So yesterday morning I read the blog post that the solar water heating field trial report has been released. Yes, a little later than advertised, but like all such technical documents it is better late and right than on time and wrong.
So what happens behind the scenes to make these studies ‘right’, and how could they be ‘wrong’ anyway? Surely the hard facts are the hard facts?
Well yes, but sometimes the hard facts you are looking for are not the hard facts you find. In the case of the solar thermal field trial, the team started the trial by looking at how solar water heating panels work.
Sounds obvious doesn’t it? However an answer (amongst others) that seems to be coming out of the study is…the panels, well they’re fine, it’s the hot water cylinders you have to worry about.
If you haven’t read the report already, I encourage you to have a look. Now fortunately I have had a sneak look at the report. Well less sneak and more formal peer review, but still it was an early look.
And it even then one of its findings seemed to confirm one I had gathered from checking the meters on our own solar thermal system. The first day the meters were installed, we harvested a whole 21kWhrs! Fantastic! But then looking at the hot water we used, we only used four! Where did the rest go?
Even looking at the longer-term readings I’ve been recording since July on my iphone app, I seem to harvesting an average of 10kWhrs a day and only using four. Now this can lead you to two conclusions. The first, perhaps the engineer’s version, might be that solar water heating is only 40% efficient…
But no! The second conclusion is that on those days, 100% of the hot water we needed was produced for free, therefore actually as far as us householders were concerned, the efficiency was infinite as we got 4kWhrs out and put nothing in.
So as I say – time is needed to work out what the right conclusions are. And what have I done in light of the results of the trial?
Well, for the last week I have been ‘super’ insulating our thermal store cupboard (the rest of my family call this the airing cupboard). I’ve even fitted doors with draft excluders so that the heat escaping from all those pipes going into and out of the tank that are tricky to lag just heats up the cupboard rather than the rest of the house.
Hopefully as we head into the foggy grey days of Autumn, and the daily solar harvests slip down to single figures, any heat we do harvest will still now be in the store by the time we want a warm shower. Maybe then even the engineers will be happy!