Data center coolant switch

A system comprising:

• a data center cooling system configured to operate in a first mode, the data center cooling system having an indoor portion wherein heat is absorbed from components in the data center, the data center cooling system having an outdoor heat exchanger portion wherein outside air is used to cool a first heat transfer fluid present in at least the outdoor heat exchanger portion of the cooling system during the first mode, the first heat transfer fluid being a relatively high performance heat transfer fluid, the first heat transfer fluid having a first heat transfer fluid freezing point;
• a control unit configure to determine that an appropriate time has been reached to switch from the first mode to a second mode;
• and
• a switch configured to switch the outdoor heat exchanger portion of the data cooling system to a second heat transfer fluid, in response to the appropriate time being reached, the second heat transfer fluid being a relatively low performance heat transfer fluid, the second heat transfer fluid having a second heat transfer fluid freezing point lower than the first heat transfer fluid freezing point, the second heat transfer fluid freezing point being sufficiently low to operate without freezing when the outdoor air temperature drops below a first predetermined relationship with the first heat transfer fluid freezing point.

A computer program product useful for controlling a data center cooling system, the computer program product comprising a computer readable storage medium having computer readable program code embodied therewith, the computer readable program code comprising:

• computer readable program code configured to operate the data center cooling system in a first mode, the data center cooling system having an indoor portion wherein heat is absorbed from components in the data center, the data center cooling system having an outdoor heat exchanger portion wherein outside air is used to cool a first heat transfer fluid present in at least the outdoor heat exchanger portion of the cooling system during the first mode, the first heat transfer fluid being a relatively high performance heat transfer fluid, the first heat transfer fluid having a first heat transfer fluid freezing point;
• computer readable program code configured to determine that an appropriate time has been reached to switch from the first mode to a second mode;
• and
• computer readable program code configured to, responsive to the determining, switch the outdoor heat exchanger portion of the data cooling system to a second heat transfer fluid, in preparation for operation in the second mode, the second heat transfer fluid being a relatively low performance heat transfer fluid, the second heat transfer fluid having a second heat transfer fluid freezing point lower than the first heat transfer fluid freezing point, the second heat transfer fluid freezing point being sufficiently low to operate without freezing when the outdoor air temperature drops below a first predetermined relationship with the first heat transfer fluid freezing point.