4.6. Economic analysis
An economic analysis based on the investment costs was car- ried out in order to investigate the most cost effective solution among the alternatives presented in this study especially between system equipped with fixed and sun tracker array and AC and DC pumptechnology.Thisanalysiswasperformedinordertocombine both economic aspects and performances in terms of water pumped according to the crop water requirements previously discussed. The prices of the PV modules are highly variable depending on the market and the manufacturer company. Nevertheless it repre- sents one of the major costs for a photovoltaic pumping system, accounting for more than the 40% of the overall costs. Using the sun tracking system permits a smaller area of PV modules which resultedin a deductedcapitalcost of PV cells and powercondition- ing system. But at the same time the tracker can highly contribute on the overall cost of the system mainly due to its high accuracy technology. Moreover, DC pump are more expensive compared to AC pump but on the contrary the controller used as interface be- tween the PV modules and the DC electric engine is more afford- able then DC/AC inverter. Comparing the 1.8 kWp two-axis tracking system with the 2.4 kWp fixed solar array powering the
Fig. 9. Pumped water flow during an irrigation turn in June with tracking PV array.
Fig. 10. Monthly water demand and supply estimated through dynamic simulations.
Fig. 11. Hourly dynamic simulations of water demand and water supply from AC pump powered by 2.1 kWp solar array.
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DC pumping system, although the tracking system has a power peak about 30% less than the fixed system, the former offers better performances than the latter due to the daily higher exploitability of solar energy. The AC pump driven by the fixed 2.1kWp PV array fulfilled the water requirements as the DC pump powered by the fixed 2.4kWp solar generator saving 0.3 kWp of solar cells. Even the AC pumping system powered by the 1.6 kWp solar generator mounted on the tracking system fulfilled the water requirements avoiding the installation of 0.8 kWp of solar cells compared to the DC 2.4 kWp fixed system and 0.5 kWp of PV modules compared to the AC 2.1 kWp fixed system. The PVWPS systems compared in terms of initial investment costs (IICs) in this economic analysis were the same systems com- pared in terms of water pumped in the previous section of this pa- per. The possibility to install tracking system instead of fixed system and DC instead of AC pump was estimated. All the prices used in the investigation, summarized in Table 4, were taken from a business-to-business online platform and refer to the Chinese market [16]. The results of the economic analysis are presented in Fig. 12, outlining the total initial capital cost together with the costs contributions. On the basis of the economic investigation carried out, the most cost effective solution was the AC 2.1 kWp fixed system with an overall initial capital cost of 2450 $ followed by the DC 2.4 kWp system marked out by an initial capital cost of 2950 $. The reason that the DC fixed system has a higher investment compared with the corresponding AC fixed system was mainly due to the cost dif- ference of DC and AC pump, 640$ against 150 $, rather than the cost difference of PV modules, 1440 $ against 1260 $. Despite of the reduction in cost due to the installation of DC/DC converter on behalf of the installation of DC/AC inverter, the AC fixed system was the most cost-effective solution. Comparing the fixed system with the corresponding systems equipped with the sun tracker de- vice, the formers presented lower investment cost than the latter especially because of the high investment cost due to the tracking system. The tracked DC 1.8 kWp system had an investment cost of 4350 $ of which 1620 $ were due to the sun tracking device
accounting for 37% of the overall cost. The cost reduction due to the lower investment in PV modules and power conditioning system using sun tracking technology had no positive effects. A possible application of PVWPS equipped with solar tracker could be economically supported in the case the system is used for multipurpose applications during the months where the irrigation is not needed.