**8. Conclusions**

248 Renewable Energy – Trends and Applications

0 1000 2000 3000 4000 5000 6000 7000 8000

0 1000 2000 3000 4000 5000 6000 7000 8000

0 1000 2000 3000 4000 5000 6000 7000 8000

Fig. 13. Hourly generated power of PV arrays and hourly expected amount of stored energy

*NWG NPV NBat Pinv (kW) θPV Hhub(m)*  - 96 13 44.3 56.74 11

*ELF LOEE (kWh/yr) EENS LOLE(h/yr)*  0.0022 504.79 0.0024 49.59

With compare of these scenarios together, it could be seen, the number of batteries in windbattery system is more than the hybrid system and PV-battery system. That's reasonable because in this region (and almost all of regions) fluctuations of wind are more than the fluctuations in radiation, so, when the wind turbine is used, we needed to add more storage system to be sure that the load would be met in all steps. Also, in this region, the peak load is nearer to the peak of PV generation compared with the peak of wind generation. On the

Time (hour)

10

0

in the battery during a year.

Table 6. Optimal combination in PV-battery system

Table 7. Reliability indices of PV-battery system

200

400

Battery energy (kWh)

600

20

30

Load power (kW)

PV power generation (kW)

40

50

In this paper, a hybrid generation system is designed for a 20-year period of operation for the North west of Iran. The major components are PV arrays and wind turbines. The major advantage of these components is that when used together, the reliability of the system is enhanced. Additionally, the size of storage systems can be reduced as there is less reliance on one method of power production. Often, when there is no sun, there is plenty of wind and vice versa.

The number of components is directly dependent on the load pattern. The region has a cold climate thus electricity demand in summer is not significantly more than the demand in winter. This is an advantage because the needed battery will decrease and the design system will be more economical.

In this study, the batteries are employed as the energy storage system. Optimal combination of components is achieved by particle swarm optimization. The optimization problem is subject to economical and technical constraints. Best configuration with considered reliability constraint is achieved and the system is simulated.

In the future work of this study, uncertainty factors such as generator failures and renewable power availability will also be taken into account in calculating system reliability indexes.
