Despite not getting much shed time in, I have been plotting and planning and amassing supplies for the next experiment.
Hydronic heating. This is the description of any heating system where the heat transfer medium is pumped water. A radiator is an example of a hydronic heater. Hot water is pumped through the rad, which gets hot and thus radiates heat. The water, now cooler because of thermal energy transfer, is returned to the boiler, heated up again and recirculated.
So I got to thinking. If the sun is out, then the solar panel heats my washing up water. If there isn't any sun, there isn't any hot water. So, I could use an immersion heater, only the 'hole' for the immersion heater element has been used for the microbore heat exchanger. Scratch that notion, unless I can find a way of injecting some heat elsewhere.
At the shop, we sell heated towel rails. Designed to plumb into the central heating just like a radiator, except they can have an element fitted to run them off electricity. Either way, they rely on the towel rail being filled with water for both heat transfer and for thermal mass. Which got me thinking. If I use the electric element to heat the water in the towel rail, perhaps I can pump it out, pump some more cold water in and then use it as both a water heater and a space heater.
Just by chance, I have a 'spare' microbore loop in my calorifier, so the plan is to use another circulator pump to circulate the water between the towel rail and the calorifier. In cold weather, or on very overcast days when there isn't any solar to be had, I can not only take the chill off the inside of the box, but possibly generate hot (or at least warm) washing up water.
The towel rail, with heater element fitted and hydronic connections. This is located in the kitchenette area, so if it only functions as a towel rail after all, I can at least dry my teatowels!
The pipework goes through the stud wall and into the 'facilities'. This might get an insulated jacket to minimise losses, or it might end up radiating some very low level heat into the loo. We'll see what happens once I commission the system.
I need some more pipe and a couple of 15mm to 10mm adapters to link into the second calorifier coil, and I also have to shoehorn in another Grundfoss circulator pump. One happened to avail itself thanks to me stripping the old oil boiler a couple of years ago. It was lurking in the chicken shed. I've just finished cleaning it up, wiring in a power cable and bench testing it. All looking good.
I may have to think about a feed and expansion system, but it might just work as a partially sealed system.