Earth Notes: Statscast - Normal-ish June, Heating Re-viewed (2020-06)

Statscast

Hi, I'm Damon Hart-Davis, and welcome to Earth Notes podcast on all things eco and green and efficient @Home!

5th July 2020, for June's stats.

Turn-of-the-month update of home energy and related stats, and poking at data from 16WW.

Here's a mystery sound to keep you guessing until later: [...]

As the UK's Met Office said, the very sunny and warm weather of late May continued into the start of June, but then petered out into a more typical mixed bag. Old joke: If you don't like the weather in the UK, wait 10 minutes.

Thus, for example, 16WW PV generation was a pretty normal 19kWh/d, and close to the original PVGIS prediction.

Weather and life are clearly nowhere near normal in all sorts of other ways, from much more rain than average across the UK in June, to pandemic infection relapses requiring new lockdowns into July from Leicester to Lubbock, Texas.

[01:20]

Back here in slightly-less-sunny 16WW, gross electricity and gas consumption are still elevated, though maybe a bit less so with the younger Xbox-ing child back in school two days each week.

Because the sunshine has been less consistent and predictable, timing loads to match the sun being out (eg when should we run the dishwasher?) is harder. So self-consumption dropped a bit since May even though we continue to export heavily overall.

Another local stat... By an advanced scientific process known as "counting", which I seem not to be very good at, mid-month I estimated that my 'normal' lockdown exercise jaunt, to and around the edge of the cemetery, seems to be about 2000 steps, so maybe 20% of what should be my daily target!

And my Captain Caveman look isn't going away any time soon, given the catch-up pressure on local barbers!

[02:13]

Visualisation

Today's visualisation came about because I'm trying to better understand some heating-related stats, and I prodded my own data to get there.

In the building physics world there is a simple model that says (for heating climates such as the UK), that above a certain 'base' temperature the building won't need heating. That may be because outside is warm enough generally, or because even if it's a little cooler outside than would be comfortable inside, heat gains from people and appliances make up the difference. The default base temperature assumed for UK buildings is 15.5°C. Though it makes sense to try to compute a more accurate value by observing how a particular building works. For 16WW I use 12°C as the base.

[02:57]

For every degree below that base temperature the heat demand is assumed to go up linearly, so that a day with 2HDD (two "Heating Degree Days") should require about twice as much space-heat energy as a day with 1HDD.

The fewer kWh of heat needed per additional HDD of demand to keep the building comfortable, the more efficient the building is. Low is good!

(You can read more about how all this works at my favourite DegreeDays.Net.)

[03:25]

One assumption is that the kWh/HDD figure should be roughly constant, at least when there is space heat demand. The kWh/d figure often won't drop to zero even when there's no heat demand, such as in summer, where the same energy or fuel is used for other things such as cooking or DHW (Domestic Hot Water) as it often is in the UK.

I plotted 16WW daily gas consumption against HDD (with 12°C base) for 2016 up to the end of June 2020. Although it's messy, I think it's true. Heat demand (kWh) rises massively mid-winter as you'd expect, but the kWh/HDD shape seems much flatter, which is what I wanted to check. Note that we generally only have the heating on November to March.

The pattern recognition built into our brains is pretty good. For those of you looking at this episode's page and Show Notes you can see if you agree with my interpretation or not!

For 16WW kWh/HDD is now around 2.5. Before conserving it was over 4.

[04:31]

For 2019, the metrics were 2.3kWh/HDD and a baseload of 2.7kWh/d. Those are about right, extracted from our messy real-world data! The years 2016 through to 2019 show similar values.

For 2020, for the first six months including a record-warm spring and lockdown, the figures are 1.7kWh/HDD and a baseload of 4.8kWh/d. The latter up (and the former down) likely due to unusually high occupancy.

(As of this episode only half the data for 2020 exists, but the data set and graphs for it should update as more comes in.)

Have a look, in the Show Notes, to see all the graphs and the raw data, and see what you think.

I'd like to go back and do the same for previous years, though instead of daily data from Loop for gas demand, I have manual meter readings already captured electronically at about weekly cadence. I have more detail that I could transcribe from paper records if needed.

[05:38]

Bonus Soundscape and Number

Though I didn't audify any numbers this time, I didn't want to leave noiselessly.

Over the last couple of days I've been enjoying the field recordings [then hosted at, gone by 2023] at Cathartic Audio. So I made another of my own, a 'daytime' 16WW capture to go with previous dawn and dusk.

Here's a little of it, with birds and cars and DIY, oh my!

[06:01]

[suburban noises and birds chirping]

[08:48]

The full raw track is available from the Show Notes.

And since you asked, that (mystery) repository revision number as of preparing these words is 35359, up 675 from the last statscast, so just over 20 revisions per day.

There's more on my "Earth Notes" Web site at Earth.Org.UK.