Waste Heat Recovery Using Coupled 2-Phase Cooling & Heat-Pump Driven Absorption Refrigeration

Data center waste heat recovery is an energy efficient and economically viable option when the data center is near other facilities. This study explores boosting the vapor from a data center's two-phase server waste heat using a novel vapor recompression system. The boosted waste heat contains sufficient thermal energy to drive an absorption refrigeration (AR) chiller to obtain a stream of cold fluid. Alternatively, the chiller can be bypassed to use the boosted heat directly in the neighboring facility. These approaches are modeled to enable the estimation of energy savings and economic benefits under different cooling and heating loads. These calculations also indicate situations where the compressor should be by-passed, and the server exhaust simply sent to the condenser for rejection to the ambient. The analysis is focused on the waste heat recovery and re-use potential of a 1 MW data center with a mid-size office building in the vicinity. The paper focuses on two key issues: 1) the overall efficiency of the waste heat system, including neighboring sites, when boosted with the novel re-compression system versus a turn-key heat pump coupled with warm-water cooling and 2) a comparison of the relative capital and operating costs of the two systems. The results show that the novel recompression system has a lower cost and a higher thermodynamic efficiency than a warm-water cooling system coupled to a conventional heat pump, and the use of the novel waste heat recovery system is viable in areas with high electricity cost.