# Renewables and Advanced Storage in Power Systems: The Iberian Case
## 4 Study Case: The Iberian System in 2030 According to the National Energy and Climate Plans (NECPs)
### Sensitivity to Uncertainty of Storage Costs. Application of the Power Estimate Method
other simulations studies such as [12; 13; 14; 15] are difficult because the assumptions, considered technologies, and geographical scope are widely different. All of them, however, remark the importance of storage in an intermittent renewable-dominated power system. Since the aim of the paper is to study the need for advanced storage in the optimal generation mix and its sensitivity to storage costs, the comparison to these studies is just informative. The estimates of mean values and standard deviations for installed power and capacity factors are shown in Table 5. It must be recalled that for \(z=f(x)\), the mean value of the output variables (installed power and capacity factors) is not the output of the mean of the input variable (storage cost), i.e., \(\eta_{z}\
eq z=f(\eta_{x})\). The energy produced by all technologies is different in each case because of different storage capacities and subsequent losses. These results lead to the following conclusions:  
* As expected from the screening curve analysis (see Appendix B), OC technology is an economical option for the optimal mix, even if its capacity factor is low. The optimal capacity of OC decreases when storage increases because both storage and OC compete in peak shaving of the residual demand. * Storage reduces the spillage of wind and particularly PVs. Storage is mainly used to compensate for the daily cycle of PVs. When the storage is low, the target of 80% renewables is covered mainly by wind, while more storage leads to more installed PVs. * The energy capacity of storage is a very small fraction of the total demand (0.08% in the largest case). This point is commented in reference [30], where it is shown that even for a 100% renewable system based on PV and wind (under different assumptions), the needed storage remains low compared to demanded energy. This result agrees with the results of reference [42], which includes a detailed review of many other references. It must be remarked that the actual installed capacity of storage in real systems would likely be higher because of the distributed storage facilities. This would not be an optimal scenario, but to design a regulation that fosters the optimal deployment of storage is challenging. * The number of hours of storage changes slightly because storage is used for the daily cycling of PVs. The optimal number of storage hours has a mean value of 6.26, which is over the limit of the technological possibilities of the Li-ion family. This means that to use massive Li-ion storage in the optimized power system, further technological enhancements should be expected. The scenario with high reduction costs for storage would require an even higher increase in capacity to reach the optimal point. For the base case, the average depth of discharge is approximately 20% on a daily cycle basis, \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{2}{c}{**Mean Value**} & \multicolumn{2}{c}{\(\sigma\) (\% of Mean Value)} \\ \cline{2-5}  & **P (GW)** & **CapF (\%)** & **P** & **CapF** \\ \hline Comb. cycle & 12.87 & 63.29 & 0.70 & 1.77 \\ \hline Open cycle & 8.87 & 2.55 & 24.13 & 15.52 \\ \hline Wind & 66.91 & 21.97 & 28.65 & 5.87 \\ \hline PVs & 90.74 & 17.75 & 18.76 & 3.49 \\ \hline Storage (batteries) & 18.72 & - & 66.60 & - \\ \hline Storage (hours) & 6.07 & - & 17.72 & - \\ \hline Storage capacity (GWh) & 113.51 & - & 98.04 & - \\ \hline Spillage wind + PV (\%) & 9.38 & & 56.61 & \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Sensitivity analysis with the considered uncertainty. which means that the technical life of the battery is longer than the chosen economic lifetime, according to [6]. * The large uncertainty in the storage prices of 2030 does not produce large changes in the installed power or capacity factor of the combined cycle technology.