Heat Ventilation & Air Conditioning (HVAC) plays a critical role in the design of data center plants and any plants in general. Data centers work all through the day. Hence, providing a scientifically backed system-design to remove the heat generated is an important aspect of plant design. HVAC study is based on this very premise of the scientific approach to provide a safe ventilation system.
Data centers host critical information for which continuous access has to be provided. In an energy starved world with ever-growing demand for electricity, lead acid batteries provide the much needed solace in making data centers work round the clock.
The HVAC system design employs the principles of thermodynamic analysis and the heat transfer rate from the hardware to the environment and analyses the ambient conditions to design the tonnage of air conditioning necessary to maintain the air temperature, humidity and air quality.
The ergonomics of data centers must give importance to human safety, since hydrogen gas is evolved during the electrolysis process in batteries. Since hydrogen is a highly flammable, there should be an efficient design to safely remove the hazardous gas.
Batteries classification based on ventilation systems:
- Ventilated lead acid batteries use sulphuric acid as its electrolyte, also commonly known as ‘wet cells’. They release hydrogen gas through vents during electrolysis, hence the name ventilated.
- Valve regulated lead acid (VRLA) batteries are used commercially, since they generate higher power density and are easy to maintain. The term valve regulated indicates the use of safety valves that allow pressure to be released in case of faulty operations and as a safety feature.
- Modular Battery cartridges (MBC) are strings of VRLA batteries packaged into cartridges. MBC’s are designed for use in a data center, network room or office environment.
Apart from hydrogen toxic gases such as arsine, stibine and hydrogen sulphide(H2S) are also emitted. H2S is also another highly flammable volatile gas and can cause explosions easily.
Ambient operating conditions for batteries
Batteries generally work across a wide range of temperature, but if constantly worked at high temperatures the life of the battery is significantly reduced. The optimum working temperature for battery is 18° to 27°C at a humidity ranging from 35 % to 55%
Generally mechanical ventilation is used and monitored using special heat sensors which ensure the optimal temperature is maintained. Besides these gas detectors are also employed to constantly monitor the flammable gasses that are produced.
Ventilation system for stationary batteries must primarily address the human safety and equipment safety. Gasses such as hydrogen and hydrogen sulphide is a major concern for safety and poses a major threat to the human safety factor in designing a safe ventilation system. Vented batteries require the expertise of a professional engineering firm to design and maintain a safe working environment. Whilst VLRA and MBC system can work in an environment suitable for human occupancy, this makes VLRA and MBC’s more sought after compared to the hazards of working with a ventilated batteries.
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