Cooling Systems and Thermal Energy Storage

• Introduction
• Central Plant Design
• Chillers
• Thermal Energy Storage
• Pumps
• Heat Rejection
• Auxiliary Equipment
• System Design Considerations
• System Performance
• Operation and Maintenance
• Additional Resources

Introduction

Central cooling systems are an attractive method for cooling individual buildings by connecting them onto a common cooling loop. Central cooling systems can displace several small localized chillers with central systems that have options that are not feasible at individual sites.

Facilities managers should consider a number of factors when evaluating the merits of central cooling systems. These factors include annual operating costs, annual use of energy and domestic water, the age and condition of the existing system, and availability of capital.

Advantages of Central Cooling Systems

Central chiller plants offer several advantages over individual building air conditioning systems. Central chiller plants can take advantage of the diversity factor in the sizing of equipment and operation of the plant, as all connected loads will not peak at the same time. Less capital is required for central cooling equipment than for equipment in many individual buildings. Operations and maintenance (O&M) staffing costs are minimized and easier to control due to the centralized equipment location. Increased efficiencies are possible with large heating and cooling equipment, which reduces operating cost per unit of energy output. Part-load performance efficiencies are substantially improved by the ability to meet the system load with the most efficient equipment. Continuous and accurate monitoring of operating efficiencies is practical when the equipment is centralized. Single-point delivery of purchased utilities allows for favorable rates to a large-volume customer. Multiple fuel sources can also be a practical alternative.

Disadvantages of Central Cooling Systems

Central systems present some disadvantages over cooling equipment distributed in individual buildings. Thermal and hydraulic losses occur in large-distribution networks. These losses must be evaluated against the increased generating efficiencies of a central plant. The initial construction cost requires a large capital investment. Therefore, the most cost-effective options may have to be deferred if capital cannot be secured.