Efficiency Improvements of a Thermal Power Plant by Making Use of the Waste Heat of Large Datacenters using Two-Phase On-Chip Cooling

Cooling of datacenters is estimated to have an annual electricity cost of 1.4 billion dollars in the United States and 3.6 billion dollars worldwide. Currently, refrigerated air is the most widely used means of cooling datacenter’s servers. Modern datacenters require a heat dissipation rate in the order of 5 to 15 MW and current air cooling technology represents around 45% of the total energy consumed. Based on the above issues, thermal designers of datacenters and server manufacturers now seem to agree that there is an immediate need to improve the server cooling process. On-chip cooling research is being developed in this context to propose a new, more efficient cooling technology. This also allows the recoveryof the heat rejected by the servers in a proper way, making it possible to reuse elsewhere, in another application. The present investigation develops a case study considering two different cooling systems applied on a datacenter and exploring the application of energy recovered in the condenser on a feedwater heater of a coal power plant. The effects of the evaporating and condensing temperatures on the cooling cycle performance and the potential to recover energy, and consequently the effect on the power plant efficiency, are evaluated. The analyses consider the main objective function to be the minimization of energy consumption, the corresponding CO2 footprint and operating costs. From the datacenter’s point of view, when compared with traditional air-cooling systems, energy consumption, without considering energy recovery, can be reduced by as much as 45% when using a liquid pumping cycle and 35% when using a vapour compression cycle. From the power plant point of view, the results showed that, when the pressure of the feedwater heater is optimized, an increase of up to 6.5% of the overall power plant efficiency can be obtained when using a vapour compression cycle to cool the datacenter. Considering the vapour compression cycle and a datacenter of 100000 blades, overall savings (considering the power plant and the datacenter as a whole system) of 2170 tons of CO2 and $0.34 million per MW of electricity production were obtained. Additional investigation was developed considering the effects of partial operation of the datacenter and/or the power utility on the parameters mentioned beforehand. For such an investigation the start-up was the ideal match between a datacenter of 100000 blades and a power plant, both with 100% of operational uptime. It has been shown that some cases could lead to impossible thermodynamic operations, meaning that special attention must be given when the design of such integrated utilities (datacenter and power plant) is made.