Status Report on Thermoelectricity.
Quarterly rept. no. 7,
NAVAL RESEARCH LAB WASHINGTON DC
Pagination or Media Count:
Progress in Thermoelectricity continues on schedule. A gratifying number of materials improvements have appeared both in government sponsored and industry sponsored work. Some of the results are still proprietary such as the material that appears to have a Z that approaches 1 x 10exp -3 at 1800 deg C. Others have been announced such as the Bell Laboratory work that produced Z of 5 x 10exp -3 at 80 deg K. Some of the announcements including some of the data in this issue concerning extremely high Z factors are highly suspect but some very respectable gains have been confirmed. While it is encouraging that Z values continue to rise, some of the most important results are on material with only moderate Zs at moderately high temperatures but with other virtues that make them extremely valuable. It is important to recognize that efficiency per se is a dominating requirement in only a few power source requirements. It is widely accepted that efficiency can be sacrificed for weight size, silence and long lived, unattended reliability in many military and commercial applications. It may be less obvious that a low efficiency results in no sacrifice in many applications. In waste heat utilization, capital investment is the important consideration. Installation and maintenance costs are the determining factors and the efficiency of thermoelectric materials is related only indirectly to these costs. With a more efficient material, fewer pounds of thermocouples are required to produce a kilowatt but a less efficient material may cost so much less per pound that it is the better investment. For example, one design study showed that to produce a kilowatt generator for 100, material with a Z of 1 x 10exp -3 would have to be produced for 5.00 per pound of thermocouples.
- Electric Power Production and Distribution