DamonHD

For us the Thermino was able to fit under the then extant combi, but hold ~2 days' heat. https://www.earth.org.uk/note-on-solar-DHW-for-16WW-UniQ-and-PV-diversion.html#2022-03-09

FWIW I use microzoning to mean control per room or per emitter (eg radiator).

I'd quite like a small lump to sit on top of my Thermino, maybe to instill a sense of mortality in it! B^>

No and no.

Avoiding getting the batteries out of balance is important, and what @ProDave suggests seems like a decent temporary workaround.

I do not think that 'everything open' is always right (formal paper https://www.mdpi.com/2071-1050/16/11/4710 - TL;DR https://www.earth.org.uk/To-Zone-Or-Not-To-Zone-with-TRVs-for-Retrofit-Heat-Pumps.html - discussion on the Heat Geek thread here), but definitely go for weather compensation: you do not need to run at anything near the maximum temperature most of the time and so WC will improve CoP and reduce cycling.

There are standard calcs I suspect, likely in part dependent on 99% percentile windspeeds in your area.

To add: being the H&S governor too, I did ask for additional steel fixings / ropes to the edge of roof surfaces to further reduce the risk of takeoff or at least stuff sliding on to kids below, but I don't think there was any evidence of anything shifting in even quite high winds. The panels were initially on frames with ballast weights. I think that on the new roof trays may have been used in part, but it is the ballast that is doing most of the ... uh ... heavy work... as suggested above, AFAIK.

16kWp on a school roof many years ago - all fine. Largely survived building works and some being shuffled to an entirely new roof also. https://www.earth.org.uk/solar-powered-schools.html

See live-ish charts of TRV open %-age further up the thread. To avoid various problems they open fairly fast but close as slowly as they can without temperature overshooting too far. They do not close fully if temperature does not significantly overshoot.

I have been out all day so I may not get to respond to everything... OpenTRV / Radbot are intended to just this where possible by bringing rooms up to temperature when occupancy is predicted. And indeed my bedroom Radbot did so this morning. Some of the other things that you mention are things that I have considered since handing over the Radbot IPR and there is space in my research plan to think about and maybe model or prototype some of them.

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But plain WC does not increase flow temperature in response to anything other than falling outside temperatures. If you are saying that someone might shift the whole WC curve up then that is a different matter which I address as "fiddling with the settings". Notionally that WC curve is *computed* from the heat loss calcs at installation time and left alone. 😀

@JamesPa I hear what you say and I shall think about it: thank you for tussling with this. But where you say "I think the latter results prove that the saving in the former is really attributable to the reduced temperature of the inhabited rooms, not to the setback in the uninhabited ones!" taken literally and simplistically is untrue: it is a simple matter of physics that all internal spaces that are at a lower temperature than they otherwise would be lose heat to outside more slowly than they otherwise would, and thus reduce heat demand, and where WC is in use that reduces electricity demand and thus cost. Note that the initial HG claim being countered was that reduced heat demand could cause increased electricity demand, which is again simply not true with use of plain open loop WC. Whether that arrangement is acceptable for other reasons, some of which we have discussed in this thread, is a separate issue.

FWIW my own live-ish TRV percentage-open chart (for most of the rads): and call for space heat: Note that there is currently a problem with this system and it hasn't been fully commissioned (or paid for!) yet, and I am continuing to tweak as householder and researcher. So have a good laugh! B^>