## 5 Results  
An appropriate inlet water temperature for chillers on a full-load day is illustrated in Figure 8. As expected, the water temperature in the CCCP system fluctuates more frequently than that in the DVFP and WS system because there is no water storage. However, with the implementation of water tanks, the DVFP and WS system stores cold water at night when the inlet temperature is lower and  
Figure 7: Simulation flow chart of the DVFP and WS system. releases it during daytime hours. It is found that this low inlet temperature improves the average chiller COP Figure 9. Another advantage of the proposed system is the implementation of the DVFP, which distributes water flow as required, and regulates the temperature difference \(\Delta\)T to ensure high chiller efficiency. The effective total electric power of all equipment, including the chillers, pumps, and cooling towers, is shown in Figure 10. It can be observed that, although the new system consumes more power at night, the benefits afforded by this system during the daytime hours are more significant, particularly during the peak hour at approximately 12:00, when the cooling tower and pump usage is reduced and the water tanks release cold. However, as it is limited by the size of the water tanks and capacity of water storage, the low temperature of the cold water stored in the tanks can only be sustained for a few hours. During the second peak hour of the day, which occurs at approximately 18:00, the comparative advantage of the proposed system is insignificant. A summary of electricity consumption on a full-load day is provided in Table 2, which also provides details of the field test results for comparison. Figure 8: Inlet cooling water temperature for chillers. Figure 9: Box chart of chiller coefficient of performance (COP) for the two different systems. The labels CTF and CTP in Table 2 are abbreviations for the cooling tower fans and corresponding cooling tower pumps, respectively. It is observed that the simulated energy consumption in the CCCP system is lower than that measured via field testing, particularly for the pumps and cooling towers. This can be explained by the control strategy and the actual performance of the equipment. During operation, the pump control precision was observed to occasionally decrease to an undesirable level; moreover, the equipment was aging in some way that decreased efficiency, specifically affecting pump efficiency and cooling tower efficiency. However, regarding the total energy consumption, as compared to the CCCP system, the DVFP and WS system consumes 2696 kWh less electricity, equating to an approximately 10.3% in energy saved. As for transportation system (including all of the pumps), the DVFP and WS system consumes 1739 kWh less electricity than CCCP system, accounting for 57.4% of the energy in transportation system. Furthermore, as compared to the field test results, the total energy saved on a full-load day is 3674 kWh, equating to nearly 14%. Although CTPs are added to the DVFP and WS system, the sum of DVFP and CTP remains as less than PP for reasons, such as fluctuation in frequency and water loop pressure optimization. Despite this, the transportation system only consumes less than 15% of the total energy, thereby limiting the energy-saving potential. Based on the simulation results of energy consumption, the daily electricity cost is calculated as according to the current tariff in Beijing. Calculations reveal the daily cost for the CCCP system to be 30,855 RMB, whereas the cost is 27,585 RMB for the DVFP and WS system. The daily cost saving equates to 10.6%. In addition to the full-load-day study, energy consumption on a partial-load day is investigated to present a comprehensive view of system performance. The date is 30 May, and the simulated cooling load as simulated via DeST software is 56,000 kWh, which is 80% of the maximum cooling load. The simulation described above is performed, and energy consumption and cost are calculated. Table 3 provides a comparison of the two days.