ارزیابی اقتصادی سیستم پمپاژ آب با تغذیه برق فتوولتاییک (PV)در مزارع تحت آبیاری قطره‌ای

In Iran, the use of pressurized irrigation systems is increasing. Supplying energy to pump the water is one of the pressurized irrigation system’s requirements. Because of non-renewal, extraction costs and environmental hazards of fossil fuels, the solar energy utilization has become inevitable. The solar energy is one of the most important and cleanest forms of new energies, which can return the initial cost of solar system to the customer in long term. One of the reasons for Iran's failure to use the large part of its cultivated land is the long distance from the national electricity network and high electricity costs. In this study, the solar and electric pumps were compared economically to pump water in nine gardens under cultivation of three crops of pistachio, almond, and walnut, using drip irrigation networks. The gardens are located in Tehran and Hamedan Province.
The drip irrigation system is applied to these gardens. The gardens were classified into three groups: small (less than 5 hectares), medium (5 to 60 hectares) and large (more than 60 hectares). First, pumping station was designed and then, investment costs were estimated for all the studied gardens. The Lorentz solar pump special design software was used in order to design and simulate the photovoltaic system. It is assumed that electricity would supply for these areas in two ways including: 1) installation of photovoltaic systems in remote areas without national electricity grid consumption 2) electricity transmission through the construction of transmission lines and trans-installation. These two conditions were compared by the present value method at two interest rates of 5 and 10%. In order to convert the future costs to present value, real interest rate index is required. Considering the difference between the service life of equipment for electric pumps and solar pumps, as well as solar panels, the lifetime of the projects was considered unequal in calculating the current value.
The results showed that the utilization of photovoltaic pumping near the electricity distribution network is economic only for 60-hectare pistachio garden with an interest rate of 10%. In the medium-size walnut garden , with the same interest rate, despite the slight difference in investment cost, it does not differ from electric pumping. In the case of distance from the power distribution network, photovoltaic pumping will be more economical by decreasing the size of the farm (less capacity and pressure) and increasing the distance from the power distribution network. However, other factors such as temperature, sunshine, radiation intensity and solar angles may also affect the photovoltaic pumping during different seasons. The results also showed that the photovoltaic pumping of irrigation system is economic for small and medium pistachio and walnut gardens, 0.5 km far from the electric distribution network, by the interest rate of 5 and 10%. By increasing the distance from the electricity distribution network, only the costs of power lines transferring to electric pumping increase and the use of photovoltaic pumping is more justifiable. Changes in the current value of costs for both pumping methods at a rate of 10% relative to 5% interest rate will lead to cost reductions. In remote areas, which it is difficult to access the electricity distribution and transmission networks, the use of photovoltaic pumping is reasonable and economic. Therefore, in this study, there is a specific distance from the electric distribution network for each area.