Economic comparison between solar PV and diesel operated system for irrigation application in Lesotho
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Date
2023
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National University of Lesotho
Abstract
Access to electricity is improving in Lesotho although the use of energy for economic growth is still stagnant. Sustainable economic growth is essential for improving livelihoods; however, this is difficult to achieve in rural areas where agriculture is the main industry. Hence in this study, an innovative economic analysis of solar and diesel-operated pumping devices for irrigation application in Lesotho is put forth. The main objective of the study is to scrutinize the concepts related to the effective characteristics of irrigation pumps, their design, selection, installation, and possible diagnosis of their problems in order to assist farmers and stakeholders. Furthermore, the aim is to compare the economic costs of solar and diesel-pumping systems.
Several novel solar photovoltaic models and solutions have been proposed in an effort to circumvent some of the challenges. In addition, a recent intervention that serves as an example of the new study technique is discussed. A thorough technique for sizing and performance forecasting of photovoltaic (PV) solar pumps and a diesel generator is also given. The empirical data on the performance of the solar pump, the prescribed model of sizing, and the performance extrapolation approach made use of data on solar radiation and ambient temperature of the location. The empirical functions of the flow rate, as opposed to solar power, were similarly derived for different pipe size diameters of 63 mm, 75 mm, 90 mm, and 110 mm.
Additionally, depending on the pump, pipe diameter, and PV array size that resulted in the lowest pumping cost per unit of energy, the optimum solar pumping system was chosen. This method of designing solar pumping systems was advised because it produced significantly different and more accurate results than the frequently employed straightforward method, which ignored the fact that the total dynamic head (TDH) fluctuated as the solar irradiance deviated.
The simulation results drawn indicated that the best system configuration that resulted in the least unit cost of pumping is comprised of a 4 kW Lorentz PS2-4000-CS-F32-20-2 centrifugal solar surface pump, a 110 mm pipe size, and a 2110 watt PV array. As a stipulation, it is important to point out that solar photovoltaic (PV) seems to be a promising energy alternative to support irrigation development in Lesotho. In that matter, the unit cost of pumping for a solar PV-operated pump for irrigation application is 3.58 USD cents/ m³ while for a diesel generator it is 16.1 USD cents/ m³.
Based on the life cycle cost analysis (LCCA) of both systems, the annualized cost of solar PV at a 10% discount rate is $1263.00 and that of a diesel generator is $5517.00, with 35314 m³ of water pumped per annum. The cost of solar PV per watt, including installation at the initial stage is 0.42, $/watt, while for the diesel generator it is 0.41 $/watt. However, for a long run, solar PV is more cost effective as compared to diesel generator. The proposed system was also found to be not only cost-effective but similarly environmentally friendly, as it emits zero amounts of greenhouse gases (GHG). The amount of greenhouse gases to be emitted as per simulation when using a diesel generator for irrigation purposes is 32.3 tons of carbon dioxide (𝐶2) per year.