A measurement system with dual Modbus connections linked through MQTT/TLS to a remote server: internal details and first operation results

Abstract

This work presents a renewable energy measurement system with two Modbus protocol connections (RTU/Serial to internal modules, TCP to external units) and achieves a TLS-encrypted link between the datalogger module and a centralized remote dashboard application. Recent installation and commissioning of high quality instruments allow for reliable information to be collected, and the system offers remote monitoring and data persistence. The logger acquires wind data using Thies sensors installed on the wind turbine tower, and current and voltage from both the wind turbine and an array of photovoltaic panels. Energy is stored in a battery bank and is used to supply electric power to a greenhouse. In this nearby building, an additional module to measure temperature and humidity of the plant-growing environment was developed and programmed. The module communicates via RS485 using Modbus RTU with the main datalogger, which also uses an internal network connection through Modbus TCP to a Raspberry Pi4B board. The Pi board converts the readings to MQTT/TLS, an added security feature before sending data to the remote server which runs the dashboard application. A continuous performance analysis of the renewable energy unit is possible due to the availability and persistence of real-time data on the server and also on the CF card of the datalogger.