Boilr

Water boiler automation with a Fronius pv inverter on a Raspberry Pi.

The objective was to harness the surplus generated by the PV system and enhance daytime self-consumption through water heating. This approach not only reduces the energy fed back to the grid but also curtails the need for heating resources like pellets, oil, or other fuels.

The yellow area illustrates the self-consumed energy after using Boilr (this program) to increase self-sufficiency. The blue line is the overall energy consumption. The gray region represents the surplus energy directed into the grid. The green line corresponds to the battery charge level, depicted as a percentage, while the green segment represents the surplus energy channeled into the battery.

Here, it's evident that all the energy generated by the PV system serves either to charge the battery or for direct consumption (inclusive of electrical devices and the water heater's heating element).

Features

• Heat water with surplus power from PV
• Active date & time spans
• MQTT contactor status
• Operating modes
  • Interactive
  • Daemon
• Manual contactor override

Setup

Refer to this for setup instructions: Setup.md

Check out this Sample configuration for reference.

Usage

Starting service:

boilr start

Stopping service:

boilr stop

Run verbosely in command line with custom config path:

boilr -c ./config.yaml -v run

Complete guide (boilr -h):

usage: boilr [-h] [-c CONFIG] [-v] {start,stop,status,restart,run,manual} ...

Water boiler automation with a Fronius pv inverter on a Raspberry Pi.

options:
  -h, --help            show this help message and exit
  -c CONFIG, --config CONFIG
                        Path to the configuration file. (default: None)
  -v, --verbose         Increase verbosity (default: False)

commands:
  Choose between the following positional arguments

  {start,stop,status,restart,run,manual}
    start               Start boilr service
    stop                Stop boilr service
    status              Show the status of boilr service
    restart             Restart boilr service
    run                 Start boilr in command-line
    manual              Manually override contactor

Additional hardware required. Please check:
https://github.com/PeterBrain/boilr

Important

In all operating modes Boilr needs permission to create a file in /var/log. If you run boilr as a daemon it needs permission to create a file in /var/run. Pytest needs write permission to /var/log too.

Requirements

Check out Requirements for more details.

Weaknesses

The existing design exhibits a significant limitation: in contrast to Ohmpilot¹, a comparable Fronius product that boasts notably higher efficiency due to its use of PWM (Pulse Width Modulation), my setup operates solely in two states. It's either fully activated, providing maximum power to the heating coil, or completely deactivated. The optimal efficiency advantage is sacrificed on days when PV production falls just short of meeting both the household's current consumption and the water heating requirements.

Additional resources

• Fronius official API documentation: Documentation - Fronius Solar API V1
• Postman request collection: Postman Collection - Fronius Solar API V1

Footnotes

1. https://www.fronius.com/en/solar-energy/installers-partners/infocentre/news-row/ohmpilot-hot-water-with-solar-energy and https://www.fronius.com/~/downloads/Solar%20Energy/Brochures/SE_BRO_Fronius_Ohmpilot_B2C_EN_MEACA.pdf ↩