This paper investigates a method to lower the cooling plant energy consumption by modifying its regulation while keeping all the IT equipments in the ASHRAE allowable environment.
A virtual 32 kW datacenter has been considered to perform the tests. The infrastructure is cooled by the Integrated WaterSide Economizer proposed by Myer and Sorell [10].
The air flow and the heat are predicted using the CFD code Thé- tis, while the cooling plant is modelled using TRNSYS. A POD reduced order model using Snapshot technique is created with the software MATLAB. It is used in the TRNSYS simulation to per- form interpolations between computed CFD results.
Two main effects have been identified. First the increase in blown air temperature allows the system to raise the evaporator loop temperature. As a results, the number of WSE or IWSE opera- tions increase and reduce the load on the heat pump. Doing so, the HP reduces its energy needs by 78% when the blow air temperature TCO rises from 16 °C to 24 °C. On the other hand, an increase in the CRAC fan flow rate, required to maintain all the servers under the maximum allowable temperature 32 °C is observed and raised the fan energy consumption by 43%. Thus the simulations determined that the optimum cooled air temperature for this system is 24 °C. In this configuration, the cooling plant reduces its energy con- sumption by 10%, compared to case where TCO = 16 °C.
However, the indicator HAOC shows that operating in WSE mode at TCO = 16 °C required 26% less energy than at TCO = 24 °C.
The simulation with the proposed TACS regulation showed an energy gain of 18% in winter time period compared to a fixed
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Finally, integration of TACS system does not require any addi- tional component in the cooling plant. There is only a need to mod- ify the main regulation which involves a very low maintenance cost. In returns it can provide up to 17% of electric energy savings on the cooling plant requirement. Hence, it strongly reduces the datacenter annual cost, making this system economically competitive.
In the future, further simulations will be carried out with blade server introduced in [8]. It will probably require different control strategy and optimal TCO set-points. Furthermore the effect of Air Distribution System modification on the cooling plant consump- tion will be investigated. New POD reduced order model will be created with cold aisle containment and the effect on cooling plant energy consumption will be calculated.