Sunday, 1 April 2012

Difficult decisions... Counting the number of angels that can dance on a pinhead

February 19th. One of those really cold mornings after a bitter snowy day that was followed by a starry night, and weather that seems to have come straight from the Arctic. Minus eleven when I got up and looked at the data logger in my room that's connected to the outside thermometer. It was under 14 on the thermometer on the window sill, strategically placed in the coldest spot in the house.
The panels were already making 0.7 kW just after 7 am, highly efficient supercooled by the ambient temperature and then some by radiating beyond the stratosphere with nothing coming back.
And I wanted to make a cup of tea.
Usually I turn the IH stove onto a high middle setting to boil the kettle. There are ten bars, and I'll put it to number seven. I think gas stoves are most efficient at a middle setting. They may boil the water quicker if you turn it right up, but they will use more energy to do so. I assume the same for IH heaters, although they may be equally efficient at any level.
Anyway, I was thinking about all those lovely kilowatt hours, and wanting to sell as many of them as possible. Putting the kettle on at any level was going to exceed the 0.7 kW we were generating, and mean buying electricity. Given this, the logical thing to do was to turn the IH stove up as high as possible, and while it was on, put the shutters up, which use a couple of hundred Watts, to keep the time that we were buying electricity short, and we were back to selling electricity as quickly as possible.
This must have saved at least some fraction of a yen.
These are the kinds of calculations that we are forced into by the economics of solar power. Surely I have better things to do. The best thing, of course, would have been to drink water rather than tea.
I did notice, after switching the kettle off and setting off proudly with my tea, that we were still using 400 Watts, which seems strange when everyone's still asleep and nothing's on. I realised it was the pump for the underfloor heating, which I'd set to come on from 7 to 7:30 as well as an hour before 6. This was because I'd left it on too long the previous morning and it had used up all the hot water, so it didn't come on in the evening, as I'm mean and didn't let it start working till cheap electricity rates kicked in at 11pm.
With the sun already beating down, we aren't going to need heating until tonight, so it's a good thing I noticed it. That will actually have saved a few yen.