Mechanical Drives - General Design Attributes

Chiller compressors can be driven by electric motors, reciprocating engines, gas turbines, or steam turbines. The selection of alternative drive technologies rests primarily on the issues of first cost and operating cost, as well as any fuel diversity and power reliability criteria. While there are other issues involved in the selection process, including CFC phaseout and other refrigerant-related issues, the selection between the alternatives just mentioned will probably not be driven by CFCs. In other words, a refrigerant that might be applicable for a chiller driven by a reciprocating engine would also work for an electric motor drive. A discussion of these criteria can be found elsewhere in this digital reference library.

While mechanical drives other than electric motors are also discussed, the primary alternatives presented will be reciprocating engines in the 100-500 ton range and steam turbines which are typically much larger. Gas turbine-driven chillers are seldom seriously considered for three reasons:

1. The limited number of gas turbine sizes available

2. Their economic reliance on heat recovery and

3. Their relatively poor on-peak performance during hot weather.