A Low-Cost IoT-Based Irradiance Estimator for Photovoltaic Modules

Eustáchio, Pedro Henrique da Costa, Azevedo, Gustavo Medeiros de Souza, Barbosa, Eduardo José, Cavalcanti, Marcelo Cabral, Bradaschia, Fabricio, Neto, Rafael Cavalcanti, Fernandes, Tiago Alves, Castro, José Filho da Costa

ISES Solar World Congress 2025 · Fortaleza, Brazil · 2025-11-03
Published by International Solar Energy Society (ISES)
DOI: 10.18086/swc.2025.04.30

Abstract

This paper presents the development of a low-cost and low-complexity irradiance estimator for photovoltaic (PV) systems, combining a Lookup Table (LUT)-based approach with an Internet of Things (IoT) communication framework. The proposed system integrates hardware improvements, including a highresolution external ADC and an ESP32 microcontroller, to overcome previous limitations in measurement accuracy. A key innovation is the decentralization of data processing, executing the estimation algorithm via a Python process on a remote computer, enabling the use of larger LUTs and facilitating system maintenance. Simulation results demonstrated high accuracy with a Mean Absolute Percentage Error (MAPE) of 1.56% using an optimized LUT, while experimental validation yielded a MAPE of 2.42%. The system successfully implements MQTT protocol for real-time data transmission, establishing a foundation for remote PV monitoring. Analysis under partial shading confirmed the estimator's capability to identify predominant irradiance levels, while revealing limitations in transition regions due to the uniform-irradiance assumption of the underlying global nonlinear model (GNLM).

Keywords

Irradiance Estimation, Photovoltaic Systems, IoT, GNLM, Lookup Table

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