ASSESSING THE GREENHOUSE GAS EMISSIONS AND COST OF THERMOELECTRIC GENERATORS FOR PASSENGER AUTOMOBILES: A LIFE CYCLE PERSPECTIVE

摘要

Toward realizing a low-carbon society, a thermoelectric generator (TEG) is promising for energy harvesting by generating electricity from thermal energy, especially waste heat. While there are various technologies available for energy recovery, one of the strengths of TEGs is to retrieve usable energy from waste heat whose temperature is as low as 200～300 degrees Celsius. Yet, the conversion efficiency of the current thermoelectric materials remains low at 5～10%, which makes it difficult to diffuse TEGs in our society. In order to clarify required performances of TEGs to diffuse them in the future, this paper aims to assess the life cycle CO_2 emissions (LCCO_2) and life cycle cost (LCC) of TEGs based on several product lifecycle scenarios, each of which assumes different future situations in, e.g., conversion efficiency of TEGs. In this paper, we focus on TEGs for passenger automobiles since a range of the temperatures of their exhaust gas is suitable for TEGs. Additionally, we focus on bismuth telluride (Bi-Te) materials to develop TEGs since they have already been available for commercial use. A case study of installing Bi-Te TEGs in passenger automobiles is carried out. The region of interest is Suita City, Osaka, Japan. By describing two scenarios that assume different conversion efficiency of thermoelectric materials, we compare assessment results from the viewpoints of LCCO_2 and LCC. The results reveal that using TEGs has the potential to reduce CO_2 emissions of the city by 0.07～0.30%. It is also shown that the TEG cost needs to be drastically reduced to make the usage of TEGs profitable.