Earth Notes: On Website Technicals (2024-12)
Updated 2024-12-09.2024-12-09: Frequency Response
In the gap between the gas boiler coming out and the heat pump generating DHW I tried to demonstrate how to to force a boost on the Eddi, but my grid frequency response system (stopping any boost and diversion when grid frequency is too low) kept cancelling the boost. So I temporarily removed the response test from cron.
I have now modified the script to avoid cancelling boost with more than ~17 minutes (1000s) left, as longer than that is likely a manual boost, and less than that is likely automated and will be retried automatically so is safe to cancel.
I took the opportunity to take advice from shellcheck and tidy up the script too.
16WW Recent Utility Stats
I tweaked the recent utility stats to be a little more compact when no electricity is being exported.
I note that in the 10-year+ cases we were importing about twice the gas kWh compared to net electricity exports, which suggests that a heat pump CoP of more than 2 should reduce our carbon footprint overall. This seems likely.
At 16WW over 7 days from 2024-12-02 to 2024-12-09: electricity import 10.4kWh/d.
At 16WW over 14 days from 2024-11-25 to 2024-12-09: electricity import 9.9kWh/d.
At 16WW over 28 days from 2024-11-11 to 2024-12-09: electricity import 7.9kWh/d, gas consumption 1.0kWh/d.
At 16WW over 371 days from 2023-12-04 to 2024-12-09: electricity import 4.3kWh/d (net 0.6kWh/d), gas consumption 2.6kWh/d.
At 16WW over 3662 days from 2014-11-30 to 2024-12-09: electricity import 3.1kWh/d (net -3.8kWh/d), gas consumption 7.7kWh/d.
At 16WW over 5558 days from 2009-09-21 to 2024-12-09: electricity import 3.1kWh/d (net -4.4kWh/d), gas consumption 9.0kWh/d.
2024-12-08: Pasteurisation Pending
I added a flag ('w') to the heat-battery status page to note when a pasteurisation cycle would run, but is being held until grid conditions are good, ie 'super green'.
Maybe this page should renamed more like a heating control overview...
2024-12-05: Grid Responsive Pasteurisation
Currently the Eddi is programmed to boost heater 1 (ie the DHW tank) early Sunday morning boost ( (UTC) for 3h30) for pasteurisation ie to kill off Legionella.
A weekly boost is probably more often then needed, and even though on Sunday morning the grid will often be at low demand and low carbon intensity, it may not always be so.
The adjustment to waste less CoP energy is to run a pasteurisation cycle at predicted grid low demand (the wee hours), when the DHW tank has gone ~14 days without reaching maximum temperature, else any time over ~7 days without when the grid is super-green.
No explicit pasteurisation should be needed when there is plenty of PV diversion, eg in summer, as the DHW tank has diversion priority. Otherwise this reduces the pasteurisation frequency to below weekly, and where possible using low-carbon energy.
I have added appropriate code to the heat-battery script that will apply even when general grid boost to store energy is not allowed.
The new code would in practice be ineffective until the Eddi weekly boost is disabled, so I have disabled it.
2024-12-02: JQ For Heat-pump H4 Data
To capture the heat-pump H4 boundary consumption being measured with the Eddi external current clamp 2 (CT2), I needed to switch from per-hour to per-minute Eddi data. I also needed to really understand the data format and jq. It seems that group_by is one of my new friends...
I had to go back and regenerate and re-commit a couple of the Eddi archive log files generated by the updated scripts.
I also added a new synthetic variable conexeh — consumption excluding electrified heat — ie excluding immersion and heat-pump. This should reasonably reflect all other household uses and be back to ~5kWh/day.