Well this has been the fortnight the house woke up from hibernation and it wasn't a gradual sleepy start either but a very definite throwing off the covers and flinging back the curtains approach to spring.
Two weeks ago, in my previous post, I was writing about how cool (in the temperature sense) the house was and how we were waiting for it to come up to temperature; then the weather changed. For all but one of the last fourteen days the solar panels have been generating more power than we've used and the average temperature inside the house has gone from 18 to 22-24 degrees (for the less scientific amongst you that's the difference between wearing a fleece in the evenings and grumbling to wearing a T-shirt).
The chart here is our record of how much energy we've been using each week (the brown bars) and how much energy the PV has been generating (green).
You can easily spot the time round the winter solstice because the PV produced the least energy then. The combination of short days and the sun being at its lowest height in the sky meant that the panels didn't receive enough direct sunlight to work much. You can also see the icy weather in early December and the cold and snow in February because the energy consumption goes up as we run the heating more. The fluctuations in the brown consumption bars are caused by the amount of sunshine and illustrate clearly what I've said before about the sunshine warming the rooms and reducing our need for backup heating. Then, of course, there is the green trendline that shows how as the days get longer and sunnier our energy production increases.
The sunshine has also made a difference to how we've been working with the house. As the days got warmer at the beginning of the month we were opening the porch door and blinds to let the sunlight into the house. In the past week, when the external temperatures here were around 20 degrees, we started closing or tilting the blinds to reflect the light away from the rooms as it was getting too hot inside. We're also now opening some of the roof windows at night to cool the top floor as 24 degrees is too warm to get to sleep. If we didn't have blinds on the south-facing windows the house would be getting too hot already and as it's working rather like a greenhouse we're improving our environment even further by getting more houseplants.
We still don't know what will happen to the consumption-production balance on grey days as the days get longer but, so far, the data from the eco frontier suggests that solar energy is beginning to look like a no-brainer even here in the grey West Midlands. This begs the question of why the UK government isn't doing more to encourage its adoption, though after the recent newspaper reports one wonders if perhaps the solar industry simply lacks the lobbying power of its energy competitors; a depressing thought.