Results and Discussion for the System of Kythnos

The analyses of the existing PV-diesel autonomous power system and the envisaged PV-hydrogen autonomous power system have been performed using the HOMER tool. The results of the existing system simulation, hydrogen-based system optimisation and the comparison between these systems are presented in the following sections. 

More specifically for photovoltaics a capital cost of 6,750 /kW was used in this analysis, resulting in a total capital cost 59,400 for a PV array with a total installed capacity of 8.8 kW. In addition the O M for photovoltaic arrays is considered practically zero. 

The capital costs for diesel generators range between 200 and 500 /kW, depending on the size of the generator. Since a relatively small generator is used in this system, a cost of 500 /kW was used in the analysis. If we take into account also the cost of a 3 m3 diesel tank, which accounts for 3300 , we come up with a total cost of 7300 for the diesel generating set. 

Batteries represent the most significant cost factor in small-scale autonomous power systems like the one of Kythnos Island. In the above-described power system a battery bank of units having a capacity of 1000 Ah each is used. The total capacity of batteries is 420 kWh, resulting in a total capital cost of 42,000 (Zoulias and Lymberopoulos, 2007). The estimated lifetime of the battery bank is 5 years. 

Finally, an AC-DC power converter is also installed in the system, having a cost of ca. 670 /kW (Khan and Iqbal, 2005). The total installed capacity of the converter is 10 kW, therefore the total capital cost of the converter accounts for 6700 . 

---