Optimizing Chiller Efficiency

Whether they are centralized or decentralized, chillers are central to any air conditioning system in institutional and commercial facilities. As one of the biggest energy users in the building, they must be managed properly to minimize operational expenses. Often overlooked and missed opportunities for chiller efficiency savings can be significant. A focused approach to cooling needs, smart maintenance and correct refrigerant management can help managers deliver long term savings.

Chillers use a compressor, expansion valve and evaporator to circulate a liquid or refrigerant. Industrial chillers transform the coolant from its low-pressure and low-temperature state to a high-pressure, high-temperature vapor by the compressor, which then goes through the condenser where fans circulate outdoor air over the heat exchanger to absorb the heat (the second law of thermodynamics dictates that hot moves to cold). The vapor returns to the evaporator where it is cooled by ambient air and becomes a liquid again before being pumped back to the process.

A key to optimizing a chiller system is matching its capacity with its cooling load. A common mistake is to oversize a chiller and underutilize its capacity. Oversized chillers consume a lot of electricity and operate inefficiently. A better strategy is to utilize a “chiller bank” of different sizes so that each chiller is operating at its best performance for the current cooling load. A lead/lag sequence also helps to balance run-time hours on individual chillers which can significantly reduce overall energy consumption. chillers