## 4 Application--Results
### Economic Assessment  
To answer the question whether large-scale integration of Wind--PV with the parallel development of hydro-pumped storage is feasible, the levelized cost of energy is used. The levelized cost of energy is calculated as follows:  
\[\text{LCOE}=\frac{\text{CAPEX-CRF}+\text{OPEX}}{E},\;\text{CRF}=\frac{\text{ DR}}{1-\left(1+\text{DR}\right)^{-N}} \tag{8}\]  
where, CAPEX is the capital expenditure, CRF the annuity factor, \(E\) the annual energy produced, OPEX the operation and maintenance (O&M) expenditures, DR the discount rate and \(N\) the lifetime of the investment. The levelized cost of energy is a valuable cost indicator because of its relative simplicity which allows the comparison of different technologies. At the same time, it is a useful tool for benchmarking the cost of different technology units, considering the lifetime of the units. The levelized cost of energy has been calculated for the current power supply system and for the examined scenarios for 2030 and 2050, based on the simulation results and the data collected [26; 27; 28; 29; 46; 47; 48; 49; 50; 51; 52; 53; 54; 55; 56; 57; 58; 59; 60; 61; 62; 63; 64; 65]. Studies conducted and demonstrating projections for costs data, such as CAPEX and OPEX, have been considered for the calculation of the LCOE. The final values used constitute an average value of the costs identified in other publications. A discount rate DR equal to 7% is considered in all cases to secure that estimations of LCOE are modest and relative risks are considered. After a long period of economic uncertainty in Greece due to the economic crisis, in the last 3 years, Greek government bonds had constantly relatively low rates, less than 3%. Tables 4-6 show the details about LCOE components, data, assumptions and results for the years 2019, 2030 and 2050, respectively. All the prices presented in the three tables are not harmonized. In some cases, different sources are available and mean values are used. The extracted value of LCOE evaluates not only the relative CAPEX and OPEX for each type of units but also their utilization, as it is introduced by the energy output in the denominator. Then, the results of LCOE are useful for the specific cases studies in Greece, under the assumptions of the current methodological approach and conclusions cannot be universalized. Additionally, the various parameters of cost in case of hydro and hydro-pumped storage are site dependent, and then, results are not useful for other case studies. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & & & **2019** & & & \\ \hline
**Technology** & **Lignite** & **Natural Gas** & **PV** & **Wind** & **Hydro** & **CHP** & **Biomass** \\ \hline Nominal power \(\rm{P_{nom}}\) (MW) & 3904 [27] & 4900 [27] & 2639 [27] & 3283 [27] & 3411 [27] & 105 [27] & 86.89 [27] \\ \hline Produced Energy (GWh) & 10,418 & 16,228 & 3249 & 6565 & 4052 & 186 & 362 \\ \hline CAPEX (\(\rm{\xi/kW}\)) & 1850 [46; 47; 48] & 700 [46; 47] & 1100 [48; 49; 50] & 1300 & 1800 & 1800 & \\  & & & & [47; 49; 50] & [49; 53] & 1100 [53] &  
In Figure 7, the size of the bubbles corresponds to the amount of energy generated by each type of technology, whereas on the horizontal axis the LCOE of each unit type is presented, and on the vertical axis, the share of the cost of the different types of technologies in the total cost of the system is depicted. In the current power supply system, the participation of lignite and natural gas units is crucial in order to meet electricity demand. The LCOE of the system is estimated to 107.59 \(\upepsilon\)/MWh, and the largest share of the cost is due to the conventional units. Although CHP and biomass units are characterized by high levelized costs due to their limited nominal capacity, they do not participate significantly to the final composition of the cost of the system. The weighted average LCOE of the power system in Greece by 2030, according to the calculations, is decreased to 79 \(\upepsilon\)/MWh.