2.5.1 Storage and Refrigeration Systems

It may be feasible to combine some cooling system components, such as chilled water thermal storage and ice thermal storage (Cross et al. 1995). The increased complexity of combined storage systems would need to be assessed relative to the actual benefit of potential increased capacity enhancement and decreased capacity costs.

The use of two-stage refrigerating systems, where two separate refrigerant evaporator coils arc used at two different temperatures, can help to improve thermodynamic efficiency. The combination of equipment allows smaller individual cooling equipment and could help to utilize relatively small amounts of waste heat. For example, this combination could feasibly include a single- or double-effect lithium bromide/ water absorption chiller operating at approximately 44 F (6.7 C) and yield an exit air temperature of approximately 52 F to 54 F (11.1 C to 12.2 C). The air could then be cooled further by a vapor compression ammonia chiller or an ammonia/water absorption chiller to operate near or below 35 F (1.7 C) to cool the air to 40 F or 42 F (4.4 C or 6.7 C).

Any design incorporating a combination of air-cooling equipment would be dictated by the full- and part-load efficiencies of the equipment and the hours of operation at full- and part-load conditions. Operation of the inlet cooling equipment for only a few hours at the peak ambient conditions would, of course, define the normal operating equipment efficiency. Additional equipment would probably increase cost by approximately 15% but improve operating energy use and, hence, decrease parasitic equipment...