Yet another immersun thread

balbecdaze · May 13, 2013

In my house I've got a 4kW PV array and a solar thermal array. The solar thermal array is connected to a 120L vented tank before the mixer taps before the combi boiler.

I've noticed that there's an electrical immersion element included in the tank (3kW). It strikes me that to pop in an Immersun or similar connected to the electrical element in the tank would be an efficient use of generated energy on site.

I'm an MCS PV installer so the costs are basically the cost of the proportional controller but I don't really understand plumbing and heating and the like. If anyone can see any reason why I shouldn't go ahead, I'd really love to know ...

If you've given this a quick read and think that it's a sensible thing to do I'd appreciate being told that too, thanks.

I can provide loads more information about the PV but I'm still awaiting a handover pack for the solar thermal stuff (installed over a month ago!) so I'm a bit sketchy on its details - I could provide photos if required.

p.s. I've also got a Rasberry Pi which I currently use for watching TV, if a proportional controller is a good idea, and if my memory serves me well, there's a thread about this which I can't find, can anyone point me in the right direction?

Worcester · May 13, 2013

Raspberry pi - go to openergymonitor.org - the Pi runs as both emonbase and emoncms ..... - I've got 5 of them here from an XMBC server to one running all out power and weather monitoring

Here's a Pi specific thread Solar PV power diversion with emonTx, emonGLCD and temperature measurement | OpenEnergyMonitor you'll need to be good with a soldering iron (circuit boards, not plumibing

) and happy to do a bit of C and Python programming.

There is absolutely no reason why an Immersun wouldn't work with your setup, the only challenge is that they'll both be working at the same time. 120l is quite a small DHW tank..... hope there's only a couple of you living there.

Gavin A · May 13, 2013

I'd have to go with no, no point. You've only got a 120l cylinder, which is tiny for a solar water heating system, and both will be generating at largely the same time.

mostly what you'll end up doing is having the solar water heating system stagnating for much longer than it should do, which isn't a good thing for the long term life of your solar water heating system.

You will get some marginal benefit from doing it, but even at trade prices it's going to take a hell of a long time to pay back because of the overlap with the solar water heating system's production, and it'd be pretty dubious on environmental grounds as most of the leccy used could have been exported and the heat supplied by the solar water heating system instead, instead of which the solar water heating system will be left sat there stagnating with all that potential energy wasted.

balbecdaze · May 13, 2013

Thanks for the opinions/advice. Makes sense. I hadn't realised that 120L was a bit small for a tank either.

Energy monitor / diversion sound a great little project!