The Thermoelectric Conversion Group of the Energy Technology Research Institute (ETRI), Japan's National Institute of Advanced Industrial Science and Technology (AIST), exhibited a "stack-type thermoelectric power generation unit" whose output density is as high as 12W/L at PVJapan2014.
The unit operates at a relatively low temperature and small temperature difference. It can use hot spring water whose temperature is 100°C or lower and water warmed by solar heat. Also, it can be made at a low cost.
The highest output density of a thermoelectric power generation unit using warm and cold waters was 8.2W/L, which Panasonic Corp announced in April 2014. The output density of the new thermoelectric power generation unit is about 50% higher than that.
The high output density was realized by densely arranging 10 commercially-available BiTe-based thermoelectric power generation modules such as Peltier devices. Warm and cold waters flow the paths between modules alternately (every other path) so that high and low temperature areas are densely arranged.
When 95°C warm water and 10°C cold water (temperature difference: 85K) are used with a flow volume of 7L per minute, the output electricity has a voltage of 17V and current of 0.6A (about 10W). The volume of each unit is about 0.8L. So, the output density is 12W/L.
It is possible to change the number of thermoelectric power generation modules used in the unit as well as to make a larger power generation system by connecting multiple units. Also, the entire shape can be designed as if playing with building blocks.