## 4 Results and Discussion
### Air Conditioning Systems  
The performance of the air conditioning system equipped with DPCT and WBCT is presented in Figure 10. For the purpose of comparison, both systems are referenced to a chilled water system operating with an air-cooled heat rejection system (i.e., a dry cooler).  
Figure 9: Capacity obtainable by a gas power plant with air pre-cooling using water from different cooling towers. (**a**) Relative capacity—DPCT and outdoor air. (**b**) Relative capacity—WBCT and outdoor air. (**c**) Capacity obtainable by 600 MW power plant—DPCT and outdoor air. (**d**) Capacity obtainable by 600 MW power plant-WBCT and outdoor air. (**e**) Natural gas consumption: DPCT and WBCT.  
The performance is analyzed for different cooling load levels: the performance under 100% of the nominal cooling load is presented in Figure 10a,b; the performance under 50% of the nominal cooling load is presented in Figure 10c,d; the performance under 30% of the nominal cooling load is presented in Figure 10e,f.  
The performance of the cooling system is analyzed based on the energy efficiency ratio (EER), defined as the obtained cooling power divided by the input electrical energy (W/W), as described in Section 2. Using the obtained water temperature values and the functional relationship for the unit's EER, the EER levels for dry heat rejection and switching to WBCT and DPCT were determined. It can be seen that during operation at 100% of the nominal cooling load, the system, while operating with dry cooling heat rejection, is able to achieve EERs varying from 3.7 to 9.8 during colder days (Figure 10a,b). When DPCT is applied, the EERs vary from 5.5 to 13.8 (Figure 10a), and when WBCT is applied, the EERs range from 4.2 to 11.1 (Figure 10b) under 100% cooling load. During reduced cooling load (50%), the EERs obtained by the system with dry cooling vary from 4.1 to 11.8 (Figure 10c,d), with DPCT achieving EERs from 6.2 to 15.9 (Figure 10c), and with WBCT achieving EERs from 5.7 to 13.0 (Figure 10d). During operation at 30% of the nominal cooling load, the EERs for dry cooling vary from 4.9 to 12.2 (Figure 10e,f); with DPCT, they range from 7.5 to 16.2, and with WBCT, they range from 5.9 to 14.0. The maximum difference in EER between the system with DPCT and dry cooling is 7.2; the minimum is 1.0; the maximum difference between the system with DPCT and WBCT is 5.1; the minimum is 0.3. The change in average EER between DPCT and dry cooling is 3.5, and between DPCT and WBCT is 2.1.  
To perform a simplified analysis of the level of energy savings achieved by implementing DPCT compared to WBCT and dry cooling, a cooling system with a nominal capacity of 1 MW is assumed. The average operation scenario is based on [20; 21], with average EERs, 10 h a day of air conditioning, and operation at maximum capacity occurring 15% of the time, at 50% capacity 60% of the time, and at 30% of nominal capacity 25% of the time. In such a case, a 1 MW cooling system would consume 64.5 MWh of electrical energy annually with DPCT, 79.2 MWh with WBCT, and 94.5 MWh with dry cooling. This means that the savings in electrical energy between dry cooling and DPCT would be 30 MWh, and between DPCT and WBCT would be 14.7 MWh. It can be seen that the application of DPCT can improve the performance of cooling systems and provide significant energy savings.  
Figure 10: _Cont._  
Figure 10: _Cont_.