Peltier Cooling

The third type of cooling is pretty weird, so bear with me. Peltier cooling is based on something called the Thermoelectric Effect. In 1821, a physicist named Thomas Johann Seebeck discovered the presence of an electrical charge in a metal rod when the ends of the rod were at different temperatures. This effect was studied and eventually quantified into equations and applications (thermocouples). It is the ability of this effect to work in reverse, as discovered in 1834 by Jean Peltier, which actually has applications in cooling. Peltier discovered that if a current was passed through two different metals at two different junctions, then heat variation within the metals occurs. This came to be known as the Peltier Effect, but it’s more commonly referred to as the all-encompassing “Thermoelectric Effect.”

From Thermoelectric Effect we get something called a Thermoelectric Cooler (TEC) that can be used to cool all sorts of things, most pointedly the heat-producing microprocessors in your computer. Without getting too technical, a TEC is basically a flat plate comprised of different metals that sits in between your processor and heatsink. Current runs through the plate and allows its underside (the part that contacts the processor) to transfer heat to the other side of the plate at a very fast rate. This allows the contact side to be very cool, often times in the 10C range. Depending on certain characteristics of the rest of the cooling components, and the ambient temperature, Peltier coolers can be either extremely beneficial, or a total waste of money. The ideal scenario for a Peltier cooler is making contact with a heatsink that has very low thermal resistivity (R). This allows the heat to be transferred from the heated side of the plate instead of bogging down and consequently reducing the overall effectiveness of such an ungainly setup.

Design

The design of Peltier coolers is the most complicated thing you can encounter in the realm of extreme cooling solutions. Everything from supplemental cooling, right down to the selection of the basic metals used – it’s as though everything is a variable. What’s more, the effectiveness of a Peltier cooler depends heavily on just as many variables (such as the amount of power that the cooler can transfer, the amount of heat being produced, ambient room temperature, ambient room humidity, and the thermal resistivity of the attached heatsink).

When it comes to supplemental cooling, aspiring TEC users should be looking for a heatsink or thermal dissipation device that has the lowest possible value for R (Thermal Resistivity). Certain forced convection heatsinks are capable of remarkably low values of thermal resistance, often approaching 0.1 C/W. However, these heatsinks cannot transfer that much heat. A water cooling setup, despite having a higher amount of thermal resistivity, can dissipate much more (for reasons discussed earlier). This is why the most commonly used supplemental cooling in Peltier devices is water-based.

Peltier cooling devices also have large power consumptions. They use a lot of power to dissipate heat very quickly. Rapid heat dissipation is typically desirable, but in this instance it presents users with a critical ultimatum: Do I want to use more power to get rid of a lot of heat, or do I just want to stick to traditional methods and settle with higher temperatures?

Bottom Line

Unless you have a water cooling system capable of transferring heat from the device, Peltier cooling is quite a difficult option to justify. Pre-assembled Peltier systems usually incorporate water cooling and cost considerable amounts of money. Peltier plates are available for purchase by themselves and are rather inexpensive, but incorporating them successfully into a system is often more trouble than it’s worth. Effective TECs (ones that allow nearly 16V across them) are hard to come by. Due to the countless variables and relative difficulty of applying them, Peltier cooling solutions aren’t frequently used. No current CPU will benefit from running at sub-ambient temperatures (they are designed to run above ambient), and the only major advantage is for people that are overclocking their systems and producing ridiculous amounts of heat. Even then, other types of cooling, like Phase Change, are likely to be more fruitful.