An economical and efficient system for locations with natural gas available is a gas-driven chiller. Depending on the service, the payback versus an older electric chiller is from 1 to 4 years. This is quite good, for a system that will have a 20-year life.
There are two significant problems most people associate with the gas-driven installation: maintenance and noise. Most manufacturers offer long-term maintenance contracts with their systems, which relieves the owner of assigning staff to the task (this maintenance cost is included in the above payback figures), or in developing the expertise in-house to maintain the equipment. The noise problem has been resolved too, by some manufacturers that package the whole system in a soundproofed enclosure. The noise that emanates from this casing is little different from an electric chiller. A third problem in some locations, air pollution, has also been resolved by effective flue-gas emissions controls.
A bonus available from this system is to use waste heat from the engine jacket or the exhaust (at 900°F). These can provide hot water or steam in liberal quantities and relieve a part of the burden on the cooling tower. A large gas-driven chiller needs only about 0.25 gal/ minute more flow than an electric chiller of the equivalent size. With waste-heat recovery, this value is even lower, perhaps to the point that the cooling tower will not have to be changed out in the retrofit (they’re usually installed with a little extra capacity anyway).
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Excerpt from Energy Conservation Projects.