Hah I've been researching that too. I've got some whacky ideas of my own but there are companies that sell the units and install them - search for "water cooled air conditioning" as I don't want to link to any specific company. They're designed for flats and listed buildings that can't have outdoor units, and they're normally plumbed into the mains water supply. There's a thread on mumsnet where people talk about their experience: https://www.mumsnet.com/talk/property/4193494-Info-on-water-cooled-air-conditioning-Not-evaportaive-cooling-but-ordinary-ac-with-water-cooled-condensers

I thought about calling them up and asking if they can plumb it into radiators, rather than mains water. But in the end I decided against as I think normal ATA mini-splits would be much cheaper. The benefit would be no additional outdoor units (and any planning permission that would require).

One of my whacky ideas involve dehumidifiers rather than portable AC units, mainly because I have a dehumidifier which I don't use and don't mind ruining. Dehumidifiers have the same refrigeration cycle as AC units, but the "hot" side is right next to the "cold" side and the air passes over both. In winter you actually get a mild heating effect as the water gives up some of its heat when it condenses, but if we separate the hot side from the cold side and cool the hot side with (cold) water from the ATW radiator loop, we can dump the heat outside of the building instead.

It's fantastic that the actual professional engineers at Octopus are trying to build units that work with their existing ATW heat pumps. I do hope they make a marketable product out of it before next summer's inevitable round of heatwaves. It also looks simple enough that you could probably DIY install it...

Posted by: @scrchngwsl

↑

"water cooled air conditioning"

Heat capacity of water is 4180 J/(°C.liter), therefore 1kW = 0.24 °C.liter/s

Assuming inlet water temperature 20°C outlet 65°C deltaT 45°C, 1kW cooling power uses 20 l/h or 7.6c€/h at 4€/m3

Assuming lowish EER 2.5 due to the high outlet temperature, electric consumption 400W or 8c€/h

Total 16c€/h per kW of cooling power.

On the other hand, a decent split aircon will have EER 4-5 so running costs about 4c€/h per kW of cooling power.

When cooling the slab (17°C water, 30°C air) my A2W heat pump casually flexes EER above 8, it consumes 500W and outputs 4kW cooling power lol ; running cost zero (powered from PV) ; obviously the best time to cool a slab is at night when air is at 25°C, EER then goes 🚀 but at night electricity is not free.

Conclusion: by needlessly preventing people from installing AC that actually works, the result is people will either use mobile units (terrible cost efficiency) or water cooled units (also terrible cost efficiency, plus waste of water).

Always compost your greens!

Posted by: @scrchngwsl

↑

It's fantastic that the actual professional engineers at Octopus are trying to build units that work with their existing ATW heat pumps. I do hope they make a marketable product out of it before next summer's inevitable round of heatwaves. It also looks simple enough that you could probably DIY install it...

Potentially a winner this idea if it can be made cheaply enough, because its also potentially a fancoil radiator, good for 'difficult' rooms where rads end up too big, which are in many cases likely to be the ones needing cooling.