The project

Ok, here's the plan: We have a server that mirrors our online data backup server for off-site replication. We don't want to keep it in the same building as the main data backup server in case there's a fire (naturally). So we would like to house it in our second building, a 25'x25' outbuilding on a concrete slab, which is not climate controlled.

Cooling with ambient air will not be sufficient, because it can reach 125 degrees (F) in this building on hot days. I also don't want to draw moist outside air into the server. I would like to keep the server at a maximum of 80 to 85 degrees, with no sudden temperature changes (no, servers don't need to be kept at 65 degrees as some people believe. As long as the temperature is steady, they're perfectly happy at 85 degrees. Swing the temperature 20 or 30 degrees too quickly too often, and you'll see frequent failures.

The server will be in a 24"x24"x24" steel cabinet, and it makes sense to try to climate-control *just* the cabinet to minimize cooling costs. I think it will be difficult to cool a very small space with a standard A/C unit without causing huge changes in temperature as the A/C compressor cycles on and off throughout the day.

I thought about Peltier junctions, but they are horribly inefficient and the energy required would cost more than an air conditioner.

I want a solution that is reliable and inexpensive to run, and it would be nice if it was a fun and unique project too. After a little research, I found several people who had done successful "micro-geothermal" projects for cooling computers or small spaces, and I'm really interested in that idea. Instead of running an A/C unit full-time, or purchasing an expensive outdoor server cabinet climate control system, I will attempt to circulate coolant through a fan-coil unit in the server cabinet, then through a ground loop to take advantage of the relatively constant underground temperatures to dissipate the heat generated by the server and associated electronics.

This project is my attempt at cooling our server with a geothermal ground loop. I refer to it as a "micro" geothermal system because it will not involve a deep, professionally-drilled well, or a large horizontal ground loop covering hundreds of square feet of ground and requiring heavy equipment to excavate. We'll only need about 1500 BTU of cooling, so instead I will attempt to use several 4' to 6' deep wells drilled by hand with an auger drill near the foundation outside the building.

I *could* dig a large trench near the building for a small horizontal ground loop, and indeed that is the backup plan if the small wells don't do the trick. But I really like the analogy that a few 6' deep wells will draw to a "real" vertical geothermal system. This design will also be scalable, in that I could drill additional wells to add cooling capacity without disturbing the running system.

So there it is... one of those projects that costs 10 times more in time and about as much in materials as it would cost to do it the "standard" way with an air conditioner. But I like the uniqueness and "greenness" of the project, and I'm confident that this will work. I like the idea of a project I can learn something with, which is also a "green" solution that will produce some real-world data and establish a usable baseline for others to follow in building practical and economical very small-scale geothermal systems.

-Tom Rusnock