www . refrigerationandaircon . co . za RACA Journal I January 2025 25
Feature
Indirect cooling system “ This is less used but is highly efficient because you use an external unit that exchanges the heat via external air , creating free cooling . Adiabatic cooling is used to support the cooling process at higher ambient temperatures . Mechanical cooling may be supplied as a top-up beyond the standard cooling process .”
He lists the pros as : enabling modular solutions for a large data centre ; a low achievable pPUE ( partial power usage effectiveness ) due to adiabatic cooling operations ; and a clean room environment without external pollution . On the other hand , he says they require increased maintenance for water treatment , filters , fans and pumps ; but primarily they are impractical where there are space restrictions . They are also sensitive to climate profiles , while water is required to be stored due to the high water consumption .
“ Usually , one would run two internal units at 100 % capacity and have one on standby , but an option is rather to run all three at 66 % capacity with the benefit of improved air distribution within the data centre , thereby reducing hot spots . The system also works more efficiently . Operating at partial load can optimise performance , allowing facilities to reduce energy usage while still maintaining effective cooling – especially if they are inverter compressors and fans ,” he says .
Case studies presented during the session illustrated these strategies ' effectiveness , revealing that a 42 % reduction in energy consumption was achieved by running four 145 kW cooling units at partial load , as compared to a plant running three such units with one on standby .
OPTIONS FOR CHILLER EFFICIENCY EER IMPROVEMENTS EER is the ratio between output cooling energy and input electrical energy . The single most important method to improve the ratio is adjusting water temperature settings higher , whereby data centres can leverage existing systems more efficiently , minimising energy waste . Implementing dynamic or variable set points can help adapt to varying cooling needs , ensuring that systems operate only as much as necessary .
The new generation of chillers designed for data centres supply water up to 30 ° C ( compared with 15-20 ° C previously ) with external temperatures up to 46 ° C . Free-cooling and glycol-free configurations can enhance the energy savings . This means in many countries free cooling can be used year-round as it kicks in when external air temperature is 2 ° C lower than the water return temperature . Even in South Africa temperatures are below 30 ° C 70 % to 80 % of the time . A rise of 5 ° C produces a 10 % improvement in EER , which Preato describes as “ a big improvement for a chiller ”.
Moreover , Preato underscored the advantages of increased Delta T ( the difference between two temperatures ). It increases
Image by AERMEC
P series , direct expansion units with cooling capacity from 7-100kW .
cooling operation , reduces pumping energy costs and reduces piping dimensions and water .
In terms of free cooling regulations , Preato noted that “ the condensing pressure regulation is done excluding the condensing coil ’ s sections through proper two-way valves , thereby reducing the exchange area without slowing down the fan speed ”.
CHALLENGES AND CONSIDERATIONS Preato acknowledged the complexities involved in designing efficient data centre systems . A customised design must consider variable loads and all-year-round operation , evaluate climate profiles and cooling loads .
He discussed the challenges associated with different cooling technologies , including the efficiency of chilled water systems , potential hazards with flammable refrigerants in PX systems , and the limitations of space in air-cooled systems .
Aermec ’ s energy simulation software ( ACES ) considers the current and future installation site design , the required cooling load , the climatic profile , the use of the facility , potential renewable energy integrations , the available space , noise constraints , redundancy , maintenance and more . “ All these inputs are applied in an interactive analysis process which calculates the best possible solution considering all the involved variables , to generate a customised and optimised proposal . All the benefits of the new cooling technologies can be maximised
using the proper system control . The key to the new generation controller is its logic based on the chiller ’ s actual working data : the controller features have been developed using extensive laboratory data obtained in real simulation and the sampling points are gathered , mapped and transformed into a simulation model which characterises all the real possible working conditions for chillers .”
“ One of the most striking aspects of data centres is the level of secrecy surrounding their operations .”
www . refrigerationandaircon . co . za RACA Journal I January 2025 25