Solar Panel Monitoring

Introduction

2016 we got our 1kW solar panel system installed. It is an on-grid system, so excessive energy is send back into the public network. We started the process with the local energy supplier Meralco to get registered for “net-metering”. “Net-metering” means that we get paid for energy that we send back into the public network. But we stopped in the middle of the process, because it was tiring, complicated and the additional requirements (additional breaker, evtl. additional watt meter, updated electrical plan by a certified electrician) would have cost us a lot of money.

Without having net-metering  we are invoiced for every kWh that is send back to the net as if we have consumed it. The net meter counting our consumption is a modern digital style, he shows whether we are consuming energy from the net or if we are sending out energy.

Inside the red rectangle the net meter says either Receiving (energy supplier is receiving energy from us) or Delivered (we receive energy from the the energy supplier). But the counter goes up in both situations.

As we have only a small 1kW system and we are at home during the day we decided to just adjust our energy consumption so that we do not push back too much energy into the public network. But how to know if the solar system is producing more energy than we are consuming? The supplier of the micro inverters offers a monitoring system. But the cost is 10% of what we paid for the whole system. Too much! And on top it is a proprietary system, using power line communication but the protocol is not available (One of the things I hate in this world!). To monitor we are limited to use our web browser and get the data from the companies web server, where they store all the information they receive from our system.

So I started searching on the internet for an alternate solution to monitor our power consumption and production. The best site I found is:

OpenEnergyMonitor

©OpenEnergyMonitor.org

Everything I did on the monitor system side I could only do with the information, source codes and hardware explanations I found on their site. And when I got stuck, their forum is very helpful for research and to get answers.

I decided to build up my own system instead of buying a pre-built system from their shop.

The monitoring system can be split into 3 parts:

  1. An Arduino based measurement system
  2. The necessary sensors
  3. A Linux based web server
  4. An Android application to visualize the data

Luckily for 1) and 3) only one device is necessary. This is possible with the

Arduino Yun

©arduino.cc

This nice small and affordable piece of electronic has an 8bit Atmel AVR ATmega32U4 microcontroller to do real-time measurement and in addition a Linux system based on the Atheros AR9331. The Atheros runs a Linux distribution based on OpenWrt named OpenWrt-Yun. The board has built-in Ethernet and WiFi support and a SD card slot. Perfect for IoT solutions. Of course the web server has limited performance, but for my requirements it is sufficient. The built-in Ethernet and WiFi gives the connectivity needed and the SD card provides the storage to save the recorded data in a database.

The Android application was developed from scratch, but thanks to

stackoverflow

it was no problem to find the necessary libraries and answers to upcoming problems during the development.

For the sensors and the Arduino board I found

as a reliable and customer friendly company here in Manila!

A list of all parts used in this project can be found on the last post of this series.

All schematics and source code can be found on my Github repository spMonitor.

Head on to the next page which is all about The Hardware.

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