Earth Notes: Heat Battery Top-up DatasetUpdated 2023-04-19.
A script on the main Raspberry Pi runs every 10 minutes to compute target maximum heat-battery top-up level from the grid. This depends on a a number of factors such as time of day, grid carbon intensity, and sunshine forecast.
The heat-battery system is a Sunamp Thermino powered via a myenergi eddi.
- Eddi installed 2022-02-23.
- 16WW heat battery top-up limit from grid
- 16WW heat battery top-up limit from grid and myenergi eddi solar diverter state.
- heat, heat-battery, Sunamp, Thermino, top-up, storage, grid, carbon, intensity, myenergi, eddi, London, UK
- variable measured
- % topup limit
- date created
- date published
- date modified
- temporal coverage
- spatial coverage
- UK centre 51.406696N,-0.288789E elevation 16m
- directory of recent 10-minute heat-battery top-up-limit log data files named
- directory of batched monthly 10-minute heat-battery top-up-limit log data files named
- canonical URL
- this descriptive text with markup
- is part of
- 16WW Dataset
- this dataset is licensed under CC0, ie it is effectively public domain; if you make use of this data, attribution is welcome but not obligatory
- is accessible for free
2022-01-17: Sample Deep Overnight Fill
After being deeply discharged (to almost ~12°C mains inlet temperature) during the 17th, eg by baths etc, and not topped-up up because of high grid carbon intensity for a couple of days... (And no diversion!)
Overnight from a fraction before midnight until ~6am over 9.4kWh was absorbed by the Thermino at ~120gCO2e/kWh grid intensity. That is 'full' in terms of the indicator lights on the Thermino, but not to the point where the heater relay turns off.
There was a small space of ~20 minutes at the end of topping up where it would still have been permitted, but was not needed.
(There were 16 minutes in which frequency response cut in, and top-up stopped, including a little cluster around the turn of 5am.)
2023-04-12: Algorithm Outline
This is an outline of the part of the heat-battery control algorithm that sets the maximum top-up level from mains, as of just over 1 year's system operation. Most elements seem to be working reasonably well at this point, after tuning through all seasons.
- Only ever top-up from grid if current grid intensity (ie gCO2/kWh DHW) is significantly lower than burning gas locally. The threshold is manually set and is currently 151gCO2/kWh.
- Allow more (higher) top-up when grid-intensity is lower, and preferably towards bottom of recent lower intensity range.
- Avoid any top-up at all in known common grid peak-demand times.
- Reduce top-up when grid is in top-quartile ('red') real-time demand.
- Encourage top-up when the grid is in bottom-quartile ('green') real-time demand and no grid-visible storage is being drawn from ('super-green').
- Reduce top-up when tomorrow is forecast to be sunny.
- Always try to leave some space for diversion, ie diversion is allowed to fill higher than grid top-up.
- Do not top-up from mains when the heat battery can likely be kept full (filling up completely most days) from PV diversion. Limit the maximum grid top-up level more as more recent (~1 week) days have completely filled the heat battery by diversion, implying sunniest part of the year (and over a weekly usage cycle).
- On the Eddi the system is set to allow ~400W to spill before diverting, explicitly pushing diversion merit below at least some grid spill.
- When grid frequency is low then diversion / top-up to heat battery stop, explicitly pushing heat merit below grid frequency support.