5) The Stirling Cycle Cryo Cooler

The stirling engine was invented in the late 1800's, and it works through a combination of compression and expansion cycles of gas in a closed environment. The action of a fixed amount of helium undergoing the following cycle: compressing the cool gas, heating the gas, expanding the hot gas, and cooling the gas can be used to create work (ie. motion). For more info, I'll confess I must default to Wikipedia.

A stirling cycle cryo works on a similar process, except that an electric motor used to generate the work, which when applied in reverse to the equation creates a temperature differential between the hot and cold portions of the device. It literally pumps heat from one area to the other. The point of all this is that Stirling cycle cryo coolers can achieve temperatures as low as a few degrees above absolute zero - that's 0 Kelvin or -273°C!

Stirling Cycle Cryo cooler. Small but powerful enough to bring a 0.35W load to -193°C.

Sounds great doesn't it? A small device that can cool a CPU down a couple hundred degrees below 0°C! The caveat is that most stirling cycle cryo coolers will only achieve this sub-zero miracle with very small heat loads, and generally the cold tip must be well insulated from the surrounding environment.

The unit pictured above, Frostytech has been told, fits into the palm of a hand. It runs on 16V DC, and within about a minute the tip of that pencil thin stainless steel rod drops to -70°C. Very cool, yes. Unfortunately this particular 1/3W cooler is totally impractical for the heat loads involved in cooling an Intel or AMD CPU.

Twinbird Corporation of Japan has put up this video illustrating a variety of Free-Piston Stirling Coolers. There is a cut-away model of the device in the video that provides a clearer sense of how it all works. These larger scale coolers have capacities of up to 150W, which makes them practical for insulated freezers.

Cooling potential is not quite as straightforward as a wattage figure might seem though. Take for example the Twinbird SC-UE15 module, it's rated for 150W load but at that load the best it will manage is 10°C. If the load is say 85W, the unit could reduce temperatures to about -55°C. In other words, cold finger temperatures are directly related to cooling capacity.