Experimental Results of Computer Monitoring of PV-based Energy System

Abstract

Renewable energy emerges as a cleaner and sustainable alternative for generating electricity. This chapter proposes development of an experimental monitor and control scheme for stand-alone photovoltaic (PV) systems. The proposed system comprises a set of PV panels, a number of storage batteries, a charge controller, DC/AC inverter to feed electrical load, and a backup generator. A monitoring and control unit was designed and implemented to operate the system using a specially developed computer program based on LabVIEW software. The main task of the proposed scheme is to manage and protect the batteries from over discharging that may destroy batteries. To do so, the developed control scheme disconnects the load from PV and battery system, using switching control, when state of charge (SOC) of batteries falls to 35 % or less, and switching on a petrol engine/AC generator unit. The control panel that employs a USB data acquisition card (DAQ) connected to the PC was built, installed, operated, and calibrated with the system. The cost of generated electricity was not taken into consideration as the system is built on experimental scale. Results of the study indicate a significant decrease in the battery useful capacity with higher discharged current (load requirements). It is also possible to use the I-V curves to identify the batteries SOC, particularly at low SOCs to protect the batteries when SOCs are lower than 35 %. A significant output is the possibility for continuous, through monitoring of the system performance setting an accurate archive of generated power, battery performance, effect of electrical load, and control of the backup generator to ensure the continuity of electrical load supply.