How Hybrid Cooling Works 

Hybrid systems can be classified as either traditional or non-traditional.  In the traditional configuration, the system consists of two equally sized chillers — one electric and one alternatively fuelled chiller, such as a natural gas engine-driven, steam turbine-driven, or gas or steam absorption chillers.  During hours of high electric rates, the alternative chiller handles the base load while the electric chiller covers the remaining load.  In the non-traditional arrangement, the alternative chiller handles the entire load when electric rates are higher and a smaller, electric chiller operates only when electric rates are the lower cost choice,  Tests of both designs have shown that a non-traditional hybrid system can be cheaper to operate and provide more redundancy than a traditional hybrid plant.  (see Chiller Plant Design in a Deregulated Electric Environment)