Earth Notes: Heat Battery Top-up Dataset

Updated 2023-04-19 09:13 GMT.
By Damon Hart-Davis.
Top-up limit from grid (and diversion of PV) to heat-battery. #heatBattery #microgen #dataset
20220205 heatbatterytarget
Live and batched logs from the heat-battery top-up subsystem on the primary Raspberry Pi.

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.

Note:

Live

recent heat-battery top-up target and related data

Dataset

name
16WW heat battery top-up limit from grid
description
16WW heat battery top-up limit from grid and myenergi eddi solar diverter state.
version
1
keywords
heat, heat-battery, Sunamp, Thermino, top-up, storage, grid, carbon, intensity, myenergi, eddi, London, UK
variable measured
% topup limit
date created
2022-03-06T08:31:32Z
date published
date modified
2024-04
temporal coverage
2022-01-29T21:25Z/..
spatial coverage
UK centre 51.406696N,-0.288789E elevation 16m
distribution
directory of recent 10-minute heat-battery top-up-limit log data files named YYYYMMDD.log
distribution
directory of batched monthly 10-minute heat-battery top-up-limit log data files named YYYYMM.log.gz
canonical URL
this descriptive text with markup
is part of
16WW Dataset
licence
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
true

2022-01-17: Sample Deep Overnight Fill

20230118 heatBatTarget

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

sample heat-battery top-up target and related data

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.

Basic Principles

  • 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).

Other Points

  • 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.
~648 words.