Thermoelectric generators for efficiency improvement of power generation by motor generators – Environmental and economic perspectives

The use of waste heat from exhaust gas of internal combustion engines in power plants and CHP plants is considered a promising application field for thermoelectrics (TE). Some recent studies have provided important knowledge on the energy efficiency of current and future thermoelectric generators (TEGs). The focus of these studies has been primarily on the precise modelling of power units and their operation, i.e., the quantification of power production by TEGs. One of the studies additionally assessed the costs and the CO2 emissions of fuel combustion, without equipment and fuel supply. Until now, there was no life cycle-related analysis considering TEG and power unit manufacture, environmental impacts beyond climate change and competing technologies for waste heat utilisation. In order to fill this gap, the present study applies the life cycle approach, takes account of a variety of environmental impacts and costs and compares TEGs with the competing steam expander technology. The results show that, under many conditions, TEGs in power units can save energy costs and reduce the environmental burden, i.e., they are eco-efficient. With additional expenditure, energy savings and environmental benefits can be achieved even under disadvantageous conditions. However, in the upper power range the performance of steam expanders in terms of electricity production and eco-efficiency is better. The reduction costs of greenhouse gas emissions and environmental impacts as eco-efficiency indicators show identical patterns. Under reasonable operating conditions, i.e., sufficient capacity utilisation of a TEG (lowest value set in the study on hand: 50%), the impacts from the manufacturing of the TEG play only a small role in the overall assessment.