What happens without internet?

Today we are increasingly reliant upon the internet. During the current crisis when many are confined to home the internet provides opportunities unimaged to previous generations. Whether it’s online shipping, entertainment, using zoom or other online meeting tools to maintain family, society or church connections; the internet provides the means to supply us with our material needs, entertainment and social contacts in ways unimagined previously.

However our home, and other smart homes, may be particularly vulnerable should the internet become unavailable either in general or a particular service upon which we rely becomes unavailable. I thus thought that for this post I’d reflect upon the services our home relies upon for normal operation and what the impact of their absence would be. I will also reflected upon other failures of the service where such failures have been previously observed.

HEMS schedule for 11-12/04/2020
ServiceEffect if unreachableeffect of other observed failure
Solar forecastingIn unreachable when daily schedule being generated then schedule assumes no solar production like mid-winter.On April 7th I observed several hours around the middle of the day when there were no forecasted or estimated actuals reported, but the service continued to accept our measured readings. No impact on HEMS operation.
Agile electricity price data.If unreachable when daily schedule being generated then schedule carries over from prior. Schedule may be generated by manual initiation of the script when the required data becomes available.
If necessary operation of the car charger PLC could be suspended causing the car to charge at full power immediately and the car’s own timer used to set operating hours if needed.
If tomorrow’s price data is not yet published (i.e. it’s overdue), then the optimisation is performed using the most recent day’s price data. Since today will no longer be within the dataset provided by the solar forecast (as it’s no longer in the future) then no solar window will be found and so all the required number of hours will be bought assuming today’s (not tomorrow’s) prices, so the battery will still be charged but at a sub-optimal cost. The optimisation can be started manually once the overdue pricing data is available.
Immersun APIIf the real time generation data wasn’t available at all then solar car charging would be disabled. Car charging based on bought electricity price would continue.I have observed occasions when the real time data ceases to be updated (presumably because communications between immersun and cloud is lost) which then throws out the upload to the solar forecasting and the disabling of solar car charging at low generation levels. The forecasting site doesn’t seem to be phased by some erroneous data having never yet dropped below 0.96 correlation. The solar car charging has once been enabled later than it should which had some impact on battery state of charge, but was disabled slightly later via the immersun relay output.
An API is also used to switch the immersun into or out of holiday mode on days with significant periods of negatively-priced electricity. Unavailability of the API could leave the immersun locked in holiday mode and thus completely unable to heat water, or not in holiday mode when it should be causing self-consumption to continue when export would be more optimal to allow for negatively-priced import later. Vacation mode may be enabled or disabled manually via the immersun’s front panel to mitigate.
Powervault APILack of availability of the API would disable the ability to switch operating modes. This would leave the Powervault either charging from solar only or force charging, and may or may not permit discharge. The unit can be reset to normal state via repeated operation of front panel button which would disable scheduling but provide default solar operation.
WIFIPLUG APILack of availability would prevent the wet goods being turned on via API. Operation via the bushputton on the plug and indeed via Apple Homekit should remain.
Apple HomekitThe heating and other automations are run from Apple Homekit. My understanding is that the local service is provided from the two Apple TVs acting as hubs which should continue. Remote access via devices not in the home would be disabled.
Hildebrand APII have access to an API giving data from the HAN side of my smart meter and independent current measurement, but this is not currently used for control so no operational impact.
Impact assessment for loss of different cloud services

Overall I would conclude that there’s no significant issue here. The house would continue to be heated and appliances will still work. Any impact would be around energy consumption and cost only.

Some mitigation could be arrived at by:

  • resetting the Powervault storage battery to restore default normal operation,
  • manually starting or stopping vacation mode on the immersun’s front panel, and
  • suspending operation of the PLC on the car charger to enable car charging.

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