Monday, September 9, 2013

Solar performance

While researching our solar installation I came across a website, PVOutput which records the solar output of thousands of (mostly grid-tied) installations all across the world. Basically, owners of solar PV installations configure their systems to send generation data to PVOutput, and there it's logged, graphed and analysed a thousand different ways.

Being the nerd that I am, I knew that I'd have to hook our system up once I got it operational, if only so that I can keep tabs on it remotely when I'm not there. But the first problem is, how to get the place on the Internet?

As it turns out, we have fantastic 3G mobile coverage with Telstra, and I've been using one of their 4G USB dongles on site for some time with my laptop. But we're on a power budget, so how to maintain an Internet connection without running a full size, power hungry PC?

I found the answer in one of these.  They're an Intel-compatible PC (running a 1.6GHz Atom processor) but only use .. get this .. 5W of power idle, and 8W flat out! And they're tiny, about the size (and as it turns out, the contents) of my wallet.

On it I'm running a Linux operating system (CentOS 6.4 to be exact) and I'm using a little application called SMA-Bluetooth, which connects to our Sunny Boy inverter using .. you guessed it, Bluetooth, reads off the power generation data and uploads it to PVOutput.

The result is pretty amazing :) Click the pictures for the live graphs - you can even see what power is being generated every 15 minutes (during the daytime, of course ;) ). We live in the future!

Being an off-grid installation and we're not yet using much (if any) power, the system has the batteries fully charged and so we're basically only generating around 100W of power during the day, which serves to power the inverters (about 40W) and trickle charge the batteries. The spike in the morning serves to replenish what the inverters (and my little 5W PC!) has used overnight.

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