Solar monitoring app

Monitors solar panel output using the Fronius inverter API and power consumption in realtime and persists the data to a MySQL database for display in Grafana.

• Monitors instantaneous power generation and consumption
• Calculate cost of power used
• Monitors per-string power generation
• Retrieves Solcast solar forecasts (https://solcast.com/)
• Uploads actual generation to tune the Solcast forecast

Usage

Configure solar panel system in Solcast

Setup and run the app:

• Build the application using Maven: mvn clean package
• Install and run MySQL (https://www.mysql.com/ or https://mariadb.org/)
• Setup the database using /src/main/resources/mysql/setup.sql (substitute your own passwords)
• Add power tariffs (see below for details)
• Configure properties in application.properties
  • app.inverter.host - hostname/IP of the inverter web API
  • app.solcast.api-key - your Solcast API key value
  • app.solcast.site-id - your Solcast site ID
  • spring.datasource.username - your MySQL app user
  • spring.datasource.password - your MySQL app user password
• Run the application

To view the output, use Grafana:

• Install and run Grafana
• Configure the MySQL datasource
• Import the Solar dashboard found in /src/main/resources/grafana/Solar.json

Sample output:

Power tariff configuration

There are two types of tariffs:

• Usage - what you are charged for using electricity
• Feed-in - what you are paid (or possibly charged) for exporting electricity

Both tariffs must be configured for each day of the week, from 00:00 to 23:59:59.

The tariff table structure is:

Column	Type	Description
feed_in	boolean	FALSE for a usage tariff, TRUE for a feed-in tariff
start_effective_date_epoch	bigint	The time when this tariff begins to be effective, in seconds since the epoch
end_effective_date_epoch	bigint	The time when this tariff stops being effective, in seconds since the epoch. Can be null.
day_of_week	varchar(9)	The day of the week, in capitals. For example SUNDAY.
start_of_period	time	The time of day when this tariff starts being effective. For example, 00:00 or 15:00.
end_of_period	time	The time of day when this tariff stops being effective. For example 10:00 or 15:00. Ensure that the last period for each day ends at 23:59:59.
price_per_kwh	numeric(5,4)	The price for one kilowatt-hour (kWh). For example, 0.2174.

The following examples use Sunday, 10 November 2024 GMT (epoch time 1731196800) as the starting effective date for the tariff.

Flat tariff example

If you are paid $0.033 per kWh for export, regardless of the time of day, then the insert statement for Sunday would look like: INSERT INTO tariff (feed_in, start_effective_date_epoch, day_of_week, start_of_period, end_of_period, price_per_kwh) VALUES (TRUE,1731196800,'SUNDAY','00:00','23:59:59',0.033);

Time-of-use tariff example

If you are charged different amounts depending on the time of day, then you will have multiple rows per day.

If you are charged $0.2174 between midnight and 3pm, $0.4082 between 3pm and 9pm and $0.2174 between 9pm and midnight, the insert statements for Sunday would look like:

INSERT INTO tariff (feed_in, start_effective_date_epoch, day_of_week, start_of_period, end_of_period, price_per_kwh) VALUES (FALSE,1731196800,'SUNDAY','00:00','15:00',0.2174); INSERT INTO tariff (feed_in, start_effective_date_epoch, day_of_week, start_of_period, end_of_period, price_per_kwh) VALUES (FALSE,1731196800,'SUNDAY','15:00','21:00',0.4082); INSERT INTO tariff (feed_in, start_effective_date_epoch, day_of_week, start_of_period, end_of_period, price_per_kwh) VALUES (FALSE,1731196800,'SUNDAY','21:00','23:59:59',0.2174);