Chilled water generation plays a particularly important role in many healthcare, institutional, and commercial facilities, cooling water to facilitate centralized air conditioning systems and process cooling.
When optimizing a water-cooled chiller plant, the selection of equipment and chilled water-pumping scheme are two of the most obvious places to start. But they’re not the only options – and if you stop there, you may stand to miss some significant opportunities for further optimization.
Condenser System Considerations
Larger chilled water systems tend to utilize condenser water to reject heat from the chiller. For these larger facilities, it’s important to make sure you’re optimizing the operation of the condenser water system to get the most out of your equipment and processes.
Although variable frequency drives are often installed on cooling towers and pump motors in order to maximize the efficiency of the condenser and chilled water system, one commonly overlooked aspect is the condenser water temperature. Chiller efficiency is directly affected by the condenser water temperature which can increase up to 15% by using colder condenser water.
Since outside weather conditions impact cooling tower performance, you can use automated control schemes to adjust condenser water temperature based on your needs, providing a notable improvement to your system efficiency in any condition. A well-engineered plant automation system can be programmed to adjust the condenser water settings for conditions as they vary throughout a day or an entire cooling season thus optimizing the entire system efficiency.
Chiller Operating Efficiency
To identify additional chiller plant optimization strategies, you can also look to the chiller itself. A chiller generally achieves maximum efficiency when it operates between 60 and 80 percent of its full capacity (with poor performance below 50 percent). Although sometimes difficult, operation within the 60-80 percent range can provide significant electrical savings for a large facility.
By reviewing the normal operating loads and parameters, facilities can create an economic dispatch algorithm that will optimize the starting and stopping of chiller plant equipment. The goal of the algorithm is to consistently run each machine within its ideal performance range, thus optimizing the overall system efficiency for a given system demand. This is undoubtedly a more complicated process, and may not appeal to facilities managers who wish to keep things as simple as possible, but the trade-off for complexity is a significant opportunity for savings.
Finding opportunities
Facilities managers exploring any type of chiller plant optimization strategies must first launch in-depth investigations and efforts to find specific opportunities in a given system. These investigations can require a significant amount of detail; however, the performance enhancements you make can translate to serious savings over time.
Eric joined Fosdick & Hilmer in 2000, and is now the Manager of Mechanical Engineering as well as the Lead Engineer within the Central Utilities Group. Eric is an expert in the design and analysis of central heating and cooling plants and distribution systems. During his time with the firm, Eric has been the project manager for numerous central plant and distribution projects including steam and chilled water plants, combined heat and power systems, fuel oil storage, and integrated HVAC systems.
