Harvesting Wasted Heat in a Microprocessor Using Thermoelectric Generators: Modeling, Analysis and Measurement

Harvesting energy from previously unemployed ambient sources can play important role in saving energy and reducing the dependency to primary power sources (ACpower or battery) of an electronic system. High-performance integrated circuits such as microprocessor, typically suffers from high surface temperature (in the order of 80-100degC) resulting from the high power density and limited cooling capacity of the package. In this paper, we consider the scope of harvesting thermoelectric energy from the wasted heat in a microprocessor leveraging on the temperature gradient between processor die surface and environment. First, we develop analytical model to accurately estimate the recycled energy considering the non-uniformity of temperature distribution in the die surface. Next, we analyze the effectiveness of the approach for thermoelectric generator (TEG) with different efficiencies (measured in terms of its figure of merit, ZT) under varying processor workload. Finally, we propose a possible arrangement for using the TEG on a processor and provide measurement results on the amount of harvested energy. The measurements on a Pentium III processor running at 1 GHz show that we can harvest ~7 mW of power from the processor for average workload using a commercial TEG.