*3.6. Economic Performance*

The LCCs of alternative cooling systems configurations are compared in Figure 10.

It is interesting to observe that at the resource cost conditions considered (average conditions, labelled as "Mean" in Table 4), the life cycle costs for configurations using CTs were slightly higher than corresponding configurations using DCs. In the long run, the lower capital costs and lower electricity cost of CT-based solutions did not compensate the additional economic impact of water consumption.

The proposed FC strategy requires few components and a simple regulation, which means that, compared with the baseline, additional investments are basically negligible. As a consequence, the life cycle costs of FC configurations were always lower than those of corresponding MVC configurations.

The proposed waste-heat to cooling ABS configuration requires significant investment but generates major savings in electricity costs and—for CT configurations—small savings in water costs in most climates. As a result, the life cycle costs of ABS configurations at average price conditions were always lower than those of corresponding MVC configurations, but in some climate regions (4C, 5A, 5C, 6A, 6B, 7 with either DCs or CTs, and also in 4A with CTs) they were higher than those of FC configurations, as shown in Figure 10.

**Figure 10.** Life cycle cost (LCC) analysis based on climate zone and case study at mean electricity and water prices. CAP. is for plant capital costs, Elec. and Water are the life cycle operational expenses for electricity and water, respectively.

This is highlighted more generally in Figure 11, which shows the simple payback time (PBT) of ABS with respect to corresponding FC configurations according to Equation (5). Figure 11 also shows the dependence of PBT on climate zones, electricity prices and, for CT configurations, on water prices. In particular, Figure 11a shows the sensitivity of the economic performance of ABS with DC to the electricity price by presenting PBTs at minimum, mean and maximum levels of electricity price according to Table 4. Similarly, Figure 11b shows the sensitivity of PBTs in the ABS with CT configuration to the electricity price and Figure 11c shows the sensitivity of PBTs in the ABS with CT configuration to the water price (at the minimum, mean and maximum levels reported in Table 4). It can be observed that lower electricity prices resulted in smaller savings and consequently longer payback periods, which stretched even beyond the investment time horizon for CT configurations from climate zone 3C and subsequent. Similarly, high water prices in CT configurations increased operational expenses of ABS configurations, and hence led to longer payback times. Grey areas, corresponding to regions 4C, 5A, 5C, 6A and 7 with either DCs or CTs, and also in 6B with CTs) indicate the climate zones where the electricity consumption of ABS configuration was mostly higher than that of FC configuration: depending on price levels, the payback times of ABS configurations in these cases would either be negative (i.e., ABS never pays off) or at least longer than the system's service life.

It can be observed that:


**Figure 11.** *Cont.*

**Figure 11.** Payback times of ABS cooling solutions with respect to FC solutions depending on electricity and water prices (**a**) FC with DC, sensitivity to electricity price; (**b**) FC with CT, sensitivity to electricity price; (**c**) FC with CT, sensitivity to water price.
