Inverted Charting

So I considered naming this week's post "Climb Up On My Roof Sunny Boy", but I'd probably get sued by Al Jolson's estate. Though, as we're now officially inverted here at chez Derbyshire, it did seem appropriate. What I wasn't expecting was the domestic strife that is a direct result. They don't tell you about that in the glossy brochures...

The inversion we've encountered is, of course, a direct result of the team of local guys who came and nailed solar panels all over our roof and installed a box the size of my huge Dell workstation in the garage to invert the volts from the panels into real electricity. I did ask the guy if it meant they come out upside down, but he didn't laugh. I suppose he's heard that too many times before. But why don't they just call it a "converter"?

At first it seemed like a great idea. The little red light on the generation meter was flashing like mad and I could envision the pound notes rolling in. Until the RCD earth leakage thingy tripped out. Regularly. Turns out that, along with the seven 1000W UPSs and who knows what else in the way of technological magic there is plugged into the house circuit, the additional leakage from the inverter was too much for the mandatory RCD.

However, after they came back and moved the inverter and my server cabinet to separate consumer units (it really should have been done like that from the start), we're up and running again. It's just a shame that the sun hasn't come out since. If we have a miserable summer this year, you can blame me.

And then I discovered the next problem with going photo-voltaically green. I suggested to my wife that she should use the tumble drier only when it was really hot and sunny so it used the free electricity, but on days like that she wants to put the wet laundry outside on the washing line. When it's raining, and there's no free electricity, she uses the tumble drier. And you can imagine the response when I suggested she stay in and do the ironing on nice warm days, then go shopping when it's snowing.

Still, it's nice to know that for part of the day all my computers are costing me nothing to run; and it even diverts any spare volts we generate to the immersion heater to reduce the amount of gas we use to provide hot water. With the current rate of climate change supposedly due to global warming, I should easily recoup my investment by 2050.

But having a new technology device available to play with is, of course, too much for a computer geek to ignore. Having discovered that the inverter exposes its generation log data over Bluetooth, it was inevitable that I'd need to find a way to add the data to my weather website. And I can justify all this effort by the fact that I don't need to spend a couple of hundred pounds buying a rather boring-looking remote monitor device to see what's going on.

So out came Visual Studio and, after a couple of days, I have an automated system for generating data and charts; and I can expose the data over my internal network and publish the charts on the web. If you're interested, you can see them here. And if, by some remote chance you have an SMA Sunny Boy inverter (or you're prepared to modify the code to suit your inverter) you can download the utility and the .NET source code form here .

What I need to discover now is if, on a typical English summer day, we're actually generating enough electricity to run the inverter and the computer that monitors it...

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