Making sense of thermoelectrics for processor thermal management and energy harvesting

A thermoelectric (TE) device can be used as a heat pump that consumes electric power to cool a processor chip, or it can be used as a heat engine that generates electricity from the heat dissipated during processor operation. To better understand the use of TE devices, we develop a fully instrumented processor-based system with controllable TE devices. We first examine the use of TE devices for energy harvesting. We identify a pitfall in previous works that can lead to wrong conclusions for TEG use by demonstrating that TEGs increase the processor's leakage power which offsets their harvested power. For thermoelectric cooling (TEC), we elucidate the intricate relationships between the processor power, thermoelectric power, and fan power. We propose a dynamic thermal management scheme (DTM) that maximizes performance under thermal constraints and given total power budgets by controlling the processor's dynamic frequency and voltage scaling (DVFS), TEC current, and fan speed. For the evaluated thermal constraints, our results demonstrate good improvements to performance at the cost of additional cooling power compared to standard DVFS+fan DTM techniques.