Energy Usage Monitor

This application is a real world example of a web application built on libzeep. It can be used to enter the current value of multiple usage meters and display the usage of energy over time.

Additionally, this software can monitor the status of one or more Sessy batteries and it will read data from a P1 port of your smart meter, if configured. When you have a Sessy, you should use a splitter and a P1 to USB converter like the one from Cedel.

Installation

To build and install energyd, you first need to install various other packages. Of course first of all you need libzeep. If you successfully installed libzeep, most of the requirements are already met, the remaining requirements are:

• Postgresql including the development files (on Debian use apt install libpq-dev)
• The javascript package manager yarn
• mrc, a resource compiler

Building the software is done by entering the following commands:

git clone https://forge.hekkelman.net/maarten/energyd.git
cd energyd
cmake -B build
cmake --build build
sudo cmake --install build

This should give you an executable called energyd installed in /usr/local/sbin.

Database

The software uses a postgresql database to store data. The following commands are executed as a user that has admin rights on your postgres installation. First create a new user for this database, this command will ask for a password which you will have to add to the connect URL for the database.

createuser -P energie-admin

Then create the database with the newly created user as owner:

createdb -O energie-admin energie

Finally fill the database with tables:

psql -h localhost -f db-schemal.sql energie energie-admin

Configuring

Command line arguments can also be specified using a configuration file called energyd.conf. A file with this name is searched at startup time in the current working directory and in /etc.

All command line arguments can be specified in this file in the usual ini file format.

A minimal config file might look like this:

databank=postgresql://energie-admin:geheim@localhost/energie
address=localhost
sessy-1=http://192.168.178.25/api/v1/power/status
p1-device-power=/dev/ttyUSB0
p1-device-heat=/dev/ttyUSB1

Running

Now that the database is ready, we can start the application. There are several options you can give:

$ /usr/local/sbin/energyd --help
energyd [options] command
  -h [ --help ]                          Display help message
  -v [ --verbose ]                       Verbose output
  --version                              Show version information
  --address arg (=0.0.0.0)               External address
  --port arg (=10336)                    Port to listen to
  --context arg                          External web address of this service
  -F [ --no-daemon ]                     Do not fork into background
  -u [ --user ] arg (=www-data)          User to run the daemon
  --web-user-name arg                    User account
  --web-user-password arg                User password
  --web-secret arg                       Secret hash for web tokens
  --databank arg                         The Postgresql connection string
  --autolog-time arg                     The time of day to automatically log the status
  --p1-device-heat arg (=/dev/ttyUSB0)   The name of the device used to communicate with the P1 port
                                         (Stadsverwarming)
  --p1-device-power arg (=/dev/ttyUSB1)  The name of the device used to communicate with the P1 port
                                         (Elektriciteitsmeter)
  --sessy-1 arg                          URL to fetch the status of sessy number 1
  --sessy-2 arg                          URL to fetch the status of sessy number 2
  --sessy-3 arg                          URL to fetch the status of sessy number 3
  --sessy-4 arg                          URL to fetch the status of sessy number 4
  --sessy-5 arg                          URL to fetch the status of sessy number 5
  --sessy-6 arg                          URL to fetch the status of sessy number 6
  --read-only                            Do not write data into the database (debug option)

Command should be either:

    start     start a new server
    stop      stop a running server
    status    get the status of a running server
    reload    restart a running server with new options

The option --databank contains the connection string to connect to postgresql in the form of a URL.

The default is to run the application in the background. In that case a daemon process is forked off. This daemon process opens the log files in /var/log/energyd and writes a process ID in /var/run/energyd. Then it starts to listen on the specified address and port.

In case you want to run the server in the foreground for debugging purposes you can use the --no-daemon flag.

The --web-user-name and --web-user-password arguments are optional. The password should be a pkdf2 hash, you can create that with the (hidden) energyd passwd command.

Usage

This software actually combines two different things. Originally it was used to manually enter the readings of a smart meter and stadsverwarmingsmeter. I've done this for many years and this software can render nice graphs for electricity and warmth usage showing the current year in the context of history.

The meters are hard coded, so this is perhaps not very useful for others. To complicate matters further, all text in the user interface is in Dutch. The idea is that you regularly enter (Voeg toe button, or Invoer) the current values for the various meters. The graph (Grafieken) will then display your usage over time.

The second part was bolted on later when a Sessy battery entered our home. To monitor the loading and unloading of the battery a new graph was added using a new data table. This data is stored every two minutes automatically.