A chilled-water storage system is to be evaluated. The system schematic is shown in the sketch below:
The tanks are 15 ft high and SO ft in diameter. The chiller is run 14 hours a day to charge the cold-water tank. The space-cooling system consists of a series of air-handling units (AHU) that feed from the cold-water tank. Water from the AHUs is stored in the holding tank. The AHUs run 10 hours a day. 216,000 gallons of cold water are required daily. The piping characteristics are as follows:
The system is used 25 days per month. Electricity costs $0.05 per kWh, and the electrical demand charge for the chiller if run during the first shift is $500/month. The pumps are 71 per Cent efficient. Estimate the pumping costs associated with the storage system (the AHUs and chiller would be used 10 h per day if the storage system were not in place). Assess the effectiveness of the cold-water storage system.