jwd@cblpe.UUCP (04/01/87)
A series of articles in this group discussed thermoelectric generators. I was very interested in this topic in the early 60's while I was in high school. At that time there was a lot of work going on in this area. The fact is that metals are not very good as some contributors pointed out. What is needed is a material which has good electrical conductivity (resistance causes losses) and poor thermal conductivity so that a high temperature difference can be maintained. This is like having your cake and eating it to! The Russian Kerosene Lamp generator used compound semiconductor materials. For generators, the material most common is lead telluride. For thermoelectric coolers, the most common material is bismuth telluride. These materials are doped N and P type. The elements are grown to be poly-crystalline for improved performance. Elements are connected with metal straps so that they are electricly in series and thermally in parallel. Many couples are connected in series. To reduce contact resistance losses, the generators use large diameter elements. The nature of the generators is to produce high current at low voltage. In most generators, a dc-dc converter is used to convert the output to useful voltage levels. Heat Source (Flame, Solar, Nuclear) Metal strap > _____________________ _____________________ | | | | | | | | Semiconductor > | P | | N | | P | | N | | | | | | | | | Metal strap >______|______| |______|____________|______| |______|_____ Heat Sink (Ocean, Fins) 3M made (makes ?) a generator for use as a remote power source on gas pipe lines. The generator powers telemetry equipment. The SNAP nuclear power generators used in some satellites use nuclear decay to power a thermoelectric generator. A lot of the work was done for the military. A thermoelectric generator heated by a nuclear reactor and cooled by sea water makes a great silent power source for submarines. Solar thermoelectric? There was some work done in that area. Hamilton-Standard built some solar powered generators. Each thermocouple had a metal ball on the top electrode which was in the focal point of a reflector. An array of reflectors was mounted on a sun following mount. At the time, it was hoped that a breakthrough in materials would make thermo- electricity competitive. That hope was never achieved. Thermoelectric cooling and power generation are only used where the high cost is justified by a feature like silent operation. If anyone wants more specific information, I'll dig out my old material. Joe Darnell cblpe!jwd (614) 860-3975
ams@briar.UUCP (04/03/87)
In article <479@cblpe.UUCP>, jwd@cblpe.UUCP (Joe Darnell) writes: > What is needed is > a material which has good electrical conductivity (resistance causes losses) > and poor thermal conductivity so that a high temperature difference can be > maintained. This is like having your cake and eating it to! > At the time, it was hoped that a breakthrough in materials would make thermo- > electricity competitive. That hope was never achieved. Thermoelectric cooling Any speculations about all the exciting things going on in superconductivity these days- the materials are thermal insulators, aren't they? Should be some time before they reach >> room temperature, however! Ali Shaik ihnp4!philabs!ams