Design and analysis for a feasibility study of a floating solar PV power system for Metolong Dam

Abstract

Over the past years, an increasing capacity of floating solar photovoltaic (FSPV) technology utilizing water bodies to install solar power has been implemented, showing an alternative for countries where land use is constrained, land is not easily accessible, or land leasing is expensive. In addition to reducing land use competition, FSPV is promoted as a more efficient solar technology, bringing with it additional benefits such as reduced water evaporation and decreased algae growth. Based on previous field studies and industry insights, this study aims to analyse whether an FSPV project can be a feasible and cost-effective option for electricity generation and usage at Metolong Dam and water treatment works (WTW) located in Maseru district, Lesotho. Furthermore, PV module temperature analysis is another critical area, governing the efficiency performance of solar cells. In this study, the initial approach entailed the modelling of the Metolong reservoir water temperature (using Microsoft Excel) due to insufficient water temperature data at a selected location (since simulation software does not have features for FSPV). Then water temperature was used to investigate the photovoltaic (PV) module temperature on water bodies. The optimal sizing and performance prediction of a proposed power plant was modelled using a set of mathematical equations in a spreadsheet application (Microsoft Excel) and PVSyst software. Both models were compared to analyse the difference in annual electricity generation. Then, an economic analysis was performed to showcase the Levelized Cost of Electricity (LCOE) and Net Present Value (NPV). Finally, an evaporation model was proposed with the objective to quantify the potential savings an FSPV could provide using the calculations adapted from the Penman-Monteith model. The results indicated that this FSPV power plant would significantly contribute to the reduction of carbon dioxide (CO2) emissions. The recommended FSPV, with total installed capacity of 7.8 MWp, would consist of 3 platforms with an installed power of 2.6 MWp each. The study reveals that the proposed FSPV energy generation system is about 3.4% higher than ground-mounted PV (GMPV) generation system predicted by the PVSyst software due to the cooling effect provided by water just below the panels. From the simulation results, the value of performance ratio (PR) comes out as 90%, and the capacity utilization factor (CUF) value is 15.21% with a total effective energy generation at the output of the array of 17,345 MWh per year. The system could meet up to 70% of load demand during a typical day in winter months at the selected facilities. The FSPV system could cost US$ 10 Million with a payback period of 13 years, where the largest contributors to this cost are related to the floating structures and anchoring system of this plant. The proposed FSPV plant will substantially reduce the cost of energy as the plant cost is expected to be considerably reduced based on the low LCOE of 36.4 $/MWh. The economic feasibility of a FSPV system on a Metolong reservoir was thus established, and may be considered an efficient use option for electricity generation in Lesotho. Additionally, the shading provided by the FSPV system can save up to 84,136 m3 of water annually. The annual reduction of greenhouse gas (GHG) emissions was analyzed and found to be 17,329 tCO2 per year. Future studies should include more in-depth research into factors such as the impact of substation upgrade costs, variable interest rates, economies and environmental impacts