Smart Integration of Solar Power Using LabVIEW

Abstract:

Today, with rising fuel costs and growing worldwide demand for electricity, utilizing renewable energy sources such as solar power becomes a necessity rather than luxury.This paper aims at developing realtime, intelligent D.C source connected solar panel in order to provide power to loads from solar panel at day time and switch power to constant D.C source as soon as solar power falls below pre-defined limit. This switching of power was controlled through LabVIEW using Data Acquisition Card and power relay. The system can deployed for guarantee access to power at home or industry, even if solar energy fails or insufficient.

Description: Most of the electrical equipments used in buildings operate with electrical energy in dc form (computers, mobile phones, and, lighting, etc.) a direct supply with dc will eliminate ac/dc converter and increase the overall efficiency. This paper aims at monitoring the functioning of 36V solar panel using LabVIEW and Smart Switching between Solar Power and Constant D.C Source. Solar panel of rating 70 watts and 36 volt and a controllable supply of D.C source is used .The load designed for switching and monitoring consists of two D.C bulbs (12V each) in series combination. Various protocols have been used for communication among the dc source, load and solar panel like a digital oscilloscope, fluke multimeter, a switching circuitry consisting of an op-amp, an optocoupler and a relay and a data acquisition card. The real time monitoring of Voltage and Current of Solar Power in On-load and off- load condition was done in LabVIEW using oscilloscope. For smart switching between solar panel and constant DC Source, the process involves the use of Data Acquisition Card which will take command from LabVIEW, and gives output to actuate the switching circuitry. The switching circuitry consisted of Operational Amplifier LM324, Optocoupler 4N35 and OEN57 Relay mounted on Printed Circuit Board. The Solar Panel voltage was acquired by oscilloscope which was found to be of the order 36V (Off-load) and between 22- 28V (On-load) depending upon the intensity of sunlight. The data acquired with the help of oscilloscope was simultaneously interfaced with LabVIEW. The voltage signal acquired was connected to comparator while same signal of Voltage was connected to Mark and Limit testing Block. The purpose of mark and testing block was to limit On-load voltage between 22V and 26V. The outputs of mark and testing block and comparator block was sent to OR Gate Block. The output of OR Gate was fed to DAQ Assistant block present in LabVIEW. According to the conditions in DAQ block, relay trips and load switches to solar power and constant D.C source accordingly. In our case, switching takes place at 4:00 pm from solar panel to constant D.C source and at 10:00 am from constant D.C source to solar panel during normal weather conditions. At the end of the day the load successfully shifted from solar panel to constant D.C source and vice versa. The graphs obtained from monitoring helped in designing the switching logic for the project.