Which pipes for SandBattery (whole underground of my Winter Greenhouse)

[Michelle Konzack]

Good evening,

I need a technical advice to Heat Pipes.

I build a WinterGreenhouse with 21,5m x 7,2m but dig it 2,5-3m deeper out because I want to install 500m of pipes which contain a Water-Glycole mix and is heated trough a 9kW In-Flow Heater Using the Fronius Ohmpilot and a Fronius Symo 10kW with 18 Solarpanels 650Wp.

However, if I use the standard HDPE pipes 32x2,4mm PN8 for Ground-to-Water Heatpumps, I am probably limited to a temperatore of 50degC, because HDPE Pipes can not be used above 70degC and I suspect, is I have 2,5-3m Sand on top of it, with temperature above 50degC they can deform (become flat).

Which cost effective Pipes can you recomment to archive maybe a temperature of 70-80 degC?

Someone suggested me alread PEX-Al-PEX pipes, but the would be quiet expensive if I need 500m.

Any suggestions?

Thankyou
Michelle

P.S.: I will start the project in spring 2025.

 

[wpns]

Metal would appear to be best for conductivity, but of course expensive. You also need to know the insulating value of the pipe you choose.
/* PVC can handle temperatures up to 140°F (60°C). CPVC handles temperatures up to 210°F (99°C). */

 

[Steve_S]

The reality of it is that you pretty much have to use PEX which is designated for Radiant Heating and that is not a bad thing. It won't corrode or anything and "Radiant" grade is awfully tough compared to regular waterline. There are TWO Types of Glycol, I use (Non-Toxic) Cryo-tek Propylene glycol. As you are embedding the pipes into sand you won't have issues in general just ensure your turns/loops are gentle. PUMPS can be tricky, do NOT screw around, the GrundFos NON-Submersible Circulation Pumps are the way to go for zero issue pumps.

Hope it helps, Good Luck

 

[Michelle Konzack]

The reality of it is that you pretty much have to use PEX which is designated for Radiant Heating and that is not a bad thing. It won't corrode or anything and "Radiant" grade is awfully tough compared to regular waterline. There are TWO Types of Glycol, I use (Non-Toxic) Cryo-tek Propylene glycol. As you are embedding the pipes into sand you won't have issues in general just ensure your turns/loops are gentle. PUMPS can be tricky, do NOT screw around, the GrundFos NON-Submersible Circulation Pumps are the way to go for zero issue pumps.

Hope it helps, Good Luck

I think, I will dig a 4m3 hole and make a prototype insert a Pipe if a One-Wire Temperature sensor all 10cm and see what happen.
As people sayed, there is a problem with sand and conductivity, hence it is not possible to put a Pipe on the bottom of a Sand-Heat-Storrage, heat it up and then put another Pipe on the Top and get the Heat out.

If I see this right, a single Pipe has to go trough the WHOLE Sandstock and I have to use it for "charging" and discharging.

Hence I will use 20mm PEX pipe of 30m lenght (If I can get this into the 4m3) a DIY In-flow Heater with 3x900W/24V (I live mainly with 24V DC and have cable wich support without any problem 300A continiuous and 2000A max).

Then I will see, what it give.

If it works, I can go next year to my 450m3 project under the GreenHouse

 

[wpns]

If I see this right, a single Pipe has to go trough the WHOLE Sandstock and I have to use it for "charging" and discharging.

That's correct. Besides, why would you ever be charging and discharging your sand battery at the same time?