Solar panel update

After a few false starts and complications (nothing is ever simple with this house…) the panel has now been running for a few days.

Nothing is quite perfect – the panel is in shade in the afternoon because of a tree, and doesn’t get the earliest sun anyway. The last few days have been very mixed in terms of weather. The end of September is clearly not the best time to get sun.

And yet every day so far, the panel has got solar gain. Not much, admittedly: four and five degrees a day – but that’s still taking a bit of gas out of the equation. Hopefully we’ll get more in strong sun.

Before I went away from the weekend, I toggled something in the controller that now makes it display how many watts of heat it’s gaining, and keep a running total. During Saturday and Sunday, it thinks it got 19kWh of heat out of the sun. I think that’s roughly equivalent to 80p worth of gas.

I paid extra to have a top range controller I can use across my computer network. So I can have a program on my computer that tells me what the panel is doing – here’s it’s current readout:


On the right-hand side S1 (sensor 1) is the temperature at the panel (which is actually double the current air temperature outside). S2 is – as the diagram shows – at the bottom of the tank; S3 at the top. It’s at 62deg at the moment because after sunset, the gas comes on to get it to the right temp for showering in the morning. On the left side, the black spot represents a green LED that comes on when the pump is turning, and the pump triangle in the diagram also turns.

It does all this both on the program on my PC and on the digital read-out of the controller. If you’re the sort of person who checks what the temperature is several times a day, or who taps a barometer when passing, a little readout like this is grist to the mill. I find myself making detours to the airing cupboard to see how hot my water is now.

The reason it needs these temperature readings is that the controller turns the pump on whenever there’s an appreciable difference between the temperature at the panel and the temperature at the hot water tank.

Although the controller is pretty cool, there doesn’t seem to be a way of getting at the data without the fancy graphics. I was hoping there was going to be a platform independent doodad that just let me read the temperatures and keep a record, and make calculations separately. In my mind, I had Automator on the Mac keeping records at quarterly intervals, and creating a web page to say how much solar gain I was getting at any given point. Maybe it could even be linked in to Skype so that my solar panel could send a text message when it turns on…


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