What excess PV energy diverter to DHW tank with battery storage system ..

[andyj007]

can anyone recommend a excess PV energy diverter to teh immersion with a solis  hybrid inverter and pylontech batteries  pls.. ..

 

thanks

 

Andy

 

[JamesPa]

Is there any point given that you already have energy storage, or are you looking for a cheap way to store more energy?

 

In terms of the actual question my first instinct would be that, unless your inverter specifically supports this function, it might be tricky. 

 

Solar diverters basically work by measuring the exported electricity using a current clamp and turning up the wick on the immersion to make that equal to zero.  Your inverter is trying to do essentially the same, but instead diverting the excess to battery.  So the risk is that the two fight. 

 

Perhaps you can somehow get the diverter to measure the flow to the battery instead of the flow to the grid.  Then it would look, to the inverter, like a regular load and the inverter would only divert to battery once the dhw load is satisfied. Alternatively some solar diverters have a secondary output which triggers once the primary is satisfied.  Perhaps this could be used to signal to the inverter that it should now divert excess to battery.  

 

Just some initial thoughts given that nobody else has responded yet with a ready made answer.

[JamesPa]

Over on the ashp forum @Wil says he has batteries and a diverter.  His posts imply that the batteries charge first, then the diverter kicks in.  This would, having thought about it a bit more, most probably  be the behaviour if you don't link them in any way and just instal both as if the other does not exist.  You may want to check out his recent posts and think about whether this is the behaviour you desire (or if, indeed, it matters). 

 

It's probably the best behaviour if you also have ashp, because it maximises the probability that the water is heated by the ashp (with an efficiency of 200-400%) rather than the immersion (efficiency only 100%).

 

[Conor]

How do you heat your water? If you've an ASHP then a immersion diverter is near to pointless. If you can heat your water off peak / solar battery power then you might find selling back to the grid makes more sense. It does for me, as I buy in at 10p off peak and sell back at 8.5p. efficiency of the ashp means heating water costs less than 5p per kWh. Then factor in £200+ for a diverter.

[Wil]

I've taken my diverter out of circuit (had it before the batteries were installed and they fought as above and either drained the batteries into the HW tank or just threw a fault on the diverter). Until then the solic  diverter was a solid and useful piece of kit.

 

Now I just monitor the battery state of charge and when the PV is >x and battery SOC >x  I switch the immersion on for a burn. The batteries allow me to ride out peaks and troughs in production such as clouds passing the panels. I use a shelly 1PM to switch the immersion although rated at 16A this is probably right at it's limit and there are many reports of shelly devices failing with switching 3kW loads. Mine has been fine so far and I'll run it til it fails before looking for another solution.

 

TL;DR don't bother with a diverter, just switch your immersion on full whack when the batteries are nearly charged and the sun is shining.

[andyj007]

A solic was tried, and near useless with batteries, Solic confirmed it does not work.. it just drains them...  so it was removed ..

The idea was to heat the water automatically so as to cost me nothing.. 

I have no heating and tiny electric bills ..

I have now set my hot water timer to 12.30 - 2 pm. via the heat pump.

even on a cloudy day from march onwards it appears  my array has enough power at that time to run my ashp and heat my water it takes about 2-2.5 kwh ..  so no cost 

during winter i use a log burner with back boiler for hot water & underfloor heating..  when my house needs it,, which isnt very often.. 

 

thanks

 

Andy

 

[RichardL]

Hindsight now, with off peak about 30p+ from peak - I'd spend on extra batteries until you don't have excess solar.
(Up to a point anyway)