Think of all the excess heat that's generated and subsequently dissipated as "waste." What if we could harvest that heat and convert it into electricity? The thermoelectric effect is well-known among physicists, but it's terribly inefficient, which may not bother a physicist but it's unacceptable to an engineer. However, if someone could develop a small and inexpensive thermoelectric generator (TEG), some of that wasted heat could be converted into electricity instead of being dissipated into the air.
A team of researchers led by Dr. Aljoscha Roch of Dresden's Fraunhofer Institute for Material and Beam Technology IWS has developed a TEG that's about 30 microns thick, using a 3D printing process. Using electrically conductive non-toxic polymers, Roch's 3D printers produce a paste with thermoelectric properties. When the material is exposed to a temperature differential of even one degree, electrons from the "hot" side are energized and migrate to the "cool" side (because every electron wants to hang out with the cool particles), effectively generating an electric current.
In this picture, a flexible TEG is wrapped around a sample component:
Image: Fraunhofer IWS
Dr Roch is demonstrating his TEGs on the inside of nuclear power cooling towers where the temperature differential is pretty high. However, since these devices are very small and inexpensive, I can imagine one attached to every heat sink on an electrical device. I'm listening to the fan on my laptop blowing heat on my desk. I take my cell phone out of my pocket and it's warm. Electric cars use regenerative braking but they also require traditional friction brakes which generate heat. Imagine that heat being used to help recharge the batteries on those devices.
I wonder how much energy Google uses to cool its servers. (If only there was a way I could search for that information.) Oh, here it is: Google's data centers use a whopping 2.2 TeraWatt-hours per year. Roughly 12% of that goes to overhead such as power conversion and cooling. Let's say half of the overhead is for cooling. That means Google uses 137 GigaWatt-hours every year to cool its servers. A TEG is about 8% efficient, so in theory, TEGs could reduce the cooling requirements by about 8%. That would save about 10 GWh (over $1M) per year. On top of that, the TEGs would be generating electricity. Now that's a cool idea!