Data Center Cooling With Thermal Storage System

Data centres maintain several IT equipments that store, organize, process and disseminate significant amounts of data. These data centres require an uninterrupted power supply for the equipment to function accurately. This also means that it is important for data centres to have reliable cooling systems to prevent the temperature from rising which can lead to the failure of critical electronic equipment. So, if and when there is a power outage, stored chilled water in large buffer tanks provides continuous operation of the cooling system whilst the generator backup power supply cuts in.

As data center power and heat density increase, transient losses of electrical utility power potentially have more significant impacts and require special design considerations. Data centres these days use thermal storage tanks or chilled water buffer tanks in their cooling system to ensure that the equipment does not overheat the racks at the time when Grid power goes off and captive power kicks in.

There are several methods for increasing the resilience of Data Center cooling systems to counter power disturbances/switch from EB to Captive power & vice versa. Some data centers requiring very high power use standby generators for chillers. However, these add significantly to data center costs. Also, generators take several seconds to start up, after which it can take a few minutes to restart the chillers.

The other option is having a thermal storage tank and chillers with a quick start option. Thermal storage can extend the ability to cool data center IT equipment in the event of a power failure (till the captive power kicks in), by using thermal reserves to provide temporary cooling during a power outage.

VPF With Thermal Storage Concept:

Normal Scenario:
The pump will operate based on the field demand from DPT and the Bypass valve will run based on the chiller minimum flow value set.
The Thermal Storage tank will get bypassed by opening the main header valve. Hence, chiller(s) directly supply chilled water to load/field equipment.

During Power failure, Pump continues to circulate the water through chillers with the supply header motorized valve closed and the Thermal Storage Tank outlet valve kept open. Chilled water will be supplied from Thermal Storage Tank directly to the load/field equipment. The pump speed shall be modulated based on the field demand (from the DPT sensor).

It is therefore recommended to choose a system that is simple, reliable, and efficient that operates with normal Chillers, and provides a quick start when a power failure occurs. Chilled Water Thermal Storage System proves to be an effective solution for emergency supply of chilled water for data center cooling.

An additional Chiller will be switched ON for charging the Thermal Storage Tank based on water temperature. Once the chiller starts, the supply header valve and the tank return water valve will open. This will allow chilled water from the chiller directly to the load/field equipment and simultaneously, the Thermal Storage Tank will start to get charged.