Organic Rankine Cycle as a Waste Heat Recovery System for Data Centers: Design and Construction of a Prototype

Due to the increasing demand for data center utilization, many significant challenges have arisen for thermal engineers over the last few decades. Advanced cooling systems for servers are of significant interest, including technologies which can also reduce electricity usage. The Organic Rankine Cycle (ORC) is considered a viable option for this purpose. It can both absorb the heat from a server and then transfer that heat into a power cycle to generate electricity. This study focuses on the operation of an experimental 20kW ORC prototype, which represents two common rack servers operating at full capacity. The range of server waste heat temperatures examined is between 60°C to 85°C, which is far below the normal operating range for ORCs. Thermodynamic modeling on this ultra-low-grade waste heat system predicts thermal efficiency between 2%-8%. Tests on the experimental rig showed a maximum thermal efficiency of 3.33%. However, the system is both absorbing all the heat from the data center and at the same time providing an economic benefit back to the data center in the form of electricity. Through experimental investigation, this study illustrates that the use of an ORC system is a valid solution for ultra-low-grade data center waste heat recovery.