expensive and there is a real lack of installers.

Ammonia is flammable, and poisonous, but cheap to make.  It is a good refrigerant and can also be used to power ICE, we make billions of litres of it every year.

Edited May 30, 2023 by SteamyTea

[Big Jimbo]

Very interesting read. The only thing for me is you are again tied into a big company for your hot water and heat. My preference would be for us all to be able to supply our own power for the running of our properties. Solar, wind, or whatever comes next.

[Gone West]

3 minutes ago, SteamyTea said:

Basically the refrigerant gasses, and much sturdier engineering.

You can get CO₂ heat pumps for domestic installation, they just tend to be expensive and there is a real lack of installers.

So what refrigerant could be used in a domestic heat pump to produce water at 90C with a CoP of three to four?

[Big Jimbo]

@SteamyTea So do we in GB have anything similar ? Or are we being left behind ?

[SteamyTea]

2 minutes ago, Gone West said:

So what refrigerant could be used in a domestic heat pump to produce water at 90C with a CoP of three to four?

Not sure.

One thing that is a problem is that the gas must not be corrosives, and play nicely with lubricants.

Water and hydrogen can both be used, but they cause problems.

From my limited understanding, hydrogen plays an important part in the phase change of the current generation of gassed, but it is bonded strongly to the carbon atoms.

[SteamyTea]

1 minute ago, Big Jimbo said:

@SteamyTea So do we in GB have anything similar ? Or are we being left behind ?

I was chatting to a heat pump guy a few years back and he said there had been a few commercial CO₂ installations, mainly cooling.

I also seem to remember there were a number of domestic CO2 units available about a decade ago.

Maybe @markocosic knows more.

[Big Jimbo]

@SteamyTea has posted about that Joe

 

[Merged from another thread]

[SteamyTea]

@@joe90

 

Won't be big enough to heat your place in Wales, Zoothorn will be sucking all the power to keep his place warm.

[joe90]

3 minutes ago, SteamyTea said:

Won't be big enough to heat your place in Wales,

Ah, most of the  Forest of Dean is in England and I am in that part!

[SteamyTea]

12 minutes ago, joe90 said:

Ah, most of the  Forest of Dean is in England and I am in that part!

They will still speak funny.

 

https://en.wikipedia.org/wiki/Welsh_phonology

[joe90]

24 minutes ago, SteamyTea said:

They will still speak funny.

Actually I find they speak better English than some parts of Devon.

[SteamyTea]

15 minutes ago, joe90 said:

Actually I find they speak better English than some parts of Devon.

We have known that for generations.

[markocosic]

On 30/05/2023 at 10:59, SteamyTea said:

I also seem to remember there were a number of domestic CO2 units available about a decade ago.

Maybe @markocosic knows more.

 

It's not really an appropriate refrigerant.

 

CO2 operates transcritical. You need a large deltaT on the output side (e.g. 70C supply/30C return) to get meaningful performance with CO2.

 

That's not useful for heating domestically. The output from radiators would be about the same as at 52/48C. The COP would be lower.

 

It could be kinda useful for domestic hot water. 

 

But the much higher operating pressures and heavier components that result mean it's really not worth the effort vs straight propane.

 

Communal heating schemes that operate at say 60/30C (to keep distribution pipe sizes low and to allow production of domestic hot water on demand via plate heat exchangers are another matter. Those play very nice with the operating temperatures of CO2.

 

Bigger ones will just use ammonia though. It kicks butt as a refrigerant but isn't practical at small scale for safety reasons as much as anything else.

[SteamyTea]

19 minutes ago, markocosic said:

CO2 operates transcritical. You need a large deltaT on the output side (e.g. 70C supply/30C return) to get meaningful performance with CO2.

Yes, I had forgotten that.

Apparently when they go wrong, you can get a very big bang.