Data center hvac system with hybrid thermal control

A method to serve a cooling load of a data center facility comprising one or more computers in a rack group of one or more computer racks, the method comprising:

• obtaining a load balance constraint that requires balance between (i) a heat production comprising an amount of heat generated by the one or more computers of the rack group and (ii) a heat rejection comprising a first amount of heat to be rejected from the rack group into cool air provided by an air cooling system and a second amount of heat to be rejected from the rack group into chilled liquid provided by a liquid cooling system, wherein the air cooling system and the liquid cooling system operate in parallel to provide both the cool air and the chilled liquid to the rack group;
• allocating the amount of heat generated by the one or more computers of the rack group into (i) the first amount of heat to be rejected from the rack group into the cool air provided by the air cooling system and (ii) the second amount of heat to be rejected from the rack group into the chilled liquid provided by the liquid cooling system, wherein allocating the amount of heat generated by the one or more computers of the rack group comprises determining target values of the first amount of heat and the second amount of heat using the load balance constraint;
• operating the air cooling system to reject the first amount of heat from the rack group into the cool air;
• and
• operating the liquid cooling system to reject the second amount of heat from the rack group into the chilled liquid.

A data center HVAC system comprising:

• an air cooling system operable to reject heat from one or more computers in a rack group of a data center facility into cool air provided to the rack group by the air cooling system;
• a liquid cooling system operable to reject heat from the one or more computers in the rack group into chilled liquid provided to the rack group by the liquid cooling system;
• and
• a controller configured to:
• allocate an amount of heat generated by the one or more computers in the rack group into (i) a first amount of heat to be rejected from the rack group into the cool air provided by the air cooling system and (ii) a second amount of heat to be rejected from the rack group into the chilled liquid provided by the liquid cooling system, wherein allocating the amount of heat generated by the one or more computers of the rack group comprises determining target values of the first amount of heat and the second amount of heat using a load balance constraint that requires balance between (i) a heat production comprising the amount of heat generated by the one or more computers in the rack group and (ii) a heat rejection comprising the first amount of heat to be rejected from the rack group into the cool air provided by the air cooling system and the second amount of heat to be rejected from the rack group into the chilled liquid provided by the liquid cooling system;
• and
• operate the air cooling system and the liquid cooling system to reject the first amount of heat from the rack group into the cooled air and reject the second amount of heat from the rack group into the chilled liquid.