The Earth Cooler Project

The Earth Cooler

Part One

Date Log; March 4, 2009

Have you ever had one of those ideas that is just off the wall. Not crazy crazy but pretty close. The sort of thing that happens usually after a little bit of coaxing by your friends or just a little too much lubrication from your favorite beverage.You know the sort of thing that you wouldn't think of doing except for that one particular moment in time when your resistance is weakened. Well that's where the Earth Cooler came from. It started out with a number of animated discussions about how to get rid of heat from a computer cooling system. Then it progressed on to the inevitable "my radiator is bigger than yours" and finally a suggestion to just "stick it in the pool to cool it". I might add not to much support from the majority for that idea so it was canned.

The ultimate off the wall suggestion was to bury the cooling system in the ground. This was felt by all to be the most bio-friendly option. By that time everyone present seemed to have had expended all of their ideas and suggestions and the idea just lay there until the we decided it would make an interesting project for the beginning of 2009.

Okay so how do you go about building a cooling system using the Earth as a heat transfer medium. The answer is to follow the footsteps of others who have taken the same route before you hopefully with a little bit more compactness in the design and implementation. Lets have a look at some of the ideas of merit that precede our endeavor.

The Tube in the ground Design

Self explanatory really get the spade out dig a whole heap of trenches then bury metre's of copper tubing in the trenches. Cover the whole lot up and connect the tubing to your computer with a pump to circulate the coolant and you have yourself an Earth cooler.

Caution; your partner may not appreciate you destroying the lawn.

The Cylinder in the Ground Design

A bit more sophisticated this design. A used oxygen or whatever cylinder connected to tubing buried down say a meter or so below the surface.Then pump coolant down and then back up to the computer to create the cooling loop. Advantages are that it saves your back having to dig so many trenches as described in the first design. As we have a major aversion to digging at any level for any period of time we will be modifying this particular design with our own Earth Sink.

Radiical Earth Sink

Our Earth Sink will be made up of two cylinders instead of one big one. We have chosen copper to assist with heat transfer and to provide longevity in the ground. Here are some of the pictures of our prototype version during construction.

Tubing Cut to length and end prepared.

Copper end caps for the Earth Sink seals.

No not a smiley face but a mock up of the end seal with the tubing connector.

Mock up of completed lower assembly.

Lower and upper end seal joints soldered and prepared.

Next we have "turned off" the threads on two brass barbs. At this stage the external or OD of the barbs is slightly smaller than the internal cooper tubing diameter. We have done this so we can add in a capillary solder joint to seal them.

machined barbs

Next we solder in the barbs and we have completed Earth Sink Prototype. Just as a matter of interest the volume of the prototype assembly is 2.25 liters.

Final process is to pressure test our Earth sink for any leaks and then its on to the hole digging.

Ground Preparation

We have been testing our selected ground space for some time trying to establish the Earth temperatures in various places. During the course of these tests we found a number of slow springs which emanated within one space. To facilitate an efficient system we will be accessing this spring area as it forms the wettest of the ground areas under consideration.

Here are some of the early ground temps at various depths in the selected area.

Ambient 29.20 degrees Celsius

Ground Temp at 1 foot or 300mm = 23.6 degrees Celsius

Ground Temp at 2 Feet or 600mm = 23.6 degrees celsius

Ambient and Dew point.

The interesting value in the sub ambient temperature reading is the correlation between sub ambient and condensation or dew point. As a matter of interest at the time of writing this project the predicted daily ambient today is predicted to be 31 degrees Celsius. The predicted dew point for 28.4 degrees at 0900hrs was 24.0 degrees that is 4 degrees below the ambient. At 1300 hrs on the same day the ambient was 29.8 degrees and the dew point was 21.5 degrees or 8.3 degrees below ambient. The point to be made here is that the dew point wanders around a bit during the day. It would be relevant to note that there may be a chance of fairly high levels of condensation formed from the Earth coolers and as such precautions may be necessary to avoid component failures.

Soil Ph

The last ground preparation testing was soil Ph. In the various soils horizons we were able to measure an acid value of Ph 5.9. In the scheme of things a Ph of 5.9 does have some predictable affect on the longevity of the Earth Cooler however I don't think it is of any real consequence for the short time it will be used.

Next; The hard work begins as we dig out and prepare our Earth cooler hole