DamonHD

Just finished my yearly CO2 calcs for electricity and gas, about +225kgCO2 for the year. I now hope to see this drift back to slightly negative as the grid gets greener, etc. https://www.earth.org.uk/saving-electricity-2024.html

1) The static calcs I did in the model in my paper suggested very significant energy savings by doing TRVs right, which back up my experience. 2) Dynamic response to occupancy is another significant saving, eg heating unoccupied bedrooms during the day even if people are home all day. Again, reinforces what I saw in substantial trials. 3) Given how cheap and easy to use TRVs are (~1% of the rest of the heating system ish) and can save 10--30% of consumption and footprint for <2Y financial payback, never mind comfort, why NOT put them in by default, even if you leave them a bit high if in doubt and lean on WC as much as possible?

Because one curve for the whole home is clearly insufficient at some level when the heat losses and gains of rooms relative to one another is changing.

Whoops, I borked that image by moving it and I can't edit my post. Here's a newer and betterer one for the whole of December:

Yes, these things are debatable, but a core issue for me is that no one WC curve (with static balancing however good) is perfect for all combinations of variable occupancy, solar gain, wind, etc. And comfort suggests wanting to maintain some differentials anyway where possible. Note that I am primarily concerned with retrofits into relatively thermally leaky existing UK stock which may skew things. Note also that I did reduce (~10x) some inter-room uncontrolled heat transfer in my house between the living room and a bedroom above while doing other works, so that option helps and is available too, if one knows about it and why it might help.

Data Science is a thing (though has a newer more fashionable name this week I think) and all the data scientists that I know are amazing multitalented people... I have a pile of EOM and EOY data capture / munging lined up for tomorrow too...

Note that the bad setback effect applies if rads are only just large enough AND pure weather comp is not used. That would not in general be allowed for an MCS install as I understand it, so I don't think it is a real problem if thought about. (Maybe an installer noticing that a user is zoning and wants to carry on doing it should suggest upsizing rads a bit more than they would otherwise.) Also note that the maximum temperature sag occurs when it's warm enough outside that you barely need heating - it's usually less. See the end of https://github.com/DamonHD/TRVmodel/blob/main/SampleComputationsOutput.txt I don't know of any paper dealing with your last para (I would be keen to read it too) but the research strand that I'm currently on may look at that and test it in a physical model too. I really have to get up to speed on EnergyPlus and heat pump simulation in a hurry!

You are indeed not most people. For gas heating, relationship is typically linear above a baseline temperature and baseline (non-heating) consumption, eg per https://www.degreedays.net/ For HP changing CoP with exterior temperature will complicate things, which I haven't entirely worked through in my head yet.

@ProDave I absolutely think that that is part of the deal. I went back to check whether the circulation pump counts within the SCoP value or not, and have a relevant paper open, but have not convinced myself yet... If I only need 4kWh of heat pumping in a day but my circulation pump runs continuously at ~40W, I just severely dented overall real efficiency. Exclusively chasing CoP, particularly a version that excludes these ancillary but significant items, and assuming that comfort can only be rock steady higher temperatures, may be a mistake. (I take that 40W as ultimately adding to the space heat at a CoP of 1.)

Please read my paper: it explores exactly this. https://www.mdpi.com/2071-1050/16/11/4710 Demanding overly tight temperature control WILL waste a lot of energy. If running pure weather comp as I am the flow temperature is only determined by external temperature.

Don't get me started on the condensing boiler issue: I took a cheap (~£1/home) solution to both Ofgem and Lord Callanan and neither were interested (or understood)... https://www.earth.org.uk/OperationTuneup/ The https://moneysavingboilerchallenge.com/ thing showed it could be done!

I realise that I have now hijacked this thread. Mods, if you wish to spilt off these posts into a new one, fine by me!

@JohnMoI can't share the 60% figure as that wasn't published, but the second one is from https://www.mdpi.com/2071-1050/16/11/4710

Note also that we have room temps set ranging from 17C up to ~20C for comfort, not too outlandishly 1C below CIBSE/etc norms. Having those maintained with open circuits while sunshine and wind (and people) come and go is hard. But we also (c/o OpenTRV) set back automatically when rooms are vacant. No one WC setting is going to magic all of those!

The WC curve is based on (1) Octopus heat loss calcs at design temperature at the low end and (2) my observation of best fit HDD base temperature over many years at the top end. In other words I'm pretty much going by the book here. I suspect that it *is* a bit too high but we haven't been anything like cold enough to calibrate (1) yet. But in any case my own experiments (eg at Energy House) suggest that it is a silly waste of energy to heat unoccupied areas except in a very air tight modern (PH-ish) home where maintaining temperature differentials on purpose would be hard. Eg ~60% waste heating bedrooms during the day in EH1 on a 'working family' occupancy pattern, ~15% whole house in my recent paper.

IMHO (and the opinions of several plausible studies) insisting that comfort is all about very steady and uniform temperatures is overblown. I spent some years living in a farmhouse partly heated with open fires for which neither is the case and yet many people see them as some sort of comfort ideal. These things are partly a matter of (learned) personal preference, but overselling them will result in excess emissions and climate damage and ultimately will hurt us all. Because I'm working around a problem with our shiny new heat pump install I have been trying several modes of operation and was probably not doing things optimally, but continuously on, even with a flow-temperature setback at night, felt stifling and oppressive and used *double* the electricity (kWh/d) of the intermittent (OpenTRV driven) call for heat that I am now back on. Note: electricity in, not CoP or any other intermediate measure. Intermittent, albeit in a house with reasonably good fabric, is *more* comfortable and much lower footprint and cost, in this instance at least.

Note that the antifrost feature will run the circulation pump and possibly the compressor if outside temperatures are at/below 7C. I'm also seeing my Altherma eat a lot more energy that I exepct when running it open loop with a weather-comp LWT target, cf running it when needed with an external call for heat.

You could smoke something to fix that, or we could...

Our overall electricity demand curve this month up to yesterday shows some successful load shifting for DHW at least: https://www.earth.org.uk/heat-pump-16WW-control.html#2024-12-20 Load profile over 2020-12-01 to 2020-12-19 inclusive, gross and net/imported. DHW consumption spikes starting at 07:40 and 19:10 are clearly visible.

If at some point the current grid intensity is less than half its average over the last week, then I am claiming that filling my storage boots now is the same as (in CO2 emissions terms) using the heat pump with a CoP of ~2 at some random point during the last week. Similarly looking forward a couple of days. We are all aware (eg including @Ed Davies!) that there is some contention about that reading, though maybe less so now that constraining excess renewables for reasons other than transmission is becoming more of a thing. In any case I take very low relative grid carbon intensity (and no drawdown from grid storage, aka "supergreen") to be indicative of abundant low-carbon generation and minimal strain on the transmission and distribution system, so a good time also to fill boots. How should I have worded those paras better in my talk?

I gave a talk last night on how my heating system is developing... https://www.earth.org.uk/home-heat-carol.html

Might he simply be ill?

Everything seems to be working nicely. I have captured current settings/configuration. I shall do some tweaking over the next few days. Nothing major by the looks of it, certainly less than I had expected. One thing that I wanted to do does not seem possible (schedule/clock AND external call for heat) but I can live without it, as the external call is reasonably well-behaved. https://www.earth.org.uk/heat-pump-16WW-control.html

I'm a fossil - a greybeard that doesn't have long to wait for a bus pass...

Gas supply is capped, so fossil-free at home (other than me!)...