We all know that solar panels can save us a bundle of money. But it turns out that tracking the true energy output of a solar array isn't as easy as one might think. This was a lesson David Berkeley, a tinkerer/inventor with a soft spot for renewable energy, discovered after finally installing solar panels on his home in South West England just a few months ago.
"There are lots of commercial power meter readers around, and many homemade ones too," writes Berkeley on his website. "But they all seem to simply count the 1Wh optical pulses. This does give you an accurate measure of instantaneous power usage/generation, but does not give accumulated totals."Tired of never having an accurate picture of how much energy his panels were actually producing, Berkeley decided to hack together a more accurate alternative, reports HackADay. "I decided to use an Arduino Duemilanove to decode the data because they are easy to use," writes Berkeley. "I replaced the photodiode with a TSL216R optical sensor, which provides amplification and filtering of visible light, removing the need for a separate amplifier. This 3 pin device can be connected to +5V, 0V and one of the interrupt pins on the Arduino. No other hardware is required."
Using a simple Python program running on a Linux server, Berkeley is able to log data from the Arduino in 60-second intervals. "I can then generate graphs showing the usage over time," he writes. "This is done by another Python script, interfacing to gnuplot which is used to generate the actual graphs. This runs on a web server that I can access over an ssh tunnel from my phone, so I can view the graphs when away from home."
Berkeley also reports that since installing the solar panel's his family's electricity consumption has dropped by one-third and they now generate four times the amount that they import. Find full details of the project here.