DynaCool - Simulating Efficient Liquid Cooling for Current and Next Generation Large Scale Data Centres
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Energy consumption in Large Scale Data Centres (LSDC’s) doubled from 2000 to 2006 reaching 61 TerraWatt-hour (TWh) per year. Most power generation sources are sadly fossil fuelled, which is increasing the effects of anthropomorphic climate change. 99-100% of the energy consumed by IT equipment is dissipated as heat from the servers, which creates a real problem of cooling in LSDC’s. Air cooling systems in LSDC’s are struggling to handle the increased cooling demands, which is why they account for 40% of the total energy consumed. The rest of the energy consumed is used to power the IT equipment and data centre infrastructure facilities like lighting. The ratio of power consumed by the data centre facility to the power consumed by the IT equipment is known as Power Usage Effectiveness (PUE), which is a metric used to measure data centre efﬁciency. Reducing the PUE by even fractions of percentages can prevent millions of tons of greenhouse gases from being emitted into the atmosphere. One of the methods of reducing PUE is by using alternate forms of cooling technologies like liquid cooling. This thesis explores novel optimisation methods for cooling control in liquid cooled LSDC’s. The three strategies focused on are Static Flow Rate, Variable Flow Rate (VFR) and the proposed Pulsed Variable Flow Rate (PVFR) cooling control strategies. The power consumption of coolant pumps and the effect it has on reducing energy consumption and PUE are investigated for all three cooling control strategies using computer simulations. Current simulation software were limited to air cooling and as such we needed to develop a proprietary computer simulation software. The software we developed was DynaCool and the simulation data we gathered was used to analyse the effectiveness of the different cooling control strategies. DynaCool was built using requirements engineering and model driven design to ensure the validity of the software, as these methodologies are commonly used in large complex industrial systems. The data analysed indicated a PUE reduction of at least 15.4% for the novel PVFR liquid cooling control strategy over the static and VFR cooling control strategies. This reduction equates to savings of 2.84 million tons of greenhouse gas emissions and 18.788 TWh of power consumption per year for an adoption rate of 100%. Realistically speaking, an adoption rate of 10% would yield power saving of 1.88 TWh or 284 thousand tons of greenhouse gas emission per year. This adoption rate is easily achievable by the industry as recent trends indicate data centre operators are moving towards alternate cooling technologies. This is evidenced by Google aiming to achieve carbon neutrality by 2017 using liquid cooling technologies.