Invited Paper IPF-MoM5
Thermoelectrics and Waste Heat Recovery
Monday, October 15, 2007, 9:20 am, Room 602/603
Thermoelectric (TE) devices are reversible, solid-state heat engines. When a temperature difference is applied across a TE array, electric power is produced; and when electric power is applied, a portion of the array cools (sinks thermal power) and another portion heats (produces thermal power). Increased needs to lower energy costs and reduce green house gas emissions have renewed interest in the technology. TE applications have been limited most importantly by lower conversion efficiency, but also by the cost of the materials and systems. Recent advances in performance through the development of more efficient thermodynamic cycles, laboratory demonstrations of improved materials, and the availability of more comprehensive design tools, have increased interest in the application of the technology for power generation uses. The recent recognition of the need to reduce CO2 emissions has renewed interest in TE technology with respect to waste heat harvesting from vehicle exhaust. Since the 1960's, TEs have been employed in critical military and space applications where their demonstrated ruggedness and maintenance-free operation has outweighed energy conversion efficiency limitations. Target applications are small to midsize (up to 40 kW) sources of exhaust waste heat and include: vehicle exhaust residential, commercial, and industrial fuel-fired heating systems; diesel powered electric generators; and other similar applications. TE technology is evolving to the point where systems with conversion efficiencies of 6% to possibly 20% are being investigated. Prospects for successful implementation of TE technology for waste heat recovery to reduce CO2 and other green house gas emissions are discussed for a range of business sectors for which the technology appears attractive. Examples of current approaches to implementation are given, along with estimates for critical system characteristics including projected size, weight, efficiency, and rough costs. Important current programs funded by various U.S. and foreign government agencies are described and their level of technical and commercial readiness are assessed.