Thermal Piles (There not painful)

Thermal Piles

This post discusses the often forgotten opportunity of incorporating thermal piles into your project.

‘Thermal piles’, you could use the term thermo-active foundations, if you prefer.

What Am I on about?

You need to dig a big hole as part of your development. This needs a piling rig and lots and lots of piles. Insert a reo cage, pore some concrete and finish up with a capping beam. Hey presto a piled retaining wall.


What opportunity did we miss?

Insert a plastic pipe in each pile and you’ve just removed the cooling towers from your project!

Piling with tube

How it works

Simple. You have just created a massive heat exchanger in the ground. You haven’t had to hire in a bore hole drilling rig. That came free of charge with the piling rig.

Hot water that normally went to a cooling tower to have the heat removed, with typical water temperatures at 29.5 oC and 35 oC, is now sent to the piles. So we have a heat exchanger maximum temperature difference of 35 to 17 oC (18 oC difference). This is great.


Ideally you would have the pile completely surrounded by earth (central structural pile). With edge piling you will have an exposed side. All good. This is taken into account and the number of piles with tubes in adjusted. If, as is typical you are building a dry wall in front of the piles, add air movement (as you would d in a car park exhaust system, from example) and you’ve just created another improvement to your ‘natural heat rejection system’.

The Detail

You need to consider:

  • Ground conditions for thermal sizing of tubes
  • Consideration of the concrete in the piles is required, for good thermal heat exchange. Thermally enhanced concrete means less tubes and is definitely recommended.
  • Excess tubes should be allowed in case of breakage and as a general safety.
  • You will need sign off from your structural engineer. My reading of the literature is the plastic tubes will have almost an irrelevant effect.
  • Dependant on the no. of piles you can achieve and given ground conditions will determine if you can do all of your cooling or heating or just base loads, with supplementary towers for peak loads.
  • Piles, driven, into the ground are obviously not up for consideration. Pile cages, pipes attached and concrete poured in after cage insertion is a preferred choice.

 Further Reading

As ever, the school of Google is a great source for all you will need on this subject.

Author: Jorgen Knox

Date: 15/08/2014

Contact: e:, t: 02 800 33 100, w: KAE, LI