Energy neutral hybrid cooling system for high performance processors

We present the design and testing of a hybrid energy neutral cooling system for data centers' CPUs. The system operates as a passive heat-sink at normal operating conditions, and can provide active cooling when a boost in performance is required (i.e., overclocking) at zero cost by exploiting thermoelectric generators (TEGs) to harvest the energy from the CPU heat dissipation. Server rooms have plenty of wasted heat that can be used to drive low power subsystems that work in symbiosis with servers. Our prototype has been tested on ARM based CPUs, the future core of low power data centers. We firstly evaluated the most suited TEG to supply the conditioning circuit which drives the fan. Then, we defined a governor that allows the active cooling to be exploited when overclocking is necessary and that provides several thermal management policies. Finally we built the proposed system to evaluate the real performance. Experimental results demonstrate its effectiveness in passive and active cooling achieving up to 13 minutes overclocking by recovering the dissipated heat.