Desenvolvimento de um calculadora web para dimensionamento de sistemas fotovoltaicos off-grid aplicados ao bombeamento de água na cidade de Russas-CE pelo método do mês crítico

Abstract

The use of off-grid photovoltaic systems for water pumping has become a technically and economically viable alternative for agricultural properties located in regions with limited access to the conventional electricity grid. However, the correct sizing of these systems still represents a practical challenge, especially when the client only has basic information about the existing pumping system. In this context, this work aims to develop an automated webbased calculator for sizing off-grid photovoltaic systems applied to water pumping on agricultural properties in the municipality of Russas-CE, based on the critical month method, using information easily obtainable by the client and official solarimetric data from the city of Russas-CE. The proposed methodology is based on the daily energy balance, considering the nominal power of the pump motor, the reported operating time, and the local solar irradiance obtained from the SunData/CRESESB database. The method adopted is the critical month method, as it evaluates the sizing in the most unfavorable scenario of solar resources throughout the year, ensuring greater operational robustness of the system. The method also establishes an objective criterion for the inclusion of battery banks, adopting systems without electrical storage as the standard and considering batteries only when there is nighttime operation. To demonstrate the applicability of the methodology, a theoretical case study was conducted in the municipality of Russas–CE, concerning an agricultural property with an existing pumping system. The results obtained in the theoretical case study applied to the municipality of Russas–CE demonstrated the technical consistency of the methodology and the coherence of the estimated values with practices adopted in the market for isolated photovoltaic systems. However, it was observed that the adoption of conservative criteria, based on critical values of solar irradiance and high safety factors, can result in oversized systems, with a high number of photovoltaic modules and a large energy storage capacity, directly impacting the total cost of the project. Thus, it is concluded that, although the proposed methodology presents a high level of reliability, its application can be made more flexible according to the user's profile, through the use of less conservative parameters, such as average irradiance values, in order to promote a better balance between technical robustness and economic viability.