TITLE:
Modeling and Optimization of Solar Photovoltaic Pumping in Chad: The Case of Maralfalfa (Pennisetum purpureum) Irrigation across Climatic Zones
AUTHORS:
Yacoub Nassian Nimir, Moussa Ahmat, Haroun Abba Laban, Djongyang Noël, Mackaye Hassan Taïsso
KEYWORDS:
Solar Photovoltaic Pumping, Irrigation, Forage Crops, Maralfalfa, Modeling, Water Requirements, Different Climatic Zones of Chad
JOURNAL NAME:
Engineering,
Vol.18 No.10,
October
30,
2026
ABSTRACT: Chad is located between 7˚ and 24˚ North latitude and 13˚ and 24˚ longitude. It comprises three main climatic zones: the Saharan zone in the north (precipitation: 50 - 200 mm), the Sahelian zone in the center (precipitation: 300 - 800 mm), and the Sudanian zone in the south (precipitation: 900 - 1200 mm). Actual data for the study area, covering a 32-year period from January 1, 1991, to December 31, 2022, were collected from Chad’s National Meteorological Agency facilities and processed using CROPWAT software. Although the software did not initially include the forage crop Maralfalfa (Pennisetum purpureum), it was subsequently configured to recognize and account for this plant. The research aims to replace the solar radiation component (G) of the Penman-Monteith model (FAO 1975) with radiation estimates derived from Hussein’s solar radiation estimation model (Gh) in order to evaluate the influence of relative humidity and temperature on system efficiency. The proposed methodology relies on using this evapotranspiration model within CROPWAT. The software calculates crop water requirements and irrigation volumes based on FAO irrigation and drainage manuals and schedules tailored to various cultivation practices; it also enables the assessment of the impact of water deficit on crops and the efficiency of different irrigation methods. The study focuses on a one-hectare plot cultivated with 30% potatoes and tomatoes and 70% Maralfalfa. The selected planting date is January 1, 2022, and the harvest date is December 31, 2022, spanning a 365-day period. The crop coefficient (Kc) is 0.4 during the initial stage, which lasts 30 days. The critical soil moisture threshold is set at 0.65, with a yield factor of 0.5. The growth phase lasts 60 days, with a yield response factor of 0.75. The mid-season period extends over 180 days with a yield response factor of 1.20, while the late-season period lasts 95 days, with a crop coefficient of 0.75 and a yield response factor of 0.10. The initial root depth is 0.25 meters, the maximum depth is 1.50 meters, and the plant reaches a height of 3 meters across Chad’s various climatic zones. Our simulations reveal that each climatic zone requires a tailored solution. This solar photovoltaic pumping system, based on the specific PS2-4000 C-SJ8-15 pump model, demonstrates its ability to adapt effectively to Chad’s climatic conditions. By analyzing the solar array—comprising SL250CE-36P polycrystalline modules—and adjusting storage tank sizes for each zone, the system aims to supply 7.5 mm of water per day to a field planted with 70% Maralfalfa and 30% tomatoes and potatoes. Thus, in the Saharan zone, the pump meets high water demands thanks to a higher power output of 4.5 kW and a high-performance system; meanwhile, in the Sahelian and Sudanian zones, technical choices—specifically regarding the number of panels and storage tank volume—make it possible to reduce energy requirements while maintaining flow rates. This study demonstrates that a properly sized pump can provide a solution that is sustainable, cost-effective, and resilient to climate variability. Overall, this work presents a decision-support tool for solar photovoltaic irrigation, specifically for cultivating Maralfalfa fodder across Chad’s various climatic zones.