Thermal Time Shifting: Decreasing Datacenter Cooling Costs with Phase Change Materials

Datacenters are rapidly increasing in size and power consumption. However, this growth comes at the cost of an increasing thermal load that must be removed to prevent overheating. In this paper, we propose to use phase changing materials (PCMs) to shape the thermal load of a datacenter, absorbing and releasing heat when it is advantageous to do so. We evaluate three important opportunities for cost savings. We find that in a datacenter PCM can reduce the necessary cooling system size by up to 12\% without impacting peak throughput, or increase the number of servers by up to 14.6% without increasing the cooling load. In a thermally constrained setting, PCM can increase peak throughput up to 69% while delaying the onset of thermal limits by over 3 hours, and a wax-aware scheduler can enable batch job placement to increase average throughput 36-52% without violating datacenter thermal limits.