# Economic Analysis of a Zero-Water Solar Power Plant for Energy Security
## 3 Results and Discussion
### Economic Analysis of the Overall CSP Plant
#### 3.2.3 Studying the Effect of the Cost of Water  
Future water scarcity, predicted for large regions of the planet, will cause an increase in the cost of water that will be proportional to the magnitude of the conflicts that arise. Specifically in power generation, the price of water could reach values of up to EUR 50/m\({}^{3}\), while the possibility of water trading between different sectors has been recently confirmed with the entrance of water in the Wall Street markets [50; 51]. A water cost of EUR 50/m\({}^{3}\) is much higher than current water costs for water-cooling systems and water generation technologies [9]. Nevertheless, in a comparative analysis, this price should include other associated costs on top of the base price of water used. For example, it should account for water generation and treatment, transport, power penalties related to water shortages, lower power output due to the deterioration of physical characteristics of the water, and economic or environmental impacts to the local climate and population [52]. Such external \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Pipe Number** **(–)**} & **Material and** & **Labor Costs** & \multirow{2}{*}{**O\&M Costs** **(EUR/year)**} & **NPV (MEUR)** \\  & **Equiment** & & & \\  & **Costs** & **(MEUR)** & & \\ \hline
10,965 & 102.71 & 45.58 & 67,106 & \(-\)139.59 \\
8000 & 74.93 & 33.25 & 48,960 & \(-\)99.15 \\
5000 & 46.83 & 20.78 & 30,600 & \(-\)58.24 \\
3000 & 28.10 & 12.46 & 18,360 & \(-\)30.96 \\
1000 & 9.37 & 4.14 & 6120 & \(-\)3.69 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Influence of the pipe number on the associated costs and the NPV of the project. ities are usually currently neglected in economic analyses found in the literature but could help to better evaluate the cost of water and establish a fairer basis for the comparison of different cooling technologies. The cost of water in the power generation sector will play a decisive role in the implementation of the Earth-CATs as an alternative cooling system. The variation of the water cost on the NPV is presented in Table 8 (again, for a 25-year lifetime and a discount rate of 2%). The design starts being economically viable for a water cost higher than EUR 15/m\({}^{3}\). For a water cost of EUR 16/m\({}^{3}\), the NPV value is equal to MEUR 9.51 and the PBP is equal to 17.4 years. Furthermore, if future research improves the thermal performance of Earth-CATs and reduces the number of pipes required to 8000 while having a pipe unit cost of EUR 25/m, the project will be viable for a water cost of EUR 10/m\({}^{3}\) with a NPV of MEUR 4.12 and an investment recovery after 17.8 years. These hypothetical cases allow us to understand how competitive an Earth-CAT system is relative to a conventional water-cooled system as a zero-water cooling alternative, and they set important references for future research. In the case of plants using wet cooling, the LCOE is expected to increase with the water cost. Figure 4 shows the effect of water cost on the LCOE of the studied CSP plant if wet cooling is used. It is for a water cost of approximately EUR 28/m\({}^{3}\) that the obtained LCOE meets that of the plant using Earth-CATs (EUR 505.97/MWh). Although this water cost would include the externalities associated to its use and may be a potential future, there is a need to reduce the large initial investment of the project, involving the improvement of the heat transfer between the Earth-CAT and the soil, applying economies of scale on the unit price of the pipes, and accounting for the cost of water. In addition, policies supporting sustainable energy reforms could favor the economic viability of the system, reducing the investment costs and promoting the use of Earth-CAT systems over conventional cooling systems.