Looking for guidance on liquid cooling home

[mapsofilti]

I am looking to engineer a system that maintains and stores 1,000 L of a glycol/water mixture at -50 C during the day. My calculations are that it is more economic to store a large volume of cold liquid rather than buying the batteries to compress on demand in the night time. I also have an opportunity to incorporate additional geothermal cooling (e.g. a first pass through the ground on the return from the zones back to the coolant resevoir) if that's economic.

It will either be circulated through radiant floor cooling within the building or used with heat exchangers to blow cold air in each room.

Can you guys give me input and point me in the right directions? What are some good value compressors I can use to cool the liquid and some energy efficient pumps for the night time? My plan is to have three phase available as well. How should I regulate the temperature? I was thinking of using an Arduino to activate the pumps in bursts or a controlled VFD to slow down the flow of the coolant in each zone as needed.

This is in a country in South America where the sun is always plentiful and the temperature 95% of days will be 100+ F. I am going to have a series of windmills and the cooling system won't have as much demand for the other 5% of days.

 

[Hedges]

Assuming non-toxic propylene glycol, this chart says 60% by weight solution to get freezing point of -50C.

https://corecheminc.com/wp-content/uploads/2020/06/Freeze-Point-Chart-GlycoChill-Propylene-Glycol-Heat-Transfer-Fluid.pdf

Fluid is handy for heat transfer. Do you think rocks and gravel might be a more economical heat (cold) storage medium? How about just H2O ice? How about salt water?

Sodium Chloride Water Solutions

Freezing point, density, specific heat and dynamic viscosity of Sodium Chloride and Water coolant.

www.engineeringtoolbox.com

I think producing -50C takes extra effort, different refrigerant. There is energy stored by having the medium much colder than your house but phase-change materials store more energy in a given mass. H20 phase change to ice is about same as 100C temperature swing. Extracting cold is easy, brine carries heat from tubes to ice. Building ice is more difficult, because ice is good insulator around tubes.


Windmills - we tend to hear they provide very low amount of power for the dollars and maintenance invested, whereas PV is cheap and easy.

Refrigeration isn't my field, but there are types of refrigerants used for colder temperatures. Some facilities use -40C. Design around something readily available.

 

[Supervstech]

Wow… -50C is going to require MASSIVE refrigeration compressors…

Chilling water solution on he scope to maintain a cold room… much less a house would be huge.

Likely a 20hp compressor… would need to know the volume of the storage tank, also, you will require massive insulation on the storage area, figure a solid foot of closed cell foam… or the air around the tank will freeze and cause massive frost buildup.

 

[mapsofilti]

Assuming non-toxic propylene glycol, this chart says 60% by weight solution to get freezing point of -50C.

https://corecheminc.com/wp-content/uploads/2020/06/Freeze-Point-Chart-GlycoChill-Propylene-Glycol-Heat-Transfer-Fluid.pdf

Thanks for confirming that, this ratio lines up with my previous research.

Fluid is handy for heat transfer. Do you think rocks and gravel might be a more economical heat (cold) storage medium? How about just H2O ice? How about salt water?

Sodium Chloride Water Solutions

Freezing point, density, specific heat and dynamic viscosity of Sodium Chloride and Water coolant.

www.engineeringtoolbox.com

I think for sure filling the tank with mostly gravel could work well. This idea is resonating with me quite well. Water is free for me, but the propylene glycol is a bit inconvenient for the initial set up otherwise. Do I need to consider the side effect of possibly contaminating and affecting the pumps with dust or soot from the gravel? Perhaps putting a filter before the pumps would help. Some sort of manufactured carbon pellet comes to mind...

Windmills - we tend to hear they provide very low amount of power for the dollars and maintenance invested, whereas PV is cheap and easy..

For sure; sorry, my comment was a bit misleading. I am planning to have a 100 kW solar system operating during the day and minimal battery storage at night time. Instead of investing in batteries, I will invest in more economic things like a larger hot water tank (250 L, 6 kW 380 V) and the DIY cold storage system that we are discussing here. I am thinking to have a contactor to kill power to a panel with various circuits after sun down, like EV chargers for example.

The weather is usually sunny, but there is occasionally temperamental weather a few times per year where it makes it practically feel like night time, so I would expect there to be little solar output on those days. Fortunately at those times, the wind picks up very strongly. I believe I can get enough out of a few windmills just to keep the lights/modem on and the water circulating if the panels are not producing. This is sort of an edge case and I will cross that bridge when it comes. A generator will also be available until I get it right, if needed.

I think producing -50C takes extra effort, different refrigerant. There is energy stored by having the medium much colder than your house but phase-change materials store more energy in a given mass. H20 phase change to ice is about same as 100C temperature swing. Extracting cold is easy, brine carries heat from tubes to ice. Building ice is more difficult, because ice is good insulator around tubes.

This makes sense; I am trying to envision how that exchanger would work. Perhaps some ice cube producing machines operating all day filling a large tower with ice. I would need to recycle the water and keep it clean enough for the ice generating machines to work well.

 

[Supervstech]

Thanks for confirming that, this ratio lines up with my previous research.


I think for sure filling the tank with mostly gravel could work well. This idea is resonating with me quite well. Water is free for me, but the propylene glycol is a bit inconvenient for the initial set up otherwise. Do I need to consider the side effect of possibly contaminating and affecting the pumps with dust or soot from the gravel? Perhaps putting a filter before the pumps would help. Some sort of manufactured carbon pellet comes to mind...


For sure; sorry, my comment was a bit misleading. I am planning to have a 100 kW solar system operating during the day and minimal battery storage at night time. Instead of investing in batteries, I will invest in more economic things like a larger hot water tank (250 L, 6 kW 380 V) and the DIY cold storage system that we are discussing here. I am thinking to have a contactor to kill power to a panel with various circuits after sun down, like EV chargers for example.

The weather is usually sunny, but there is occasionally temperamental weather a few times per year where it makes it practically feel like night time, so I would expect there to be little solar output on those days. Fortunately at those times, the wind picks up very strongly. I believe I can get enough out of a few windmills just to keep the lights/modem on and the water circulating if the panels are not producing. This is sort of an edge case and I will cross that bridge when it comes. A generator will also be available until I get it right, if needed.


This makes sense; I am trying to envision how that exchanger would work. Perhaps some ice cube producing machines operating all day filling a large tower with ice. I would need to recycle the water and keep it clean enough for the ice generating machines to work well.

Ice machines rarely dip below -15C

 

[mapsofilti]

Wow… -50C is going to require MASSIVE refrigeration compressors…

I agree, I am dedicating the size of a two car garage for the equipment room and storage tank. Fortunately, land and bricks are cheap as chips here.

Chilling water solution on he scope to maintain a cold room… much less a house would be huge.

My calculations are roughly 1,000 L of -50 C liquid to maintain 22 C over 12 hours for a 2,000 square foot house. I am configuring at least three different zones (Sets of pumps/air exchangers); in the day, the living area would be primarily cooled and in the night, the bed rooms. I am assuming that the ambient environment is going to be 40 C. Sometimes it's a bit higher or lower, but 40 is typical for the heat we need to work with.

Likely a 20hp compressor… would need to know the volume of the storage tank, also, you will require massive insulation on the storage area, figure a solid foot of closed cell foam… or the air around the tank will freeze and cause massive frost buildup.

Thanks for the input about the foam and frost issues.
I am planning to use a series of current transformers and contactors to implement my own load management controlled by an Arduino. If I use a few smaller compressors, I think it will be more economic and flexible with the load management. I am budgeting for 100 kW of solar panels and a beefy inverter to go along with this. There are a lot of other loads, for example EV chargers, hot water tanks, a 60,000 BTU air conditioner, electric cook top, electric oven and electric dryers for day time use. We are planning these appliances for day time use only. I would expect our power usage to be a couple kW max at night time just to keep some electronics on and circulate the cold water. This way, I do not need to have an excessive quantity of batteries.

The tanks I am looking at are something like this: https://www.tradeindia.com/products/1000-litre-stainless-steel-water-storage-tanks-c5024155.html, but I am completely open to suggestions.

 

[Rednecktek]

Wow… -50C is going to require MASSIVE refrigeration compressors…

Chilling water solution on he scope to maintain a cold room… much less a house would be huge.

Likely a 20hp compressor… would need to know the volume of the storage tank, also, you will require massive insulation on the storage area, figure a solid foot of closed cell foam… or the air around the tank will freeze and cause massive frost buildup.

Not really, we have shipping containers that rock -60c at sea on a semi regular basis on the Japan-Korea-Guam run, it uses a dual stage system, piston compressor to condenser coil to scroll compressor to second condenser coil, using R123. Draws about 6kw or so on 440v 3ph loaded up. I think it's a ThermoKing unit. Looks like a total kludge but it works!

Edit: It's the ThermoKing SuperFreezer line.

 

[AntronX]

Just freeze more water versus trying to chill to -50C. You cooling setup will be more efficient.

 

[mapsofilti]

Just freeze more water versus trying to chill to -50C. You cooling setup will be more efficient.

I am calculating how much more would be required. What do you think? The cost of the 1,000 L tanks is also a factor to consider, whereas investing that money in additional solar panels for a more powerful compressor could mean having surplus power down the road that can be more useful (e.g. sold to the grid, crypto mining, additional EV charging capacity).

 

[Partimewages]

I'm going to use imperial numbers.
Water contains 1 btu= 1 degree F = 1 pound of water.
If you take water through the phase change 32 F water to 32 F ice you remove 144 btu's.
There's a tremendous amount of heat energy in the phase change. You just need to calculate how fast you want that to happen. You don't need a compressor to make your storage tank colder using this method.
Ice tanks have been used commercially for years.

 

[upnorthandpersonal]

I actually cool my place with my hydronic system, but I don't go to -50C. You're limited with how low you can go due to the dewpoint: if you go too cold, you'll have condensation issues. In my case, something like 15C is the coldest I pump into the floors. Making that cold water is done using a Monoblock air-to-water heatpump coupled to a 3000L buffer tank with 40/60 propylene glycol. The heatpump is then used in the spring/autumn to provide heat to the tank for heating purposes. I have enough excess solar to run the pump day and night if I have to, but typically I don't need to run anything at night and the house stays cool. Granted, we have about one week of summer per year...

 

[OzSolar]

I believe the bulk of the energy to be stored happens at the phase change from water to ice.

I'm going to use imperial numbers.
Water contains 1 btu= 1 degree F = 1 pound of water.
If you take water through the phase change 32 F water to 32 F ice you remove 144 btu's.
There's a tremendous amount of heat energy in the phase change. You just need to calculate how fast you want that to happen. You don't need a compressor to make your storage tank colder using this method.
Ice tanks have been used commercially for years.

Exactly, so my layman's understanding is that the bulk of the energy storage is going to happen at the phase change.

For example the phase change by itself gets you 144 BTU's per lb of water vs. getting down to -58F (-50C) from 32F only another yields another 90 BTU's/lb. (I think I did that math right)

As has been mentioned storing a little bit more ice seems to make more sense then trying to get down to -50C.

Has anyone else seen any articles about how people created ice in the desert in ancient times? Fascinating.

https://www.realclearscience.com/blog/2018/07/09/how_people_created_ice_in_the_desert_2000_years_ago.html

 

[Partimewages]

@OzSolar
Yes you are correct.
This comes from my hvac geothermal background.
If you go from 32 F water to 32 F ice you remove 144 btu's per pound of water. Same calculation the other way ice to water.
To bring this into perspective.
@32 F water add 144 btu's and you end up with 176 F water. There's a tremendous amount of energy transfer in the water phase change. This is why geothermal ground loop works so well.

 

[Supervstech]

Not really, we have shipping containers that rock -60c at sea on a semi regular basis on the Japan-Korea-Guam run, it uses a dual stage system, piston compressor to condenser coil to scroll compressor to second condenser coil, using R123. Draws about 6kw or so on 440v 3ph loaded up. I think it's a ThermoKing unit. Looks like a total kludge but it works!

Edit: It's the ThermoKing SuperFreezer line.

Sure, for keeping a fish storage area cold… nothing like needed to cool a large mass of LIQUID withe intention for maintaining comfort in a house…

 

[Rednecktek]

Sure, for keeping a fish storage area cold… nothing like needed to cool a large mass of LIQUID withe intention for maintaining comfort in a house…

Maybe, but it does have to get the contents of the container to set point pretty quick and it's nowhere near a 20hp motor to do it.

 

[Supervstech]

Maybe, but it does have to get the contents of the container to set point pretty quick and it's nowhere near a 20hp motor to do it.

Yup, i service ice cream blast cooler walk ins.
3 to 6 hp usually is all thats needed in a 10x10x8 box.

Its wild working in an ice cream store, on 100F days, and walking into the store in a parka and boots covered in ice.

The customers look at you like ya just teleported in from the arctic...

 

[JimJr]

water temp change per pound per Btu

gas 212f to 212f gas = 970.4 btu

liquid 32 f to 212f =1 btu

liquid to solid 32 to 32 = 144 btu

solid below 32f = 1/2 btu

 

[Hedges]

Need a couple changes, add "/ degree F" to water and ice. So 180 BTU to raise 1 lb. water from 32F to 212F (As chart shows, and very close to what phase change takes.)

You meant water 212f to gas 212f.

I had thought vaporization was similar, but 970 BTU is 5x as much.

 

[AntronX]

Melting 1 ton block of ice will absorb 92.8 kWh of energy. Same is true for freezing water into ice. COP of ice freezer is around 2 meaning it takes at least 46.4 kWh of electrical energy to freeze 1m³ of water. You can do same amount of cooling using efficient mini split air conditioner at 3.5 COP needing only 26.5 kWh of electricity. Cost of 33kWh of LFP batteries is around $2500 - 3300.

 

[S Davis]

I actually cool my place with my hydronic system, but I don't go to -50C. You're limited with how low you can go due to the dewpoint: if you go too cold, you'll have condensation issues. In my case, something like 15C is the coldest I pump into the floors. Making that cold water is done using a Monoblock air-to-water heatpump coupled to a 3000L buffer tank with 40/60 propylene glycol. The heatpump is then used in the spring/autumn to provide heat to the tank for heating purposes. I have enough excess solar to run the pump day and night if I have to, but typically I don't need to run anything at night and the house stays cool. Granted, we have about one week of summer per year...

Like this monoblock Spacepak unit, it is going 30’ from the house with underground supply and return lines, it is heating radiant floor and chilling water for a chilled water coil for a/c in the attic.